Hello All, I have a D7F serial number 92E1986 with the Cat 3306 engine and i am told that model has the lastest of the D7F transmissions, better than the earlier ones, but not as good as the D6C trans. A bit of History, purchased from a deceased estate as a very tidy machine, worked it on a few projects with this current transmission over heating problem. the motor got a knock in it so we pulled it out did a full out of chassis rebuild including the torque converter, the mechanic said he was 90% sure that the overheating was from a worn converter. so $50k later we still have a brand-new motor and a transmission problem. Outline, the tractor will start working for the day build temp to normal working temps and stabilize, work it hard the water temp and the trans temp will rise and fall together, trans will change and work as it should, after about 3-4 hours the trans temp will start to climb ahead of the engine temp and from there on there is nothing you can do to correct it. You pull up and let the temps normalize the minute you work it the trans temp will climb faster than the engine temp again, we dont work it into red but once it gets hot the trans will stop pushing and the right-hand foot brake plays up. Its like a valve opens and is bypassing oil inside the transmission. shut it down and walk away. tomorrow morning it will start up and work like new again. it has a lot of blokes beat. What we have done, checked and cleaned the suction filters, nothing worth reporting in them, pulled the cooler apart cleaned and checked, dropped the oil, replaced with a slightly heavier oil. checked the pressure on the Hyd pump and scavenger pump all tested ok (note i would like if someone had the pressures so i can double check) replaced the torque converter, none of this changed it in any way. We have been doing light work with it over the past 12 months nothing has changed, now we have another dozer coming to chain some country, so really want to get it sorted so we can work a full day. any help would be greatly appreciated. note the machine is out on one of our properties a few hours west so my response time to check things will be delayed.
I cannot help you out but I found the S/N interesting as 92E1985 is located in my part of the world. It was ex Main Roads Department.
Thanks for that, that is very interesting. it would explain why it was tidy for its age
Here is it's sibling some time ago. Yours has no tree spear (the one in the photo's below was added after the MRD sold it) and I doubt it came out with that ROPS fitted, as the has the same sweeps design welded onto the hard nose.
Sorry I didn't notice the serial you quoted was the unit before ours.
Yea it is the one before yours. I notice you said the right footbrake plays up. The brakes on them have no power boost, entirely manual in operation. So is the steering clutch not disengaging? Maybe due to low pressure? You mention you checked hyd pump and scavenger pump pressures being fine, but not the transmission pressures when it is playing up. Is the transmission slipping once the oil gets hot? When you say it does not pull, is the output shaft from the torque converter spinning? I take it you do not have a service manual?
What oils were you using before and after changing grades.? Have you ever had the transmission pump apart.? You say you checked pump pressure. Did you ever check transmission P1 & P2 (speed & direction clutch) pressures.? Maybe it might pay to have some gauges installed all the time the tractor is working so that you can observe any changes as the powertrain oil temperature increases. I’ll look up the pressure specifications and post them up.
It should have. They were fitted from 92E01752-Up as far as I can tell. Attached is the Test & Adjust. I think it is the correct one for your style of transmission. Check the physical location of the pressure test points on your machine against what the illustrations show. If they match up 100% it is the correct one, because the "old-style" transmission test points are in different places. If they don't match up let me know and I'll find the one for the other style of transmission.
If you want a Parts Manual for it then you will have to get one for a 94N US-built machine because from what I can see there is no Parts Manual for anything above 92E1751 (D333C engine & old-style transmissoin). Search for UEG0735S.
Hello RC, thanks for this. I haven't checked the Transmission pressures, I don't have a Manuel as i have never been able to find the correct one, yes the output shaft is still spinning and the transmission is slipping, it could well be the steering clutch and the driver is telling me brakes.
Hello Nige, thanks for your help with the above 3 posts. I will track down the correct Manuel, install gauges on the transmission and put it to work for the day and come back with the pressures we have cold, operating temp and Hot. It will take me a few weeks to get this sorted. if there are any other tests while we are out there let me know. Thanks again.
The Service Manual for the "higher series" of 92E (above 92E1752 in other words) is the same Cat Publication REG00691 manual as a 94N machine with a Serial number above 94N5660. It's available on CD for US$198 from HERE . Unfortunately it will have to come from the US unless you can find a copy of REG00691 in Oz.
Lift the floorplate and with the systems cold at first startup in the morning, try this - with the engine idling engage first gear. The shaft between the converter output and the transmission input should stop absolutely dead as though someone stuck a prybar in one of the U-joints. Then try all the other gears, forward and reverse, but at idling speed only.
50K for and engine and TC overhaul, wow. Could have got another newer larger dozer for that. Spent lots of time on D7F's big toy with no push in my opinion.
Thanks Nige, we will try this when we get out there to test pressures.
Should have mentioned to also do it when everything is hot and the transmission is overheating as well.
If you want the info for testing the transmission, I can get a service manual for the later 92E early next week and scan in the relevant section.
That would be great if you could, we are going to start the testing Nige has put up at the end of this week. I have tried to find one in AU but no luck. Will order one from the US.
Hello Nige, I was out at the property today today and got on the dozer for a hour or so. Cold with engine lifted just above stalling idle. The drive shaft slows down and then snaps to a stop when selecting all gears. Worked for an hour or so hard same result at full working temp. But I didn't have time to work it until the fault showed its head.
