Th200 to th350

[MrSony]

Thanks for the clarification

Can you tell me how to identify a 200c
One that has or uses a lockup converter

They'll say METRIC on the pan, and DOESN'T have this little doodle on the side.
That doodle is the vacuum modulator that controls part throttle upshifts based on engine vacuum/load. Leave it unhooked, will shift high an bang into gear, 3rd probably wont even happen. As far as I am aware, every Th200 put in a 78-87 g body (last year for TH200) was a TH200c, and therefore uses a lockup converter. It will have a black(most of the time) female plug on the driver's side above the pan rail.

 

[Mike Geepers]

It's basically one of the easiest swaps you could do. The only thing easier would be swapping in another TH200.

Like Mr. Sony said, you'll need a vacuum line to run from the intake manifold to the vacuum modulator on the rear, right side of the transmission. You may also need a different bracket to hold the kick down cable. It is possible to run a TH350 without the kick down cable hooked up at all but if you do you'll have to manually down shift the transmission and then manually shift back up in situations like passing. Both my Monte Carlo and my Chevy truck have TH350's without the kick down cable hooked up. I'm used to driving them that way. Newer transmissions like the TH200, TH200-4R and 700R4 have a Throttle Valve (TV) cable instead of a kick down cable. You must have the cable hooked up and set correctly for proper transmission operation. Unhooking it or setting it improperly will result in burning up the transmission.



The TH200 is an entirely different transmission that uses a TV cable instead of a kick down cable and it doesn't have a vacuum modulator. The TH200 is weaker than the TH350. There was also a TH350C which has a lockup converter. It typically isn't used for performance applications.

If you run into any problems with the swap let us know. We'll try to help you sort them out.

It's basically one of the easiest swaps you could do. The only thing easier would be swapping in another TH200.

Like Mr. Sony said, you'll need a vacuum line to run from the intake manifold to the vacuum modulator on the rear, right side of the transmission. You may also need a different bracket to hold the kick down cable. It is possible to run a TH350 without the kick down cable hooked up at all but if you do you'll have to manually down shift the transmission and then manually shift back up in situations like passing. Both my Monte Carlo and my Chevy truck have TH350's without the kick down cable hooked up. I'm used to driving them that way. Newer transmissions like the TH200, TH200-4R and 700R4 have a Throttle Valve (TV) cable instead of a kick down cable. You must have the cable hooked up and set correctly for proper transmission operation. Unhooking it or setting it improperly will result in burning up the transmission.



The TH200 is an entirely different transmission that uses a TV cable instead of a kick down cable and it doesn't have a vacuum modulator. The TH200 is weaker than the TH350. There was also a TH350C which has a lockup converter. It typically isn't used for performance applications.

If you run into any problems with the swap let us know. We'll try to help you sort them out.

Thanks for the input, I've gathered all your info to form the best plan for R&I. I'll take pics and post along the way, ask questions if I run into any walls. Much appreciated

 

[AlBreland]

I too am contemplating a 350/350 swap for my 4.3/200 and have some of the same questions. What about the crossmember and the driveshaft. Is the yoke spline and length the same on the driveshaft. I want to collect everything I need before starting. I found a new crate 350/350 that a buddy has in a custom olds. He also has a 30 year old olds engine built (3o years ago) with tri carbs. Trying to convince him that engine would be period perfect in his 49 custom and he could sell me the 350/350. That would solve my smoking problem (embarassing as hell) and give me a better engine and trans. I've been told all the front accessories are the same. So I'll need a bigger radiator otherwise should be a straightforward swap....anybody know otherwise? Al PS This has got to be way simpler than an LSX engine transmission....I'll save that for the next project!

 

[Opie Knievel]

I too am contemplating a 350/350 swap for my 4.3/200 and have some of the same questions. What about the crossmember and the driveshaft. Is the yoke spline and length the same on the driveshaft. I want to collect everything I need before starting. I found a new crate 350/350 that a buddy has in a custom olds. He also has a 30 year old olds engine built (3o years ago) with tri carbs. Trying to convince him that engine would be period perfect in his 49 custom and he could sell me the 350/350. That would solve my smoking problem (embarassing as hell) and give me a better engine and trans. I've been told all the front accessories are the same. So I'll need a bigger radiator otherwise should be a straightforward swap....anybody know otherwise? Al PS This has got to be way simpler than an LSX engine transmission....I'll save that for the next project!

If you have a 4.3 and a TH200 I'm guessing you have an '86-'88 Monte Carlo. I have an '86 Monte that has the 4.3. I swapped in a TH350 a couple of years ago. I used my original driveshaft and crossmember. If you want the kick down cable you'll have to find or make a bracket for it. I still haven't done that. You'll also need a vacuum line for the vacuum modulator. It's a very easy, very straightforward swap.

To put in a 350 engine you'll need V8 motor mounts, a V8 sized radiator and fan shroud and the radiator hoses may be different. I'm not 100% sure about the radiator hoses. Another thing to consider is the fuel system. The TBI (Throttle Body Injection) system on the 4.3 runs 9-13 psi. If you're gonna use a TBI on the V8 you'll be fine. If you're gonna use a carburetor you'll need to get a fuel pressure regulator to keep the pressure around 4-5 psi. If you're gonna use a multi port set up that uses 50 psi or somewhere in that range you'll need a higher pressure pump.