Hi all, I have a new to me Cat 973 I bought at an auction with minimal movement allowed (allowed to move it about 3ft). I am totally new to any tracked equipment, and got this to dig/push out tree on my farm in addition to some earth moving projects. It has 18332 hrs on it, and the visible filters are labeled as replaced at 18002 hrs, and is serial number 86G03137. The engine starts and runs well. The fluids all look clean and were within proper fill levels. It drives well in a straight line both forward and reverse, and can spin the tracks when up against a root ball, but doesn’t spin them real fast. I’ve pushed out about 25 trees so far, but had questions about a few behaviors that I was curious if they were normal or signs of a problem. I did order a shop manual from eBay, but it’s taking a long time to get here this time of year. The questions I have are if it is normal to make a lot more noise (sort of hydraulic whining) when turning? It also seems to lose power and strain the engine more when turning. It will reverse one track, but both slow substantially when one track pedal is depressed, and it seems to strain the engine. The track pedals also seem to have a bit of play, but the linkages under the cab don’t feel like they have much play. I found another post on brake pedal adjustment, but haven’t had a chance to check that yet, though it slows and stops the machine as expected. I’ve also noticed that I can slow the engine when pushing into a root ball, which, in other posts, seemed like was not supposed to happen since the trans has a circuit to back off if the engine slows. I’m not sure this is related to the slow turning, just another observation. I do the farming as a hobby, so only get around to using the machine every few weeks. I was expecting this job (push out ~40 trees) to take quite a while given my experience with a tractor with loader, but this machine is really good at it! I’ve managed to take out 25 trees with roots in about 3 hours of work! Thanks, Reuben
A 973 compared to a farm tractor loader is like a 5 HP go cart compared to a Formula 1 car. I expect ippielb who has a 973 will be along shortly.
Welcome to HEF! Cmark is the resident expert on these. Need to measure engine speed and go from there.
Thanks! From the past posts I’ve read folks on here are very helpful. On the engine speed, I looked into the lower-cost laser tachs, but the reviews made them seem a bit inaccurate relative to what Cmark had posted for the acceptable range in the past. Does anyone have a recommendation for a reasonably priced meter that’s good enough? The other option is a standard diesel tach. I’ve read that there’s a place to connect one on the engine, but haven’t found where. I have an extra tach from a tractor that I could use. Does anyone know where the electrical connection is on the engine, and if there is a multiplier on the output? Thanks, Reuben
Lots of them pick up from the alternator.
If it spins the tracks, travels straight and turns OK then there won't be much, if anything wrong with it. As mentioned above, engine RPM measurement will confirm. High idle should be 2320+-50 RPM. Full load speed should be 1950+-100 RPM or in other words, it shouldn't drop below 1850 RPM. Hydraulic noise and whining is to be expected. Is all the insulation still in the cab? The engine is a 3306 and the take off for a mechanical tachometer is on the back of the governor. This is an example of a cheap photo-tach that I can get here in Australia. I don't use one myself but the specifications seem OK for the job. Can you get something similar in Canada? https://www.jaycar.com.au/digital-tachometer-with-memory-includes-min-max/p/QM1449
FWIW 25+ years ago I had the pleasure of running this 973. At that time it had a 12' AC blade on it and was used to build terraces. I only got to run it for about 2 years when the owner retired and it was sold. This pic is from an auction website that sold it about a year ago and it has the same track pads on it that it did when I ran it. The grousers were a fair bit taller back then and it would spin the tracks on a hard push. If you have double grouser tracks on your machine I would think it should be able to spin the tracks fairly easily.
Thanks Cmark. I ordered a very similar laser tach from Amazon, thanks for the suggestion. That model had much better reviews than others I had found. It should be here later this week. DB2, good suggestion on the alternator. Unfortunately the tach I have is setup for an inductive sensor, so won’t work with the alternator. I was kind of hoping the engine had an inductive sensor on it, but Cmark identified the pickup as mechanical, so no dice there. bam1968, thanks for the reference point. I can spin the tracks in a straight push, I just don’t have a feel for what ‘easily’ means in this type of equipment since I have 3 hrs of seat time in one machine. I would say if I’m not trying to lift with the bucket it always spins the tracks, but if I’m trying to lift a tree root ball while pushing it sometimes won’t spin the tracks. thanks again. I will post RPM readings when I can get them. Cheers Reuben
It has a built in load sensing system and I think most loaders the bucket/boom hyd's. have priority.
