Normal Leaking Spots on a TH-400
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Pro
Joined: Mar 2004
Posts: 686
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From: Southeast
Normal Leaking Spots on a TH-400
My 71 has been sitting in the garage for the past couple of weeks while I'm doing some things under the hood. I've noticed that I've got quite a leak under the transmission. Haven't really gotten under to look yet, but just want to know what the likely culprits are for the leak. I'm guessing the pan gasket. Anywhere else I need to look too?
Intermediate
Joined: Feb 2006
Posts: 46
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From: Tyler TX.
"quite a leak" is a little vague. If it didn't leak before letting it sit, it may be as simple as the torque convertor leaking down. Drive the car (after topping off the trans fluid- check hot, in neutral before driving off). Park in a 'clean spot' and see if there really is a leak or, as noted, just the torque convertor. May be nothing to worry about. Crawl under it and have a look when parked on the clean spot...
Melting Slicks
Joined: Feb 2003
Posts: 2,529
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From: Auburndale Florida
2025 C2 of the Year ('64-'66) Finalist - Unmodified
St. Jude Donor '03-'05-'06-'07-'09
Fubba I have the same issue on my '72. Replaced the shifter seal a few months ago and all was good. Now a few weeks ago I have a small puddle uder the car. I drive the car -2 times a week. Like you, I need to crawl back under and see what's going on.
I am not familiar with a convertor leaking down....
I am not familiar with a convertor leaking down....
Thread Starter
Pro
Joined: Mar 2004
Posts: 686
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From: Southeast
Originally Posted by Dragonwycke
"quite a leak" is a little vague. If it didn't leak before letting it sit, it may be as simple as the torque convertor leaking down. Drive the car (after topping off the trans fluid- check hot, in neutral before driving off). Park in a 'clean spot' and see if there really is a leak or, as noted, just the torque convertor. May be nothing to worry about. Crawl under it and have a look when parked on the clean spot...
Racer
Joined: Mar 2006
Posts: 366
Likes: 1
From: Houston Texas
If I do not evenly torque the bolts on the transmission cover it will leak a bit until I get them the same. So any time I do anything underneath where I even touch one of the bolts, I will develop a bit of a 'drip' until they are all re-adjusted.
Last edited by justanotherdoe; Oct 18, 2006 at 11:11 AM.
Drifting
Joined: Feb 2005
Posts: 1,438
Likes: 2
From: Melrose Florida
Front seal, especially if more likely after some sitting. The fluid pressure behind the seal will bulge it out, and if it is not pliable or has any cracks in it, it will leak after sitting.
Short-term, easy attempt: Lucas trans stuff.
It really needs a new front seal. ~$200 to R&R trans and replace front (and rear seal), at most shops; but not a very difficult home repair, parts are only ~$40 including seals, pan gasket, filter, fluid.
Steve
Short-term, easy attempt: Lucas trans stuff.
It really needs a new front seal. ~$200 to R&R trans and replace front (and rear seal), at most shops; but not a very difficult home repair, parts are only ~$40 including seals, pan gasket, filter, fluid.
Steve
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Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
As NHVette implied, every single gasket and seal is subject and prone to leak - none are more common than others - I've seen them all leak. Since ATF flows out all over the place, pinpointing the source can be tricky. What I do is as follows:
Pull the dust cover off the flexplate. Wipe everything down really well so there are no traces of leak. Then, take white paper towel and tape it to every seal location: wrap and tape a piece around the speedo cable location; tape a string of towel around the pan gasket; place a towell under the front pump and tape it there; wrap a piece around the dipstick tube; etc. Whichever towell turns red is the location culprit.
Pull the dust cover off the flexplate. Wipe everything down really well so there are no traces of leak. Then, take white paper towel and tape it to every seal location: wrap and tape a piece around the speedo cable location; tape a string of towel around the pan gasket; place a towell under the front pump and tape it there; wrap a piece around the dipstick tube; etc. Whichever towell turns red is the location culprit.
Safety Car
Joined: Oct 1999
Posts: 4,101
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From: NorCal
Front pump seal and filler tube are the most common, then shift seal, rear seal with pan being the least likely. Also rare is the modulator O-ring. I like to throw a large piece of cardboard under the trans after I've wiped it down and run it a short distance, then wait overnight. That usually gives me a good idea as to the location of the leak. Very front out of the bellhousing is front pump, RF corner of the pan area is usually filler, LH side is shifter or (toward the back) the speedo, and all the way back is rear seal. I'd use any "conditioner" sparingly, as they typically just soften and swell any rubber parts in the trans.
When I patch up a poor, starving, local college kids car tranny, I try about a cup of Wynn's "Trans-X" and often get more miles out of a weak trans, but I gaurantee nothing. Some go a week, others I never see again. The whole quart just ruins them.
Hans
When I patch up a poor, starving, local college kids car tranny, I try about a cup of Wynn's "Trans-X" and often get more miles out of a weak trans, but I gaurantee nothing. Some go a week, others I never see again. The whole quart just ruins them.
Hans
