approximate rear end ratio?

[73-charger-383]

is there any way to approximate what your rear end ratio is without pulling the cover and counting "teeth"?

[Blown70]

Spin the tires and cound the shaft turn.   Or use a nice marker


Tom

[73-charger-383]

okay, like how many times??
you mean rotate the tires once and count the times the shaft spins, or turn the shaft once and count tire rotation?

[John_Kunkel]

The procedure is different depending on whether or not the rear end has limited slip (Sure-Grip, Posi, etc).

If the car has limited slip, jack both tires clear of the ground and spin one tire a full revolution while counting the driveshaft turns; the number of driveshaft turns is the gear ratio.

If the car doesn't have limited slip, jack only one tire and turn the tire two full revolutions while counting the driveshaft turns.

[73-charger-383]

k.....i went to start to jack the rear end up and noticed a tag on it.   It says 2 7 1   --- is this the tag that identifies my rear end ratio?

[TylerCharger69]

Yep....that's the tag.....providing it's never been altered and someone just put that tag back on it of course...

[73-charger-383]

Is there any way i'm going to get decent performance out of my 383 with a 2:5.1 rear??

[TylerCharger69]

that's worse than a 2:71...you want to go UP in numbers...not down

[73-charger-383]

my bad, mis-typed that..............will i ever get decent performance with a 2:7.1?

[TylerCharger69]

Well....if you want a car with mid to high range performance  (top speed)  probably.   But if you want something quick off the line,  a 2:71 isn't going to help you much.  A 3:23 is a nice gear that will give you some decent performance and still be able to cruise the highway.  A 3:55 would work well too.  It all depends on what you want the car to do, and how much cash you want to spend!!!  I used to have a 2:76 rear end (489 case)  and I was still able to roast tires.  I imagine  that 2:71  is an open differential so don't expect both tires to light up.

[73chgrSE]

k.....i went to start to jack the rear end up and noticed a tag on it.   It says 2 7 1   --- is this the tag that identifies my rear end ratio?

Where exactly on the rear end is said tag located? I did not see it on mine.

[TylerCharger69]

It's a silver tag that would be on one of the bolts on the differential....You may need to do some cleaning to see it if it's dirty.   I'm not sure which bolt..but if it has never been touched...it should be there.