#1  
Old 06-10-2024, 02:59 PM
Commissar Commissar is offline
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Default Shifting Question - TH400

Hey everyone, I have a recently new to me 68 GTO that I bought and have been tinkering with now trying to get it right. The Engine is a 400 bored 0.030" over and sounds to be running strong attached to a TH400 his/hers hurst shifter.

My problem is when I am at WOT the shifts are very slow, like the car takes a few seconds to figure out what gear to go into (RPM according to hood tach is around 4-4500 when it starts thinking about shifting). Normal driving it shifts fine. Where do I start trying to troubleshoot this? When it does shift it shifts hard. I believe there is an 1800 stall in there. What is some other information that you all need to help me figure this out.

I have some other issues that I need to address as far as timing and carb setup, but those will be a different thread.

  #2  
Old 06-10-2024, 04:01 PM
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65 Lamnas 65 Lamnas is offline
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Location: Pontiac, IL
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Quote:
Originally Posted by Commissar View Post
Hey everyone, I have a recently new to me 68 GTO that I bought and have been tinkering with now trying to get it right. The Engine is a 400 bored 0.030" over and sounds to be running strong attached to a TH400 his/hers hurst shifter.

My problem is when I am at WOT the shifts are very slow, like the car takes a few seconds to figure out what gear to go into (RPM according to hood tach is around 4-4500 when it starts thinking about shifting). Normal driving it shifts fine. Where do I start trying to troubleshoot this? When it does shift it shifts hard. I believe there is an 1800 stall in there. What is some other information that you all need to help me figure this out.

I have some other issues that I need to address as far as timing and carb setup, but those will be a different thread.
I'd start with a gauge and monitor your pressures. Sounds like a leak.

  #3  
Old Yesterday, 05:36 PM
Commissar Commissar is offline
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Originally Posted by 65 Lamnas View Post
I'd start with a gauge and monitor your pressures. Sounds like a leak.
Where should I monitor from and what would I be looking for? I am pretty sure I can hear a vacuum leak under the hood, but havent been able to pintpoint it yet.

  #4  
Old Yesterday, 09:31 PM
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gtohurstjudge gtohurstjudge is offline
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Fix your vacuum leak.....you have poor vacuum to the vacuum modulator on the right side
of the transmission. That could be causing your problem.

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