jobber26

I just had my trans mechanic design & install a 1987 TH700R4 transmission with extra HD bands (esp. 2nd gear), and a 2200RPM stall speed converter in my 1976 Corvette C3. I have around 200 miles on it and 3rd & 4th gear have failed. Has anyone else had a similar experience with this transmission?

billschroeder5842

What do you mean by "design?"

These are usually pretty bullet proof transmissions. Since if failed (almost) immediately upon installation, my thought is that your mechanic rebuilt it wrong or some of the "design" items conflicted with the factory tolerances.

Take it back to your mechanic and call for a "do over!"

fishslayer143

or your T.V. cable linkage was not properly configured, and cable adjusted by pressure ..and the clutches burned due to lack of fluid pressure ... doesn t take long to fry one.. The 700r4 can be built to withstand big Horsepower , mine does......ask him for a DO-OVER like Bill said... BTW, when its installed properly, you will love it

jobber26

I am in the process of scheduling a return of the car; it's not easy to drive with just 1st & 2nd gear... late night is the time I can do it. The trans was designed inside to be built for a 550HP stroker motor with 3.90:1 gear ratio rear end; so basically Heavy Duty everything... I was hoping someone else might know what failed after 4-5 trips in the car and only getting down on it 2 or 3 times... I told the mechanic the car had extreme 500+ horsepower and I shift at 6500RPM... not uncommon for a street/strip car. When I had the TH350 in there I actually did dog the crap out of that trans without a problem and 40K+ miles...

jobber26

The man who built it is a drag racing veteran who has owned his own trans shop for 38+ years; I find it hard to believe he couldn't set the TV cable correctly...

jobber26

For the short period I had the TH700R4 installed I was still pulling 0-60mph at just over 3+ secs and the car didn't chirp 2nd gear... it spun out and fishtailed; pretty cool... I have done this about 1000 times in my old beefed up TH350, that the same mechanic built 10+ years ago...

7T1vette

He might know how to build the transmission internals to support that level of horsepower. But, does he know how to set up the linkage with the correct geometry and adjust the T.V. cable to have it work correctly?

BTW, if that cable is NOT set correctly, you will lose 3rd and 4th gears. Sounds to me like he wants you to think he knows what he's doing.

'nuff said...

fishslayer143

like I said...

gkull

For a high HP motor you need more stall and an efficient TC. i always recommend Precision industries vigilante 9.5 inch with mid 3000 stall.

I've run as high as 3800 stall behind my 434 small block and 3500 when i had 383 and 396 ci strokers

Look up setting a TV cable with a pressure gauge

96 lt-4

If he did all the work (build and install) then I hope he plans on covering all the expenses.Have him foot the tow bill back to the shop for that matter.

fishslayer143

If he is a professional builder , surely you got a WARRANTY?

akdale

Agree on the TV cable. Sounds like you had him do the conversion. What carb? Holley? The the adapter that corrects geometry was hopefully used.

What is the condition of the fluid? Burnt?

I agree with the other posts. If this was a turn key project, he should send a truck to come pick the car up. All you did was drive the car.......

jobber26

I just got the Corvette back and it looks like the "O" ring on the input shaft was torn in assembly, so this was replaced and so were 3rd and 4th gear clutch assemblies at no charge... Can't wait to get in and drive this weekend!!!

cv67

Somebody screwed up wasnt you upgrading

Edit:putting a GOOD quality good sized trans coolers on one of these is key in helping it live. Heat is their worst enemy esp the earlier ones that easily push the front seal out. Happened to me

jobber26

I hope to get a trans cooler added to this TH700 before the winter sets in. The installer went through the whole trans and replaced the broken seal, 3rd & 4th clutches, coast clutches and a few other items to make sure it was back to new and a little better than before (more HD). BTW, this trans is from an 1988 Corvette before it was rebuilt and then set up for hi-perf; it's got the widest 2nd gear band he said he could install...

fishslayer143

as we tried to tell you, if TV geometry and adjustment is not right, 3rd and 4th clutches go quickly .... glad he make it good... enjoy it..