1977 TH350 not upshifting.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
1977 TH350 not upshifting.
Interesting drive this afternoon. Got the interior almost all finished, minus a shift boot that doesn't fit the shifter plate and an overheating problem...
...I found that the transmission did not upshift out of first.
I checked fluid. Clean, red, smells great, and at filled level when warm.
I verified the detent cable was in place on the throttle linkage on the carb and that it seemed to be adjusted properly.
Could the pump be going out and it doesn't have enough pressure to shift? It shifts from park to reverse and neutral just fine, same as going into drive. It stay is first gear.
Any ideas?
...I found that the transmission did not upshift out of first.
I checked fluid. Clean, red, smells great, and at filled level when warm.
I verified the detent cable was in place on the throttle linkage on the carb and that it seemed to be adjusted properly.
Could the pump be going out and it doesn't have enough pressure to shift? It shifts from park to reverse and neutral just fine, same as going into drive. It stay is first gear.
Any ideas?
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Safety Car
Joined: Dec 2005
Posts: 4,270
Likes: 20
From: Central Michigan
Matt, check the governer also. It's located on the pass side, under a stamped sheet metal cap held in place with a piece of stiff wire, similar to a brake master cylinder. Check that the governer isn't frozen up, and everything moves freely.
Centrifical force causes the weights on the governer to move outwards, pushing in on the valve, and enabling the shift from 1st to 2nd. Hope this helps out
Centrifical force causes the weights on the governer to move outwards, pushing in on the valve, and enabling the shift from 1st to 2nd. Hope this helps out
Drifting
Joined: Jan 2004
Posts: 1,991
Likes: 3
From: Piscataway NJ
Matt, check the governer also. It's located on the pass side, under a stamped sheet metal cap held in place with a piece of stiff wire, similar to a brake master cylinder. Check that the governer isn't frozen up, and everything moves freely.
Centrifical force causes the weights on the governer to move outwards, pushing in on the valve, and enabling the shift from 1st to 2nd. Hope this helps out
Centrifical force causes the weights on the governer to move outwards, pushing in on the valve, and enabling the shift from 1st to 2nd. Hope this helps out
Put vaccuum to the modulator valve it should hold a vac.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
There is a hard line that goes from the back of the modulator - it's on the passenger side of the rear of the TH350...looks kinda like a fuel filter - to a fitting on the intake manifold. Most likely it's just worked loose and you just need to slide it back on.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I'm familiar with the line. I'll crawl under there this afternoon when I get home to check.
Thanks for all the help guys.
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Crawl under???? You dont have a lift yet??
............. ..........
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Well I need to get under the car because I never disconnected the line at the top that goes to the manifold. It's dedicated...meaning it's the only vacuum draw from that port at the back of the manifold. I know the line is solid there and must now check the bottom.
I wish I had a lift but I do not have the height in my garage for one and I can't afford a steel building yet.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I had another thought. I did not attach the vacuum lines for the headlights to the headlight switch. I am going to mount a stand alone switch for the actuation of the headlights so I can control them independently of the light switch. Similar to the stock switch but with more control.
Anyway, I did not complete that task and left the tubes dangling under the dash. I totally did not even think about the resulting vacuum leak.
Since that part of the vacuum system comes off of the carb and the transmission line comes from the port on the manifold...
...would the loss of vacuum in the cab like that cause there to be so little vacuum that the transmission would not upshift?
I know it shifts into reverse just fine, and I always thought that it takes more pressure to shift into reverse than any of the forward gears.
So, knowing it shifts into reverse just fine and that I have a huge vacuum leak...can I rule out or pinpoint anything?
Anyway, I did not complete that task and left the tubes dangling under the dash. I totally did not even think about the resulting vacuum leak.
Since that part of the vacuum system comes off of the carb and the transmission line comes from the port on the manifold...
...would the loss of vacuum in the cab like that cause there to be so little vacuum that the transmission would not upshift?
I know it shifts into reverse just fine, and I always thought that it takes more pressure to shift into reverse than any of the forward gears.
So, knowing it shifts into reverse just fine and that I have a huge vacuum leak...can I rule out or pinpoint anything?
Instructor
Joined: Aug 2006
Posts: 134
Likes: 0
From: Apple Valley MN
Last month I had the same thing happen. When they installed my headers and pipes, they accedentally knocked off the Vac line to the trans. I was able to shift it manually from 1st to 2nd to get to a tranny shop. Good Luck DB.
Thread Starter
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Interesting. Mine will not upshift manually. I did not think they were even capable of doing that except within the normal standards of it wanting to like in drive gear where it will decide.
I know that you can start in first, and shift manually into second but that's because the transmission already wants to and you're not manually changing the gears.
It'll shift up as high as you let it but the shifter doesn't seem to move it to second before it's ready to shift anyway.