W20 Case wheel loader

[DWB]

W20 Case wheel loader, Problem engaging in forward and reverse.

I have a W20 case wheel loader that will not engage in forward or reverse. Always worked fine untill now. I checked straners in transmission, linkage, the spool on the control valve. From the foot valve there is an air line which goes to a valve that pushes the spool, thats works fine also. The foot valve for the torque converter, trans, has an air leak could this be the problem. I checked the foot valve and that is returning all the way up and is not stuck from dirt etc. Pump seems fine, I have all my hydralics, bucket etc. It acts like the trans is in netural.? Wanted to see if anyone has had this problem or may know whats going on with it, before I head to case. Thanks :ointhead

 

[BillG]

The air line of which you referred is for the clutch cutoff, your left pedal. it disconnects the directional pack when you need rpm and power for lifting without putting the transmission in neutral. Just disconnect the air line and see if it moves. It has been many years since I worked on a W20 but it seems to me there is also an inversion valve that prevents the transmission from engaging when the park brake is on, so you may want to check it also.

 

[alrman]

You might try to remove that cut-out valve from trans & check out the internals.
Sometimes they rust up from moisture in the air lines.
You may be able to clean it out & free up the piston / plunger or you may have to replace it.

 

[DWB]

To BillG: Thanks for the information concerning my Problem with the W20. I earlier took the clutch cutoff valve off and it is working good. Would the inversion valve be located in the control valve on the side of the transmission at the same location as the cutoff valve.

 

[DWB]

To: alrman: Everything seems to be working free in that area, I now believe I may know the problem, I am losing the prime and now believe it may be the convertor pump, behind the hydralic pump.

 

[BillG]

DWB, That hit a memory recall for me. I remember that the Allison in the W20 (TT2221 or maybe TRT2221 can't remember) had a problem with the pickup tube where it goes to the bottom. If I recall correctly the tube in some cases was put in a bind which caused the seal ring at the pump end to be distorted and over time loose its seal. Unfortunately the ones that I did had to come apart and a relief ground in the housing to eliminate the interference.

 

[DWB]

Bill; Will I be able to see the seal in question on the end of pump ? And what do you mean by a relief ground in housing ? Thanks for you help . Dean

 

[BillG]

Dean, From what I recall there was interference between the pickup tube and the inside of the housing, maybe at the radius of where the tube bends. Unfortunately it has been too long since I have done this to remember particulars. If this is your problem it will be quite evident as the tube is difficult to remove or install. And yes the transmission has to come apart in order to fix it. One question, how long has it been since this machine was operated ? The reason for the question is, at one time I went on a service call for this problem but the machine was in such a position as to be almost impossible to load on a lowboy or drag it out to a better location. I took a chance and lightly pressurized the housing with air and forced the charge pump to pick up oil. I can't stress to much the lightly as you don't want to blow out the converter seal (miserable to replace). If it has been sitting for awhile you might try this or remove the charge pump and liberally oil it and take a chance that it will pick up the oil. Another trick on a different application that I have done is to way overfill the transmission to the point where the charge pump is almost flooded and doesn't require any negative pressure to get it started. But make sure that once it does pick up and charge the transmission, shut it off and drain down to the normal level. Bill

 

[DWB]

Bill, This machine is ran a few times a week, just finished up a clearing job for a 6 acre cemetery. Machine was good, then all of a sudden I could not get into Fwd/Rev. I thought it was foot valve , took apart and it is working correct, checked spool in control on right side of trans, working free. I pulled the cover off the fillter, pulled out filter and started tractor to see if I would get a flow of oil and there is none , also right where the fill and return lines hookup right behind the pump that go to the filter canister I broke it there and there is also no oil or pressure. Thinking back I think I may have also heard some cavatation sound not sure. A few times I was able to get her to move by raising he tractor front off the ground with bucket and rocking the machine back and forth but now this does not work either. I am hoping at this point that it may be the pump that went. I will be taking apart in a couple of days. The only kick in the you know what is the pump is $2,200.00 and they at Case said it is not rebuildable, we will see. Step foward 2 and go back 3 !!!! Part of the Buusiness. Dean

 

[BillG]

Dean, You don't need to go to Case for these parts. Do a Google search for Allison Transmission parts and you will come up with a bunch. Also the TT line of transmissions was sold off to Twin Disc many years ago. Go to their web site for a local distributor. I have completely rebuilt a TT transmission for not much more, there is just not that much to them and to spend that kind of money for a charge pump is crazy. Get the model and serial number off the tag on the trans and let me know, I will look up the part number for you if you need.

 

[DWB]

Problem solved it was the charge pump, back and running great . Thanks to everyone for all the help and sugestions !!!.