What Chevy auto trans to swap in place of my 3-speed?

[madmax087]

Here is the deal gents: I'm looking to replace my 3-speed (I think a T-156? Not positive) manual with a GM automatic, either 3- or 4-speed. Overdrive would be cool because sometimes Green Thunder sees the freeway, and 3k RPM is obnoxious. As I have no real-world experience in this, I have come to ask your advice!!

First, which to use? Turbo 350? 700R4? Anyone with experience, please chime in!!

Second, What will the swap take? A (few) new driveshafts? New Transfer Case ?

Like I said, I have just about zero experience with swapping a tranny, so any knowledge I can gain from others' mistakes and/or triumphs will be great. Thanks in advance guys.

 

[Old Dog]

I like my TH350 but no Overdrive is a pain sometimes.
The 700R4 is tricky to get the front driveshaft to fit sometimes.
Yes you probably will need new driveshafts. Even with the 350 you need a skinny shaft to miss the pan.
You will also need an adapter from the Transmission to the tc. check out Novac or advance adapters.

 

[madmax087]

Very cool, thanks for the info.

What tranny would you go to if you were going to swap to something with OD?

 

[Old Dog]

Not sure, I'm happy with my 350 but I don't do any freeway driving with mine, mostly side roads 55mph at most and trails.
I have a buddy with the 700R4 in a CJ8 , he had to mod. his tranny pan to make his driveshaft fit, but he's happy with it.

 

[Incommando]

A 3spd auto like a TH350 or 400 is not going to change your highway RPM as,like your AMC 150 , top gear is 1:1 iirc. You need an O/D tranny like a 700R4 or 4L60/80. If you have an AMC to GM adapter or an AMC motor try an AW4

 

[cerberus75154]

I'm running into the problem of not enough space. I have a chevy 350 with a th350 tranny and theres only about 1 1/2 ft to the rear axle.I would like to add a Transfer Case but i dont think i will have room. Any suggestions?

 

[derf]

The relatively short wheelbase of the CJ limits what transmissions work well.

I'm running a 5.3 with a 4L60E (which is really a newer model 700R4). The 700R4/4L60 is a long Transmission front-to-back. I don't have my Transfer Case for it yet but the Dana 300 was going to be a tight fit for the front drive shaft and I was looking at having to run a 2 piece shaft to make it work the way I wanted. Also, I was looking at setting the Transmission mount lower to compensate for the spring over with a short driveshaft.

When I welded in the motor mounts for my engine, I put it as far forward as I could so I'd have room for the rear driveshaft. It ended up not being a huge problem because I ended up moving the rear axle back about 8 inches too. With the stock engine in the stock location and a 700R4 with a Dana 300 , you're looking at a pretty short rear driveshaft that doesn't like a lot of lift.

That being said, fitting a 700R4 isn't a terrible chore. You just have to plan it from the beginning to make sure you deal with the cramped quarters. The Overdrive gives you a much better axle gearing option and still lets you drive the Jeep down the freeway without blowing up the engine.

If you're really concerned about fitting everything, then the TH350 is the way to go with a GM engine. It's a nice and short Transmission that can handle a mild to moderate V8 just fine. It's easy to mount almost any Transfer Case to it.

For either, you may want to give thought to just using the GM version of the NP208 that came behind the TH350/700R4. Though you'd want to install a slip yoke eliminator to reduce the length of the Transfer Case . Either way, adapting a Dana 300 or using an NP208, you'll have a good combination.

 

[derf]

I'm running into the problem of not enough space. I have a chevy 350 with a th350 tranny and theres only about 1 1/2 ft to the rear axle.I would like to add a Transfer Case but i dont think i will have room. Any suggestions?

Move the engine forward as far as you can. It doesn't have to sit back against the firewall. The 74 has the long nose to accommodate the AMC 232 i6 /AMC 258 i6 / 4.2l , which is a much longer engine front-to-back than the Chevy V8. There's enough room for a 350/350 with a normal Transfer Case in a CJ5 if you build it the right way.

 

[cerberus75154]

Thanks for the info. I'm gonna have to redo the motor mounts anyway due to a very bad welding job so I guess I'll just move it up then. Thanks again.

 

[Incommando]

I'm running into the problem of not enough space. I have a chevy 350 with a th350 tranny and theres only about 1 1/2 ft to the rear axle.I would like to add a Transfer Case but i dont think i will have room. Any suggestions?

Most 2wd trannies ( it sounds like you are 2wd now) have a longer tail shaft. Often the 4wd version + a Transfer Case isn't much longer that the 2wd tranny alone. Unless you go with something like a 203 which is silly long.

 

[madmax087]

Good luck with swaps guys. This information no longer applies to me because my CJ7 was stolen last night, and found this morning burned down in the desert. A very sad day.

 

[Kane]

Good luck with swaps guys. This information no longer applies to me because my CJ7 was stolen last night, and found this morning burned down in the desert. A very sad day.

WHAT!!!! Damn man that is the last thing I would expect to here. Sorry about your loss of your Jeep.

 

[Old Dog]

Man that sucks. Did you have any insurance?

 

[madmax087]

Yeah it really sucks, that thing was so awesome. I had full coverage on it so I will be taken care of, just such a hassle with the police and insurance and all that BS. At least my hard top and doors werent on it at the time, so I can get some money back from the sale of that stuff.