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Discussion Starter · #1 ·
having a problem with 3rd gear shifts just need confirmed or a slap solid lifter 560 lift 255 duration cam not much vacuum . had to rebuild it once already burned up clutches and steeles for high gear feels like same thing is happening again should i go for a manual valve body like a ati or tci deal ?
 

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A bit more history and specific symptoms would be helpful.

The direct (3rd) clutch pack is the weakest clutch in a stock TH400, however it is easily resolved during a rebuild or with the addition of a TransGo Reprogramming kit.
 

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HD clutches and steels is also pretty vague.
Friction material isn't going to cause late shifts or no shifts though.

The shifts may be a bit late with a low vacuum application but under light throttle as you gain speed even a radical engine builds more vacuum than at idle so the trans should shift.
Have you checked the vacuum level at the modulator?
Is the kickdown wire hooked up? Does it have 12V at any time other than WOT?
I'm assuming you have the proper fluid level.

When you rebuilt the transmission how did the governor look? Gear OK, diameter of the governor body?

Did you make any valve body modifications when rebuilding the trans?

Do you have a pressure gauge for a transmission (0-300 psi)?
 
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