I've got an '87 v6 700r4 with about 130k miles that developed a massive leak (think waterfall) from the front end. I'm assuming its the front seal. The failure occured on the highway, it stuck in third gear, then when i stopped on an offramp and tried to start agian there was absolutely no pull. Had it towed back to my driveway, and put in a bunch of fluid to try to get it up the hill into the garage. I wsa able to move it and it actually pulled pretty strong at first but began slipping as the fluid leaked out.

The question is, can I replace the seal without a total rebuild, and if i can replace it, is there a good change the tranny is ok or is it most likely dead. If its most likely dead im not going to put in the money to rebuild it.

Thanks.

 

I would be curious if the seal "blew" or walked out of the pump. I don't know when GM first started using the seal retainer, but older trannies didn't have the retainer and they had instances where seals would "walk" out of the pump body.

If the seal is "blown" you need to inspect the Torque Converter bushing in the pump. If the bushing is worn, then the TC can move just enough inside the seal to damage it.

Depending on how long you drove it w/ no fluid will determine how bad the tranny it. I once worked on a '99 GMC Sierra (it was brand new then) that had 150 miles on it. They were driving it home from the dealer in Florida and a cooler line came off. They did not realize what had happened untill the 3-4 clutches were completely smoked. How it drove that long is beyond me.

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Since the pump will have to come off to inspect for damage, pump bushing movement/condition and to drill out the drainback passages, it is not much more to take the drums out and see what condition the parts are in. Besides, with 130K you will deffinately want to change the Input Sprag since it is on borrowed time by now.

 

I've got absolutely no expenience working on autos other then changing the filter. How much work is involved in taking off the pump and drums. Input sprag? Will I need special tools for this? After the tranny began to act strangely due to the low fluid, it was probably only a mile or maybe two until the offramp where it stopped totally.

 

Once, right after a rebuild, my convertor's input spline cracked, and took out the front seal. I had the same waterfall during the same driving conditions that you did- I always wondered what the people behind me thought when they got covered with trans fluid! The stuff was all along the underside of my car, muffler, and rear bumper!

To pull the pump you need a puller; looks like you could make one. Find the Haynes "GM Transmission Overhaul" manual; either at your local auto parts store or online at haynes.com - it gives a step-by-step pic-by-pic overhaul of the TH-350, TH-400, TH-200-4R, and TH-700r4 trannies. Then you'll know what you're getting into; and you'll also learn a helluvalot about the trans too. The ATSG trans service book ( http://transbuilder.com/store.html and order from http://www.naparts.com ) is also a "must".. both books are about $15.


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I once experienced that "waterfall" leak.
In my instance it was with a TH-350. the pump bushing walked forward and pushed on the front seal. I was driving from Atlanta to Orlando and still had 250 miles to go So I stopped picked up about 2 1/2 cases of tranny fluid and continued on my trip. By the time I got there I weht through a total of 30 quarts of fluid and smoked the direct and forward clutches/steels.
Hopefully you will have better luck since you did not push it that far.

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