Info Please - Rear Axel Ratio

boblyon1 · #1 (**permalink**) 02-13-2008, 01:02 PM

I'm a third owner of a MkIII SPF, Number 633, completed in 1999. I've looked over all my owner literature and cannot find what the standard or "default" rear-end ratio was for that series. The owner's manual says I have a Ford 8.8differential. The first owner installed the 351W and Tremec 3550. The SPF invoice does not give any info in this regard.

Stenhouse's gearing calculator indicates that the ratio could be any of seven, the lowest being 3.08 and the highest being 4.56. Any suggestions? Thanks.

Randy Rosenberg · #2 (**permalink**) 02-13-2008, 01:32 PM

Stock, they came with 3.73's.

Bill Wells · #3 (**permalink**) 02-13-2008, 01:43 PM

The switch from Ford to Dana rear ends occured about March 22, 2005 with chassis # 2068 . The Dana rear ends are a 3.46 ratio .

As Randy stated, your serial is within the Ford range and had a 3.73 ratio. Bill.

Anthony · #4 (**permalink**) 02-13-2008, 04:52 PM

Likely 3.73's as was said before, but, you can Jack the rear up, and while in neutral, spin the tires one revolution, and count the revolutions the driveshaft makes. That'll tell you the ratio.

Bob In Ct · #5 (**permalink**) 02-13-2008, 06:53 PM

It's a 3.73. If you have a Tremec 5 speed with a 0.68 OD there is too big a jump between 4th and 5th. I wish I had the 3.46 (or even a little taller gear) with a 0.80 OD.

Bob

boblyon1 · #6 (**permalink**) 02-14-2008, 02:04 AM

The popular wisdom seems to be a 3.73 rear end. This makes a lot of sense. Thanks to all that responded.