I've got an auto 91 rs with stock wheels and 245/50/16 tires and lsd. I'm just wondering what gears I have...I'm doing 2250 rpm cruising at 60mph. I read in a haynes manual that my model was only available with open 3.23's and lsd 273, don't know how true that is though. Either way, help is appreciated.

 

The stock tach is worthless as any kind of reality indicator. All it is, is a trim piece; designed to enhance the interior's "sporty" image.

If your car is a 305, it most likely came with 2.73 if it's an auto and 3.08 if it's a stick.

If it's a 6-cylinder, the ratios will be higher, but I have no clue exactly what, as I know nothing whatsoever about 6-cylinder cars (except that I don't want one).

What it HAS, and what it CAME WITH, can easily be 2 totally different things; especially since if it REALLY and TRULY has a posi, and not just a "my car leaves 2 stripes" posi, then it's about 99.99999% certain that somebody's already been inside it. Which means that all bets are off, as to what's in there.

If it really matters to you what's in there, take off the cover and look. It's the only way to accurately know. And of course, if you haven't looked, then you don't really know you have a posi, anyway; you're just guessing.

 

Sofa, you're becoming predictable

Here's how to determinne what ratio the rear is (jerk the diff cover and look): numbers are stamped on the ring and pinion:

41 : 15 = 2.73
40 : 13 = 3.08
42 : 13 = 3.23
41 : 12 = 3.42
41 : 11 = 3.73

JamesC

 

So an open diff can "leave two stripes"?

 

yes it depends on the wieght over the rear tires, mine is balanced perfectly with my sub and will leave 2 strips, before, it only left one

to truely find out, jack up the rear of the car, stick it in neutral, and turn the tire, if the other tire turns in the same way, it has an LSD, if it turns in the opposite way, its open

 

old wives' tale - A torsion type posi will react like an open diff when "tested" in this manner. - To truely find out, pull the cover and look. The fluid probably needs changing anyhow.....

If it's actually turning 2250 @ 60mph it would be somewhere around 3.73, depending on tire size. - As stated though, that factory tachs are know for being less than accurate.....

 

ok thanks...but about the weight balance deal....both tires spin with nothing in the back except the spare and jack. I'll pull the cover one day and see.

 

For the weight balance, every car is different. If the weight happens to be sitting in a manner that your tires are seeing close to equal traction, then even an open diff may spin both tires.

- The only way you'll ever know what you have is to pull the cover. If the gears happen to not have numbers stamped in them, count the teeth on the ring and the pinion. Divide the number of ring gear teeth by the number of pinion teeth - this # will be your gear ratio(rounded to the nearest hundredth)