Tranny won't go into 4rth"OD" at WOT

this has been happening for awhile, tranny drives great doesn't slip at all, but it won't go into 4rth at full throttle. so in 3rd it will just peg the limiter at about 135 mph and just sit there, if i roll out to about half throttle it will catch 4rth but when i get back in it it kicks down to 3rd and hits the limiter again.

Tonight at about 2am i headed out onto the highway and got her up to red line in 3rd (135mph) then rolled out half throttle till it caught 4rth then i LIGHTY featherd the car up to 142 mph well out of 3rd gears range, so i punched it agian and it kicked down to 3rd and i just let off the gas. Anybody know why this is happening? :confused: FYI: tranny has about 16k miles on a rebuild, stick was in the OD position.

thanks for your help!

Ttt

The computer won't let it do that.....it's the same for all auto trannies from 93-02...you hafta let off a little to go into od and then put it down again like you were doing.


EDIT i just read your post again and why it goes back down into 3rd i dont' know...i've never had my car past 130 before

you can try a tune check.. the pcm controls the tranny

not on '93's i believe, sense the tranny isn't electric. Also my tranny short shifts at 4,500 rpm's at wot, so i manually shift when i race, could that be the linkage?

since it's not electric would this downshift kit (http://store.summitracing.com/partdetail.asp?part=BMM-70237&N=120%20300215) make any difference?

that kit would help, but not totally solve the problem. it would still downshift if he applied more than 3/4 throttle, as the ad says..

since it's not electric would this downshift kit (http://store.summitracing.com/partdetail.asp?part=BMM-70237&N=120%20300215) make any difference?


When I had my '93 tranny rebuild, I requested one of these(dont believe it was B&M), and it did help.. In stock form, you have to let off the gas pedal to shift into forth..I didnt like it.. Now, it will shift into forth on its own at WOT.. No more letting of the gas pedal... :)

my 88 Formula will upshift to 4th at WOT and I think it is a stock tranny.
From what I understand, there is a small part you install into the valve body to give you this feature. I think it was a sleeve or something.

The computer won't let it do that.....it's the same for all auto trannies from 93-02...you hafta let off a little to go into od and then put it down again like you were doing.


EDIT i just read your post again and why it goes back down into 3rd i dont' know...i've never had my car past 130 before
Um no, mine shifts into 4th at WOT, I've done it countless times. I don't know of anyone with a 4l60e that has that problem, I think it has to do with the 700R he has, the same thing happened to my dad when he used to have a 91 trans am.

not on '93's i believe, sense the tranny isn't electric. Also my tranny short shifts at 4,500 rpm's at wot, so i manually shift when i race, could that be the linkage?

your right our trans arent elec. in what gear does it shift into 4500 rpms . so you saying you start from 2 to D to OD ? how does that help you? does it shift at higher rpms?

your right our trans arent elec. in what gear does it shift into 4500 rpms . so you saying you start from 2 to D to OD ? how does that help you? does it shift at higher rpms?

if i leave it in drive it will upshift at 4,500 rpm's for some reason, so i jus shift it manually 1->2->D like that

I've been told by a couple of people that it wouldn't go at wot into od....i've never done it but i've been told by a countless number of people that it wont...but like i said i have no idea i haven't done it before and i don't think i will

regardless of whether the tranny is electronically controlled or not (which in the case of the 93, its NOT), shifting into OD at WOT is torture on the tranny. Overdrive is not meant to engage under that torque load. honestly, isn't 135 mph enough?!?!?!?!?!

This is quite common on 3rd gen F-bodies. First time I've heard about it on a 4th gen. Though it probably has to do with your car being a TH700R4/4L60.

As for which cars have it? It's hit and miss really. I've driven my fully loaded L98 GTA perf axle ratio, WS6, the whole deal, and it won't shift into O/D, yet I drove a previous plain jain IROC would shift into O/D. Corvettes don't seem to have this problem.

I'm not a transmission guy, but your tranny isn't broken. It's just missing the one part needed to do the WOT 4th shift.

99% of 4th gens don't have this "feature." You can tell by the huge amount of people here who have done 150 mph in their auto cars.

my car shifted from 3 to 4 at WOT, and I wound her up to 155. Also, driving that fast is incredibly dangerous and stupid, even if there isn't any traffic. I came to that realization when I had to dodge a truck tire carcass doing 150+ :eek:

Upgrading the Servo to a vette servo will help out alot with this. It should allow full or at least 3/4 throttle in OD. I hated that about my 91 Z28. I could get over 120mph since it wouldnt shift into OD.
Upgrade the servo and it will work. I got all the part#s in my third gen folder at home. THere are a few pieces you will need, all available at the local dealer.

Good luck

Steven

thanks i've heard about the corvette servo i might try that


and i had no idea going 140+ was dangerous thanks to those who pionted that out :rolleyes:

It sounds like you might have this issue I read about on LT1Tech

http://lt1tech.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=7;t=000426;p=1

Apparently there is a cable that needs to be adjusted, this happens on 94s and 95s.

Take a look at the thread it might solve your poblem.