Does anyone know what the torque capacity of the auto tranny that was used in the 1987 vettes. If anyone knows what the torque capacity of the manual tranny used in 87's that would also be great. I am afraid i am gunna over build my motor and blow the tranny. Oh yeah and if anyone knows if there is some kind of feature that protects from these happening (i.e. u-joints break before tranny gets over loaded with power) or if they know of a site that could provide me with information on building higher capacity trannys it would be much appreciated. Thanks

 

Stock 700R4's will start slipping at 370-400 lb/ft of torque which is almost what the motor makes stock (about 350-360)...Add to that equation sticky tires and you have a recipe for a failing 700. However, a properly built one (Art Carr, Mike Kurtz, Yank, etc) will hold 500 lb/ft or better. The trick is getting the tranny to hold up under extreme line pressure. As for the rest of the driveline; the Dana 36 rear that was standard on all auto Vettes has always been viewed as somewhat of a glassjaw. When you plug a powerful motor and drag slicks into the D36 it tends to break. However, there are some coming solutions...My company (sorry for the advertisement) is currently doing some R&D with the D36 in the hopes of strengthening it enough to withstand the abuse associated with drag racing. We will be cryo treating the entire assembly, installing billet caps and studs, as well as building chromoly halfshafts and adding preload studs to the rear cover. Testing will actually be done on my 550+ hp stick shift Vette in the hopes that if it can withstand stick launches on slicks it can surely take the hit of the less abusive auto. Work should be finished in about 90 days and pricing should be less than swapping over to the stronger D44...I'll keep everyone posted on the development.
-Jeb Burnett

 

There's nothing you can do to a 700r4 to make it hold up. Anyone who tells you differently is a snake oil salesman... Just ask how many people have blown up an Art Carr "bulletproof" tranny... Your best bet is to convert to a M6, or do a Th350/400 conversion. If you're willing to lose the overdrive, I've heard that you can make an adaptor plate for the C beam fairly easily. At that point, you just have to lengthen the driveline.

 

Mojo does have somewhat of a point here... The TH350/400 trannys are much stronger, particularly when built properly. But to say there's no way a 700R4 will survive is a little foolish. I, too, have grenaded an Art Carr 700... A 250 shot of N20 on top of a 482" big block in a 3400lb car will definitely do that. But I've also seen built 700's running in the 9's in the 1/4 and living...So to say it "can't be done" is a little bit of a falsehood... If you want the ultimate in OD trannys though I would suggest looking at the massive 4L80E or do what Mojo suggested and switch to a Th350/400 and add a Gear Vendors overdrive to it!!
-Jeb Burnett

 

Here's another vote for canning the 700r4 and doing the th400/Gear Vendors! My car should be driveable soon with this setup. Reports to follow (I hope). You can check my web site for the page on the tranny conversion, with pictures and everything, hahahahaha.

 

I recently asked the same question, seems that you could make one hold up but it would fail eventually. 700R4 will barely handle what they put in it stock, so i think i might convert to ZF6 or get something made from Gear Vendors.

 

I have a 91 Corvette 700r4 in my pickup behind a Olds 425 (435 HP 510lb/ft at the flywheel). I keep blowing up 700's about once every 12 - 18 months. 400's lasted a little longer and were cheaper. They didn't have the first gear launch or the overdrive though. What usually fails is the primary clutch. Even though they are built to the hilt with hardened parts, HD clutches, valve body work...the list goes on. The problem is the torque curve of the motor and the weight of the vehicle. A light car with top end power and torque will probably survive. A heavy car (or truck in my case) with lots of low end torque will break stuff. So get it built as tough as possible lighten the load, and only give it power after the car is moving or keep rebuilding trannies. Even a ZF6 (early design) is only rated for 450 lb/ft of touque. Too much power to a ZF6 will break things too.

Cubic inches brings cubic power but costs cubic money. As seen in the equation, in³=HP³=$³ :yesnod: ³

 

GM rates the 700R4 at 360ft-lbs of torque.

Most of the high performance off the shelf 700R4 aren't much more than a stock rebuild with a few extra parts. In Syclone and Typhoons, there are AWD trucks with 600-700ft-lb of torque running 700R4. Built 700r4 aren't cheap though either.