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Tranny puked out fluid and caught fire!!

1K views 18 replies 3 participants last post by  HighSierra 
G
#1 ·
Hi guys!

Well, it looks like me ole T350 tranny is toast!
Yesterday we went out wheeling and for some reason it burnt the crap out of the fluid and sent a bunch of fluid out of the dipstick which in turn caught fire on the headers. She was slipping very badly by the time I got er home.

No fun!

Anyways, it's time to do a tranny swap.

So I have a few questions:
1) If I buy a T350 that was mated to a BB, what's involved in the swap? I think my bellhouseing and flywheel are still OK.

2) What's involved in a T400 swap?

3) Do I have to purchase a tranny out of a 4x4 or can I use my existing parts to make a tranny out of a 2wd work?

4) How can I identify if I have the t350 or t400 tranny in my truck? I've been told it's "probably the T350" but need to know for sure.
 
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G
#2 ·
Hmm, lost my sig.

Anyway, the truck is a 85 GMC 3/4T 4x4.
Powered by a 350 Small block. She came factory with a 14BSF rear, 10B front axle, 4:10's, tow package, and the big brake setup.

Thanks guys!
 
G
#7 ·
Thanks guys!

So what about the driveshafts? Will I need new ones for a TH350 to TH400 swap?

What are my other tranny choices? An overdrive tranny would be really cool! Mnorby, is this basicly the opposite of what you did? Swapping a 4sp for a 3sp?
 
G
#8 ·
I have had bad luck the the 700R4 overdrive tranny. I have gone through 4 of them now before stepping up to the TH400. Depends on what t-case you use also for drivlines. You may have to get a different case or at least input shaft if you go to the th400 cause it is a 32 spline wheseas the 700 is 27.
 
G
#10 ·
Well, it turns out that I do have the TH400 tranny.

The pan doesn't even come close to being square. And the TH350 gasket is worng.

Hmm. OK. And everyone seems to think that a swap to the TH700 is a waste of time.

Looks like my options have been narrowed down to:
1) Buying a different TH400
2) Rebuilding my current TH400

Man I wish I knew more about trannies! Can anyone reccomend a good resource for instructions on rebuilding the TH400?
 
G
#11 ·
The only people who don't have trouble with 700R4's have either baby engines, or they spent too much on beefing it up (i spent too much). you'll be much happier with a different tranny and damn cheaper
 
G
#13 ·
Wouldnt recomend rebuilding one yourself.....too much crap inside there. I would stay with a 400, if you can have your truck out of comission for awhile I would have it rebuilt, otherwise I would talk to a shop to have em build you one, then swap it.

I would go with a transgo shift kit(rv mode or what ever they call it, you dont need a level 3) I really dislike B&M TCI makes deccent stuff too. A shift kit should not make the shift hard if you are barley on it.

Tell the shop you plan to wheel it, some dont want to touch that kind of stuff. Be upfront with what you do so you find a shop that will somewhat stand behind thier stuff. If you just say rebuild it and later they ask why it puked and what you were doing they might get flakey. Dont reuse the torque converter if your tranny is chewing itself.....its to hard to get it fully clean. Have em install a trany drain plug.....makes life much easier. Buy an aftermarket trany cooler, the bigest honking mother you can find. Heat is what kills transmissions. 400's and 350's arnt as picky about being run cool as 700's are.

Sounds like she is toast:(
 
G
#14 ·
find a cooler like what Joe has that is massive and has an electric fan on it so when you are in the mud running 4,000 rmp and only going 2 mph you are still getting air flow through it.

All together now in the key of C, "Clutch packs roasting on the open road"
 
#16 ·
Will a Th 350 bolt in place of a 700? Thinking of doing this since my 700 is starting to go again a year later and some where around 15K miles.
I know they both have the same out put shaft splines and that, but my question is length I plan on reusing my 208 because of it low range. Trying to do this cheep most likely use the 350 out of my dads jeep thats been done up some but not going any where any time soon.
 
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