TH350 to 200R4 coversion

[dedub]

I have an 80 Elky I want to put a bullet proof 200r I had built. My question is what kind of mods will I have to do. It has a 383 with a TH 350 now with a GN rear end. The rear end swap made me cut the drive shaft about 7/16. I'm clueless as to whether or not I can use my original cross member (which has be modded for true duel exhaust), if I'll have to buy some type of after market one or if Ill have to cut the shaft again or maybe even lengthen it? Has anyone got any experience in doing what I want to do?

Thanks.

 

[Blake442]

You won't need to cut your driveshaft again.

You will however either need to modify, or replace your crossmember.

If you're going to use a lock-up torque converter, you'll need to wire up a controller for that as well.

Make sure you set up the TV cable properly. That trans couldn't have been cheap, it'd be a shame to damage it.

 

[dedub]

Thanks Blake,
I'm looking forward to that lower 1st gear and an overdrive. I understand I'll need a new crossmember, does anyone know where this transmission will sit? I'm going to take a guess and say the mount will be much farther back than the TH-350. Is there a kit that someone sells or maybe a bone-yard crossmember I can look to pull from another car that will fit the G-Body?

 

[blk74nova]

The mount does sit back farther. I have used an iceman crossmember (up 4 sale lol) and they are really good.Since your elky is an 80 you will need frame extensions also. Summit racing has crossmembers and extensions as does Iceman and probably a few others. Most 84 and up gbodies came with the 200r4(4r) so any one of those should work, but youll still need the frame extensions.

 

[dedub]

I checked out the iceman website and I think I'm getting closer. I spent a considerable amount of time cutting, fabing and welding the X member I have now for the duel exhaust. Why isn't it possible to just slide the older X member back and drill new holes? Is it that far off? Does the frame have some kind of obstruction to prevent it from sliding back?
edit...
I think I answered my question.... My guess is that I'll need the frame extensions regardless and could probably use the x member I have now. (I think)

 

[BrownGP83]

I dont think you can use your original crossmember even if you slide it back. It will throw the transmission mount off to one side.

 

[blk74nova]

The drivers side of the frame doesnt go back far enough to bolt the crossmember to it. If your welding and fab skills are up to it, you might get away with the original or grab one from the boneyard and weld in the hump you have already made. Or make a new one up. I have the old style iceman crossmember which is the one summit racing sells now, they are different than what he has on website. The frame extension could probably be fabbed up too.

 

[78PontiacGP]

What!,Why did you cut the driveshaft for?

 

[Blake442]

What!,Why did you cut the driveshaft for?

The 8.5" rear end requires you cut an inch out of the driveshaft.

 

[dedub]

That is true. If you go from a 7.5 open diff. (peg leg) to an 8.5 limited slip (posi) you will have to cut. I don't remember how much exactly I cut but I measured and scribed lines on mine and then brought it to a shop and had it done. Worked out great. As stated before I was nervous about having one too short if I went to the 200r but from what folks say I won't have to cut... or add..