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GlennC1
Novice
Nov 30, 2015, 12:38 PM
Post #1 of 6
(2059 views)
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I have a '79 Buick with a TH350 non lock-up. It has worked fine after being rebuilt a few years ago. Now it wont up-shift. First and reverse is all I have. This happened immediately after I had to "floor it" to get out of another cars way. Since it was working fine before this I suspect something broke or stuck in the valve body or governor. The kick down cable has been disconnected for years,in case that has anything to do with it. I tried shifting it manually going from 1st to 2nd, it wont up-shift that way either. I don't want to take the trans out of the car if I don't have to. If anybody has any suggestions or ideas that would point me in the right direction I would appreciate it. Thanks.
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kev2
Veteran
Nov 30, 2015, 2:35 PM
Post #2 of 6
(2049 views)
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Re: TH350 No shift
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might ck vacuum modulator- is there vac at modulator?
do not want to see any trans fluid in vac line.
(This post was edited by kev2 on Nov 30, 2015, 2:37 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 30, 2015, 2:38 PM
Post #3 of 6
(2048 views)
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Re: TH350 No shift
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Site has a working transmission expert I hope stops by but have some suggestions:
If that kick down cable to the carburetor was/is broken in what way? Cable or can't hook it up and could it be pulled making trans think you are pedal to the metal or at full throttle? Not sure if this year also used a vacuum diaphragm you can look for one on side with a hose as that too if hose has no vacuum will cause trans to hang onto lower gears to the limits of RPM generally forced upshifts to second @ about 40MPH and third @ about 70-75MPH or so by a governor. That can be overridden with your shifter if physically not in correct position at trans or inside goes to valve body.
Owned the exact year and trans in an Electra for years and can't recall every detail of how it shifted. Cable, vacuum and a centrifugal governor forced upshifts except as said if locked into lowest gear only or trans needs another overhaul IMO,
T
PS: Vacuum hose just falling off if mushy at either end could do this on some - check and hope it's that simple. If wet at a diaphragm with ATF that diaphragm has to be replaced and can swell hose to fall off too...........
(This post was edited by Tom Greenleaf on Nov 30, 2015, 2:48 PM)
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gsferraro
Veteran
Nov 30, 2015, 5:07 PM
Post #4 of 6
(2038 views)
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Re: TH350 No shift
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Hello,
First pull off the modulator hose, the modulator is located right rear of trans, make sure no fluid comes out, if no fluid comes out, with the hose dissconnected start the car and make sure you have vacuum at the hose by putting your finger to block the hole of the rubber hose, you should feel vacuum, if you dont follow the line upto the engine and see if its off on top. If that is ok, on the left rear of the trans you will see a cover(next to speedo cable) behind that cover is the transmission govenor, its common for the govenor gear to strip or apple core. The govenor works on centrifugal force as it spins the trans will shift, if it doesnt spin the trans will stay in first gear. Gary
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GlennC1
Novice
Dec 3, 2015, 9:47 AM
Post #5 of 6
(1999 views)
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Re: TH350 No shift
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Turned out to be just a broken vacuum line. Thanks for the help.
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gsferraro
Veteran
Dec 3, 2015, 11:44 AM
Post #6 of 6
(1994 views)
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Re: TH350 No shift
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Glad you got it fixed. Gary
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