Rear end

[born2saw]

Anyone have a book that will tell me what were the standard & optional rear end ratio in my 75 L48 wide ratio 4 speed? Is it hard to find the stamped codes on the housing? My mechanic says we may need to take down the spare tire carrier to see them. If I know what the possible ratios are I can jack the rear up, turn the wheels & count revolutions on the drive shaft.

Thanks

 

[JohnZ]

The ratio and date code are stamped into the flat surface on the bottom of the diff, just forward of the joint with the rear cover and the spring lower mounting plate - you don't have to remove anything to see it, but you'll probably have to clean the surface with a stiff brush in order to see the codes.

The 1975 L48 4-speed came standard with a 3.36, and the optional "highway axle" was a 3.08.

 

[resto75]

Was a 3.55 rear end offered by GM as a option in 1975?

Some paper work that came with my 75 showed that the rear was rebuilt and notes 3.55 ratio. I was wondering if that was even a offered rear or was aftermarket.

 

[69MyWay]

Check out the C3 specifications page right here on CAC.

 

[born2saw]

Thanks JohnZ.

69MyWay I checked the specs page for 1975 first & there is no info on what axle ratios were available. Did I look in the wrong place?

 

[JohnZ]

Was a 3.55 rear end offered by GM as a option in 1975?

Some paper work that came with my 75 showed that the rear was rebuilt and notes 3.55 ratio. I was wondering if that was even a offered rear or was aftermarket.

Yes, it was, but only with the L-82, where it was standard with the 4-speed and optional with the THM-400. 3.55 was not available with the L-48. Info is from my NCRS Specs charts.