Automatic Transmission Leak: Rebuild or not?

delling3

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1996 GT, with automatic. 95,000 miles. Car has been driven sparingly - less than 1,200 miles in past 6 years, and under 35K over the past 15 years. I just purchased it last month. I have put about 1000 miles on it since I bought it, and I have not noticed any issues with slippage, or shifting.

When I bought the car I was aware that it had a transmission leak. I took it to a transmission shop to have the fluid changed, filter, pan gasket, etc. The guy put the car on the lift, and informed me that the front seal on the transmission was leaking, and that the transmission would need to come out. His recommendation was to rebuild the tranny while it was out, estimated about $1500.

Decided to go to another shop for a second opinion. They said that they would not recommend a rebuild. Suggested dropping the tranny, replacing the seals, and performing routine service (i.e. filter, pan gasket, etc). His estimate was about $650.

So, interested in seeing what the collective wisdom is here. Should I do a rebuild? Or simply replace the seals and service the transmission, and call it good?
 

lwarrior1016

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I do transmission for a living, so take that for what its worth.

The problem with a front end leak is that its not typically the seal that is the failure point. Most of the time you will pull it and change the seal only to have it leak again. When I get a front end leak, customer gets new pump seals, new pump bushing, new front seal, and a new torque converter. Ive been burned before and had to pull a 4wd f150 transmission 3 times because I was chasing a front end leak.

How did the pan look when it was dropped? How did the fluid look/smell? If the answer to both of those is good and clean, then I would pull it and reseal the front end.


Whats your final goal for the car? There are a couple simple mods you can do to the transmission to make its life better and make the car more fun.
 

OLD H2S

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Will what options are there in a stick to auto conversion as far as far as power/torque increases? I know PA has some stand alone systems but the price is big and going the Tremec t56 or Magnum route is pricy too.
 
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delling3

delling3

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Thanks for the feedback so far.

To answer LWARRIOR's question, my plan for the car is basically a weekend street cruiser. I am not planning any major power mods. It is a stock NPI motor at present. While I won't rule out some basic mods for more HP, my plans would be limited to a few bolt-ons, and maybe a tune.
 

lwarrior1016

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Will what options are there in a stick to auto conversion as far as far as power/torque increases? I know PA has some stand alone systems but the price is big and going the Tremec t56 or Magnum route is pricy too.

For a car that is stock wired and has a stock pcm I would recommend getting a pcm from an auto car and an automatic trans harness. There are a couple different trans controllers, US shift makes one, and I use microsquirt for mine, I think there are a couple others. The 4r70w is a pretty stout transmission right off hand, and with a few internal hard part upgrades, you can make it last while holding some power. A lot of it has to do with getting a good torque converter and those get pretty expensive.
 

lwarrior1016

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Thanks for the feedback so far.

To answer LWARRIOR's question, my plan for the car is basically a weekend street cruiser. I am not planning any major power mods. It is a stock NPI motor at present. While I won't rule out some basic mods for more HP, my plans would be limited to a few bolt-ons, and maybe a tune.

If you are pulling the trans down to fix the front end leak, I would recommend getting a higher stall converter and doing the j-mod. You could get a converter in the 2800-3000 range and it would leave you some room to grow if you decided to cam it at a later date.
 
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delling3

delling3

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Showing my ignorance here, but what is the j-mod that you reference?

If you are pulling the trans down to fix the front end leak, I would recommend getting a higher stall converter and doing the j-mod. You could get a converter in the 2800-3000 range and it would leave you some room to grow if you decided to cam it at a later date.
 

lwarrior1016

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Showing my ignorance here, but what is the j-mod that you reference?

It a free "shift kit". You basically remove a couple accumulator springs and drill a couple holes in the separator plate. It improves clutch filling and reduces shift times. If you google 4r70w j-mod, youll get a bunch of results and one of them is a youtube video. Go check it out if you get a chance.

If youre thinking about torque converters, check out roadrunner converters out of Arizona. Ive got a 3600 stall from them and its awesome.
 

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If it were my car, it would depend on what I see. If the fluid is red and the magnet isn't swollen to a golf ball size, I'd change the seal. At this age I'd expect dry rot more than anything. If instead the fluid is black, smells burnt, and the magnet is trashed, I'd be sorely tempted to just go through the whole thing and rebuild it. When the TC burns the clutch inside up, it trashes the seal rings on the output shaft. Mid95 and newer ones are better than the earlier ones, but at higher mileages it still happens. And yes, do the jmod if you don't want to change valve bodies. Well worth it. And use Mercon V only.
 

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