84 vette, hits 132 mph, and shifts down to 3rd?

[nelson84]

I don't get it I'm at 3/4 throttle doing 132 mph and I give it a little more gas about 7/8 throttle and it shifts down to 3rd? At that speed why would it do that? It won't let my get over 140 mph because it shifted down.

 

[black_81_vette]

Are you sure the trans is the original?Non high performance 700 R4 trans will do that or if was rebuilt did the original valve body get put back in? Reason being is that only the 305 tpi and vettes had the 700 that would allow a up shift to overdrive at full throttle or stay in od at speed.

 

[MoeJr]

Only 82 and 84 Vette 700R4 Transmissions do that along with the rest of the GM lines. 85 and up Vette 700R4 Trans are the only ones that will allow WOT in 4th gear. U need to get a new upshift sleeve for your trans. I did it on my 84. Was 50 bucks for the sleeve.

http://www.superior-transmission.com/products/high_performance/k015.htm

Check this link.

 

[JrRifleCoach]

Been there!

Some of the later 700R4's do this as well. MoeJr has the trick for getting the job done. IMHO, suggest that you install Superiors K700-R4-HP kit that includes a boost valve, the full throttle upshift sleeve and a shift kit.

If your into cruising at above 130..........

 

[c4cruiser]

When Road & Track tested the 82 Vette, they were able to get the auto trans car to almost 140 and the manual tranny version to slightly less than that. In Dave McLlelan's book Corvette from the Inside, he said that GM tested the 84 to about 142 MPH.

You may have something out of adjustment (TV cable??) or enough wear in the tranny to cause enough slippage that results in the downshift that early.

If the tranny in your car is not the original one, you may have one from a later F-body or a Vette tranny with an F-body valve body in it. Some tranny rebuilders will use the Camaro/Firebird valve body as it is more common and usually have them in stock.

 

[JrRifleCoach]

You may have something out of adjustment (TV cable??) or enough wear in the tranny to cause enough slippage that results in the downshift that early.

The TV cable will not have effect on the WOT shift point. This is a function of pressure/valving beyond the TV cable.

This conclusion is based on research and trial/error.

 

[MoeJr]

No manual trans in 82. Listen to Coach and I and get the trans updated to 85 and newer and be done with it. 135-140 is max without the sleeve update. I know I read someone on here got their 84 up to 148 with the update.

 

[JrRifleCoach]

Max speed in third with the 3.07 rear gear is 129MPH!

And that really suxs when your trying to hit 130!!!!!

I have had the car up to 146, but that was unofficial of course......

 

[MoeJr]

Coach at the point in the throttle just before WOT and where the trans goes back to 3rd you can get 135-140 out of the car in 4th. That last bit of pedal travel is only worth a few mph.

 

[JrRifleCoach]

Mmmmm Hmmm, I agree.

But try finding that sweet spot when you only have a measured mile.

Sure wish I had that WOT valve last September at Bonneville

 

[IH2LOSE]

I have a 62 vette with a C4 suspension in it and 700R4 trans in it

the car would get up to about 140 then eather down shift or passing gear, Whatever it was doing it just would not go above 140.

I have been adjusting the TV cable back and forth and now the car will run up past 140, I am using a bowtie overdrive TV cable set up

I am pretty sure my trans is out of a impalla or caprice

 

[MoeJr]

Coach your 86 should not have the 4th gear WOT lock out. I talked at length about this with c4c5specialist and if I remember right he said only 82 and 84 Vettes had the WOT 4th gear lockout.

IH2LOSE TV only adjusts pressure for part throttle shifts. However it may be possible by letting the TV cable out a bit you picked up a couple mph. If you are talking 94-96 SS thats a 4L60E I believe and they do not have that 4th gear WOT lockout though don't quote me on that because I am not 100% positive.

Maybe someone else can chime in on that.

 

[JrRifleCoach]

Heres a link to a great site that has more than enough info on correctly setting the TV cable.

MoeJr. I tried making TV adjustments to acheive what IH2LOSE has done. Not to be on my early 86. I ended up "pumping" the throttle to get above 130. And man, when it shifting into 4th, it felt like the 1-2 shift!

I have the HP kit from Superior on the shelf and waiting......

 

[MoeJr]

Coach you must not have the original trans in that car. I remember when the 85's came out the big thing was its 150 mph top speed one of the mags got.

 

[JrRifleCoach]

It would seem that way. I'm told by the guy whom has built these things for 20 years that the trans was original before he opened it. It had the seven or eight vane pump and a bunch of other early parts as well. I'll install Superiors kit soon to eliminate these issues once-and-for-all.

Thanks for your concern.

Steve

 

[Mad-Mic]

i don't hit OD till 145 in my 87 with 2.59's

seen 165+ a few times and once with the top out coming down the mountains racing a sport bike

 

[Evolution1980]

Interesting posts here. I'm trying to think of what my BTO 700R4 does. I know that at full throttle it will stay in 3rd all the way up to the end of the power (around 155mph and 6200+ RPM). However, if I back off juuuuust the slightest bit, it will drop to 4th (OD), but then I start slowing down ever so little. Any attempt to put the pedal back down will drop it back into 3rd.

What I'd like to be able to do is hit 4th at WOT and have the lock-up solenoid kick in. ...for when I feel like cruising at 155+...
That "Superior" sleeve mentioned above...that might correct my want? I'll have to check and see if my 700R4 is newer than '93 though. Or were they only mfg'd up to '93?

 

[Hrtbeat1]

In '93 they changed just a bit. From '93 on they are 4L60E's, basically the same parts except for the solenoids, the 4L60E's are electronically controlled and need either a stand alone tranny computer or a PCM that controls the tranny. The computer controls shift points and converter lock up. TCI sells a stand alone computer as does GMPP, the GM computer runs around $1000, I think the TCI is a bit cheaper ... around $800. BTW I've got one of the GM computers, NIB, never installed.

G

 

[Evolution1980]

In '93 they changed just a bit. From '93 on they are 4L60E's, basically the same parts except for the solenoids, the 4L60E's are electronically controlled and need either a stand alone tranny computer or a PCM that controls the tranny.

Ahh, I must have a '93 or older then. I forget what year(s) BTO uses as their transmission rebuilds. (All I know is that mine took a dump the other day and now the car is up on blocks with a BTO 700R4 trans that isn't working... :eyerole)

 

[MoeJr]

Evo, that sleeve will fix what you're talking about. As far as I know the only 700's that allowed WOT 4th gear were 85-92 Vettes.