700R4, which donor car & what gears

[az's1971C10]

Hey guys,
If you could pick a donor vehicle for a 700R4 swap what vehicle would you choose and what gear ratio??

I have a 71 SWB with a 350 mated to a Saginaw 4 speed with 3.08 gears. I plan to do a swap next spring/summer after my daughter learns to drive the 4 speed. It's going to be her truck when she turns 16.

Thanks for your help.

[passthebuck]

87 to 92 are best & I tried, despite all the warnings here, to run a 3.08 rear gear. It it ended up being too tall a rear gear with my 29" tires & I ended up having to change it to a 3.73.

[leftybass209]

88 and up had some GM improvements. If you are getting a rebuild the year won't matter. 3.73s are great. 3.30s and 3.90s will also work but I have heard complaints of 3.30s borderline too tall.

[hugger6933]

88-93 C trucks and the Roadmasters and Caprice with the tbi engine[by the time they went to the LT1 it was a 4l60E and You don't want to open that can of worm about he electric stuff for the shifting. As far as the gears go one of my favs that has not been brought up is the best of both worlds [or so it has been called that at times by several people] is the 3:42 gear. It is still low enough to get the heavy truck moving yet high enough to let the truck throttle back some on the open road. Good luck and I hope you and your daughter enjoy your time together and the truck. Jim

[az's1971C10]

Thanks for the info gentleman.

[Rascal_one2001]

The 87 -93 700r4 is the best since it runs an auxiliary valve body and has better designed valve body. If you get one with electronic speedo you can just cut off the metal reluctor wheel and the holes to mount cable drive gears are under it. 3.73 gears will still let you cruise at 65.

[Already Gone]

Originally Posted by hugger6933

88-93 C trucks and the Roadmasters and Caprice with the tbi engine[by the time they went to the LT1 it was a 4l60E and You don't want to open that can of worm about he electric stuff for the shifting. As far as the gears go one of my favs that has not been brought up is the best of both worlds [or so it has been called that at times by several people] is the 3:42 gear. It is still low enough to get the heavy truck moving yet high enough to let the truck throttle back some on the open road. Good luck and I hope you and your daughter enjoy your time together and the truck. Jim

Ive been checking this out for years and I agree if you want the best of both worlds, city and highway driving and an occasional stoplight blast a 700R4 with 3:42's and a 27 to 29 inch overall tire height should do it for you.

[PanelDeland]

Originally Posted by hugger6933

88-93 C trucks and the Roadmasters and Caprice with the tbi engine[by the time they went to the LT1 it was a 4l60E and You don't want to open that can of worm about he electric stuff for the shifting. As far as the gears go one of my favs that has not been brought up is the best of both worlds [or so it has been called that at times by several people] is the 3:42 gear. It is still low enough to get the heavy truck moving yet high enough to let the truck throttle back some on the open road. Good luck and I hope you and your daughter enjoy your time together and the truck. Jim

I have to agree with the 3:42 gear,though the 3:73 is great also.The 3:42 was the go to gear ratio for GM with this tranny so I'm sure the engineers were close.

[Tachout]

I have seen several different sugestions of trans and what it comes out of. Just wondering why no one has sugested the 700R4 out of the Corvette. I have a Pair of 90 Corvettes that both came with the 700R4. Is there something wrong with that trans?

[WIDESIDE72]

Originally Posted by Tachout

I have seen several different sugestions of trans and what it comes out of. Just wondering why no one has sugested the 700R4 out of the Corvette. I have a Pair of 90 Corvettes that both came with the 700R4. Is there something wrong with that trans?

Great donor but few and far between. I believe they also only had an electronic speedo. Any 700r4 can be upgrded to vette specs at time of rebuild.

[Tachout]

The electronic speedo is easy to work around. If any of you are working with C4 corvette parts or want to source parts let me know. The National Corvette Forum is a great place to source parts.

[az's1971C10]

Thanks for the great info from everyone. I now know what to look for.
Cheers

[slow-1]

Just to throw a curve at you...I am running 3.08 gears with my 700r4 and am happy with them. But I've never had other gears in the truck so nothing to compare it to.

You could always try it first...unless you are having to change the gears anyway.

Don't know how tall my tires are, maybe that's the difference...they are 255/70/15's.

[Already Gone]

Originally Posted by slow-1

Just to throw a curve at you...I am running 3.08 gears with my 700r4 and am happy with them. But I've never had other gears in the truck so nothing to compare it to.

You could always try it first...unless you are having to change the gears anyway.

Don't know how tall my tires are, maybe that's the difference...they are 255/70/15's.

Your tires are 29.4 inches high. Some board members have said they were/are not happy with 3:08's and 700r4's cause you dont rev very high at highway speeds and even when you climb a slight grade you drop a gear sometimes 2. My 99 Tahoe 4 x 2 with a 350, 4l60 and 3:08's is a great combo for power and gas mileage.

[powell72]

I ran 3.73's behind my 700R4 for years with a 28" tall tire. If I did it over I'd run 3.42's.