My 973 has almost wore out double grouser pads. I do a lot of brush and pond and lake work. Even with almost no grousers I can pin it down and not spin the tracks. Remember these machines weigh 60,000 plus and a big tree with root wad could weigh 20,000 or more. I like the worn pads as it turns really good and still pushes good on dry ground. I just don't work in the mud which is fine with me. Are the hydrostats noisier when it warms up and more sluggish? Also does your two speed still work?
What model 973 do you have? My 973C is pretty quick and nimble. If there is such a thing with a 60,000lb loader. Engine rpm is a big deal. needs to run wide open. Like the specs Cmark listed. Yes mine makes some hyd noise and always smells like oil when working it. The only way I can stall the tracks is dry ground while trying to push over and lifting on a large tree. if you don't lift on the tree while pushing it will spin the tracks. 90% grouser depth. If you step on the steer pedal far enough that side should counter rotate.
Hi gwhammy. Thanks for that info. My do spin if pushing straight, but they stop when lifting. My ground is quite dry - here in Colorado we’ve had pretty bad drought this year, maybe an inch of precipitation in the last 3-4 months. We’ve been dusted by snow a couple times recently, but it mostly sublimates and doesn’t soak in. On the noise, I haven’t noticed it change as it warms up, but I wasn’t really listening for it. I guess it wasn’t obvious. It’s moderately loud in the cab. The door seals aren’t perfect anymore. There may be other insulation missing, but what is there isn’t torn. There’s none under the floor, so I suspect a fair amount of the sound comes through there and the doors. Farmerlund, it’s an original 973, no letter after. It was advertised as a 1996, but I don’t know that for sure. I do run it wide open - in the cutout at full throttle on my machine. I had read about that on here in a different thread. I think mine only has one speed setting, but could be wrong about that. My grousers are double and have been built up, and are a bit over an inch deep. I can spin either track backwards when I fully depress a steer pedal, but it slows to a crawl (both tracks) when a steer pedal is depressed at any speed.
DOM 6th February 1996.
Thanks, Nige! Interesting to see that it was originally an LGP - it's wearing ~20" shoes now, but that explains the space between the shoes and body. It has the 3rd hydraulic valve, and a diverter but only has a GP bucket on it. Does the line "Bucket AS - General Purpose" mean that it came from the factory with a GP bucket (not 4-in-1)? I assumed it had been converted at some point since it had the hydraulics for both 4-in-1 bucket and ripper and has neither now. I suspect it's last job was in a landfill since I keep finding bits of plastic bags in the undercarriage. Cheers, Reuben
Originally built with 27" double grouser track shoes. The GP bucket it was originally built with is 3.75 cu.yd. heaped, not a 4-in-1. However it was built with the 3rd valve (5G-7883 valve arrgt) so someobody had designs for it further down the line, whether that was a 4-in-1 or a ripper. The 121-3969 Modification Arrgt is interesting. That is an enclosed ROPS, rear bumper, rear tow bar, and line guards for the lift cylinder lines. That suggests something specialized such as landfill, as you surmised. The 5Q-6262 air suspension seat is unusual. That's a Custom Shop Arrgt. To a certain extent it appears to be a "Parts Bin Special". Stuff like the 111-4902 General Arrgt, 111-4914 Chassis Arrgt, 111-9300 Starting Aid Gp, 117-4002 Radiator Gp, 122-2447 Air Cleaner Gp, 7N-1721 Air Lines Gp, 7N-9617 Muffler Gp, & 7P-7666 Fuel Lines Gp are all listed as fitting machines in the S/N range 86G3000-3125 but not above 3125. Your machine is just after that and I'd bet because it had Custom Shop attachments on it that it could have been out of sequence going down the production line at the time Serial Numbers were allocated. I suspect that's why it has "early-series" components on it when in fact it is a "later-series" machine. You may have to careful when ordering parts for it.
