th 350 tranny

[86TransAm350]

i dont know much at all about trannys so im gonna ask whoever.....i have a th 350 its slippin because my freind that i bought this car from would hot rod the car naturally shift through gears and i heard that, that is bad without shift kit....i was wondering if a rebuild kit would put it back to great workin condition again or spending 900$....to get a new one...cause rebuild kits arent expensive.....and it seemed kinda dumb to dump 900 vs...rebuild kit....also would a th 400 be faster...and is it a 4 sp....cause i heard a 4sp would make my car faster...and have more top end...can you guys give me any info on this
thanks

[adryan16]

Shifting an automatic manually won't hurt a transmission, unless you shift very slowly and allow the tranny to slip more then it should between gears not allowing the pump to be fully engaged, thereby causing permanent damage. I've shifted all my cars and have never had a problem, even with ones that don't have a shift kit. All the shift kit does is help engage the pump quicker, resulting in a quicker, firmer shift. A shift kit should fix your problem most likely, but taking it to a tranny guy can let you know if any other components are damaged or need replaced.

As far as a TH400, I'd forgoe it. First off, it's not a 4 speed, it's just a bulked up TH350, still a 3 speed. You didn't list your engine, but unless you're makin over 600 horsepower, I wouldn't worry about a strength issue and on a 3rd gen, it's gonna be super tight! In addition, it adds weight, and zaps up to another 30 horsepower from your rear-wheel horsepower.

Hope this helps.

[Jeff_in_Atl]

I thought the 86 cars had 4 speed automatics in it. Isn't that a TH200R4 or TH700R4 ? I don't think the TH350 is from the factory.

[adryan16]

Yeah, I was wondering that too, it it truly is a TH 350, then it wasn't stock.

[86TransAm350]

no its not stock its a b & m....th 350 and i took it to aamco and they said its slippin bad and i need a rebuild.....startin at 1300$.....and i thought that was BS.....cause its only 900 to buy a new one...also when i took it home it was bone dry of tranny fluid......so they were tryin to break it probably.....but i added fluid and it runs better but the car is no where near as fast as it was when the 350 was first dropped...last year......so if i get a shift kit...it should stop slippege....and grip better.....and if i get a rebuild kit....it should help ...
cause i know thats a big part of the speed and driveline....what else could be a big factor in loss of horsepower and drive....this is what i changed

Batt
altern
plugs
wires
oil &
filter
air filter
havent got the trans flushed or filter changed just added fluid
injector cleaner
new fuses
thermostat

need to get probably new dist cap and rotor......o2 sensor..is pretty old...
thats about it....i cant think of anything else beside the tranny causing loss of power....

[tabahr]

Originally posted by 86TransAm350

new fuses

You changed all the fuses?

[86TransAm350]

yeah just so everything would b new

[ZMAN_DIEHL!!!]

possibly due to the lack of fluid the filter may have become clogged with some band material
did you try a fresh filter and brand new fluid?
I have a 1990 taurus that slipped real bad and I changed the fluid and filter and everything is A OK

[N20LT4Bird]

OK, let me staighten some stuff out here. I am by no means a trans expert, but I have spotted dome error here and we dont want false info spread on the board.

I agree with Zman, change the fluid and filter first.

If the trans is slipping, it could be that you need a rebuild. You are right, rebuild kits are cheap. But, the reason why it is so expensive to have a tranny rebuilt is because of the technical expertise needed to rebuild one. Granted, a TH350 is not the hardest unit to build, but still not a beginner project. If you have never had a tranny open before, do NOT attempt the rebuild yourself, seek the advise and help of an experienced builder. 1300 from aamco is steep. At my fathers tranny shop, we would get about 600-700 for a th350 over the counter; with a shift kit and hi-po parts maybe 1000 bucks, but thats going to be a nice unit.

Now, slippage has nothing to do with a pump being engaged. The pump is always turning or "engaged". Slippage occurs when the clutches or band are burnt; just like a standard tranny clutch. Slippage can also occur due to fluid pressure leakage or anything else that causes a lack of apply pressure.

A shift kit does not engage the pump quicker. A shift kit manipulates the various oil circuits, raises line pressure, and adds stiiffer springs where needed (ex. behind the accumulator pistons) to create harder, faster shifts.

A th400 is NOT just a beefed up Th350. They are a completely different transmisson. The gear train is set up completely opposite; its a very different tranny and vastly superior to a Th350 in many ways. Its very hard to blow a Th400 in a street car.

An 86 T/A would have a 700R4 from the factory. A 700R4 is very similiar to a Th350 in the way it works, but it obviously has an overdriven ratio as well.

[tabahr]

Originally posted by 86TransAm350
yeah just so everything would b new

Should change all the light bulbs too then.

I'm just funnin ya!!

[SteveH37Formula]

Don't mean to change the subject but I just replaced all the light bulbs on my dash cause they where getting dim (Bulbs getting darker). Its much brighter now!

[adryan16]

Okay, just to redeem myself in some way...
I understand and commend N20LT4Bird for not necessarily correcting, but enhancing my explanation. By engaged, I should have referred to the whole act as the clutch packs being fully engaged. Slippage is not only from these packs being severly burnt or worn, but also from pressure being inadeqate due to porblems other than the pump, such as dumping off the governor improperly during shifts.
Ditto to the shift kit "pump engagement" anecdote.
Okay, now I realize that the TH400 is a completely different tranny, but for simplicity sake, I didn't think he cared to hear of the difference in gear trains between the two. In lay-man's terms, it is simply a beefed up TH350, with the same amount of gears, similar ratios, the only difference being that a TH400 can handle more power, but of course is also the less efficient of the two.

Either way, it's good to know there's someone in here with a lot more tranny knowledge than I have.