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Senior Charter Member
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Discussion Starter #1
My Father just picked up a 1970.5 Z-28. The TH-400 will not shift from first to second until the engine reaches 7200RPM. He wants the trans to shift @ 6200rpm. This happens whether he manually shifts or leaves it in Drive. How do you adjust the shift point on this Trans. He is fearfull that he is going to grenade the motor!

Thanks for your help,
Dan
 

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FFCobra Craftsman
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1,067 Posts
The TH400s have a governor on the passenger side near the tail housing. It's under a square cover with a round raised center. The shift points are changed by changing the weights and/or springs. B&M makes a kit for doing this. For a quick fix go to a salvage yard and pull the governor out of a stock TH400 and swap it in. This should bring the shift points down. If they are too low then get the B&M kit and work your way back up. They also make shift kits that allow the trans to shift normally when in drive, but if you manually it will stay in each gear until you shift.

Good luck.

Greg


[ September 02, 2002, 09:20 PM: Message edited by: GregR ]
 

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Senior Member
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590 Posts
Also, check the vacuum modulator. My 66 Pontiac, would not shift at all, and it was a vacuum leak at the modulator.

Walter.
 

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FFCobra Fanatic
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633 Posts
You might also check the electric kick-down solenoid. The first time I re-built one I left the bolts attaching it to the case only finger tight and it allowed fluid to leak out preventing the trans from shifting. I sure felt stupid after the transmission shop guys found what was wrong!
 
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