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ZF Shifting Issue

trackitman

Active member
Joined
May 11, 2002
Messages
44
Location
Lake Orion, MI, USA
Corvette
1992 Convertible White 6 sp
I purchased a '92 conv 6 spd this spring and have enjoyed driving it this summer. It has a lot of small stuff that needs attention, but I wanted to post a question regarding the 6 speed ZF transmission.

When shifting from first to second, under normal driving conditions, with rpm's less that 2000, the shifter does not release out of first and jamb's up. Can't get it into second, and if you let the clutch out there is a slight grinding of the gears (needless to say I don't let the clutch out). It feels like it's not releasing fully from the first gear, and has a tendency to spring over into the 3rd/4th gear area. You have to wrestle it a while until it releases the first gear.

The car has 58K, I doubt the trans oil has been changed. I read a link earlier regarding changing the oil, regardless what GM says in the owners manual. Do you think this will take care of it? Do you think there is a linkage issue?

What's interesting is if I rev beyond 3000 RPM in first, it shifts perfectly into second, every time.

Thanks for any help or hints you can offer.

Trackitman
 
S

sothpaw

Guest
Are you aware of the 1 to 4 feature?

There is a feature for fuel economy which causes the transmission to lock out 2nd gear and force you to shift from 1 to 4 if you are starting out slow.

You can disable it with a $20 gismo or I think for free if you
know what you are doing.

Do you see "1 to 4" light up on your display? If so, this is what
you are experiencing. It is supposed to be there.
 

trackitman

Active member
Joined
May 11, 2002
Messages
44
Location
Lake Orion, MI, USA
Corvette
1992 Convertible White 6 sp
Sothpaw -

No, I wasn't aware of that feature. This is my first vette and it did not come with an owners manual.

So, with this feature invoked, you have to go from 1st to 4th? Do you know where the dividing line is?

Thanks.
 
Joined
Jun 20, 2002
Messages
2,509
Location
Tallahassee, FL
Corvette
none right now :(
Look at the dash, there is a light that should come on, it will say 'one to four'... if it is on, you have to go straight to fourth... I think GM got smarter in the later years too.. In my '93 I could go back into first, get going faster, and then shift normally, my '96 wouldn't let me go back to first... There is a set of rules for the one to four thing... It basically happens under light throttle.... I personally think it is dangerous! nothing is worse than pulling out into traffic and being forced to go to fourth gear, and have no power....

All you have to do to disable it (the dash light will still work) is unplug the wire under the car... You can buy the plug from Ecklers or any other corvette parts seller to plug the ends so it won't corrode.

-The plug is on the drivers side of the tranny, at the very bottom... it is mounted so you can reach over with the car on the ground and unplug it... There are other plugs down there, the one to four thing should be the smallest one, and the only one mounted to the tranny on the bottom drivers side, hope this helps
 

trackitman

Active member
Joined
May 11, 2002
Messages
44
Location
Lake Orion, MI, USA
Corvette
1992 Convertible White 6 sp
I agree it does seem dangerous. It definely is not intuitive. I thought I had a problem with the transmission. Seems a bit over engineered if you ask me.

Anyways, thanks for the info, I will most likely disable this, I have a daughter who wants to learn to drive this, and I want to try to keep it simple for her.

Take care and THANKS!

Blaise "Trackitman"
 

Rob

Site Administrator
Staff member
Administrator
Joined
Sep 16, 2000
Messages
13,763
Location
New Hampshire
Corvette
1990 Corvette ZR-1
trackitman said:
Sothpaw -

No, I wasn't aware of that feature. This is my first vette and it did not come with an owners manual.

So, with this feature invoked, you have to go from 1st to 4th? Do you know where the dividing line is?

Thanks.

It's called "CAGS" or "Computer Aided Gear Selection". It is meant to improve gas mileage. Given certain parameters such as gear selection (only happens in 1st), speed, and throttle position, CAGS causes 2nd and 3rd gear to be locked out, forcing a 1st to 4th upshift. The theory is that by lowering RPMs, fuel consumption is reduced.

It is annoying and can be disconnected. Companies like MidAmerica and Ecklers carry a CAGS plug seal kit.
 
Joined
Jun 20, 2002
Messages
2,509
Location
Tallahassee, FL
Corvette
none right now :(
Rob said:


It's called "CAGS" or "Computer Aided Gear Selection". It is meant to improve gas mileage. Given certain parameters such as gear selection (only happens in 1st), speed, and throttle position, CAGS causes 2nd and 3rd gear to be locked out, forcing a 1st to 4th upshift. The theory is that by lowering RPMs, fuel consumption is reduced.


Thanks for the technical info Rob... Here is the real reason chevy does it though: LOL

It's called "CAGS" or "Confusion Added to Gear Selection". It is meant to confuse, and be a royal pain to owners of 6 speed Corvettes. Given certain parameters such as gear selection (only happens in 1st), speed, throttle position, CAGS causes 2nd and 3rd gear to be locked out, forcing a 1st to 4th upshift. The theory is that by lowering RPMs, power is reduced. This will lead to more Corvettes getting into accidents and higher sales of Corvette parts.

---If I wanted a computer to make the decision for me, I would have bought an automatic!
 
R

RubyDropTop

Guest
Hi guys -

Just thought I'd chime in on what Gordon Killebrew has to say about the 1989 - 1996 6 spd. 1 to 4 shift...."If your car is driven from 12 to 19 mph, engine temperature is 122 degrees or more, and 35% or less throttle when shifting from 1st to 2nd - you will be forced to 4th gear. This is to help with the EPA and the CAFE requirements. The 1 to 4 light on the dash will come on when these conditions are met. To bypass this, merely go past 20mph or hesitate when shifting. The 1 to 4 shift is regulated by the second relay from rear to front of car, located on the front wheel housing opening. The 1993 or later relay is located on the right front wheel housing."

All I can say is that if I had a 6 spd., the CAGS would be the FIRST thing to go! :hb
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Cags...yeech!

get the kit from Mid America...... 10 min under the car and your CAG-LESS and it shift like a NORMAL tranny.... The reason for CAGS was SMOG......

Vig!
 

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