HELP! TH350 bad shifting

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Looter

Apprentice
Jun 27, 2016
74
22
8
About a month and a half ago I put a rebuilt TH350 in my 78 Buick Regal, I’ve driven about 1k miles since then, regularly checked/added fluid, and ensured the kickdown is properly adjusted. Today for no apparent reason, first gear has started winding out, the engine revs high and I can hear the transmission whining. I eventually get to second but never saw third (under normal throttle it would shift to third at about 40-45).

It seems to shift from first to second alright, but still winds out a lot, and whines. Dropping from second to first makes the whining much worse.

Could it be a bad governor or vacuum modulator? Or more likely will I have to tear into the transmission? It drove like new up until today.
 
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Looter

Apprentice
Jun 27, 2016
74
22
8
the rebuild was done by a professional with proper equipment and 40 years of experience, it cost me $700 and I put my faith into it working, hopefully it’s not on his end or I’m gonna have to go through hell and back trying to fix it
 

bob64

G-Body Guru
Mar 30, 2017
713
674
93
Niagara Falls, Canada
With that many miles on it take it back. Rebuilders offen change the clutch packs but cheap rebuilders never get involve with the pump other than quick look at it.
Passing gear set up/adjustment has no effect on just cruising shifting, soo torque converter, pump, modulator r valve, modulator r spring. Shouldn't be clutch packs but it is possible.
So check the vacuum line, modulator valve an pull out the spring, cheap springs can go soft quick which means it takes longer for it to shift between gears, so you get a whine.
I personally have never had a Torque converter go but they do. I have had a couple pumps go,rushed rebuilds by myself but l know better now. It took twice sitting on side of road to get threw to me.
If it just happen on a fresh rebuild l'd lean towards a pinched vacuum line or low vacuum.
 

MrSony

Geezer
Nov 15, 2014
6,791
6,675
113
Des Moines, Iowa
when the vacuum line falls off the modulator on my car it kinda acts the same. holds into 1st and 2nd for a long time, then bangs into 3rd.
 
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Looter

Apprentice
Jun 27, 2016
74
22
8
when the vacuum line falls off the modulator on my car it kinda acts the same. holds into 1st and 2nd for a long time, then bangs into 3rd.
You’re probably right, I think I remember the guy who did the rebuild saying he had to put a cheap modulator on, so it’s no surprise if it’s gone bad
 

MrSony

Geezer
Nov 15, 2014
6,791
6,675
113
Des Moines, Iowa
If trans fluid comes out of the nipple, its bad. Some are adjustable as well.
 

Looter

Apprentice
Jun 27, 2016
74
22
8
Finally had time to check, I was right. Rubber hose holding the metal line fell off and transmission had no vacuum.
 
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