C-5 ZO6

[Jeffrey S.]

Hello all! A friend of mine has a 2001 ZO6 with the 6 speed manual and asked me to ask how to disengage the 1-4 gear shift (actually, I'm not quite sure what that does but I promised I would ask). Thanks for your help.
Jeff

[Charlie P.]

Re: C-5 ZO6

That device forces you to shift from 1st to 4th for better mileage, if you are not hard on the throttle. It can be disabled easily from what I understand. Go to Corvette Forum, Z06 message board, and you can plenty of advise.

[Donald T.]

Re: C-5 ZO6

Jeff, all the major corvette parts suppliers sell a bypass for the 1 to 4 shift. It has to be disconnected at the rear of the transmission and the bypass installed. I agree the 1 to 4 shift is annoying. I wish GM had provided a button to activate or deactivate like they did the traction control.

[Donald T.]

Re: C-5 ZO6

Here's what you are looking for.




Bypass

[Joe L.]

Re: C-5 ZO6

Jeff-----

The "skip shift" can be disabled by disconnecting the connector at the pigtail emanating from the solenoid on the transmission. In the aftermarket from many Corvette vendors is sold a "plug protector" which will cap both ends of the connector to preserve the integrity of the connectors should they ever be re-connected.

The "skip shift" is not part of the vehicle emissions system. It's part of the fuel economy provisions of Corvettes equipped with manual transmissions. Consequently, it need not be reconnected at emissions inspection time.

[Duke W.]

Re: C-5 ZO6

The skip shift is easy to drive around. If your friend reads the owner's manual (What a novel idea!) he will find that it is only active between certain speeds within a certain percent range of throttle opening. When active, a light illuminates in the instrument cluster.

You can either short shift, which is easy because the engine produces so much torque, use little or lots of throttle, or you can hold first gear to above the speed where skip shift disengages.

As Joe said, it is strickly a "trick" to get good fuel economy numbers (which are determined during the EPA emission certification test) to avoid the "gas guzzler tax". If GM could figure out how to classify the Corvette as a "truck" there would be no guzzler tax as is the case with all the other "trucks masquarading as passenger cars.

Duke

[Rich G.]

WWW.ZO6VETTE.COM..Good ,too *NM*

[John H.]

Re: C-5 ZO6

The correctly-made skip-shift plugs have an internal resistor that "tricks" the PCM into thinking it's still connected to the solenoid; if you just disconnect it, it sets a code and illuminates the MIL light. Viper uses the same skip-shift solenoid and PCM logic to improve the city-cycle portion of the EPA fuel economy test.

[Joe L.]

Re: C-5 ZO6

John-----

The PCM sensor must be a feature unique to C5; the connector can be disconnected on C4s without any problem.

These solenoids have a very interesting aspect that I've never figured out. GM has available in SERVICE replacement solenoids for both C4 and C5 Corvettes so-equipped. For C4s the solenoid (used on ZF MN-6 transmissions only) is GM #10140541. GM is very proud of this solenoid and it carries a current GM list price of $779.49. For C5s, the solenoid is GM #12523292 and, mercifully, carries a current GM list price of $131.48.

Let's say that someone has a C4 or C5 so-equipped and the solenoid ceases to function. Keep in mind that "failure mode" for the solenoid is that the skip shift does not engage and, consequently, the 1 to 4 shift never occurs. If the car owner has previously disconnected the solenoid, then failure of it is moot---the car owner would never notice that it failed. But, let's say that the car owner has not disconnected it. Then, one of the following would have to occur:

1) the car owner does not even notice that the skip shift no longer occurs. In that case, the failure of the solenoid is moot and no repair (or, purchase of a new solenoid) is initiated;

2) the car owner notices that the skip shift no longer occurs and is happy about it. In that case, no repair or purchase of a solenoid occurs;

3) the car owner notices the skip shift no longer occurs and is troubled by that fact. So, a trip to the dealer or other car repair facility is initiated. The following then occurs:

a) the owner is told that the car can be repaired but that the cost will be $779.49 + labor (for a C4) or $131.48 + labor (for a C5)

Then, the car owner decides:

a) the lack of the skip shift is no longer so troubling and forgets the repair, or,

b) the car needs to be repaired regardless of cost.

Now, how many times do you think that (b) would occur, especially in the case of a C4? It's hard to imagine that GM would EVER sell one of these things, especially the one for C4s.

[Jeffrey S.]

Re: C-5 ZO6

Thank you all for your quick responses. I have passed along your comments (and an Eckler's catalogue)to my friend and he will be disconnecting the CAGS as soon as he receives the plug.
Thanks again,
Jeff

[John H.]

Re: C-5 ZO6

Exactly - I can't imagine anyone ever buying the solenoid either. Just unplugging it doesn't set a code on C4's, as the monitoring requirement didn't cut in until the OBD-II mandate took place in 1996 (unplugging it didn't set a code or light the light on '92-'95 Vipers either, but it did starting in '96 with OBD-II).