Farm Equipment - AC 7000 Power Shift Noise

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AC 7000 Power Shift Noise

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=182266
Printed Date: 15 Sep 2025 at 11:13am
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Topic: AC 7000 Power Shift Noise

Posted By: Grave
Subject: AC 7000 Power Shift Noise
Date Posted: 03 Aug 2021 at 8:00pm

Have a Black Belly S/N 8001+ AC 7000

Have a noise when we shift from 1 to 2 to 3 and back from the powershift.

The powersteering works fine.

We inspected the flow diverter and the power steering relief valve and verified the Primary pump output of 1500psi, book calls for 1600psi +/- 100psi for heavy duty front end, which I think we have. When we turn steering to the extreme we get 1500psi, while stationary it reads 450psi, which I understand is the restriction form the cooler.

We installed a gauge on the Power shift valve inspection port and am only reading 100psi, we shimmed the pressure regulating valve and got it to 180psi. Adjusted the inching valve and we are short of he 210-230 psi which is where I believe the groaning noise is coming from, the slow build up of pressure is causing a fluttering of a spool or spring. The noise is consistent with the psi dropping from 180 to 50 ish then recovering slow?

Looking for opinion on where to go next, I have a feeling we are losing oil pressure internally somewhere, but not sure where?

Replies:

Posted By: Ron(AB)
Date Posted: 03 Aug 2021 at 9:09pm

How many hours on the unit?

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405, 7000, 7050, 8050, 8070, L3, 2300 & 2600 disk

Posted By: Ron(AB)
Date Posted: 03 Aug 2021 at 9:12pm

Have you heard this noise going up a steep hill?

Does the noise away going down hill?

How long does it make the noise? Just as you shift or continuously?

Does it vary under load?

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405, 7000, 7050, 8050, 8070, L3, 2300 & 2600 disk

Posted By: DrAllis
Date Posted: 03 Aug 2021 at 9:23pm

Black belly 7000's were good at blowing the gaskets in the power shift valve. They are a different gasket and need to be the correct ones for that model.

Posted By: Grave
Date Posted: 07 Aug 2021 at 8:30pm

Thanks for responces.

8000hrs.

Its all flat ground here and she doesn't do much heavy pulling anymore.

It makes the noise when the pressure is low on the control valve.

We currently have the control valve removed and inspecting all components. Have a feeling there may be an internal leak where the hydraulic feed comes into the body on the valve, hoping anyway.

Posted By: Grave
Date Posted: 09 Aug 2021 at 8:42pm

removed the control valve and the inner gasket was torn between two of the port to the inching valve, hopefully thats our issue. Surprised how loose the bolt holding the valve onto the plate was?

An way of inspecting the powershift clutch packs while we have the valve off?

Posted By: MACK
Date Posted: 09 Aug 2021 at 9:15pm

Use some blue loctite on bolts and torque them in proper order. MACK

Posted By: Hurst
Date Posted: 10 Aug 2021 at 9:52am

You will see ports to your left in the casting once the valve bodies are off. You can use an air nozzle in those to engage the clutch packs. Visually, you can get a little snip of a side profile of the plates, but to really see the clutch plates, you need to split at the rear (if you end up doing this, make sure you pull the thin steel tubes connected to the ports mentioned above and the trans brake shaft! Don't ask me how I know...)

Hurst

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1979 Allis Chalmers 7000
5800 Hours

Posted By: Grave
Date Posted: 18 Aug 2021 at 9:24pm

Thanks for all your help, turns out that the gasket had a blowout in between the inching valve ports, new gaskets, new o ring, set the pressure to 215psi and she shifts like a dream.

So happy, because I love this tractor, to me it's what a tractor is suppose to looks and feel like.