differential swap
Tech Contributor
Joined: Jan 2007
Posts: 19,360
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From: Dyer, IN
Safety Car
Joined: Mar 2005
Posts: 3,742
Likes: 1,205
From: Wisconsin
The VSS is on the top passenger side of the diff. Auto or manual.
You need a tuner to change the pcm for the ratio change in a auto, and TCC slip tables and shift points need to be changed in the PCM to compensate for the gear change. the diff is a bolt in
You need a tuner to change the pcm for the ratio change in a auto, and TCC slip tables and shift points need to be changed in the PCM to compensate for the gear change. the diff is a bolt in
Tech Contributor
Joined: Jan 2007
Posts: 19,360
Likes: 1,127
From: Dyer, IN
Who did you speak with at RPM? I have never heard any such thing. This is a very popular mod for the last 20 years. It would not be as popular if it required that level of intervention.
Safety Car
Joined: Aug 2011
Posts: 4,439
Likes: 405
From: Portland OR
Most folks put the stick 3.42 diff into an auto car.
I believe he wishes a to get an auto trans diff, change the gears and put it in a stick car.
This is only viable with the 3.15 auto trans diff not the 2.73 diff.
Seems to be some things lost in translation here.
I believe he wishes a to get an auto trans diff, change the gears and put it in a stick car.
This is only viable with the 3.15 auto trans diff not the 2.73 diff.
Seems to be some things lost in translation here.
Thread Starter
8th Gear
Joined: Sep 2023
Posts: 8
Likes: 0
You are correct, diffs from auto cars are cheap and plentiful compared to manual cars. I was thinking if it would fit, I could build one from an auto car and just do a simple swap.
I'm still learning these cars. I did not know you need to start with a 3.15 to do the ratio change I was thinking about.
I sent a email to Camren at rpm and that was the answer I received.
I'm still learning these cars. I did not know you need to start with a 3.15 to do the ratio change I was thinking about.
I sent a email to Camren at rpm and that was the answer I received.
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Tech Contributor
Joined: Jan 2007
Posts: 19,360
Likes: 1,127
From: Dyer, IN
You are correct, diffs from auto cars are cheap and plentiful compared to manual cars. I was thinking if it would fit, I could build one from an auto car and just do a simple swap.
I'm still learning these cars. I did not know you need to start with a 3.15 to do the ratio change I was thinking about.
I sent a email to Camren at rpm and that was the answer I received.
I'm still learning these cars. I did not know you need to start with a 3.15 to do the ratio change I was thinking about.
I sent a email to Camren at rpm and that was the answer I received.
Good luck.
Race Director
Joined: Oct 2004
Posts: 12,859
Likes: 4,658
I am puzzled as to why the OP is doing this? If it is because the A4 diffs are more plentiful, and therefore somewhat cheaper, wouldn't you end up spending the same amount of $$$ in the long run? Assuming you want the 3.15 diff for the 3 series carrier, and are going to open it up to go with a 3.42, or lower gear? Say a 3.73 or??? I must be missing something. Yeah, that's what she said!!
Thread Starter
8th Gear
Joined: Sep 2023
Posts: 8
Likes: 0
I was thinking about changing the diff ratio in my manual car to 3.90 or 4.10. Not sure how I would like it or the amount of down time to change it. I didn't want it to be stuck on my friends lift for a long time. So, I noticed auto diffs are plentiful and cheap compared to manual diff. I'm also aware that the auto to manual swap is what is usually done.
So that was what was driving my inquire into the auto, manual swap.
So that was what was driving my inquire into the auto, manual swap.
Safety Car
Joined: Mar 2005
Posts: 3,742
Likes: 1,205
From: Wisconsin
Here's a very detailed thread on doing a gear change in the diff including the tools needed
https://www.corvetteforum.com/forums...ld-how-to.html
https://www.corvetteforum.com/forums...ld-how-to.html