Big Block Differntial Match Up

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Dec 27, 2014 | 10:55 AM

SS Vette

Thread Starter

3rd Gear

Joined: Nov 2014

Posts: 3

Likes: 0

From: Harwood Heights Illinois

Big Block Differntial Match Up

I have a bone stock '77 with an L48 and Th350. I recently came into a GM crate 454 backed by a 700R4 (dirt cheap, I couldn't pass it up). My question is about the differential gear ratio. What is recommended for a cruise nite car with possible highway driving? I don't plan on racing the car, I just want a "pleasurable" driving experience.
Thanks!

Dec 27, 2014 | 10:57 AM

'75

Le Mans Master

Joined: Dec 2007

Posts: 6,422

Likes: 591

From: McHenry Illinois

3.70 or 3.55 gear should work good with that trans.

Dec 27, 2014 | 11:02 AM

glackore

Pro

Joined: Dec 2006

Posts: 695

Likes: 5

From: tx

You're asking ....... 3.54/3.55 is my suggestion.

Dec 27, 2014 | 11:09 AM

zwede

Race Director

Joined: Sep 1999

Posts: 11,361

Likes: 383

From: Plano TX

The 454 may have a really mild cam in it (if it's from GM it probably does). If so your stock ratio could be fine, even with the overdrive.

Dec 27, 2014 | 12:22 PM

hugie82

Safety Car

Joined: Mar 2007

Posts: 3,652

Likes: 49

From: Bridgewater nj

With a 700R4 you have the best of both worlds. A very low 1st gear and a very high overdrive. With 2:73 gears in my 82 I'm doing 2000 rpm at 80 mph in overdrive. If you drive like me 3:23 or 3:55 would be my limit because I'm always doing 80mph. If you don't drive that fast, then 3:73 would work great!
My 74 vette with a 427 4 speed had 3:08 gears and was a good all around gear WITHOUT an overdrive.