Gear change
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,987
Likes: 6
From: Arkansas
St. Jude Donor '11-'12-'13-'14-'15,'19
Gear change
Gave my friend my 342 rear end and he put it in an 03 coupe and is now getting a code and was told he can only go up to 315 because computer will not recognize 342 is this a tune issue or fact
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Never heard of this before---Assuming your friend's car is an automatic with a 3.15 rear "sport gear" this is a very common mod which I actually did myself years back changing it to a 3.42
On a C5 with a gear change you do not have to make a speedo correction However you do have to make a shift point and TCC lock up correction This can only be done with tuning with software from HP or EFILIVE---and the tuner must also change the gear ratio to 3.42 even though the speedo may be correct the ECM may not recognize the new gear ratio unless a tuner changes the number in the base tune to 3.42
On a C5 with a gear change you do not have to make a speedo correction However you do have to make a shift point and TCC lock up correction This can only be done with tuning with software from HP or EFILIVE---and the tuner must also change the gear ratio to 3.42 even though the speedo may be correct the ECM may not recognize the new gear ratio unless a tuner changes the number in the base tune to 3.42
AMP Racing
Joined: Aug 2006
Posts: 10,753
Likes: 588
From: Washington TWP NJ
2023 C5 of the Year Finalist - Modified
2017 C5 of Year Finalist
St. Jude Donor '09-'10-'11-'12
The C5 gets its vehicle speed info from the sensor on the ring gear, so it doesn't matter what gear is in the rear, it'll still display the proper speed that the car is going...
That said, what the guy above me said is correct. You need to adjust the parameters in the PCM for the gear change. Get with a tuner to accomplish this.
That said, what the guy above me said is correct. You need to adjust the parameters in the PCM for the gear change. Get with a tuner to accomplish this.
