JD 350c problems

[BSims66173]

I have an early 70s model 350c. The other day I was pushing some dirt and the clutch pedal felt like it hung about halfway up. I pushed it up and down a few times and it started releasing all the way but on the next push with the machine, once the blade was loaded, it just stopped pushing. It will still travel in both directions but when trying to back up a small incline it wouldn't pull. I managed to get it of the hole it was in and checked the fluid in the reverser, it was low. Thinking that was the problem I topped off the oil and tried again. Still the same thing. How do I check the fluid pressure from the reverser? Could the problem be the pump in the reverser or could it be something in the valve body on the side of the reverser since the clutch pedeal was sticking? If I have to go into the reverser, is it best to pull the engine to get it out or go at from the back? Any and all advice will be appreciated and thanks in advance.
Barry Sims

[digitup]

There should be a pressure port on the top of the power shift trany hook a gauge to this and you need at least 220 LBS pressure I think.Digitup.

[BSims66173]

I plan to try and check the pressure this weekend. Is 220 psi right. I do not have a book but everything else I have seen is around 130 or so?

[Lavoy]

C models are slightly higher, but I think 220 is too high, but that is a guess, I do not have books for a C model.
Lavoy

[CatD8RII]

The port you want to check is above where the Forward /Reverse rotary valve is on the reverser control valve. It is 1/8" NPT . The valve is on the left side of the machine under the floor. Depending on your serial number the pressure should be as follows 120 +/- 10 PSI up to s/n 278391 on machines above that s/n it is 150 +/- 10 PSI. . There is no "clutch" per say like an engine clutch , but rather just a valve that cuts off oil going to the reverser clutches. See what your pressue is, you can get at the regulating valves from underneath the control valve. A piece of dirt could be clogging one of the valves. Hopefully you wont have to pull the reverser but if you do if has to come out the front.

[BSims66173]

OK, checked the pressure today and forward and reverse readings are 50 psi. Stays the same no matter what RPMs are. Now, where do I need to go from here? Oil levels in the transmission and finals are not increasing so I think I can eliminate any blown seal but not sure. Anyone have any thoughts? Thanks for all your replies and I am sure I will need more answers in the near future.

Barry

[CatD8RII]

There is a clutch pressure regulating valve underneath the valve body its the 2nd one from the front. Its adjusted via shims You could remove the valve and make sure its ok However if you had a problem with your clutch pedal id assume that you either have a problem in the linkage to the valve or the valve itself.The problem is there isnt alot of external linkage, most of its inside the control valve. Theres a lever thats attached to a shaft and a roll pin, make sure the roll pin didnt snap.If thats OK then id check the valves underneath,only because there relatively easy to check, check both the clutch pressure valve and the bypass valve. the bypass valve is to the rear and is a smaller hex plug than the others. Hopefully you find a problem there, i dont think you can work on the control valve with the reverser in the machine, there just isnt enough room.

[digitup]

If you are under 80 lbs you are in for a rebuild .Even 100 lbs is on its way out if the clutch plates don't get enough pressure they will slip Lavoy is right it is 120 lbs .I was working on a 790D excavator the other day and 220lbs pressure stuck in my head for some darn reason .Digitup.

[BSims66173]

After checking all the relief valves and bypass valve, 50 psi is still all I can get. My next question is do I need to rebuild the reverser clutches or just the reverser pump? It appeared to pull fine in both directions before this problem started and the shifts apper to be ok. Looks like I can get the parts from Deere for the pump but is there a cheaper place. Also where is the best place to purchase track chains? I guess I will tear it down this winter and repair a lot of things that need to be fixed. I also plan to look at the winch which has never worked since I have had the machine. Should be a great learning experience. Going to have to clean out the shop to make room for a longterm project. Thanks for all your replies.

Barry

[CatD8RII]

If the unit has had low pressure problems(or slippage) definetley do the clutches, you can inspect the pump as well. The pump sits out in front of everything you can actually remove it without removing the reverser from the crawler. Its a gerotor style (or a gear in a gear) typically these pumps dont loose pressure all of a sudden unless there is a failure such as a broken gear which ought to be obvoius when you open it up. I dont think you had a clutch problem because there are 2 clutches, 1 forward and 1 reverse and theyd both have to mess up at the exact same time to give you a problem in forward and reverse. However since theres low pressure the clutches probably need some attention now. If you have the reverser out of the crawler make sure you take that control valve apart and inspect the clutch valve, wouldnt be a good thing to rebuild the pump and clutches and still have low pressure.

[digitup]

Take your power shift through its gears watching the pressure it may be the pump .If not take the multiple plate unit apart and replace all seals .When apart check the friction plate for wear[with a vernier caliper ]Also check for warping by [laying on a good flat surface ] see what they are like and get back .Digitup.

[BSims66173]

Not sure what you mean digitup. Are you saying to shift from neutral to forward and back to neutral and then reverse a few times? If so. I have done that and the pressure remains aroung 50 psi. It might bump slightly but remains in that range. Pressing in the clutch pedal makes the pressure go to zero. I haven't tried any other gear on the transmission. This is in second gear.

[digitup]

Yes F-N-R-N-F is the best you can do with a 350 .where with a 450 you can H-N-L-N-R to test this .Now if the pressure bumps up between shifts then it should not be your pump.This could be your shaft seals rather then the piston seals inside .As with piston seals one direction is usually still avalible[just forward or just reverse] is working still.If the frictions have heated they will warp with a slight dish watch this as this will rob power after a rebuild if not noticed when apart . The transmission pump in one of the backhoes has just went out and with 14000 plus hours on this unit I replaced friction plates and pump unit .As well as all shaft seals and piston seals .It is just the thing to do when you are that far into the transmission . It cost around 600 dollars for all parts to do my self .I didn't think that was too bad for bucks and it sure made that old backhoe shift better as well.You got to have 120 lbs of pressure or it will not pressure multiple plate unit piston enough to work .So check the pump for even the slightest wear and check your clutch pack seals as well shaft seals and inner piston seals.When you are inside the clutch pack check the friction plates and steels for damage or wear .I measure my old existing friction plates with a vernier caliper against a new friction plate soaked in trans oil to test for wear of friction suffice on old plates .very little wear of these units makes a big difference as with every additional plate the wear multiples .Good luck .Digitup.

[BSims66173]

Well, I have resigned to the fact that I have either a pump problem or a valve problem that will require me to pull the reverser. If I am going to be in that far, what are the internal wear parts of the reverser that need to be checked or replaced? Assuming all bearings are good, do I just replace gaskets and seals and the friction discs and plates?

[digitup]

Basically you got it .Check the friction plates and re seal the piston unit and shaft seals .Digitup.