Turbo 350 to 700r4 what’s involved

[jkk]

Hey Guys
Looking to put a 700r4 in my 80 swb will the stock driveshaft work cross member etc?
Tips and tricks please
Thanks

[Palf70Step]

It might be close. Normally I think the T350 is a shorter transmission, but most squarebodies use the medium or long tail housing. I am pretty sure the 700R4 uses the same front yoke as the T400, so that would need to change at least. Again not absolute on the length thing, but I think you will need to find (or have made) a shorter driveshaft

[Ziegelsteinfaust]

Trucks use the 9" shaft housing usually in my experience. So it should work fine if your not lifted with a stock shaft.

You will need to lengthen the driveshaft if you have a 12" tail shaft, and move the cross member back to compensate.

This web site has lots of info.

https://www.monstertransmission.com/...l#.XOV5brdlA0O

[dagnabbitt]

I'm doing exactly this to my 81 next week or so, I will let you know.

[kidatheart]

There Is an article in the latest Classic Trucks magazine that goes through step-by-step installing one in a 71.

[rpmerf]

This comes from the research on swapping in my 70. Not sure how much is relevant for the 80.

I've always heard the TH350 was typically 3" shorter, which means you will need to shorten your driveshaft.

Crossmember - The mounting point on the 700R4 is further back. You can move your stock crosssmember back and redrill the holes.

You will need linkage - the TV cable. Bowtie overdrives sells kits. Don't play around here. If the TV cable isn't set correctly, you will destroy your transmission in a mile.
http://www.bowtieoverdrives.com/cata...AT&CATID=WA3A4

If you want to use the lockup torque converter option, you will need a kit to activate it.

I don't think you can use the same torque converter between a TH350 and 700R4.

[Jake Wade]

My '85 came with a TH350C (lock up). Other than setting up the TV cable correctly, All I had to do was slide the crossmember back. Original driveshaft worked.

[Axle]

I went the other way years ago in my '83 (700r4 to th350. And I'd do it again in a heartbeat).
Same yoke is used with the th350 & 700r4.
Your crossmember will need to be moved closer to the engine (approx 2 or 3", don't remember, and it really doesn't matter, bolt the trans to the engine and the crossmember to the trans; drill new holes).
If your th350 has a 9" tailshaft, you can reuse your driveshaft. If its a shorter tailshaft you will need a longer driveshaft.
You'll want to take a good stab at what speedo gears you'll need. Most 700r4's I've seen use the th400 style large diameter bullet driven gear, the speedo drive gear is interchangeable.
Check if there is an oil slinger (metal cup) on the output shaft (you'll know it if you have it when you pull the tailshaft to count the speedo drive gear teeth if its already got a gear installed. If it doesn't have a slinger, clean the vent hole in the yoke and plug it with silicone otherwise you'll leak trans fluid out the yoke.
The rest will be 700r4 related bits 'n pieces. And you have already checked into the geometry of putting the tv cable attachment point in the correct location on the throttle arm? Its not the same as the kickdown location on a th350, you can safely put a th350 kickdown in place of the 700r4 tv cable attachment point, not so much the other way. Never, ever drive the truck if the tv cable is disconnected. Never. Or you'll be removing the trans shortly afterward.

[dagnabbitt]

Got mine back from the shop today, with the new 700r4.

Surprisingly I did not need a new driveshaft, it fit together perfectly. The 350 with lock up was original - and went in the garbage - and the truck was originally a six cylinder. Not sure if that is relevant.