Rear
10-22-2014, 10:43 AM
#1
Instructor
Thread Starter
Member Since: Feb 2013
Location: Phila Pa
Posts: 104
Likes: 0
Received 0 Likes
on
0 Posts
Rear
How much difference does a 3.08 rear make as compared to a 3.70 on the hi-way. I have a big block and need the rear replaced and looking for best options for hi-way driving. Not looking to race just cruise.
10-22-2014, 11:29 AM
#2
Race Director
Member Since: Jan 2002
Location: Close to DC
Posts: 14,544
Received 2,127 Likes
on
1,466 Posts
C2 of the Year Finalist - Modified 2020
My personal pick for overall cruising and good acceleration is 3:36. 
Dennis
Dennis
10-22-2014, 11:53 AM
#3
Drifting
According to my admittedly feeble calculations, if you were turning 3500 rpm on the highway (for example) with the 3.70, the 3.08 would drop it to about 2900 rpm.
10-22-2014, 12:03 PM
#4
Safety Car
Here is a link to American Power Trains....
I used it to determine what a 3.08 would be like in a Tremec......
You can use the link to put different ratios in and ssee the difference.
Make sure you use the same entry data for tire size and so forth to get an accurate idea of what rpms you'll see at whatever gear you would like to see...
http://americanpowertrain.com/p-7584...-analyzer.html
I used it to determine what a 3.08 would be like in a Tremec......
You can use the link to put different ratios in and ssee the difference.
Make sure you use the same entry data for tire size and so forth to get an accurate idea of what rpms you'll see at whatever gear you would like to see...
http://americanpowertrain.com/p-7584...-analyzer.html
10-22-2014, 12:32 PM
#5
Melting Slicks
10-22-2014, 01:22 PM
#6
Race Director
Do you have a wide ratio transmission? A CR transmission and 3.08 rear will not be the happiest of combinations on any around town driving that you have.
10-22-2014, 01:42 PM
#7
Race Director
The key is the gear ratios in the transmission……especially first gear. Standard for many BB cars was a 3.08 rear, but the car also came with the wide-ratio (M20) transmission. First gear was 2.52.If you ordered a close-ratio transmission (M21), the standard gear was 3.36 for hydraulic cam engines and 3.55 for the SHP solid lifter engine. Close ratio first gear was 2.20.
Powerglide BB cars came standard with the 3.36 ratio rear.
Larry