Farm Equipment - 7045 Hydraulic Problems

7045 Hydraulic Problems

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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=208112
Printed Date: 10 Sep 2025 at 7:50am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: 7045 Hydraulic Problems

Posted By: DanielW
Subject: 7045 Hydraulic Problems
Date Posted: 09 Sep 2025 at 7:51am

Hi folks,

I've been in conversations with a guy I know about possibly buying his 7045 (PD trans). It's sat for a year unused due to some issues. I haven't been out to look at it myself as it's a few hours away, but from what he tells me it doesn't steer and the differential lock is staying engaged. He says it drives in a straight line fine and it seemed like the PTO engaged/disengaged, but didn't try the PTO under load. He can't remember about brakes: He thought they worked, but can't guarantee it and his health is preventing him from getting out to the farm and trying.

My only source of reference here is a hydraulic schematic I've found, so forgive me if I'm wrong. But it looks like this uses a three-stage pump (similar to the 100 series). The first Gerotor stage looks like it feeds only the PD/trans, which is (apparently) working fine. The second gear-pump stage looks like it feeds just the steering and cooler. And the third (pressure-compensated, piston-pump) stage feeds the diff lock, PTO clutch, remotes, and three-point (with a selection of priority and pressure reducing valves in there).

If the problem was only with the diff lock/third stage, I would have guessed it was probably a compensator/priority valve issue. That wouldn't worry me too much as I've dealt with these problems on other tractors (mainly Whites), and know the priority spools and compensators often need to be shimmed to correct pressures and the spools can get stuck. But the fact that it doesn't steer makes me think something else is up with both the second and third stage pumps. I'd appreciate any thoughts/ideas about what could be wrong. It looks like both the gear pump (steering) and piston pump (diff lock, etc.) are fed via the same filter? So maybe it's as simple as a plugged filter, but I'm strongly doubting it could be that easy. I wondered if perhaps the pump shaft splines/key (or whatever it is) might have sheared between the first and second stages. But if he's right about the PTO working, then I can't see how it could be completely sheared/slipping.

Any thoughts or speculation are greatly appreciated. I'm wondering how much of a risk this would be of something major being wrong, how hard (or easy) it might be to fix, and how this should factor into price.

Replies:

Posted By: DrAllis
Date Posted: 09 Sep 2025 at 8:25am

I think you need to go drive it yourself as the information given isn't the usual descriptions. The first thing to do would be verify that the rear end is actually FULL OF OIL. Doesn't steer most often is related to being very low on oil (maybe 10 gallons low) or the left hand belly filter being non-AGCO brand, installed wrong or missing the screen on the end of the filter. When was the last time this filter was changed??? and when did these problems arise ?? are great questions if he tells you the truth. The diff lock staying engaged?? is kind of weird because if the pedal is staying down, pull it back up !!! Strange thing is, it takes hydraulic pressure to keep it engaged, so if what he says is true, the linkage under the cab floor must have issues. The PTO lever itself requires hydraulic pressure to keep it engaged too, so what's going on here??? Steering not working (he says) or very low hydraulic oil levels aren't really condusive to stand-by pressure staying maintained to keep these features engaged. Like I say---check the oil for sure (remove sight glass) and drive it yourself. EVERYTHING on those hydraulic systems begins at the left hand filter and having a proper oil level. If these two things aren't right, NOTHING else can work right.

Posted By: DanielW
Date Posted: 09 Sep 2025 at 10:01am

Thanks Dr. I definitely plan to look at it in-person as soon as I can - you've given me some good tips on what to check for. I'm glad you agree that the symptoms he's describing don't seem to jive or make sense (unless it is just a lack of fluid or plugged filter).