Th400 transmission
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Instructor
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St. Jude Donor '14
Th400 transmission
I know this subject has been talked . I just got a 75 corvette and th400 trans. Car had been sitting for eight years then a new crate 350 was installed. Anyway I got everything ready to go for drive, took it easy and trans wasn't shifting. Read forum about modulator and I checked and wasn't hooked up it was the original modulator replaced it and put in vacuum lines from intake. The old modulator was full of ATF. Checked fluid and took for drive. Seems to be shifting from first to second after I gun it and let off accelerator . I checked by download shifting to first. So my question is what next? Governor? I read about flushing the trans but not sure. Any help would be appreciated only took 60 years to get corvette.
Melting Slicks
Joined: Jul 2009
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From: Vero Beach FL
Under the dash there is a switch that is mounted to the accelerator pedal bracket that down shifts the transmission (kickdown). See if its stuck down, you can reset it depressing it all the way and releasing by flicking your finger off of it.
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Instructor
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St. Jude Donor '14
Th400 trans
No I didn't change filter but I will. I did have to add about 3 quarts of ATF yes I checked ATF after she was warmed up. She didn't shift at till I installed new modulator and connected line to full vacuum at carb. Not sure if previous owner changed filter when he installed motor. But I will do it. Thanks any help is greatly appreciated.
Melting Slicks
Joined: Mar 2008
Posts: 2,023
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From: Austin Tx
No I didn't change filter but I will. I did have to add about 3 quarts of ATF yes I checked ATF after she was warmed up. She didn't shift at till I installed new modulator and connected line to full vacuum at carb. Not sure if previous owner changed filter when he installed motor. But I will do it. Thanks any help is greatly appreciated.
Thread Starter
Instructor
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St. Jude Donor '14
Th400
Ok I disconnected the kick down and took for drive, made no difference. I had modulator connected to intake and was told to put on carb full vacuum same as intake edelbrock 1406. So I am going to do transmission filter change . Would governor be a problem ?
Instructor
Joined: Nov 2003
Posts: 137
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From: Clifton NJ
Drain old fluid, pull pan and look at whats in bottom, may give a clue. I suggest adding an aftermarket drain to the pan, makes future fluid changes / drains less "stressful".
Its been too long for me to remember if there is a drain port on the converter or not, but I dont think so.
Its been too long for me to remember if there is a drain port on the converter or not, but I dont think so.
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Thread Starter
Instructor
Joined: Mar 2013
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St. Jude Donor '14
Th400
Going to service transfer myself and was told by local trans guy to pull governor and he would check and repair if needed. So I am going to use rhino ramps for front and jack up rear and put jack stands. Hope this works not a lot of room.
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St. Jude Donor '14
Th400
Changed trans filter boy what a job. Bottom of pan had some grayish thick stuff. Fluid looked good. I haven't driven yet. Tried to remove governor had to remove exhaust but was unable to get to top bolt. I think the tranny needs to be lowered.
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St. Jude Donor '14
[QUOTE=crashdog172;1583763475]should be able to pull the govenor out in the car,pop the cover off and pull it out make sure everything works nice and smooth and that the gear is not stripped[/QUOTE
There is bracket attached to trans for exhaust. It is in the way got three bolts lose but unable to get third not a lot of room. Can this bracket be taken off? This bracket is clamped to exhaust pipe keep it from rattling .
There is bracket attached to trans for exhaust. It is in the way got three bolts lose but unable to get third not a lot of room. Can this bracket be taken off? This bracket is clamped to exhaust pipe keep it from rattling .
Last edited by Rogerl; Apr 29, 2013 at 07:20 AM.
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
[QUOTE=Rogerl;1583764485]
Hi Roger
The bracket is held by two bolts that are kinda of under the transmission mount. When I replace my bracket last year I remove the cross member to get to it.
should be able to pull the govenor out in the car,pop the cover off and pull it out make sure everything works nice and smooth and that the gear is not stripped[/QUOTE
There is bracket attached to trans for exhaust. It is in the way got three bolts lose but unable to get third not a lot of room. Can this bracket be taken off? This bracket is clamped to exhaust pipe keep it from rattling .
There is bracket attached to trans for exhaust. It is in the way got three bolts lose but unable to get third not a lot of room. Can this bracket be taken off? This bracket is clamped to exhaust pipe keep it from rattling .
The bracket is held by two bolts that are kinda of under the transmission mount. When I replace my bracket last year I remove the cross member to get to it.
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
Pretty easy six bolt holding it to the frame and then two that hold the transmission mount to the trans. The parking brake cable does not have to be removed unless you want to remove the cross member totally from underneath the car. In that case just remove the pulley. You will need to jack up the trans a little to get the cross member out and support the trans when the cross member is out if not the engine will tilt and your distributor will hit the firewall and your fan may hit the shroud.
Last edited by Roco71; Apr 29, 2013 at 11:19 AM.
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
Thread Starter
Instructor
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St. Jude Donor '14
Th400
I put everything back together and took for a drive pretty much same shifts 1st and 2nd seems it try's to go into third , sounds like it wants to but it feels like it try's but feels like its in neutral and slips back into second. I talked to another transmission guy and said if governor was bad it wouldn't shift at all. Will try again tomorrow and consider taking to a tranny shop. The shifting from 1st to 2nd is better not hard actually I don't feel it or hear it.