Farm Equipment - AC 7040 power shift issue

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AC 7040 power shift issue

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=158415
Printed Date: 20 Jun 2025 at 8:01am
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Topic: AC 7040 power shift issue

Posted By: Parker
Subject: AC 7040 power shift issue
Date Posted: 22 Feb 2019 at 2:20pm

Help! My name is parker and I have hit a stumbling block with this tractor. I acquired a 7040 from a buddy of mine. The old tractor is in pretty fair shape overall. However this transmission issue is whipping me. I can crank it today and it’ll run like a brand new tractor. Shifts and pulls perfectly through all gears, high and low range. After running it for a day then the mystery starts. The second day you can crank it and it won’t move. It’ll attempt to pull but won’t go anywhere. You can leave it sitting for about 10 and then it’ll pull perfect again. I have changed filters, checked oil levels, etc. There is no grinding or noise that would make me think of a gear issue. As I mentioned it’ll pull as strong as a new one for a day. Then it acts as if something is slipping on the second day. Any ideas? I really appreciate any advice or input on this. We don’t have much for parts or service here in South Carolina so I’m kinda on my own with this problem. Thanks

Replies:

Posted By: DrAllis
Date Posted: 22 Feb 2019 at 3:34pm

You are checking the transmission oil where ?? and did you clean the suction screen for the transmission oil ??

Posted By: Lynn Marshall
Date Posted: 22 Feb 2019 at 3:45pm

Does the transmission oil pressure light come on when this happens??

Posted By: Parker
Date Posted: 22 Feb 2019 at 4:42pm

I’m checking the oil under the seat on the floorboard as well as on the sight bubbles on the rear of the tractor. I’ve taken the suction screen out and cleaned twice. It wasn’t really dirty the first time but just to double check I cleaned it a second time. This is the only Allis Chalmers tractor that I’ve ever messed with so I admit that I am not very familiar with it. I grew up on John Deere and IH equipment so this is a little different. As for the light coming on question... no lights work on this old machine. It’s an open cab tractor that has a mechanical oil pressure gauge as well as water temp gauge. It’s a great old tractor. I honestly wish that I had grown up running orange tractors. It’s much more comfortable and practical than all the John Deere tractors we had. Also I’m only using this 7040 sparingly around the farm and not a daily workhorse. However it would be nice to be able to run it whenever needed. Thanks for the replies so far.

Posted By: Parker
Date Posted: 22 Feb 2019 at 5:01pm

I’ll also add this information. The steering, hydraulics, and pto all work just fine even when the tractor won’t move.

Posted By: tbran
Date Posted: 22 Feb 2019 at 5:41pm

In your situation, you need a service manual and a pressure gauge to 500# and a 1/8" pipe hose end. Leave the rear in neutral or park and commence pressure checks for clutch packs and lube pressure. The clutch pack are # A1 B2 etc on the side housing.

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When told "it's not the money,it's the principle", remember, it's always the money..

Posted By: MACK
Date Posted: 22 Feb 2019 at 9:49pm

It sounds like a power director that needs new seals. Are you sure it is a power shift? Is there two buttons on floor or lever on side with 1-6 and R?
If it has 1-6 and R, does the shift lever feel like a good detent in all poisons? MACK

Posted By: Parker
Date Posted: 22 Feb 2019 at 9:58pm

Mack it’s 1-6 and Reverse. It has power shift decals on it and after researching I learned the difference in power director and power shift. Like this mentioned it’s a new game for me so I’ve been trying to learn about the power shift setup. The linkage and shifting feels like a brand new machine for a day. Shut the tractor down and come back tomorrow morning for nothing. You can feel the tractor hesitate when you put it in gear but won’t move. If it moves any at all it’s only a short crawl. I typically just shut her down and leave alone. Didn’t want to do anymore damage than already done.

Posted By: MACK
Date Posted: 22 Feb 2019 at 10:24pm

With range lever in park, you should hear engine change when you shift through 1-6 and R. Especially 1-R and R-1. MACk

Posted By: Parker
Date Posted: 23 Feb 2019 at 6:58am

I’m gonna test that this morning when I get a chance Mr Mack. What will it mean if I do or do not hear it cycling through the gears?

Posted By: troym
Date Posted: 23 Feb 2019 at 7:14am

You should try all gears, sounds like a2 clutch piston seals are leaking, does it work if you let it warm up for 30 minutes? Also make sure inching spool is not hanging up, going all the way in.

Posted By: DrAllis
Date Posted: 23 Feb 2019 at 7:15am

From your description, it sounds like the transmission pump (gerotor pump) isn't working. If it isn't pumping oil to build 200 or so psi, the tractor will never move because all the transmission clutches are hydraulically applied. On the instrument panel there is an 1800 RPM transmission lube light. If this was working, the light would be ON when the tractor doesn't move and OFF when it does not move. With the range lever in PARK you can shift the transmission thru all the gears and the engine sound will change some with most every selection, especially 1 to R . The dipstick under the seat needs to be looked at on both sides of the stick after sitting on a level spot. This compartment holds at least 7 gallons of oil. THE CLUTCH PEDAL MUST COME ALL THE WAY UP TO THE TOP !!! Could be a broken clutch pedal spring....

Posted By: darrel in ND
Date Posted: 23 Feb 2019 at 7:55am

I certainly do hope that you can get the problem resolved fairly easily. Glad to hear that you like this Allis tractor. Darrel

Posted By: Parker
Date Posted: 25 Feb 2019 at 10:50am

Well I cranked the tractor this morning and did as instructed. It will cycle through every gear while on park and it’s very clear as you go from one gear to the next. Very defined when you go to reverse as well. Any more ideas or thoughts fellas? Why would it run perfect today and then none at all tomorrow? I will say that on the second day that you can feel it hesitate like it may want to go then nothing. Also I’ll be glad to put my phone number on here if it would be easier for someone to coach me through this problem instead of typing! Again I appreciate everyone’s replies and help.

Posted By: DrAllis
Date Posted: 25 Feb 2019 at 11:57am

When you take it out of PARK, shift it into HIGH range and try it. Then, if it moves, shift it into LOW range and see what happens. I think you are trying to go from PARK into LOW range and your cables/shifter is just going back into PARK instead of LOW.