Transmission Swap Question

[GTSideSwipe]

Hi. So I have a question regarding swapping out my turbo 400 on my C20. It's the original 400 with a two piece drive shaft. I am wondering if there are any overdrive transmissions that would work so I wouldn't have to do anything like cutting the drive shaft.

[EARNHARDT#3]

What length tail shaft do you have? If it's 4" then the 2004r and 700r4 are pretty close.

[GTSideSwipe]

Originally Posted by EARNHARDT#3

What length tail shaft do you have? If it's 4" then the 2004r and 700r4 are pretty close.

I'm not sure which tail I have but I will be able to check on Monday. I have a 700R4 tranny that is laying around in my garage so I was thinking about swapping in to lower the rpm a bit especially at freeway speeds but just am not sure.

Thanks for the info.

[57larry]

is the drive shaft yoke the same on a 400 & 700R4?

[GTSideSwipe]

Originally Posted by 57larry

is the drive shaft yoke the same on a 400 & 700R4?

No. You will have to use a different yoke. It looks like the 700R4 4L60E TH350 are the same but the 400 is different.

[hugger6933]

If you use you3/4 ton like a 3/4 ton, you want to look into the 4L80E trans but here is the downside, it has to have its own controller. Those can run you in the $300 to up on the controller and each do nothing without it. I 4L80E is built stronger from the factory than a 700R4 that has been Modded to some small degree but can take plenty abuse.
So if hauling or towing get the 4L80E. Lots of drive line places can do a drive shaft using what you have for less than a hundred bucks, Jim

[Clavo106]

Originally Posted by EARNHARDT#3

What length tail shaft do you have? If it's 4" then the 2004r and 700r4 are pretty close.

thank for sharing that picture. makes mock ups more easier.

[Jrainman]

Originally Posted by hugger6933

If you use you3/4 ton like a 3/4 ton, you want to look into the 4L80E trans but here is the downside, it has to have its own controller. Those can run you in the $300 to up on the controller and each do nothing without it. I 4L80E is built stronger from the factory than a 700R4 that has been Modded to some small degree but can take plenty abuse.
So if hauling or towing get the 4L80E. Lots of drive line places can do a drive shaft using what you have for less than a hundred bucks, Jim

I agree here with Hugger , also with the 700R4 you will have to add kick down linkage , the TH400 is a strong trans that's why its in your truck and has been for over 40 + years

if its just fuel economy your after have you thought about changing your diff gear ratio . you could gain a couple MPG and even more depending on your drop in ratio.