transmision removal
Thread Starter
Heel & Toe
Joined: Oct 2003
Posts: 15
Likes: 0
From: lake orion mi
transmision removal
I have a trans leak and it looks like i will have to take out the trans when i brought the car a few months ago i was told it is just a pan leak and i need a new gaskit.
Im not a machanic by any means and i removed a trans from a sunbird years ago but i know its a lot tighter in this car. Does anyone have any ideas if i should take it in or try it my self I have sprayed it off and it doesnt look like its a pan leak
Im not a machanic by any means and i removed a trans from a sunbird years ago but i know its a lot tighter in this car. Does anyone have any ideas if i should take it in or try it my self I have sprayed it off and it doesnt look like its a pan leak
Le Mans Master
Joined: Aug 2000
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From: Semper ubi, sub ubi
Cruise-In VI Veteran
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Re: transmision removal (geoff4961)
I don't know which automatic you have but with either the TH350 or the TH400 (and TH700r4) there are numerous places that they can leak from that doesn't require removal of the tranny.
1.) First of all the pan is easiest to pull and replace and believe it or not it is the place that many tranny leaks originate. Remove the pan, carefully inspect the pan sealing surface for flatness and flaws. Use a new gasket and replace the pan, only tighten the bolts to 12 lb.ft. TH400, and 130 in. lb. TH350. Tighten them evenly using a criss-cross method.
2.) Then you have the front seal, that is easy to check but difficult to repair and does require removal of the tranny. To check it for leaks pull the inspection cover that covers the flexplate and torque convertor, if you have a leak there it will be obivous by fluid all over the back of the torque convertor or fluid running down from behind the torque convertor.
3.) The coolant line fittings, clean any grime off the fittings, wrap some paper towels around the fittings, hold them on with tie wraps or string. Run the car for a while and see if you pick up any fluid on the towels. If you have any seepage, tighten the fittings with tubing wrenches, and try again.
4.) Vacuum modulator, there is an o-ring that seals this off, the modulator is held in place with a bolt to keep it stable. This o-ring will cause nagging leaks and is easy to replace. The modulator is on right front of a TH400 and left rear on the TH350, there is no modulator on the TH700-r4.
5.) Governor cover, toward the rear of the tranny has four bolts holding it down.
6.) Speedometer cable connection, there is an o-ring that can be easily replaced.
7.) Shifter shaft, this seal is notorious for leaking, it is a small metal and rubber ring type seal. It can be replaced by using a sharp pick and prying it out without removing the shaft. A deep socket that will fit over the shaft can push the new seal over the shaft into place. The unfortunately replacing this seal doesn't always cure the problem because the shaft itself is often worn or rusty which will cause the seal to start leaking again. Sometimes placing a new seal on top of the old seal will move the new seal to a position that isn't worn or rusty and stop the leak. Sometimes you have replace the shaft, which can be done without dropping the tranny, you just have to pull the pan and sometimes the valve body.
8.) The final place that these trannys can leak is through the case. This is a well documented problem that is described in the Chassis Service Manual. The only way that this can be stopped is to pull the tranny, thoroughly clean the external case and epoxy seal the external case. The process for doing this is described in the 1969 Chassis Service Manual (other years too.)
If you have to drop the tranny, it isn't that difficult. Just use common sense and safe practices when dropping the tranny.
1.) First of all the pan is easiest to pull and replace and believe it or not it is the place that many tranny leaks originate. Remove the pan, carefully inspect the pan sealing surface for flatness and flaws. Use a new gasket and replace the pan, only tighten the bolts to 12 lb.ft. TH400, and 130 in. lb. TH350. Tighten them evenly using a criss-cross method.
2.) Then you have the front seal, that is easy to check but difficult to repair and does require removal of the tranny. To check it for leaks pull the inspection cover that covers the flexplate and torque convertor, if you have a leak there it will be obivous by fluid all over the back of the torque convertor or fluid running down from behind the torque convertor.
3.) The coolant line fittings, clean any grime off the fittings, wrap some paper towels around the fittings, hold them on with tie wraps or string. Run the car for a while and see if you pick up any fluid on the towels. If you have any seepage, tighten the fittings with tubing wrenches, and try again.
4.) Vacuum modulator, there is an o-ring that seals this off, the modulator is held in place with a bolt to keep it stable. This o-ring will cause nagging leaks and is easy to replace. The modulator is on right front of a TH400 and left rear on the TH350, there is no modulator on the TH700-r4.
5.) Governor cover, toward the rear of the tranny has four bolts holding it down.
6.) Speedometer cable connection, there is an o-ring that can be easily replaced.
7.) Shifter shaft, this seal is notorious for leaking, it is a small metal and rubber ring type seal. It can be replaced by using a sharp pick and prying it out without removing the shaft. A deep socket that will fit over the shaft can push the new seal over the shaft into place. The unfortunately replacing this seal doesn't always cure the problem because the shaft itself is often worn or rusty which will cause the seal to start leaking again. Sometimes placing a new seal on top of the old seal will move the new seal to a position that isn't worn or rusty and stop the leak. Sometimes you have replace the shaft, which can be done without dropping the tranny, you just have to pull the pan and sometimes the valve body.
8.) The final place that these trannys can leak is through the case. This is a well documented problem that is described in the Chassis Service Manual. The only way that this can be stopped is to pull the tranny, thoroughly clean the external case and epoxy seal the external case. The process for doing this is described in the 1969 Chassis Service Manual (other years too.)
If you have to drop the tranny, it isn't that difficult. Just use common sense and safe practices when dropping the tranny.
Le Mans Master
Joined: Mar 2002
Posts: 7,456
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From: Coming home from Luckenbach Texas
Re: transmision removal (geoff4961)
How much does it leak? If it's not much, you can always stick a metal pan under the spot where you park the car. And keep an eye on the fluid level. Sometimes chasing tranny leaks are more trouble than it's worth. Just my .02 :smash:
Le Mans Master
Joined: Aug 2003
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From: Chattanooga TN
Re: transmision removal (Smokehouse69)
I agree with him but on #6 I might add that the speedomoter gear "bullet" can also leak. Especially the aluminum ones on the TH350s. The turning of the driven speedometer gear over the years egg-shapes a groove into the adapter or "bullet". With this leak you usually see fluid dripping out of the cable connection where the speedo cable screws onto the transmission. My recommendation is to put the car on stands and clean the transmission area as well as you can. Then crank it up and look to see exactly where the leak is. Go back to 2 posts and follow his advice on how to deal with it. Good luck.
[Modified by markdtn, 1:48 PM 12/28/2003]
[Modified by markdtn, 1:48 PM 12/28/2003]
