Th400 won't downshift
Thread Starter
Instructor
Joined: Jul 2002
Posts: 125
Likes: 1
From: Fort Walton Beach Fl
Th400 won't downshift
Any advise would be greatly appreciated. When I come to a stop I have to manualy down shift to get back in first. It runs up through the gears fine but will not down shift on its own. Any ideas? Thanks
Race Director
Joined: Jan 2000
Posts: 13,014
Likes: 2,257
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Governor is likely sticking. You can remove it from under the cover with 4 bolts on right rear side of trans and replace it. You can play with it and see if you can wash it out with solvent, but I can tell you they are VERY picky and once they stick, it's tricky to get them to stay free all the time. Trans shops have them for $20 or so usually. Look for a trans wholesale parts place if you are near a big city.
JIM
JIM
Thread Starter
Instructor
Joined: Jul 2002
Posts: 125
Likes: 1
From: Fort Walton Beach Fl
I was worried it may be the converter, that sounds like a much friendlier fix. The car was stored for several years and when I started driving it, it ran fine for a little while(few weeks) then started acting up.
Race Director
Joined: Jan 2000
Posts: 13,014
Likes: 2,257
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Sometimes you can free them up by manually pulling them to low while moving slowly. But it's just luck if it works.
Probably need to change fluid and the governor.
JIM
Probably need to change fluid and the governor.
JIM
Race Director
Joined: Jan 2000
Posts: 13,014
Likes: 2,257
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
The fact that he said it shifts so well otherwise, makes me think teeth might still be OK. Yes they do strip every once in awhile. The modulator will help low speed stuff, but with no teeth or partially missing teeth...it's going to have a pretty high shift point I would think under power.
Since it's been sitting, it doesn't take much varnish to make one stick. When I used to rebuild them all the time I learned to be very careful with cleanliness and not to mess with them much. You can take one out and clean it until you can see the piston move very freely inside, but eventually it seems to always get to the same spot and stick again sooner or later. As I said, sometimes after rebuilds they would do this, and a few manual downshifts and manually pulling it to low when starting away from a stop would get one working again and they would stay that way usually.
Either way, when he pulls it out..he'll know.
JIM
Since it's been sitting, it doesn't take much varnish to make one stick. When I used to rebuild them all the time I learned to be very careful with cleanliness and not to mess with them much. You can take one out and clean it until you can see the piston move very freely inside, but eventually it seems to always get to the same spot and stick again sooner or later. As I said, sometimes after rebuilds they would do this, and a few manual downshifts and manually pulling it to low when starting away from a stop would get one working again and they would stay that way usually.
Either way, when he pulls it out..he'll know.
JIM
Melting Slicks
Joined: May 2002
Posts: 2,431
Likes: 52
From: Florida
Originally Posted by 427Hotrod
The fact that he said it shifts so well otherwise, makes me think teeth might still be OK. Yes they do strip every once in awhile. The modulator will help low speed stuff, but with no teeth or partially missing teeth...it's going to have a pretty high shift point I would think under power.
Since it's been sitting, it doesn't take much varnish to make one stick. When I used to rebuild them all the time I learned to be very careful with cleanliness and not to mess with them much. You can take one out and clean it until you can see the piston move very freely inside, but eventually it seems to always get to the same spot and stick again sooner or later. As I said, sometimes after rebuilds they would do this, and a few manual downshifts and manually pulling it to low when starting away from a stop would get one working again and they would stay that way usually.
Either way, when he pulls it out..he'll know.
JIM
Since it's been sitting, it doesn't take much varnish to make one stick. When I used to rebuild them all the time I learned to be very careful with cleanliness and not to mess with them much. You can take one out and clean it until you can see the piston move very freely inside, but eventually it seems to always get to the same spot and stick again sooner or later. As I said, sometimes after rebuilds they would do this, and a few manual downshifts and manually pulling it to low when starting away from a stop would get one working again and they would stay that way usually.
Either way, when he pulls it out..he'll know.
JIM
I never had much trouble with GM governors, it was the Ford C series I had trouble with. I'd take them apart and slap them on a steel table with the valve in place...usually worked. Throwing it in park (on Fords) at low speed would rattle the shaft enough to fix em too if it started acting up in the car.
jim
Race Director
Joined: Jan 2000
Posts: 13,014
Likes: 2,257
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
I hated the Ford C-4 valvebodies. Blasted aluminum suckers..they were so finicky it was crazy! I got to where I would gingerly lift it off trans and gently carry it to a special tray where I would lay it perfectly flat and cover it to keep any dust etc out of it. Then installing it you had to VERY careful not to over torque any one bolt or it would warp and stick a valve.
GM iron ones you could throw in the parts washer and forget about them!
JIM
GM iron ones you could throw in the parts washer and forget about them!
JIM
