th350 shifting problem
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 33
Likes: 4
From: South Florida
th350 shifting problem
When I drive the car normally the transmission goes into all three gears but when I floor the car from 0 or low miles per hour it downshifts perfectly to 1st but it sputters at high rpm's in 1st right before going into 2nd and have to let off the gas for it to go in. It doesn't slip and the tranny rides good normally, I put a brand new fuel pump and lines to be sure it wasn't that and it continues to do it. Any ideas?
Race Director
Joined: Mar 2017
Posts: 11,949
Likes: 4,507
From: Virginia
I'm no expert, and I'd certainly do your own search, but I recall that the shift modulator for these transmissions is vacuum powered, and often an issue. When you are at WOT, your vacuum is much reduced, perhaps causing issues shifting. Maybe search for "TH350 vacuum shift modulator". It appears that some of them are adjustable, too.
I'll keep my 4-speed, but good luck!
I'll keep my 4-speed, but good luck!
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Vacuum modulator for shifting is for less than wot throttle. At wot the shifting is controlled by a govenor on the trans.
however I would suspect fuel starvation if the engine is sputtering , dying just before shifting at high rpm. It could also be ignition as suggested,
is the engine stock or has it been modified for more power?
however I would suspect fuel starvation if the engine is sputtering , dying just before shifting at high rpm. It could also be ignition as suggested,
is the engine stock or has it been modified for more power?
Racer
Joined: May 2018
Posts: 297
Likes: 43
as said above is all valid another thing to look for would be the detent cable isn't returning promptly, or is out of adjustment, crud buildup or broken sprng if its hanging in between it can cause the trans to hesitate because the governor doenst know if it should be shifting up or down, dentent is activated at wot andseems to fit the problem better since you have not noticed engine issues
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 33
Likes: 4
From: South Florida
Vacuum modulator for shifting is for less than wot throttle. At wot the shifting is controlled by a govenor on the trans.
however I would suspect fuel starvation if the engine is sputtering , dying just before shifting at high rpm. It could also be ignition as suggested,
is the engine stock or has it been modified for more power?
however I would suspect fuel starvation if the engine is sputtering , dying just before shifting at high rpm. It could also be ignition as suggested,
is the engine stock or has it been modified for more power?
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 33
Likes: 4
From: South Florida
as said above is all valid another thing to look for would be the detent cable isn't returning promptly, or is out of adjustment, crud buildup or broken sprng if its hanging in between it can cause the trans to hesitate because the governor doenst know if it should be shifting up or down, dentent is activated at wot andseems to fit the problem better since you have not noticed engine issues
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
The service manual tell you how to properly adjust the kickdown cable on a TH 350. Your initial description pretty well says there is a problem with ignition or fuel delivery. Under high load conditions ignition is the first to show a failure. Take a close look at plug wires, cap, rotor, points, (you didn't say what year!) and the general condition of the coil. After that, fuel filter and carb.
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Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
If too low it may be starving the engine at high loads.
