View Full Version : Which final gear for 2nd car and weekend racer?

07-11-2018, 07:14 PM
I heard there were three options 3.35, 3.55 and 3.73. Which came stock on which SVO and how do you know what's in the rear without opening it?

07-11-2018, 08:36 PM
No, No, and Yes

1984 only - 2nd gear 2.37, rear 3.45, total ratio 8.18
1985/1986 - 2nd gear 2.14, rear 3.73, total ratio 7.98

There should be a tag on the rear diff cover. If not, raise rear, mark your rear tire, put trans in nuetral. **Be safe, wheel chocks and jack stands**
Count driveshaft rotations / 1 wheel rotation.
Approx 3-1/2 revs = 3.45 gears, approx 3-3/4 revs = 3.73 gears

Reference FAQ section

For short course Auto-X I run the '87 Turbo Coupe trans w/2.34 2nd gear w/3.73 = 8.73 total ratio.
What kind of "weekend" racing are you planning?

07-11-2018, 09:00 PM
Thanks, if we can tune an SVO to make 300whp, a 3.73 would be under driven @5800rpm. I think I remember reading Fox Cobras had a 3.08 rear, does anyone know its total ratio? Ideally, a 300whp SVO that is still polite when grocery shopping with a 7.0 total ratio seems like a plan. Does anyone have a spare 3.25 rear? Is there one in any 8.8 rears that you guys can think of?

07-12-2018, 01:00 PM
I have fun with my 4.10's in my 86, although I am only ~270rwhp ;) My choice for that gear ratio is that they were available just as I was swapping from the stock 7.5 to an 8.8 that had 3.73's that someone I knew just had to have. Since I was drag racing at the time the 4.10's were a natural setup and did get me 1.8 60' times on slicks. Now that I auto-x and HPDE, they actually work pretty well too, so I wouldn't hesitate to recommend over the stock 3.73's in an 85.5/86. I think they may be a bit much in an 84/85 though.

Now, I did have an 84 T5 out an SVO in my former 80 Mustang that had a NA 2.3L. When I crunched my 2.73 gears in that car, I moved over to a 3.27 ratio set. That really woke up the little 2.3L and worked great with the 84 T5's gear ratios. In pure stock form that car went 18.5's @ 73mph, when I had things dialed in with the engine/tranny/gears it was going 15.4's @ 85mph. Not too shabby for a NA 2.3L back in the day.

07-12-2018, 01:19 PM
Not too shabby for a NA 2.3L back in the day.Those are some good numbers for sure on a Lima. If you can remember what you did, you would be the guy to consult on getting the SVO to make 150whp without the snail.

I've only been to Sarasota and NJ Sports but I plan on others. I'd be looking at SVRA track events and the like. Straight line runs that end before they even start don't excite me :)