Thanks for the heads-up on the parts series. I'll be sure to grab numbers off the machine if I need to order parts. How much difference was there at the serial number split? I noticed the manuals have a split at serial number 2999, but you mention another split at 3125. I suspect the answer is no, but was curious if the 3rd valve comes with the diverter or not? Mine has the diverter in it. It also has posts behind the tracks to protect them now. Is that part of the bumper package, or another add-on? It also has the protectors over the tilt cylinders installed. I wouldn't be surprised if this machine has had a few different jobs and configurations in it's life, it's getting up there in age and hours. Cheers, Reuben
Parts manual for 86G1-2999 is SEBP1387. For 86G3000-Up it is SEBP2394. What will happen is that each range of Serial Numbers will appear on a different page of the Parts Manual. See below. Where you have to watch out is that alhough your machine S/N is 3137 (so falls into the group 86G3126-Up) a lot of the assemblies installed on it are actually those listed as fitting machines in 3000-3125 S/N range.
Surprisingly enough the answer is yes......... Take a photo of the rear bumper. I can compare what it looks like now to what the Parts Manual says it should look like.
Interesting. Thanks, Nige. Here’s a pic of the back of the machine. this is my first post with a pic, so hopefully works...
That appears to be landfill arrangement with the striker bars at the rear behind the finals. The center hole in the pads is designed to help keep the garbage from packing in the rails. I am located in track loader country however the only 973's I know running are at landfills and the last USS mill operating. Not a bad looking machine if it served the first part of it's life in a landfill.
Ahh, striker bars. I didn’t know what they were called - thanks cm1995. Are they strong enough to stop the vehicle if you run into something in reverse?
i suppose the answer to that question is - it depends how fast you're going........ They are not part of the 121-3969 Modification Arrgt, and neither do they appear in either the regular Parts Manual or the Custom Parts Manual for the 86G machine. Certainly the frame for your machine as shown in the Parts Manual has the attachment points for them.
Haha, I suppose it does. I guess for a landfill it may be more about pushing the obstacle out of the way since it’s literally a pile of junk you’re driving through. So even more a mash-up of parts!
I suspect the striker bars are likely OEM, I just can’t find them in the Parts Manual. I was also somewhat surprised that I couldn’t find them in the as-built arrangement.
The term "striker bar" in Caterpillar world refers to "striking" material from the tracks before it can get jammed under the fenders, not Bubba striking other things through not looking where he is going.
That's what the fcukoff great bumper bolted on the back of the chassis is for.....
That makes more sense, Cmark. It would be hard to make those strong enough to make up for my stupidity sometimes
Here's a couple videos of my 973c to compare the sounds you hear. Mine is a newer model so it may vary hydraulically. But yes, the hydraulic whine is common. It's the nature of the beast. As for spinning the tracks, you can slow the tracks/engine with load. Best practice when that happens is to slow your travel speed, if you know you're going to be in for a big load. with the travel lever half way it will slow the machine and load the engine. But if you compensate for the expected load by putting it 1/4 of the way, it will keep your engine revs and you'll actually be able to push through without spinning the tracks. You'll learn with more seat time some tricks. Also, if you're lifting the loader arms you cannot curl the bucket up to scoop at the same time. The lift function has priority.
Ippielb, thanks for the driving tips. I’m definitely in need of some learning. Good to know the hydraulic priority on the lift vs curl. I’ll try to be sure I change the speed with load as you suggest. It looks like your machine maintains speed when you steer. Mine doesn’t and is quite a bit louder when I turn than when going straight. Yours sounds pretty similar when going straight or turning, but maybe that’s just the video. The photo tach showed up last night. I’ll try to get measurements during kiddo nap time today.
Don't get too hung up on the difference between your machine and ippielb's video. His machine is a whole generation newer than yours and apart from both being hydrostatic, the drive systems are totally different.
Ok, got the photo tach out and tested the machine. Idle is about 715 rpm, throttle just befor shot off. The notch at the fast end of the throttle is wider than the lever, so here it is at both ends: 2365-69 front of notch 2376-78 back of notch. Looks like it’s at the very high end of what Cmark recommended. I’m not really sure I could measure loaded rpm with the photo tach since I have to stand on the striker bar to get the measurement off the flywheel on the back of the crankshaft. Is there a better way to get the measurement with a photo tach? Thanks, Reuben
Good question. If your phototach doesn't have some kind of remote sensing capability you may have to get creative. Just some suggestions; Rig up something with zip ties and tape so the tach can work while you drive the machine? Does it have a min/max hold feature? As above but rig your phone to video the tach screen? Take it apart and extend the wires to the sensor?
