700r4 with 4.56 gears and 35s

[Thegoose74]

Just wondering if anybody has this combo and what they think if. I currently have a turbo 350 that needs rebuilt behind a stock crate 350 so I am considering the swap this in in a 1970 jimmy that will see mostly street use.

Thanks

Jason

[special-K]

I have run that combination and it's a good one. I'd think you would like it better than with TH350.

[Jcfcamaro]

Following thread as I'm getting ready to do the same. What RPMs are you running?? I've read where the 700r4 has a really low first gear so you don't wanna go too low of a gear with the axles but you don't want it shifting in and out of overdrive either.

[Thegoose74]

Thanks for the reply. I'll be starting the swap shortly among other things on the to do list for this rig. Heres a couple pics

This is a great site. I've learned a ton from it and will continue to do so.

[4oldcars]

I changed a 350 for a 700R4 in my 71 Jimmy. Would never do it again. I'd rebuild the 350. Just sayin - - -

[truckster]

Originally Posted by 4oldcars

I changed a 350 for a 700R4 in my 71 Jimmy. Would never do it again. I'd rebuild the 350. Just sayin - - -

This needs a because...

[kwmech]

I'd have to agree with ^^^. Every 700 I've used--built or stock--just flat does not last and continue to be reliable. You want overdrive, step up to a gear vendor or a 4L80. The 700 should have been left in the cars

[57taskforce]

Originally Posted by kwmech

I'd have to agree with ^^^. Every 700 I've used--built or stock--just flat does not last and continue to be reliable. You want overdrive, step up to a gear vendor or a 4L80. The 700 should have been left in the cars

Bingo... the 700r can be built to live in a truck but correct gearing is crucial for there longevity. The 80e is the way I'd go if it were me. They hold up to big block power and big tires both at the same time.

[special-K]

Funny how some say the 700r4 is no good/won't hold up, then there are those who beat the tar out of them and they take it all. I've only had the one and my buddy's is only one example. I've always been fine with the TH350s. Had nothing but good service out of them.

I didn't beat the tar out of it, but my '85 Jimmy diesel with 35s/4.10 posi had one I planned to change out with a 4L80E/NP241 combo I had from the same 3/4t Suburban the axles came from. Once I drove it with original transmission I saw no need to swap until it failed...which it never did. I hauled the trailer with it a good bit, so I did work it.

Then there's my buddy Jason's '85 K10 305/700r4/NP208 tow pig he swapped 3.73 1t rears with 4 wheel disc. lockers, and winch on to. He dragged stuff out of the woods and from up and down the East Coast with that thing. He wheeled it, broke the Dana60 axle, but never hurt the 700r4. He overloaded that trailer many times...and it's a heavy duty trailer. He used it like a 1t even though the frame was 1/2t. That's why the frame broke. Still that 700r4 took it all. He also built a healthy 350 w/TPI for it. I gave him that 4L80E/NP241 combo for it but he never bothered installing it before he ended up selling it. He now uses a '14 K2500 Duramax/Allison for the same work he asked of that '85 with wimpy trans. He used it a long time stock, axles, 10.50/31s, rallyes. He rode that truck hard and put it away wet. Never touched the transmission.