suggestions on gear replacement for rear diff
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Thread Starter
Instructor
Joined: Mar 2020
Posts: 118
Likes: 15
From: Texas
I ran my 70 LT-1 with a 3:55 rear and a WR M-20 for 27 years of autocrossing and cruising. Not a bad compromise at all.
It did put me at 3100 at 70, which was OK in a easy reving small block. Your 373s would put you at 3300, not much difference. With your CR box vs my WR box, I had slightly more 1st gear and you'll have slightly less, as well as slightly more cruise rpm. Not a big difference.
I just didn't cruise at 70 (and certainly not over) very much I just slowed down a little. When I cruised at 3500ish (80) the oil started to heat up after 10-15 minutes (very hot like 400 degrees) enough to drop the oil pressure. I just slow down a little.
Here's a gear spreadsheet I wrote for our cars.
Yeah I took 200 mile trips in mine at 3000 rpm.. It was fine. Just 70mph was my top cruise speed. Got 15mpg too, with stock Holley.
It did put me at 3100 at 70, which was OK in a easy reving small block. Your 373s would put you at 3300, not much difference. With your CR box vs my WR box, I had slightly more 1st gear and you'll have slightly less, as well as slightly more cruise rpm. Not a big difference.
I just didn't cruise at 70 (and certainly not over) very much I just slowed down a little. When I cruised at 3500ish (80) the oil started to heat up after 10-15 minutes (very hot like 400 degrees) enough to drop the oil pressure. I just slow down a little.
Here's a gear spreadsheet I wrote for our cars.
Yeah I took 200 mile trips in mine at 3000 rpm.. It was fine. Just 70mph was my top cruise speed. Got 15mpg too, with stock Holley.
Thread Starter
Instructor
Joined: Mar 2020
Posts: 118
Likes: 15
From: Texas
Just a note to all the helped here - Thank You., I went with the 3.73 gears and its been quite the success. The rebuild is done and I also resurrected the posi which was shot. The car sounds 100% better in the rear and she handles better in the *** end on tight turns. Thanks again