I drove it a bit after taking the rpm measurements, and I did notice that it steered pretty strong when I first started, then slowed as I worked it more. The noise seemed a bit louder after it warmed up, too. This is also the coldest I’ve used it, about 35F out. The other two times it was in the low 60s to start with. Cmark, I’ll fiddle with the tach a bit and see what I can do. Cheers, Reuben
I’d just buy a magnetic trigger tach, all you need to do is put a little magnet on your balancer(glue it on), then make a bracket to put the magnetic trigger within the right proximity. Run the tach wires into the cab. Self contained I’m sure you can find them on Amazon. “Proximity tach” I believe they’re called
So, after fiddling with some of the proposed options to get rpm while moving, I remembered an app I ran across called “Engine RPM”. It uses the sounnd to determine rpm. I tested it on an old truck last night and it worked quite well, so gave it a shot on the 973 this afternoon. It ended up working, but only with the cab door open - I guess some of the sound insulation is still working the rpm at full forward speed varies from 1940 to 1990 rpm. This was over a field, so not perfectly smooth by any means. Cheers, Reuben
Hi All, A couple of updates. I got my service manual in the mail last week and have been reading about how the system is supposed to work. I got through the seven systems, but can't say I really understand it all yet. Need to read through it again. From the service manual I followed the procedure to adjust the steering linkage. That eliminated the play or free travel in the pedals, so it feels better to drive now. Unfortunately I dropped a 9/16" wrench down in the belly pan in the process. I'll need to drop the back access plate at some point to see if I can find it. I did drive the machine some more last week and tried to pay more attention to exactly how it was behaving. A few things to note. 1. The steering always starts strong, then fades. Not really so much with being warm or cold fluid, but the start of each turn is stong, then it fades. So when I push a steer pedal, it turns strongly at first, then slows way down as I keep the pedal depressed. It feels like there is not enough flow rate to sustain the higher rate when turning. 2. Lifting the loader arms when heavily loaded slows the engine RPM significantly. The engine doesn't stall, so something seems to be bypassing eventually, but the engine really slows down. I didn't have the RPM app running so didn't get a reading of it, but i sounded slow enough I was worried the engine would stall. All the other hydraulic functons don't do that (tracking straight, or curling bucket). I am digging into an old railroad grade, and know that the arm lift is the weakest, so it may just be too much for the machine. So, the question for those with more experience than I: it seems like I have insufficient flow to support turning, it seems like this is a flow problem or leak problem in the system. Is the best thing to do next a hydraulic pressure test? I did order a new filter, but the one I received wasn't a Cat brand and when I looked up the part number it didn't cross to any of the Cat numbers, though I'm a bit uncertain what the correct filter number is. The Cat site when I used it had several options, and they changed when I looked it up a second time?!? Thanks, Reuben
At the risk of repeating myself, engine RPM is the key. If the transmission won't pull the engine down past 1850 RPM then that suggests the underspeed system is working OK. If the implements will bog the engine down significantly, I would suspect a lack of engine power. Looking back at your first post, your fuel filter has 300 hrs on it, correct? Start with changing that and also check the air filters. Next easy test is for fuel transfer pressure. There should be a port in the fuel filter head that you can plug a gauge into.
I would also suggest that you find the drain tap for the fuel tank, open it and let it run a bit. See what comes out in the way of water and sediment. It probably hasn't been opened in years. Once you have sorted out your fuel system as suggested by my learned friend above, here are the details of your hydraulic tank filter elements. Element - 2 x 1R-0722 O-ring seal for cover - 2 x 5H-6733[/QUOTE]
Hi All, Sorry for the radio silence - my day job and the weather have conspired to keep me away from the machine for a while. I bought new fuel filters and changed them both (spin on, and cartridge) today. Both were filthy!! Unfortunately, a test drive after changing them had no effect on loss of power when loaded. On a related note, I could not find a Cat replacement for the cartridge style fuel filter, only a NAPA part - 3360. That was the part in there when I replaced it. I noticed that the maintenance manual says to clean the cartridge filter - was it originally a screen or some other type of filter? Unfortunately I ran out of time to test fuel pressure. I did see a plug on the head of the spin on filter mount, is that the location you were referring to, Cmark? What should the pressure be? Thanks, Reuben
I also took a video of driving the machine so you can see if me saying it’s losing power is reasonable, or if I’m just crazy. I used the audio RPM meter for about 5min while operating and despite sounding to me like the engine was really bogging down, the RPM never dropped below ~1900. So it does seem that the underspeed cutoff is working correctly. As far as draining the tank, I can’t find access to the bottom of the tank except for through a very large plate on the bottom of the machine. The manual says it weighs about 200lbs, so I didn’t try to remove it since the machine is in a field. Am I missing an access point for the tank drain? Thanks Reuben
The filter that is in the metal housing is a mesh screen. It is for large particulate. You only have to clean it. I went through and changed all the filters on my machine so I replaced that one to have an hour number on it.
