Differential Gear Change Auto - HELP!
Thread Starter
Trucker
Joined: Aug 2013
Posts: 134
Likes: 10
From: Oklahoma City OK
Differential Gear Change Auto - HELP!
I have posted before on my rear diff change saga. The latest update is this, the noise I kept hearing was due to a defective diff case. My guy has now installed another new 3.73 gears and a carrier in my original 3 rib case. The original case is a 3 rib case but it had the original carrier and the 2.73 gears that came in the standard base coupe. New issue, the speedometer does not work and the car won't shift out of first gear. I've searched the forum and I know I've seen this very issue before but I can't seem to find anything. Is there someone out there that can help this brother out? Thanks in advance for your help and your patience!
Le Mans Master
Joined: Feb 2004
Posts: 8,629
Likes: 16
From: York PA
You need to change the setting in the pcm to 3:73 (it doesn't know you switched rear gears)
Best to remove pcm & sent to ECS for a "mail in tune"
https://www.corvetteforum.com/forums...nly-149-a.html
.
Best to remove pcm & sent to ECS for a "mail in tune"
https://www.corvetteforum.com/forums...nly-149-a.html
.
Last edited by 4DRUSH; Jul 1, 2015 at 06:16 PM.
Thread Starter
Trucker
Joined: Aug 2013
Posts: 134
Likes: 10
From: Oklahoma City OK
I had it programmed when I installed the other rear diff with the 3.73 gears. I haven't changed anything electronic (except maybe a sensor in the housing), just used a different housing with the 3.73 gears in it. The speedo worked fine with the other diff. Thanks for taking time to help me out!
Le Mans Master
Joined: Feb 2004
Posts: 8,629
Likes: 16
From: York PA
I had it programmed when I installed the other rear diff with the 3.73 gears. I haven't changed anything electronic (except maybe a sensor in the housing), just used a different housing with the 3.73 gears in it. The speedo worked fine with the other diff. Thanks for taking time to help me out!
Thread Starter
Trucker
Joined: Aug 2013
Posts: 134
Likes: 10
From: Oklahoma City OK
Differential Gear Change Auto - HELP!
10-4. That's what I figured. Just wanted to make sure I didn't need to do another re-program with a change in housing. Makes sense the sensor doesn't know or care what gear set or transmission the car has in it. Probably got damaged when the carrier and gear set were changed. Thanks.
AMP Racing
Joined: Aug 2006
Posts: 10,754
Likes: 589
From: Washington TWP NJ
2023 C5 of the Year Finalist - Modified
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St. Jude Donor '09-'10-'11-'12
you put a 3.73 in a 2.73 case? Did you put a spacer in it?
I'm not exactly sure of the specifics, but you can't just install a different gearset in a 2.73 diff because of the spacing issue for the speed sensor.
So, it's possible that your speed sensor is not picking up the signal.
I'm not exactly sure of the specifics, but you can't just install a different gearset in a 2.73 diff because of the spacing issue for the speed sensor.
So, it's possible that your speed sensor is not picking up the signal.
Thread Starter
Trucker
Joined: Aug 2013
Posts: 134
Likes: 10
From: Oklahoma City OK
Differential Gear Change Auto - HELP!
That may be what is missing. It is a 3 rib case / housing. I guess I was under the impression the 02-04 3rib diff housings were all the same. What spacer is it?
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AMP Racing
Joined: Aug 2006
Posts: 10,754
Likes: 589
From: Washington TWP NJ
2023 C5 of the Year Finalist - Modified
2017 C5 of Year Finalist
St. Jude Donor '09-'10-'11-'12
Unfortunately, it's sounds like you're going to have to pull the diff back out. Who built the diff? They should have known the issue with the 2.73 diff and the spacer needed to install a different gear set.
Im not sure the thickness of the spacer, as I don't build diffs. As far as I know, most builders prefer to use a 3.15/3.42 diff to avoid the issue altogether.
Good luck with your project.
Im not sure the thickness of the spacer, as I don't build diffs. As far as I know, most builders prefer to use a 3.15/3.42 diff to avoid the issue altogether.
Good luck with your project.
Thread Starter
Trucker
Joined: Aug 2013
Posts: 134
Likes: 10
From: Oklahoma City OK
Differential Gear Change Auto - HELP!
I've already ordered an 04 3.15 diff just to get the housing. This has been one heck of an experience. Expensive experience. Save yourself time and money, just buy one from a known forum vendor up front. Geez.
Le Mans Master
Joined: Feb 2004
Posts: 8,629
Likes: 16
From: York PA
(not sure what the 4th time would be)