The Stovebolt Site Forums The Shop Area Engine Shop Replace a TH350 with a 700R4?

The truck is a '71 C-10 that was a 350/3 speed std and is now a 350/TH350. I'd like to pick up an overdrive auto for the highway. I am really new to automatics, so Is this a good idea? Will the 700R4 stand up behind the 350? I am likely to stand on it once in a while. What is involved in the swap? Suggestions for other trannys, etc.
Any other thoughts on this? Thanks in advance for any help.

The answer to standing up is yes and no. Early 700R4's that were not from a Corvette had fairly low torque handling ability. Later ones were much stronger or you can have an early one updated with the beefier parts. If price isn't a factor then Phoenix has ones that handle a lot of power. The MOST important thing is to have someone that really knows his business set the adjustment on the TV cable or it won't last till the sun sets.

The 700R4 will bolt up to your small block v-8. You'll have to move the trans crossmember back a few inches and drill new holes to bolt it down. I moved it back out of the way and then slid it forward after I had the trans bolted to the engine. The column linkage will work fine with a little tweaking of the arm at the trans. You'll have to have the driveshaft shortened, but if you have it done at the same time as replacing the center bearing and u-joints, the cost won't really show up. The TV cable hookup, speedo gearing, and converter lockup are all previously solved problems. See www.bowtieoverdrives.com as an example. As an added bonus, TCI makes a replacement valve body that protects the trans from bad TV cable adjustment (link).

Mine in my 69 C-10 has been going for 80K miles so far.

regards,
Leon

If I remember well, after 1988 are better trans. You will need a way to connect your speedo cable: the post '88 use an electric speedo; get the tailshaft housing from an older trans, with a speedo drive, easy to swap. You can also change the speedo gears so your speedo is accurate. If you buy from a junkyard, make sure you get the TV cable and all related brackets, it will help a lot!
This company http://www.transmissioncenter.net/speedometer_calibration_______va.htm
has a lot of stuff!
You need a kit so the converter will lock up, this is necessary for the health of the trans! Bowtie overdrive has that.
TH700R4 is a good choice, giving you a shorter 1st and overdrive, improved driveability! You may have to change your rear end ratio for the best result.
QUite common to modify them, or you can buy an aftermarket already modified.

Thanks gentlemen! A few more questions, if I may. What is the 700R4 found in OEM? My 350 engine has an aftermarket intake and a 600 Holley, where will I find TV cable hook-up info for that combo?
The truck also has a "B&M" shifter in the floor. It has to go, one way or another. since I already have a column without any linkage for the auto, etc, what is my better route auto column or floor shifter?

Thanks, Les

Most GM rear drive vehicles staring about 1984 until it was supersceded by the 4L60 (which is really the same transmission) in the 90's and the 4L60e which is similar but requires a computer to shift.

You don't want a transmission that was behind a V-6. The smaller V-6 has a different bell housing pattern than your 350 and the stronger parts may not be in one from a larger V-6.

If you get one from a four-wheel-drive you'll need to change the output shaft and tail shaft to a two-wheel-drive type.

If you get one from a Corvette you'll have to change the tail shaft to one with a conventional mount pad.

Roadmarks, Bowtie overdrives sells a kit that will adapt a 700R4 to work with a Holley, it works well. I have one on my 86 Chevy K/10 4x4 Pickup with a 454 & Holley truck Avenger carb.. I put the kit in about 5 years ago & havent had a problem since.
They also sell the kit to make the lock up converter work.

The whole secret of the 700R4, is the way the TV Cable is set up.
If it is not correct, it will wipe out the transmission. I found that out after the 2nd rebuild.

Check out Bowtie Overdrives article on their website called TV Made easy. It explains the TV system & how it works, it's very informative.

Can you put a new valve body in with the tranny in the truck?

Do you mean replace a valve body, yes you can replace them if they need to be replaced.

I have the TCI Constant Pressure Valve body in my '49's 700r4 , I can play with the adjustments of the tv cable and not worry about burning it up . I set it to chirp the tires at second gear with a little extra throttle when the wheather is ok and back it off for winter driving conditions .

Wow, that sounds like an even better solution... I like it!
i remember when the 700R4 came out back in 83 or 84, they had a lot of problems with them. mostly because the TV cables wern't set up correctly at the factory. they are actually a great transmission.

Hey Guys, Many thanks, good information and good ideas! So a full sized V-8 car or V-8 pickup will be a good candidate from say '85 up til about '90? Well, I have other things to do for a while, yet.

Thanks again,

Les