Spec will be around 35psi but in reality these engines will happily run on maybe as little as 5psi. Tank drain should be a hand pump on the right hand side.
And here’s the rather shakey phone video. Unfortunately I don’t have a nice mount like ippielb has. Hopefully you can see that shortly after starting to turn the tracks slow substantially.
Cmark, I saw that, but was unable to get the knob to release. I’ll put some penetrating fluid on it next time I’m there and see if I can free it up. I tried a wrench on it, but I was destroying the ribs on the knob and was afraid I was going to break the knob off, so didn’t push it further. Thanks!
Two predictions; 1. The line will be blocked and you will have to clear it with compressed air. 2. You might have to take the pump off and soak it in a bucket of diesel.
Does that old girl have rabbit and turtle mode? Seems fast to be in turtle.
If you are referring to the filter that is in the bowl directly below the fuel priming pump then yes it was indeed originally a washable metal screen that would only normally be replaced if it was found to be damaged or corroded. See attached for Part Numbers.
Ippielb, I think it only has one speed. I saw that 973s can have 2 speeds in the manual, but can’t find a lever/switch/button for speed control. Do you know where it should be? Cmark, are those predictions only for the hand pump? Is there any risk of damage if I use too high a pressure? Is it likely that the fuel lines to the engine are also plugged, or do you not see that often? Can those be blown out, too, or is there a screen on the tank inlet that could get damaged? The forecast here is for 15-30” of snow this weekend, so it may be a bit before I can use her again. Thanks, Reuben
On your particular machine the ground speed is directly related to the position of the transmission control lever. Engine RPM should always be at High Idle when operating. Think of the transmission lever as the control for a variable speed drive. You have to remember that our Canadian member has a different model of 973 that is newer than yours and differs in many respects.
Hi Nige, Yes, thanks for the reminder on models. I do always operate with the throttle lever in the high-throttle detent, and control speed with the FPR lever. Thanks also for the parts list for the screen. I had searched the Cat filters site but couldn't find anything for the primary fuel filter. The NAPA site had it, and when I removed the bowl, the same NAPA part was in there. So...do you think the NAPA filter is too restrictive and is starving the engine of fuel? I would guess it flows a lot less fuel than a screen since it has a fiber filter element in it. Cheers, Reuben
If it was mine it would get the correct parts in in and leave the secondary spin-on filter element to trap the fine particles. When you are investigating potential performance issues then really things ought to be standard so that you can rule stuff out, otherwise there will always be that "what if?" seed of doubt in your head. Also I would suggest to get the fuel tank cleaned out as soon as you can, even if it means crimping a hose with a pair of vice grips while you disassemble something and put it back together again. That will remove another question mark.
9M-2341 This is the screen for my model machine.
Thanks. I found the screen for sale and will get one. They aren’t very expensive, especially for a reusable part, so worthwhile to at least test if the current filter is limiting flow.
Check to see if all the other internal parts are there. You may need other internal parts that the previous owner possibly threw away when the Napa filter was installed.
Ok, finally got back to this. I feel like I dodged a bullet in getting the fuel tank pump unstuck without removing it. Definitely some corrosion inside, but it works. The first few pumps were pretty dirty, then it was nice and clean after that. I also tried to get a pressure gauge on the fuel filter mount, but don’t have the correct fitting and need to find one. I measured the plug and it looks like 9/16-18, but it’s pretty close to M14-1.5. Is it safe to assume it’s English threads on this machine? Or can anyone confirm the thread on that fitting? I also looked in the primary fuel filter and it appears all the parts in the diagram Nige sent are there - thanks Nige! Cheers Reuben
You mean Ref #4.?
