available rearend ratios

[Ackattack]

I have a 12 bolt out of a 73+ in my 69 pickup. It has 285/70/15 tires on the back and sm465 tranny.

Tonight I took it out on the highway for the first time to see what the rpms were like. At 65 it was only turning 2000 rpms. About 1900 at 60.

Based on ideal tires height and what not, this puts me somewhere between a 3.07 and a 2.73. I know the 3.07s were available in the 67-72s, were they available in the 73+. Was there any higher gears like 2.73?

I obvioiusly haven't popped the rearend cover, other wise I'd just read it off the ring gear.

[Max1775]

Not sure about ratios offered, but you can mark the drive shaft and the tire, roll the vehicle forward to make one full rotation on the tire and count the rotations of the driveshaft. that will give you your rear end ratio.

[veinbar]

They don't offer a 2.73 for a GM 12 bolt rear. It's more than likely a 3.07.

[Ackattack]

Originally Posted by veinbar

They don't offer a 2.73 for a GM 12 bolt rear. It's more than likely a 3.07.

That's kinda what I was thinking, but wasn't sure.

I think my tach is off (based on plotting a few points in excel). I don't like it anyways.

[jrcaprai]

Mine is a 76 and had the 3.08 Stock

[gchemist]

I have a 77 in my 83 with 3.08 gears. Run okay with the ZZ4. Towing, forget it!! The weight is definately felt. I'll probably go 3.42s or 3.73s later.

[87 V20 Scottsdale]

I had an '86 K10 with a 2.73 gear ratio, 12 bolt axle.