Trying to figure out my rear end ratio at 60 miles an hour if Speedo and tach are accurate.
at 60 miles an hour i’m about 3300 RPM and at 70 miles an hour. I’m at 3800 RPM thought maybe it was like 373 or higher?
OG trans seems correct for 71

71 olds 442 convertible

 

SC is 3.08 non posi

Don W

 

Use a GPS to verify your speedometer readings.

 

yes, I usually do. I have to download a new app. I just haven’t done it yet. Thanks. I can’t believe it’s a 308. I could feel the car revving at 3800. So someone changed the gears gotta be.

 

I can’t believe it’s 308 the way the car feels. It’s gotta be higher. Someone must’ve changed the ring and pinion. I’m gonna double check my speedo and tach
yes, single spinner way more fun than a posi. If I go around a turn, I could hit it and then the tire just smokes. Haven’t done it on this one yet but you get the idea ha ha

 

And the tach.

 

Axle tube stamps/markings are listed in the CSM.

 

Jack it up and count the revolutions of the diff and tires and calculate, that will get you close.

 

Without knowing tire diameter it is impossible to provide useful information. And that's outside diameter of the tire, not the wheel diameter.

 

Those numbers seem more like 411 gearing i would guess the rear ratio was changed . as Joe mentioned tire size would help.The best way to clear it all up would be to pull the diff. cover and see ,an opportunity to inspect ,change the fluid and gasket