Rear End

[70short]

I have A "70" with 6 lug axles 308. Found one for sale out of A "72" auto truck for sale I am going to look at. Aren't the auto trucks 373 gears and are they not A narrower rear end? How much narrower? Is the swap over to narrower when they went from 6 lug to 5 lug?

[brn agn]

I'm not sure about the gear ratio, but the 71 and 72 12 bolt rear ends are approximately 1.5" WIDER than the 67-70 rear ends. I believe that this coincides with the 6 lug to 5 lug switchover. Hopefully someone else will confirm.

[VDOG]

I can only tell you 1970 and later rearends are different from 69 on down.
Found out the hard way when I took a 3:73 rearend out of a 71 6 cyl truck to put in my 69.

Once installed, the the passenger side axle went in deeper than the driver
side. 70 and up one axle is shorter than the other.

[treveiger]

So you cant swap a 71 rearend into a 69 chevy truck?

[Longhorn Man]

67 to early 70 were narrow, mid 70 - 72 were wider by 3/4 inch on BOTH sides.
no 3.08 gears stock in 67 - 72, that was a car gear back then. The 3.07 gear was the standard gear in most non big block automatic and 4 speed 1/2 ton trucks. The 3.73 gear was the standard gearset in most 3 speed 1/2 ton trucks. There were exceptions in certian years with certian engines, but that is the generic rule on gearing.

[70short]

So is it safe to say that my 6 lug "70" is the narrow rear end since its 6 lug??


Gary

[Longhorn Man]

actually no. The odds are more likely to be yhat it is the longer one. The wide rear seems way more common over the narrow one.