NEED HELP NOW. trans swap

[85gpLE]

i have a 85 grand prix with a shot 200-4r, i am looking to swap it with a th-350 or a th-400. my question is... which should i use? also, the transmission's i'm looking at come from TCI, they have the auto/manual valve body. i am not sure what kind of torque converter i need. the ones that TCI sells have either wide, dual or small bolt patterns. I know dual is the BOP pattern, but which of the other two is the chevy? One last thing.... my GP has a stock 305, what am i looking for as far as stall speed is concerned? i don't understand it. does a stock TC have a stall speed? if not will it matter if i buy one with a stall speed since my engine is stock?
ANY AND ALL INFO IS APPRECIATED

 

[GP403]

You'll also need a new (well oldER) c-member to swap from the metric trans to a TH350. The mounts are in different locations. Unsure on driveshaft length difference.

I know the TH400 will need a different (shorter?) size though. And maybe a different mount location. (not sure!)

Stall speed if I understand it correctly is the RPM that will "lock up" the hydraulic clutch in the TC. A higher stall speed will cause the engine to rev higher before engaging the trans. If I understand it right that is.

Not sure on the wide vs. small, maybe the diff between a big block and small block flex plate? (Just guessing)

Good Luck! Sorry I can't give more info, auto trans'es are pretty much black-boxes to me

 

[85t5mcss]

Stock TC will be OK for a stock engine or even move up to a 2000 Stall.
X-Member will need changed. Just buy one for a 78-83 G-Body TH350.
The bolt pattern prob won't matter since most flexplates have the large and small bolt patterns. If u r reusing your flexplate then measure the bolt circle for the TC and give their Tech Line a call, they will be able to tell u which 1 u need.

BTW, easiest and crudest way to measure your stall speed, powerbrake it and when the engine wont rev anymore or pulls the car or spins tires u have found your stall speed. OE is about 15-1600RPM.

 

[robdman]

www.crossmembers.com for your crossmember as far as your q on stall speed it is when a converter reches full lock up this is different then flash speed flash is when the tc starts to move the car the stall and flash should be relitive to your power band i wouldnt recomend a hi stall speed with a stock 305 prob around 2000-2500 since your making your power from 2500 to 6000 this will flash around 1500-1800 not shocking the tires or giving you wiplash a turbo 350 is all you need with a 305 the 400 will slow you down since it was designed for a heaveir car with different gears and it weighs more a t350 well built will hold its own though about 500 hp a manual valve body if you dont mind shifting up and down all the time is fine a better idea is a valve body capable of full manual function in other words it shifts when you tell it to if you buying a tci unit this is a cheap option if your planning upgrades in the future (gear change ,motor ) then you need to do some more homework i think you would be better off with a bone yard turbo 350 and a slightly higher stall speed than stock with a mild shift kit it will do the job just fine save your money for that tci when you start making some power and i bet if you ask aroud you can get a bone yard turbo 350 for a hundred bucks maby cheaper and local trans shop to rebuild it if you like for short money i bet you can be in and out of the transmission for 600 including the converter call or better yet stop by a local trans shop and talk to the guys there bet youll be suprized at what they can do for you stay away from the chains like cottman they have set prices but the local guys might just have a t350 on the shelf ready to go good luck the swap isnst that bad to do

 

[N.O.S SS]

If you need the crossmember for the th-350,i have one out of a 84 monte ss,should bolt right in.Let me know and i`ll send you a pic.

 

[N.O.S SS]

Forgot.Your driveshaft will work.I swapped the same transmission`s in my monte.If your considering putting real dual exhaust on it eventually you might want to get the crossmember from jegs.

 

[mrapii]

You realize that going from a 4-speed auto to a 3-speed will cost you both performance and fuel mileage. Almost everyone with a G-Body that has a TH350 or similar trans wants to convert to a TH7004R or TH200R4. The only possible reason that you should consider a TH400 is if you have a very powerful engine and use the car primarily for drag racing.

 

[pontiacgp]

You realize that going from a 4-speed auto to a 3-speed will cost you both performance and fuel mileage. Almost everyone with a G-Body that has a TH350 or similar trans wants to convert to a TH7004R or TH200R4. The only possible reason that you should consider a TH400 is if you have a very powerful engine and use the car primarily for drag racing.

I agree with you, I have a 200 R4 that needs rebuilding so I have contacted a builder who builds them for Grand Nationals. I'll be getting a stage 1 that's good for up to 400 HP for $1,400.00...I was quoted $1,800 for a simmilar transmission from TCI. .This is the price in Canada so I'd be interested what it would cost you guys south of the border... :shock:

as far as the 700 goes I don't like the transmission due to the cliff you hit shifting from first to 2nd gear..

http://home.interlog.com/gnttype/index.htm