Yes, ref #4 in that diagram, and it says right there. Sorry for being blind!
I got the fitting, and pressure is about 50psi at idle, drops to about 40psi when full forward, and about 35psi when full steer either way (one track counter rotating). What should I check next? Thanks Reuben
Next thing to check is the air/fuel-ratio control diaphragm. This is part of the device which senses boost pressure and restricts the maximum fuel delivery until boost is up. Disconnect the tube (#12) at the fuel pump end and rig something up so you can suck on the AFR fitting. You should be able to suck a vacuum. If you can't the diaphragm will need replacing. Also check the tube for holes.
That’s a great diagram. The tube appears to be in good shape, but I could just keep pulling air through the fitting. Definitely now seal inside the housing. Slight hint of diesel taste in the air coming through. can someone let me know the part number for the diaphragm? And, it’s definitely a rebuilt engine. The block casting has the number 4P623, and the injection pump has the stamped number E27525-07 on top. Are those the relevant numbers, or do I need to provide more info? Thanks for all the help! Reuben
6I-1564. See attached. A new one is all of $4..........
You will also need the O ring #9 and it's worthwhile stripping and cleaning the whole thing and replacing seal #19. Don't disturb the settings of #7 and #16. You will need some more O rings where the AFR seals onto the governor housing which are shown on a different graphic. I'll find it for you. Before you order your parts, look at the bolts that hold it all together. You may find that some of them are tamperproof and you have to destroy them to get them out, in which case you will also need the bolts and washers #2, #3 & #4.
Order the O rings #24 thru #28. Not sure you'll need them all but it's better to buy them than to wish you had bought them.
Not to steal the thread, the 963B series I have been running fit all the bills been presented, Fast machines, Strong LARGE Machines even if not as big as a 973. Load our own trucks with stationed equipment, clean our own tracks after work day is done. Hydrostat and Cat bucket Controls were a bit to get used to as to coming off Fat Allis. GP Buckets heaped will load roughly 3.5t of product or around 3.5-4 cu yards material. One consideration as to loading out Taller Tub type trailers and truck beds is the lift arms seem to arch back too far, been Numerous Busted windshields loading bulky rock materials at full lift as the bucket is precariously close to cab lineally.
Well, I pulled the AFR control housing today, and the diaphragm is definitely broken. I received all the seals in the mail yesterday, and will attempt to get it rebuilt tomorrow. One question for the experts here: is there risk to the engine if the adjustment to parts 16 and 7 is incorrect? I ask because they were standard hex head bolts. There was some damage to the lip on part 11 (cover) so it’s definitely been apart before. Thanks Reuben
No. No danger of damage. It's an anti-smoke device.
Great. Thanks. I’ll watch for smoke once I’m running again.
Well, I used all but one of the o-rings Cmark recommended to get, so thank you! I re-installed the AFR control this weekend and test drove it. Works much better now! No bogging when I use the loader in hard ground, and no slowing on small hills. It does still slow when turning in full counter-rotation, but it goes fast longer (more rotation) before it starts to slow. I will get the fuel pressure gauge on it again since it’s drinking a lot more now. Anything else I should look at? Thanks, Reuben
If you haven't already replace the air filters. Don't give it a reason to be starved of air, you'd be surprised the performance loss on a simple air filter. Be expected to drink more fuel with a functioning AFR. Boost from the turbo means more fuel. No boost no extra fuel. Turning counter rotation takes a lot of power, all 60,000 pounds turning on a dime, dragging the tracks both directions fighting eachother, mine slows the rpm bit too. Be happy your hydrostatic is strong enough to do it. With all this extra power you're going to have you best monitor your coolant temp, check your levels and even the quality/thermostat replacement.
I bet you didn't use the 3J1907 right? That's a 9/16" O ring boss seal. I thought it was strange to be in there. Glad it's running OK now. As noted above, watch the coolant temperature. And keep up with the preventative maintenance.
Yep, that’s the one I didn’t use. I will keep an eye on temps. I do notice a slight coolant smell in the engine compartment, so will try to see which hose (hopefully) has a small leak and fix it. Thanks to all for the help getting this fixed!! This would have taken me much longer without the help of this great group!