tranny swap problems *HELP*
 

i have an 86 Chevy reg cab long box with a th350 tranny in it, im swapping it out for a 91 th700r4. the issue i am having is that the 700r4 has a short tail shaft and the 350 has a long. it is a lengthy process to have them switched out so my thinking was to get a drive shaft from a reg cab sort box truck that's post 88 (short tail tranny) . is my thinking correct ? one other issue is that the 700r4 is an electric speedometer. can i just call my local tranny shop to get all the pieces to switch is to a mechanical ? what do i all need to do so?

thanks !!

Re: tranny swap problems *HELP*
 

A 700R4 & a Long tail TH350 are about the same length.

Re: tranny swap problems *HELP*
 

I just swapped my th350, for a 700r4 and used the same drive shaft, it fit fine. I had to re-drill the crossmember holes, but that's it, you shouldn't have to change shafts. I thought the same thing before the swap, but guess I was wrong.
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Re: tranny swap problems *HELP*
 

Sorry, just looked at your post again, and noticed it said long bed, don't know if it makes a difference, but mine is a short-wide.
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Re: tranny swap problems *HELP*
 

I think the differe4nce is about "1/2 inch." With the 700R4. I just did the opposite swap which is why I say. I took out my burned up 700r4 and replaced with a turbo 350.

Re: tranny swap problems *HELP*
 

I did the same swap on a short bed, no issue with drives haft. Had to move cross member though.
Only trouble is now I have to find the right speedo gears for the trans because the newer trans is setup for electric speedometer.

Also make sure you get your throttle valve cable setup right or you will burn up that trans in no time.

Re: tranny swap problems *HELP*
 

A long shaft 350 and a 700 R4 are about the same length. I used my stock length driveshaft when I install a 700R4 in my 1974 SWB

Re: tranny swap problems *HELP*
 

That acctually brings me to my next question ! it has an electronic speedo sensor , how do i go about changinging this?
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Re: tranny swap problems *HELP*
 

That I can't help you with my 700r4 was the same hook up as the th350. The good thing about this forum is somebody knows how, hopefully they will be kind enough to share the info with you. Good luck with the truck. Hope my info helped you
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Re: tranny swap problems *HELP*
 

Same problem myself, there are speedo gear housings on epay, the gear that goes on the output shaft is the same diameter so might work if the ratio is right.
I had to cut the gear off the ouput shaft of the newer 700r4.
There is a clip that holds the plastic gear on the output shaft, you should be able to get it off your 350 trans.
Trouble I ran into is the speedo gear housing on my th350 is only about an inch big and the 700r4 is about a inch and a half.

Re: tranny swap problems *HELP*
 

These two pages can help as well http://www.bowtieoverdrives.com/cata....php?ITEMID=14 and http://www.transmissioncenter.net/sp...n_______va.htm

The second one there has a nice little conversion chart to look at for choosing the drive/driven gears too.

Re: tranny swap problems *HELP*
 

Excellent link thanks bnoon

Re: tranny swap problems *HELP*
 

No problem. I've been researching the crap out of the 700R4 swaps to try to decide if I want to do it or not. Decided to do it now, but now the decision to actually buy is held up by the upcoming holidays. Never enough money, never enough time.

Re: tranny swap problems *HELP*
 

Depending on the tranny you got now, maybe you.could find someone to trade
I had a 4l60e that was no use to me because it was to new for my 86. I put it on Craigslist for sale but put I would trade for.a 700r4, it wasn't five minutes later a guy called with a 700 who had a late 90s model and his 4l60 had just went out and needed one. I never been happier with my 700 r4. Like it way better than the th350, what im trying to say is you never know who has what, you may find a sweet deal. Good luck with it.
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Re: tranny swap problems *HELP*
 

I did the swap in my LWB and had no issue. You should be able to find everything for around 1000-1200 if you know what you're looking for. That includes the TV cable system and converter. I also just moved my crossmember back and have had no issues. Oh wait, yes I have. I dont fill it up with gas nearly as much.:metal:

Re: tranny swap problems *HELP*
 

Yeah that would work, but I have to be able to drive my truck. The most I can hope for is to buy one and do the swap, then sell the 350 trans. I have plenty more to do before I start buying parts anyway. The garage shelves are still full of parts that want to find their way into the truck LOL. The hardest one to avoid is the 6.0L with LS3 heads sitting in the corner just waiting for a project to jump into. :metal: But... that one's going in something much more special.

Re: tranny swap problems *HELP*
 

Right on I understand that. I had a brand new crate motor and a 700r4 sitting in my garage for almost 2 months before I could put it in. Didn't know it was your dd. Things will work out for you, they always find a way to. Good luck to you.
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