700r4 tranny problems

jblot

Member
I have an 87 gn with a 700r4 tranny installed. I know I should have stuck with the 200, it would have saved me lots of $$. Anyway, when I get up past 85 mph it is already red-lining and it just doesn't feel right. I don't want to blow the motor so I stopped at 90-95 mph. Does anyone know what the problem may be? Also in WOT it seems that it doesn't shift into 2nd when susposed to, but will red-line, then shift (same for 3rd, but not as noticable). We tried adjusting the tv cable but found no change. Any info would help. Thanks.
 

Drac0nic

It ain't easy livin free
dumb question, but what did you do about the 3rd gear sensor on the 1227148 ECM, just let it hang loose? I'm probably gonna end up swapping into a vehicle with a 700R4. What about the wiring to the 700, was it the same from the ECM or did you have to rewire at the transmission?
 

jblot

Member
We really didnt rewire the tranny, but got a 700r4 overdrive connection and spliced it to the origional 200 wiring and overdrive works just fine. However, when I get on the highway in d and then shift up to overdrive the rpms only go down a little and will redline at about 85?????

Does anyone know what the final gear ratio is? and how I can change it?
 

Drac0nic

It ain't easy livin free
It definitely sounds like you've got problems. Final gearing is something around .7. A 200's not too far away from that. Just FYI on a "standard" 700 the thing downshifts if you're going above 1/2 throttle, you won't get 4th out of it at WOT. If you need it I can dig up a guide on how to mod it or you can buy the new valve from TCI or similar to correct it. Corvette trannies also don't downshift to about 3/4 throttle. I know my 700 equipped Astro will break 100 no problemo with 3.42s and XXX/45R15 tires. Other then the issue with top speed, what do you think of it so far in regards to the different gearing of the 700?
 

jblot

Member
the 700 breaks loose when shifting out of 1st, but the 3rd gear is too close and I think I am loosing a lot of power because of it. If I were to do it all over again I would have beefed up my origional 200 and been done with it. Could you get that guide for me? that would be great. thanks.
 

Drac0nic

It ain't easy livin free
http://w1.605.telia.com/~u60505093/index.htm
This one's getting done to mine, the reason I'm going with the 700 is it's gonna be in the vehicle I"m using and I may go with an AWD vehicle, which would make a 200 "interesting" to make work. Yeah, the spacing on the 700's gearing isn't regarded as the best, you may be able to compensate with the back end gearing. Is it a stock 700 or a built one? I wouldn't try that unless you've tossed some parts in the trans. Right now I'm planning a pretty extensive rebuild for the 700 I do over the summer.
 

jblot

Member
awesome corvette. my 700 is fully rebuilt with lots and losts of performance parts, it is practically race ready except for the shifting problems.
 
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