The “slows down” bit before it snaps to a stop is key. It shouldn’t do that, rather just snap to a stop. Time to break out the pressure gauges I think.
Here are some scans. The speed and directional taps will be under a plate on top of the transmission. Probably 1/8NPT thread, and some others could be 9/16 UNO. Do not automatically think every pressure tap is going to use the same thread. The last lot of photo's show the location of the pressure taps and testing. Also shows the setting of the transmission controls. Also have included the troubleshooting guide from the manual. You could have air getting into the system when the oil is hot and hoses and seal soften causing low oil pressure. I also scanned in parts manual pages in case you want to get the expensive silicone O-Rings and reseal the transmission control valve.Someone may be able to decipher what you need for that. My D6D had an issue where it would sometimes when the oil was hot would not engage properly, the transmission would slip and the dozer would barely move. I replaced the springs in the transmission control valve (had to come from singapore so took a couple of weeks) and the O-Rings and adjusted the control spool valves so far it seems good, but I have not given it a decent run yet.
Hello RC, thanks a lot for your help here, this will keep us progressing until the Manuel arrives.
Hello Nige, We finally got back out there to test some pressures, see below. At cold Idle Pump direct 500PSI Pump Filter 400PSI Torque Out 57PSI Warm Pump Direct 400PSI Pump Filter 375PSI Torque Out 37 PSI Steering pump port 375PSI Converter Inlet 85PSI high idle Converter Inlet while in motion and high RPM 60 PSI The converter inlet pressure is meant to be minimum 140 PSI. Considering the Touque converter is new and the tractor had the problem before the torque convertor was replaced, we have removed the pressure control valve to clean it and check internally for damage. There was a bit of hard black Debree in the valve, the rest looks ok. we are guessing that we need to add or remove the tensioning washers under the springs to adjust the pressure. We are still waiting for our manual to arrive so are just going off the information provided. Are we on the right track?
You seem to be missing the pressures for the speed and directional clutches. What about pressures when it is playing up?
Not so. T&A is not clear on this. 140psi converter inlet is MAX pressure with cold oil. You'd usually expect something around 100-110psi. Need the answers to those questions. Is that with the transmission stalled against the brakes in 3rd speed forward.? Still need an answer to the question of what type/grade of oil you are using in the transmission.
Hi Nige, What type/grade transmission oil is correct to run in this instance?
I would go for an SAE30 oil meeting Caterpillar TO-4 specification. You don't necessarily have to go for a Cat-branded oil. Any major oil company brand will work just fine.
Hi all, So we have done an oil change on the transmission to SAE30 as we weren't 100% sure on the oil grade that was used previous to us working on the machine and we also changed the filters. We have run it up to the problem temperature and found that at 3/4 transmission temp that the speed and direction clutch loses all pressure when trying to select a gear. This is around the 4hr of stick raking work so nothing super heavy. We also did some time working it with the rippers in forward only without any long tracking in reverse and had the same result. I only had enough gauges to be able to see the pump pressure, torque converter inlet and the speed and direction clutch pressures at the same time so we could see that the pump and inlet pressures never changed but the speed and direction would drop to no pressure when a gear was selected in either forward or reverse once the higher temp was received. The speed and direction clutches where up around 350 psi at working temp and dropped to 300 when the issue starts to occur. The converter outlet pressure that was previously mentioned was with it stalled in 3rd. It didnt seem to change at all.
When you changed the oil did you remove and inspect the magnetic screen in the transmission pump suction line.? If P1 & P2 are dropping to zero, or close to, it when you make a shift then the indications are of worn/leaking clutch piston seals. Going back to the OP you mentioned an overhaul of the engine and the torque converter but it's not clear if the transmission was also removed and overhauled. Has the tranny ever been out in your ownership of the tractor.?
Yes we cleaned the magnet but only a little bit of shaving paste was evident. No the transmission hasn't been removed or touched as I am aware
Certainly if the problem only appears when the transmission gets up to operating temperature it sounds like hardened-up seals somewhere. Maybe take a good look at the transmission control valve and the seals that live between it and the transmission case. If that turns out to be a dry hole then I suspect the transmission is coming out.
We have had this machine for 4 years, the problem has always been the same, we have worked it for 3-4 hours per day until it starts to play up, park it over night and it operates normal for the same time the next day. We have checked the magnetic screen many times expecting to see signs of the problem. The filter has never had anything to talk about in it. I have no history on the transmission. I didn't want to pull the transmission if it's oil bypassing in something outside the transmission. It's like something opens up and bypasses at the same temp or operation duration with out fail and it not getting any worse over the past 4 years.
Back 3 years I asked a bloke that had run a few of the same machines about the problem. He said to drop the oil and run a heavier grade oil, and if it's something leaking it will improve. We changed it to a 50 grade, I think. It made no difference at all.
Sorry to tell you but that's BS. I'd still suggest to go for the control valve first (less invasive/less work) and if that doesn't fix it, well..........
I would be checking o-rings, springs and valves. also be checking the adjustment of the speed/direction selector spools. I would not be surprised if you have been living with an easily fixed problem for years. Springs are reasonably priced. The silicon O-rings, pricey but not too bad. Our JD grader had a problem where once the hydraulics reached operating temperature. If you stopped the engine, then restarted you would have no blade function hydraulics. Turned out it was a new priority spool valve that had been recently installed, the spool itself was slightly sticky in the bore.