Gear ratio's

Gang I need some info. My coupe is running a SBC 305 .030, Offy intake w/ 3 rochesters backed by a 350 Turbo. My rear end is out of a Ranger P/U, I think it's an 8.8. Question is how can I determine the gear ratio, will it handle approx 130-140 MPH? Any help will be appreciated.

 

Remove the rear cover and count the teeth on the ring and then the pinion. Divide the small number into the large number ... then you have the rear end ratio.

Then we need to know how TALL the tire is.

Before trying to determine a high speed

 

Probably! But it depends on what you're towing it with.

 

Dave this was discussed in depth just yesterday, do you have a posi rear or open, this will help save some time typing, or use your search.

 

Absolutely.
By removing the cover you get to visually inspect the crown and pinion as well as change the gear oil. I've seen gearsets with fractured teeth that still turned easily and had no noise.
You don't want to find out at 140 mph (cough, cough...) that your gearset or diff is compromised.

A quick check (at the junkyard for example...) of a diff like a 9" or an 8 3/4 Dodge that doesn't have a removable cover, would be to do it this way:

For an open diff...jack one wheel and let the other remain on the ground.
Mark your yoke and the housing so you can count turns.
Mark the tire and spin it slowly TWO full turns while you count the number of driveshaft revolutions.
3 and a 1/2 turns of the driveshaft...3.50 gears
2 and 3/4 turns...2.75 gears
4 and a tiny bit...4.10's or 4.11's....etc


For a Posi...
Jack BOTH wheels.
Mark as per previous.
Rotate both rear wheels (should happen automaticly by turning one wheel...but make sure its actually happening evenly or your count will be wrong.)
Count the driveshaft revs and the numbers work out the same way.

You spin an open differential twice because your allowing for the 2 to 1 reduction thru the spider gears of the open diff.
Posi's don't do it that way as the clutches keep things locked together.

 

This points me in the right direction, Thank you for the reply's, I'll check the tire height also. thanks again

 

If the 8.8 is factory fresh, it has an aluminum tag under one of the bolts near the top. The washer will cover most of the first number. Look for 3.45, 3.73, or 4.10, Those are the most common. If there is a "L" at the end of the number, it is a factory Traction Lok. Use a bottle of additive when you change the lube.

 

Respectfully correcting, 3:45 should be 3:55, thats what happens when we get old