Welcome to the Corvette Forums at the Corvette Action Center!

Auto tranny won't shift

M

My8T1

Guest
well I've done it now....took the old 81 thru a torture test this morning at a red light...now it won't shift into 3rd gear.oooops
still runs in 1st & 2nd anybody know what happened?

Ed
 
Joined
Nov 4, 2000
Messages
946
Location
Scottsville, Kentucky
Corvette
08 Jetstream Blue Z51 coupe
My8T1,

Generaly, but not always, shift problems can be traced back to the vacuum modulator. Often times it is the only item requiring replacement. It could be other problems, but there is a place to start. A good tranny shop should treat you right in trouble shooting. The modulator is not an expensive fix if indeed that is the bad actor.

Dale
 
M

My8T1

Guest
Thanks dale...it's going in Monday morning,Gonna check underneath this weekend for a stray vacume hose.

Regards
Ed
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
vac line & modulator

Ed:
Dale's so right! And vacuum modulator valves do simply fail over time. Maybe yours is not so sprightly after 20 years.

I bought a car that seller thought had a blown motor ... because it was badly smoking out the exhaust ... but he said it didn't use any oil (yea right) ... but he said it was going through 2 qts of tranny fluid a day (yikes) and it shifted poorly. Well I checked under the car and no tranny leaks ... and noted the exhaust stench was unlike antifreeze or motor oil. Well, I had a hunch most of the trouble was in the modulator ... and rolled the dice. I bought it ... ALL that was wrong was the modulator valve's diaphragm (where's the dam- spellchecker ROB?) had a leak. The carb was sucking the fluid out of the tranny through the modulator -vac line route ... and burning it. I fixed the whole thing for about $10.

So, if you're going diving this weekend, why not have a modulator valve & some vac line on hand ... you can probably change out a cold MV and vac line in less time than it takes to chill a six-pack ... and if it don't fix, you'll be out for only a few bucks and a little easy worktime. Good luck and keep us posted!
JACK:gap
 
Joined
Nov 4, 2000
Messages
946
Location
Scottsville, Kentucky
Corvette
08 Jetstream Blue Z51 coupe
Good point Jack!!!

They are easy to change, and cheap, the local NAPA or PEP Boys should have one on the shelf.

Dale
 
S

ssvett

Guest
I don't knoow

You might get lucky, but I think you will need to continue planning for your trip Monday morning. The modulator valve that is used to shift from 2nd to 3rd, is the same modulator valve, that is used to shift from 1st to 2nd. I will be the first to admit, I don't know anthing more then how to put an automatic trans in gear. But I am pretty sure there is more to this then vacuum. It is posing some interesting questions in my head though(maybe I have stayed up too late again) Usually, when a trans goes out from wear, it tries to shift to 3rd but then just slips. I know that there are solinoids in the tranny that may have come undone or somthing............Man, I don't know. I have a good 350C from an 81 if it will help ya though..............Steve
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Well ... what did you find?

Ed:
Did you or a shop find the problem? If so, what was/is it?
JACK:gap
 
M

My8T1

Guest
Jack
I had to re-schelule the tranny for next week....I'm still driving it just uses more gas driving around in the lower gear.I will post what the findings were incase it happens to someone else.

Ed

A guy in a Mustang waved to me the other day.... :)
 
M

My8T1

Guest
I finally had the tranny looked at today....Good news, it was a cable adjustment :D also had a new choke put in what a difference.
Ed
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Choke?

Ed:
Great that your tranny's ok! Was that a carburetor choke you replaced? So ... the tranny's vacuum modulator valve was ok?
JACK:gap
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Vetteskins

Advertise with the Corvette Action Center!

Double Your Chances!

Partners

Top Bottom