i have a th350 and realllllly! need an overdrive trans was there an overdrive avaliable in the 1981 chevy 4x4s.

 

I'd imagine a 700R4 would bolt right on, but I'm not posotive. Why do you want overdrive?

 

Yes indeed a 700R4 can be used. You will need a different drive shaft though. They are easy to find or you could have one made. Yours could even be shortened if you have a competent shop near you. It will definitely help with the gas mileage!

 

Thanks for replying! i drove it to work round trip 67 miles and it drank over a half a tank of gas

 

is there a certain year 700r4 i should look for

 

Yeah that ain't right. I can get over 500 miles on my 34 gallon tank with a Throttle body 350, no cats, and a 700R4. I think that any year 700R4 up til 86 will fit, which is when they made the switch to throttle body injection. I'm not sure what kind of impact that had on tranny compatability, but someone should know... so all I can tell you is that any 700R4 from 78-87 will fit for sure, and possibly others

 

There are a couple other things that might cause poor mileage...how big is your carb, what gear are you running, is the motor tuned and running properly, etc?Those trucks with single tanks and shortbed only have about 15 gallon tanks. Is yours a shortbed? I used to have a 2 wheel drive shortbed with a nasty little motor and it wouldn't go far on a single tank either. Overdrive will definitley help, but maybe look at the other less expensive options first (tuning and carb size). Alot of guys think BIG carb means BIG power and they put a 750 double pump on an otherwise stock motor and just drown it. I am just guessing here...let us know what your set-up is. Good Luck!

 

set up is stock rebuilt 305 with a qaudrajet other than edelbrock performer intake and it has stock gears with 35s. Plans are for new motor and trans hopefully a 400sb and new gears and lockers front and rear. Trucks going to be built to cruise around town and take to pipelines on the weekends for fun.But I dont want to have carry extra cans of gas every where I go.