TH400 No Acceleration
Thread Starter
Cruising
Joined: Sep 2021
Posts: 10
Likes: 1
From: Grand Rapids, MI
TH400 No Acceleration
TH400 can reverse fine but no acceleration in other gears.
I Let my C3 sit for a few years and when I pulled it out last summer I had very poor acceleration in any gears except reverse. I changed the fluid and filter and it got worse, So I pulled the whole transmission over the winter and did a complete rebuild. During the rebuild I did not find any burned clutches or really any wear on anything, I had a rebuild kit so I went ahead and replaced all the clutches and figured it must be the torque converter so I threw a new one on with 1,700 - 2,100 stall.
Put the transmission back in over the weekend and nothing changed. I can shift through all the gears and hear the rpms change with each gear selection. Reverse works fine, shifts a little hard going into it but as soon as I ease up off the gas it takes off and goes. Dropping it into 3 (or 2 or 1) is different, it does start moving when I take my foot off the gas but it has no acceleration or power, it cant even make it over the 1" hump between my garage and driveway.
Specs:
74 C3
TH400 with Trans go 1-2 shift kit.
79 LM1 Engine
77 Quadrajet 4 barrel
Summit Brand 12" torque converter, 1,700 - 2,100 stall
I Let my C3 sit for a few years and when I pulled it out last summer I had very poor acceleration in any gears except reverse. I changed the fluid and filter and it got worse, So I pulled the whole transmission over the winter and did a complete rebuild. During the rebuild I did not find any burned clutches or really any wear on anything, I had a rebuild kit so I went ahead and replaced all the clutches and figured it must be the torque converter so I threw a new one on with 1,700 - 2,100 stall.
Put the transmission back in over the weekend and nothing changed. I can shift through all the gears and hear the rpms change with each gear selection. Reverse works fine, shifts a little hard going into it but as soon as I ease up off the gas it takes off and goes. Dropping it into 3 (or 2 or 1) is different, it does start moving when I take my foot off the gas but it has no acceleration or power, it cant even make it over the 1" hump between my garage and driveway.
Specs:
74 C3
TH400 with Trans go 1-2 shift kit.
79 LM1 Engine
77 Quadrajet 4 barrel
Summit Brand 12" torque converter, 1,700 - 2,100 stall
Thread Starter
Cruising
Joined: Sep 2021
Posts: 10
Likes: 1
From: Grand Rapids, MI
I can't even get it up and going enough to pick up on slipping, it just has no power transfer when I put it in any gear except reverse. Could something be bad in the forward clutch and still allow it to go in reverse?
