65 Fury - how do I tell my rear end ratio - want a posi..

[barsteel]

Hello!

My '65 Fury has a very nicely built 440 and a factory 4 spd. I'm at the point where I'm going to have to buy a new right rear tire because if I stomp on it up to about 30mph, the rear tire will break loose and continue to spin until I take my foot out of it.

So...I'd really like to upgrade to a posi/sure grip unit so that the tires can hook up rather than spinning.

I recall the original owner telling me that had 3.23 gears, which sounds about right given that it cruises nicely on the highway, but I'd like to be sure. How can I tell what the ratio is short of pulling the 3rd member and counting the teeth?

Anyone out there have a GOOD sure grip 3rd member with 3.23 or close gears?

Thanks...

Chris

 

[Davea Lux]

If the rear end is original, it will have a metal tag with gear ratio on one of the mount bolts for the third member. If you have the build sheet, the gear ratio the car came with will be recorded on the sheet. 3.23 was the standard gear ratio with the 3.55 optional on some models with 4 speed transmissions.

Dave

 

[Newport 66]

Old school method: get the rear wheels off the ground with a jack, place jack stands on a secure place such as the axle housings. Then make a chalk mark on the driveshaft and turn the rear wheels in the driven direction one rotation. You should also mark the wheel or tire for a reference point. Count how many times the driveshaft rotates using your chalk mark as reference. You'll get really close- i.e. 3:23 etc.