77 Corvette Transmission Problems
Thread Starter
Instructor
Joined: Oct 2008
Posts: 248
Likes: 0
From: Ca.
77 Corvette Transmission Problems
For no apparant reason and no warning, my transmission won`t shift out of low gear. I drove the car yesterday approx. 35 miles, everything was fine. I shut if off about 4 or 5 times during the morning. The last time I started it to drive home I put it in drive, accelerated and it stayed in low gear. Since buying it I`ve put almost 300 miles on it with no issues. This has me puzzled. The transmission was rebuilt by the previous owner last year and has about 1200 miles on it. Any ideas fellas?
Drifting
Joined: Dec 2008
Posts: 1,336
Likes: 169
From: Westampton New Jersey
Rebuilt or not, I just dont trust a 30 year old automatic transmission, I took mine out and put in a 4 speed. If you need one I have the original still lying around and it was working when I took it out. But I like the manual one.
Last edited by dmeesq; Jan 31, 2009 at 05:14 PM.
Burning Brakes
Joined: Jun 2005
Posts: 764
Likes: 2
From: THE OLDER I GET THE BETTER I WAS! NORTHERN ONTARIO
I wonder if the shifter is out of adjustment...I am not good with transmissions so I go for all the simple stuff...I am not real sure this would make any difference, but perhaps the shift module on the pass side is blocked or clogged...that's as much as I know...hope someone chimes in with some more suggestions
Intermediate
Joined: Sep 2007
Posts: 38
Likes: 0
From: central coast CA
Same problem happened to my auto trans a few years ago, wouldn't shift out of low gear. Tracked it down to a piece of rubber hose that was connected to the modulator valve on the transmission,The hose had a split in it. Replaced the hose and it shifted fine.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
That has happened to me a few times. That tube gets cracked and loose and comes off. Without that vacuum the transmission won't shift and the engine might even run a bit rough.
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
If the line didn't fall off the modulator, your problem is [most likely] the plastic gear teeth on the governor shaft are worn off or the pin holding that gear onto its shaft is sheared.
Remove the domed governor cover (right side on tail shaft), pull out the governor, and check the gear/teeth. The flyweights should be free to move outward and when they do the valve in the shaft should also freely move with those weights. If the gear is bad, and you can find a replacement gear, just drive the roll pin out and replace with the new gear. Otherwise, replace the governor. You'll need a new governor cover gasket, too.
Remove the domed governor cover (right side on tail shaft), pull out the governor, and check the gear/teeth. The flyweights should be free to move outward and when they do the valve in the shaft should also freely move with those weights. If the gear is bad, and you can find a replacement gear, just drive the roll pin out and replace with the new gear. Otherwise, replace the governor. You'll need a new governor cover gasket, too.
Thread Starter
Instructor
Joined: Oct 2008
Posts: 248
Likes: 0
From: Ca.
Here`s what I`ve found so far, the modulator is new as is the very short piece of hose connected to it and the steel line. I traced the line to a 3 port vacume fitting on the intake manifold in front of the dist. While checking the hoses, I noticed the fitting was loose. I was able to put 4 turns on it to tighten it. I`m hoping this was the problem, I`m getting ready to take a test drive. 
Keeping my fingers crossed!
Keeping my fingers crossed!
Drifting
Joined: Aug 2007
Posts: 1,924
Likes: 6
Racer
Joined: Apr 2007
Posts: 443
Likes: 0
From: Rexton New Brunswick
I have had this same thing happen and it was the hose. Just a short piece but vital
