Hi , new to this site and have a few ? about th350 auto transmissions. putting one in a 48 2a behind a 355c.i. engine. should i get a electric lock up or non lockup.also want to install a new steering column. any ideas on what one to look for used. was thinking out of a small chevy blazer? thanks

As to the transmission, keep it simple and go with no-lock up.

Well...if your talking about the GM TH350....I think you will be hard pressed to get a lock up kit for it sence it does not have, never did, never will have a lockup converter. For that you will need the 700R or 4L60E.

The 350 is a 3 speed medium duty...the 400 is a 3 speed heavy duty. The 700R replaced both of those and has 4 speed + the lockup feature.

For what you want, the 350 is fine...small jeep....

For refereance...the lockup feature does have some advantages...first, it helps the tranny run cooler...second, the lockup is nice when you are going down rocks...makes it act just like a manual tranny.

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Well...if your talking about the GM TH350....I think you will be hard pressed to get a lock up kit for it sence it does not have, never did, never will have a lockup converter...

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Uh... yes, and no.

The classic TH350 was non lockup.

However, GM did produce the TH350c which is a lock up AT.

Often the terms, TH350 and TH350c are used interchangeably, though they should not be...

Lockups run hotter if you dont have them setup to lockup.
The TC doesnt have as much room inside for fluid because the clutch packs take up lots of room.

It would be a neat feature, to be able to lock it up on the trail and have compression braking, but I think you would find the crawl ratio is way too low. The first gear in the autos is rather pathetic, and uses the 2.2ish ratio from the TC to make it runable on the trail. When youo lock it up, your going direct drive... thats 1:1 and it will probably be too fast unless you have some crazy gearing elsewhere.


On the highway the lockup is great. It's like having 3,1/2 gears.. it just gives the transmission that little more umph at high speeds.

yes it's the GM TH350 and the GM TH350c that I am looking to install. need to keep everything as short as possible. so this is about the only two autos that will work. will be running dana 44's front and rear with 4.56 ratio ,35" tires