th200 to 200-4R

[buzz77]

Hey guys,

Need some tech knowledge. My 79 GP with the 301 v8 has the th200 3 speed transmission. Just installed a posi with 3.43 gears. Of course now I can definitely use an overdrive gear. Looking at the 200-4R transmission seems to be a direct bolt on. My questions:

1.Will the stock crossmember work or will I need to replace it?

2.Will the TV cable be easy to properly install?

3. What happens if I don't install a torque converter lock up adaptor?

4. Will the driveshaft length need to be modified?

5. Up to how much power can a 200-4R accommodate? I will want to do a mild build (350hp-400hp tops) in the future will this transmission handle a sbc 350 or possibly even a Pontiac 400 with that power?

I know a lot of questions, thanks!

 

[MeanBuicks]

1. You'll likely need a crossmember and may even need to add different provisions to the frame since '79 vehicles never had a 2004R. Someone who's done this conversion on an earlier car can chime in.
2. TV cable will be a direct transfer from one to the other.
3. If you're going to do a lot of highway driving, not using the lock-up will result in some excess slippage/heat and a tick less economy. Either way, run a good transmission cooler.
4. Existing driveshaft will go right in the 2004R. Both transmissions are the same length and use the same output spline.
5. It'll handle as much as you can spend. For 400 hp a competent rebuild that includes a bigger intermediate servo, larger TV boost valve, hardened stator support, valve body kit and high quality frictions will suffice. Going beyond that point, upgraded internal hardparts would be recommended.

 

[buzz77]

Thanks. The crossmember has me a bit baffled. Can it simply be relocated a few inches further down with new holes drilled into the frame.

 

[Longroof79]

To effectively move your current X-member back a few inches, you may need frame extensions on both sides. My friend is facing the same dilemma. He's putting a 200-4R in his Cutlass wagon and has a double hump X-member that he doesn't want to give up.
From what I can tell, you'll run out of frame rail on the passenger side as well. My friend is going to add frame extensions on both sides.

 

[V8 Rumble]

you can get the crossmember with the frame extension from summit. http://www.summitracing.com/parts/sum-7 ... grand-prix