No OD with 700R4

[corvettejoe]

I installed a TCI 700R4 trans (dyno up to 450hp) in my 81. When I drive it normally, it shifts great, including OD. When I gave it WOT, I was going about 100mph, around 7K rpm with a ZZ4, 4 bolt main & a 4:11 rear, it would not shift into OD! I read on one site that this is normal for the 700R4 trans. Any feedback would be greatly appriciated. Is there any fix so I could run the 1/4 mile? By the way, the computer is not being used.

 

[maxrevs85]

Dont know about the trans, but your gonna kill the zz4 with those rpmsThe hydrualic roller cam wont take it for long.
Dave

 

[corvettejoe]

Dave, I agree with you. I only did it once, which is enough, but I didn't know it wouldn't shift to OD.

 

[maxrevs85]

I kinda thought thats what happened. I wouldnt want ya to ruin a great engine. What a great combo... Have fun

Dave

 

[Glensgages]

corvettejoe:

I was told on my OEM '82 700R4, the OD won't engage when the pedal is more than something like 50% depressed (?), but don't take my word for it.....
:confused

I never investigated it further.

I know that I trap at 90+ MPH in 3rd Gear, even-with letting it shift for itself, so it's not in OD then.....

 

[KANE]

I installed a TCI 700R4 trans (dyno up to 450hp) in my 81. When I drive it normally, it shifts great, including OD. When I gave it WOT, I was going about 100mph, around 7K rpm with a ZZ4, 4 bolt main & a 4:11 rear, it would not shift into OD! I read on one site that this is normal for the 700R4 trans. Any feedback would be greatly appriciated. Is there any fix so I could run the 1/4 mile? By the way, the computer is not being used.

Did you use the SPECIFIC detent for the 700R4 (New shift pattern)? If not.... that is what led to the failure and subsequent burn out.

 

[corvettejoe]

Yes, I did use the specific detent/TV cable for the 700R4 trans. It upshifts and downshifts properly all other times, the problem comes when it needs to shift into 4th gear at WOT. If I let of the gas and cruise, if shifts fine, right into O/D.

Basically I'm trying to find out if this is the way the 700R4 was designed to work and if theres anything I can do to change that.

Thanks for the responses
Joe

 

[maxrevs85]

I believe thats the way its intended to work unless you go to an all maual valve body where you have to upshift and down shift manually.

 

[JohnZ]

A phone call to TCI should give you all the answers.

 

[corvettejoe]

A phone call to TCI should give you all the answers.

Thanks for the suggestion, that was my next step. I will try to call them and get an answer, I'm sure they will be able to help.

Thanks again for all the replies.

 

[Blue82]

I found with my 700r that if I adjusted the detent cable for higher RPM shifts, it will not shift very easily into OD.

Also, I had a problem when I went with 3.73 gears where the trans would kick down from OD to 3rd gear at about 1/2 throttle. The stock TV valve body is setup for this and it will send your RPM's throught the roof before you can get your foot out of it. I guarantee this will be a problem with your 4.11's. B&M sells a modified part set for 3/4 throttle, but that will only make the problem worse.

There is an easy upgrade that will not allow the trans to kick out of OD once it goes in. It will come out with normal decelleration, but not with accelleration. I'll see if I can locate the author and get permission to post it.

The downside, according to my local B&M shop, you need to be careful about slamming it with torque at low RPM in OD. You will cause the converter to chatter.

I have had my car this way for about 1 1/2 years and I genreally drive "spirited"... never had a problem, but I do keep it in 3rd gear unless I plan to be on the highway for awhile.

 

[black_81_vette]

I had a 85 trans am with a 305 TPI and a 700 r4 and at full throttle it would up shift into od. As far as I know all TPI cars including vettes of the mid late 80s had a special valve and spacer plate allowing the upshift into od under full throtle. Id call TCI or any trans shoop can hook you up with the correct parts.