TH400 does not shift @ WOT
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,408
Likes: 418
From: Chester Virginia
TH400 does not shift @ WOT
The past few times I have 'gotten on' my '73 L82 the auto trans will not shift into third gear. Yesterday I looked at the tach and it was registering 5800 rpm and it was still in second gear, slowed down to about 3000 rpm and it shifted into third. Normally around town the shifting point is about 3000 rpm. So why won't the transmission shift at WOT or close to it?
Roger
Roger
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Probably the vacuum modulator on the trans. But this will cause other anomalies like a hard shifts too. If not the modulator (the easiest thing to check and replace) it's probably a sticking or broken governor.
Melting Slicks
Joined: May 2002
Posts: 2,431
Likes: 52
From: Florida
Originally Posted by gerry72
Probably the vacuum modulator on the trans. But this will cause other anomalies like a hard shifts too. If not the modulator (the easiest thing to check and replace) it's probably a sticking or broken governor.
Instructor
Joined: Apr 2004
Posts: 166
Likes: 0
From: Troy MO
Hopefully its one of the above listed problems, but if not, mine in my truck did same every time I stepped on it and it down-shifted from third to second, it wouldn't shift back up, it was my valve body spool sticking at the end of the bore and holding it in second. Although I tried to repair it a couple times, I ended up replacing the valve body.
Good luck,
Loren
Good luck,
Loren
Pro
Joined: Mar 2004
Posts: 686
Likes: 0
From: Southeast
I'll tell you right now what I think it is. The same thing happened to me on my '71. It's the vacuum hose going to the modulator on the transmission. If it's the original hose, it's probably in really bad shape like mine was. It's most likely broken on the end allowing it to let some vacuum out which would cause it not to shift correctly. Check the hose. If not the hose, then it's the modulator itself.
