Th400 1st Gear Shudder - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

 
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post #1 of 4 (permalink) Old Apr 16th, 12, 12:59 PM Thread Starter
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Tim
 
Join Date: Apr 2010
Location: Nor Cal
Posts: 798
Th400 1st Gear Shudder

I have a Hughes Th400 with a forward pattern manual valvebody. I was having some trouble with it having a bind higher up in the rpms in 1st gear, but that problem is fixed after installing a new valvebody.

I still have an issue in 1st gear though. I will put it into 1st gear, but it will not roll forward unless I give it more throttle than should be needed. When I crack the throttle just enough to get it rolling, I can feel it struggling a bit and it will stop and go without hitting the brakes. Staging the car over the weekend was somewhat of a chore because when I brought the rpms up to 1300 and used the brakes to bring it in, it would shudder really badly. The problem was gone the second I stabbed the throttle.

Any ideas of what this could be?

1968 Chevelle - 3795# with driver
6.0 LSX with TSP 224R cam swap
S475 Turbo

16psi on 89 octane
10.95@81mph

Cageless
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post #2 of 4 (permalink) Old Apr 17th, 12, 1:11 AM Thread Starter
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Tim
 
Join Date: Apr 2010
Location: Nor Cal
Posts: 798
Re: Th400 1st Gear Shudder

No thoughts huh?

1968 Chevelle - 3795# with driver
6.0 LSX with TSP 224R cam swap
S475 Turbo

16psi on 89 octane
10.95@81mph

Cageless
timvantol is offline  
post #3 of 4 (permalink) Old Apr 17th, 12, 1:53 AM
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Join Date: Dec 2008
Location: SE Missouri
Posts: 4,623
Re: Th400 1st Gear Shudder

I think this is why everyone posts in the "performance" section. lol I posted a new thread also about some transmission problems. No solutions posted though. If you post it in the performance section they get pissed and move it but there is no traffic here. I hope you figure it out. Mine is doing something similiar and I am thinking the front pump is going bad but waiting on a definitive answer.
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post #4 of 4 (permalink) Old Apr 17th, 12, 11:00 PM
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Jake
 
Join Date: May 2002
Location: North Texas
Posts: 3,806
Re: Th400 1st Gear Shudder

You either have an issue with the low roller clutch slipping or what sounds more like an issue with the intermediate or direct clutch trying to apply in low due to a cross leak.

I would look at the seals on the accumulator piston in the rear servo. It could be lube oil leaking by at the rearmost center support seal into the 3rd gear circuit as well.

The accumulator piston on the VB is another suspect area.

I try to pop in here every day or two and answer pertinent questions but this is a very busy time of the year in the performance transmission industry and my time is limited. I'm setting up a new forum for JUST performance transmissions and eventually I hope to have quite a few knowledgable builders onboard to lend tech support.
www.race-trans-tech.com

www.jakesperformance.com
Racing and Performance Automatics
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