Transmission question

Reply Subscribe

Thread Tools

Search this Thread

Feb 16, 2024 | 07:25 PM

martybmw

Thread Starter

Instructor

Joined: Jul 2016

Posts: 163

Likes: 26

From: West Hills CA

Transmission question

I have a 22 C8 HTC Z51 and lately on occasion when somewhat spirited acceleration when backing off while in 2nd gear the it wont upshift or downshift just stays in 2nd. The trans stays in 2nd until I come to a complete stop and then drops back into 1st gear and this happens in sport, my mode and Z. Starting to happen more often so will be scheduling an appointment at my dealer and was wondering if anyone else has this issue.
thanks

Popular Reply

Feb 16, 2024, 08:55 PM

RKCRLR

Race Director

Joined: Aug 2016

Posts: 12,666

Likes: 10,080

From: Garden Valley CA

You likely entered Performance Shift mode, it is described in the owner's manual. There is an indicator in the DIC when you enter the mode.

6 Jump to Original Reply

Feb 16, 2024 | 07:30 PM

AORoads

Team Owner

Joined: Jun 2005

Posts: 46,295

Likes: 2,596

From: Northern, VA

St. Jude Donor '15

"In honor of jpee"

Could be ok but tell more on car: miles, break in, service done on car, type of use (racing?), throwing any codes, any modifications, etc.

Feb 16, 2024 | 07:44 PM

CRUZ1NN

Burning Brakes

Joined: Jun 2023

Posts: 956

Likes: 401

From: South Central Pennsylvania

I am not a transmission expert but here is an article on the C8 Dual Clutch transmission: https://www.corvetteforum.com/articl...smissions-101/

The takeaway for me is this statement:

"A dual-clutch transmission, as you might expect, has two clutches. According to How Stuff Works, each clutch controls its own dedicated set of gears. In most cases, one clutch controls the odd gear numbers, while the second one fields the even gears. In simple terms, one can look at it as if it’s two manual transmissions operating side by side. The benefit here is that the next gear is always waiting and ready to go, so to speak, which results in blink-of-an-eye shifts. "

So how is the next gear already determined and ready to go? My opinion is that if you are accelerating in 2nd gear the DCT believes that the next gear is 3rd gear. If you decelerate quickly, the DCT has to either stay in 2nd gear or determine that the 3rd gear really needs to be 1st gear. Your speed may be too high to go back to 1st gear so it stays or hangs in 2nd gear.

This is my understanding and I am looking forward to others with a more physical and technical explanation so I increase my own knowledge.

Feb 16, 2024 | 08:46 PM

Ron_Attleboro_MA

Melting Slicks

Joined: Aug 2017

Posts: 2,178

Likes: 2,184

From: Massachusetts

MartyBMW, have you tested this situation while in 'Tour' mode.

Feb 16, 2024 | 08:55 PM

RKCRLR

Race Director

Joined: Aug 2016

Posts: 12,666

Likes: 10,080

From: Garden Valley CA

You likely entered Performance Shift mode, it is described in the owner's manual. There is an indicator in the DIC when you enter the mode.

Feb 17, 2024 | 07:07 AM

Undy

Safety Car

Joined: Dec 1999

Posts: 4,712

Likes: 1,454

From: Virginia Beach, VA & Port Charlotte, FL (snowbird)

A simple manual upshift will "cure" the OP's problem. Just tap your upshift paddle after you get off the gas. Sport or track modes create these situations, Completely normal.

Feb 17, 2024 | 08:51 AM

Andybump

Race Director

Joined: Mar 2007

Posts: 11,169

Likes: 8,308

Quote:

Originally Posted by martybmw

Quote:

Originally Posted by RKCRLR

You likely entered Performance Shift mode, it is described in the owner's manual. There is an indicator in the DIC when you enter the mode.

Post 5 by RKCRLR is your most likely explanation. If you have downloaded a copy of the Owner Manual from the Chevrolet website. here

https://www.chevrolet.com/support/ve...manuals-guides

then you can search on these terms to read more about it, and decide if that is what you are experiencing:

"performance transmission", "performance shift", "driver influenced gear selection"

You will find the info is scattered in the manual which is why I suggest using the search. The manual does explain the feature, what triggers it, and how it will affect the shifting behavior.

Enjoy!