Construction and other equipment - HD7G#22938 low trans presure

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HD7G#22938 low trans presure

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=96059
Printed Date: 01 Jul 2025 at 2:53pm
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Topic: HD7G#22938 low trans presure

Posted By: sbp
Subject: HD7G#22938 low trans presure
Date Posted: 07 Oct 2014 at 9:54pm

New guy here, thanks for any help. Purchased an HD7g that was wore out, i had no experience, and have replaced the sprokets/tracks and put a very good motor/torque converter in it all by myself. Still has low trans pressure, lube pressure is good and does not have pushing/digging force. I have checked/changed filters/screens, changed valve body, changed hydro pump. It will move itself but can't work it. The higher the rpm the better it travels. I have a transmission but am almost wore out myself with the work ive already done and dont want to change the trans and that not be the issue. As most components were wore out i think the trans is shot. Is there anything i should check/change before the trans. If trans needs changed any helpful hints would be appreciated.

Thank you

Replies:

Posted By: DMiller
Date Posted: 08 Oct 2014 at 9:43am

I too have a 7G, just went thru all of this with the trans shift seals all but completely shot and leaking by so bad as to not drive.

I ended up swapping transmissions as well and have a hard digging unit now, the test I made with the shift block off was to apply air to the four ports for shift oil to figure out how bad they leaked by, mine were horrible, replacement box is relatively stout and did not leak by much at all with air application.

What oil have you put into the unit, I went to a 10W hydraulic trans oil from MFA, seems to like it very well when it isn't springing leaks from old hoses.

Search my posts for reference photos of my work on my old machine.

Posted By: sbp
Date Posted: 08 Oct 2014 at 10:08am

Thanks, I use hydo fluid. Another question my replacement trans does not have a ground speed governor do I HAVE to take the one off current trans and put on it? Did u take ur trans out from the bottom?

Posted By: ac_sd
Date Posted: 08 Oct 2014 at 9:31pm

Try an ATF (Dexron), I know most of us have used that successfully. Some Hydraulic fluids may be too heavy for this application. Also if that helps, try running it slightly over-filled. You've done a lot of work on that tractor, they are a great little machine if you can overcome remaining issues! Good luck!

Posted By: sbp
Date Posted: 08 Oct 2014 at 10:14pm

When i first bought it i busted a hose and put atf in it, then it wouldn't go at all drained that out and put motor oil with 1 gallon of lucus trans repair that worked for awhile and occassionally some 60w oil but now back to low pressure. i have resided myself having to change the trans which is OK IF that fixes the problem. I have an old friend Ronnie Watson who says you have to be a black jack dealer to operate it efficiently but im just clearing downed trees and would like to push some dirt. I've ordered the gasket and o-ring for the swap and in a warped sense am looking forward to the task. I'm a one man show so it'll take some time but i'll keep you posted. thanks for the help.

Posted By: DMiller
Date Posted: 09 Oct 2014 at 8:42am

The speed governor is all but useless in most cases, it does not need to stay as a assembly from one to the other and the trans has to come out the top. Will require pulling the fuel tank, the seat and cross rails for the fenders. There are hidden fasteners on the trans that can only be extracted with a 12 point box wrench or a 12 point 3/8" drive good grade swivel socket and no, a 12 point socket on a swivel joint may not work. The side insert panels between the shovel frame to the fenders have to come off to access the lines and bolts for the shift mechanism and you have to drain all the fluid out. It is a shoe horn assembly as it comes out.

Go to a hydraulics shop and pick up a stick of 1 1/4" suction hose, replace all the sections to the steering pump while the trans is out and no, radiator grade hose will not last any amount of reasonable time. Also replace the steering supply hoses off the little pump or you will end up where I am awaiting time to tear my leakers out. The u-joint assembly has to come completely out, if the tie straps are gone keep the joint caps on the assembly with duct tape as this little monster is over $500 to replace as can only be had as a unit. With the trans currently out, pull the suction strainer as you look at the drive flange at rough center right, clean it thoroughly, there is another in the square block on the bottom left. Use a 10W hydraulic trans oil when you go back together.

Posted By: DMiller
Date Posted: 09 Oct 2014 at 8:43am

Almost forgot, the lift point for balance is one of the bolt holes for the steering lever support. Keep all bolts separated so you know where to put them back in according to length as well as size.

Posted By: DMiller
Date Posted: 14 Oct 2014 at 8:43am

I went back thru my posts working on mine, this is where I went to work on it:

http://www.allischalmers.com/forum/forum_posts.asp?TID=87833&KW=DMiller&PID=696840&title=readying-for-the-trans-swap#696840