We have a 1974 Cat D7G that we parked last fall and now it won't move at all. It starts and runs fine, the blade goes up and down, the linkage has been checked. Any idea where to go from here? Thanks
Will it pull into gear at all? Reason i ask is because i am having a similar issue with a D7F. Noticed the Trans oil was low because of a leak somewhere in the rear of the machine, topped it off and it fixed the problem for now. I have heard that some o rings or some of the hoses can be bad toward the back of the tranny. This supposedly :beatsme causes an air gap so to speak in the system and the pump is running dry.
If we rev it up it will slow the driveshaft down a little bit but then goes back to turning again. It is full of oil. Maybe someone else has solved our problem !!
Any cat experts have any ideas? It was moving with no problem when we shut it off and the next morning it won't move.
The next morning? I thought it was sitting all winter?
Sorry, it wouldn't move the next morning last fall and we left it because of a snowstorm. I was just posting a condensed version to see if anyone had any ideas.
This fact changes things considerably. So it was only overnight that the problem developed?
yes and it hasn't moved by itself since. We tried towing it and but it wouldn't go. The transmission is full of fluid and if we rev it up you can see the driveshaft start to slow down as if it was going in gear but then just speeds back up. These are what we have tried in the last couple of weeks.
I know this sounds dumb, but are the axels in it?
Yes they are. Kind of like when I sold computers I always asked if the monitor was plugged in!
I would check trans filters for a start
That transmission probably had the safety feature that would push the lever into neutral if the transmission pump pressure gets too low. If it stays in gear then it's probably not a pump prime problem and likely in the transmission itself. These where very simple and well made transmissions and the G model was one of the best dozers made. You should have a service manual if you don't already. Best to go here and ask the question, lots of experts. http://www.acmocbb.org/ACMOC_BB/forumdisplay.php?f=4
Check the trans. pressure at the filter. If you have 350+psi the pump is good. Then check the P1 and P2 pressure on the top of the transmission valve. P1 should be close to your transmission pressure, and P2 will be 55psi less. Check each of these in nuetral, and in each gear. There is a valve in the transmission valve assembly that will put it out of gear if there is too little transmission pressure. I would check this with a fresh filter in there. Also, dont forget about the magnetic suction screen as they can restrict flow to the pump.
A simple thing not to over look is the possibility of trans pump sucking air due to a bad line pull the plug on transmission pump to check pressure and spin it over too see if there is foaming oil coming out the hole this indicated air infiltration on suction side of the pump the BIG D
have seen a trans pump seals start to go bad and after it sits will loose its prime and not pick back up. Gets air locked. sometimes if you can bleed the air off the outlet of the pump it will pick the oil back up.
like big d said, check the suction hose underneath, that pump has to suck oil clear from there, should be four clamps on the hose, not two.. good luck
No pump psi pull the pump outlet hose and dump some oil in it but good chance you have burnt it up by now. running it with no oil also check the magnetic strainer should be the last thing before the suction side.
We have not tried any of the suggestions as it has been raining. We hope to try next week in the sun?
Still raining.....
rain again today...
Rained most of the day yesterday... maybe today ?
I once had a small piece of rubber get stuck in the oil passage for the safety valve on a D8K. Had the suction lines all replaced, new o-rings in everything on the suction side, pump had piles of pressure... thought maybe the clutch housings had finally gave up the ghost, as a last resort i took the valves all apart again on the top of the transmission and found that little rubber piece.... after 2 days of aggravation and 1200 bucks worth of replacing things.
Still raining Friday afternoon.. and supposed to rain all next week ! Someday we will try everyone's suggestions !
d7 hello mikey531 ,i think you better start building an Ark ,or like johnny cash ,how highs the water mummer ,4ft high and rising ,hope you get to work on her soo ,bruce oz
Mikey531, In my past experiances, running equipment while the sun shines, and fixing equipment (or drinking beer) while it rains is usually the most productive way to do things I have found. Get yourself some tarps, put on your old rain slicker and get out there! I have changed D8 transmissions in the middle of the bush in -35F weather with the wind howling sweet nothings in your ear. You just gotta grow a pair and get at it!
It rained every day this week and more tomorrow. We have shut down for vacation so I will let everyone know when we get it going. Hey catskinner if it was mine I would do that as I have changed a twin stick tranny out of a Diamond T it took almost all night but I worked it the next day of course it was my truck so that makes a difference! Thanks
Check the spools in the valve block on the top of the tranny. I have seen them either seize or be obstructed and that will cause the exact problem you are describing.
Try to bleed the trans pump. (carefully) Older Cat pumps were prone to lose their prime and would have to be bled, sometimes daily. Best fix if this proves to be the problem is a new pump and new filter. DO NOT look into the bleeder hole when turning the engine over to re-prime the pump. Good way to get a shot of dirty oil in the eye and get knocked off the tractor when the pump gets it's prime. Keep your hands on the plug! Some old timers would install a small valve in place of the plug, which made it easier to prime the system, and avoid buying a new pump for a while......
I think we found the problem !!!!!!!!!!! I will have pictures tonight or tomorrow!!!
If its not raining
!!!
The mechanics took the pump apart and this is what they found: The seal was dented taking it out but the o-ring had pieces missing, there is a 80% chance of rain tomorrow so I am not sure if we will get it back on. The suction hose had a flanged end on the pump, is that common?
That pump was a common item on D7 and D8 tractors for years and years. I want to say it's a 2P2004, but my memory is not what it used to be. I seem to recall that Cat had a suction tube attached to the tranny by a short length of hose, with the flanged end of the tube going to the pump. I'm sure some folks and maybe Cat may have changed that for a chunk of XT-3 hose with flanged end couplings for more flexability. What you saw when the pump was broken down is not uncommon. If your internal gears and bearing surfaces are OK, the pump can probably be rebuilt. If there is any scoring on tooth surfaces or the internal chamber walls it should be replaced. Make sure you prime the pump before starting the tractor. Best check the P1/P2 pressures when you get the unit running. Good Luck!
good info to help my problem without even asking