Farm Equipment - Transmission brake 8070pd fwd

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Transmission brake 8070pd fwd

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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=137843
Printed Date: 08 Nov 2025 at 10:41pm
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Topic: Transmission brake 8070pd fwd

Posted By: Sam T-Ga
Subject: Transmission brake 8070pd fwd
Date Posted: 27 Apr 2017 at 3:29pm

I have customer with 8070 PD Fwd that the trans brake is not working. I have checked pressure at 200 psi. I am thinking I changed one in a 70XX one time without splitting tranny from rearend, went through bottom plate under gerotor pump or removed pumps and went through that hole. Any one else ever done this?

Replies:

Posted By: MACK
Date Posted: 27 Apr 2017 at 4:38pm

Have never saw a transmission brake worn out, but it can be changed through bottom plate if you want a oil bath.

Would rather think he has other problems than worn out brake. Sounds more like warped pates in PD. 200 psi won't stop PD if plates are warped very bad. MACK

Posted By: Sam T-Ga
Date Posted: 27 Apr 2017 at 8:16pm

It doesn't creep when in gear and you stop, so I don't think clutch plates are wrapped. I've seen others with wrapped plates and it doesn't act like that. If I get tranny stopped you can shift but if you let out on clutch with tranny in neutral then push in clutch, brake won't stop tranny. Trouble shoot guide in service manual list one problem could be dowel pin that holds piston from turning could be sheared and letting piston rotate, then brake is not every effective. That is sort of want it acts like to me. If you crank engine with tranny in gear and hold clutch in brake mode then you can shift from one gear to another. I guess I will drain oil and remove bottom plate and go after it. I would rather do that than split tractor.

Posted By: Lynn Marshall
Date Posted: 27 Apr 2017 at 8:46pm

I've done a couple of those over the years. One was a 7060 that I think was actually in a service recall. I remember that bulletin saying that certain tractors could shear the piston pin and cause poor transmission brake engagement. It's a long reach up in there and a lot is by feel alone but it can be done. That little brake disc can certainly wear out if the operator presses completely down on the clutch pedal with a heavy load behind repeatedly.

Posted By: joe
Date Posted: 27 Apr 2017 at 9:19pm

While were on this topic, I was under the impression that the transmission brake was simply engaging several elements at once to cause the tranny to lockup. Or is that only the case for the Power Shifts(7020)? I would have thought they would have engaged low and high together to lock it up.

Posted By: MACK
Date Posted: 28 Apr 2017 at 5:46am

Ps only uses two clutch packs at a lower pressure for brake. MACK