rearend ID

[bigcarguy]

How do I tell what gears I have in my rearend? I have a 72 C10 with a 307.

[Longhorn Man]

Pop off the cover and count the teeth. Divide one by the other (can never remember which is which) and that will give you the gear ratio. It's probably a 3.07. But your gear oil probably needs chainged anyways.

[Fast68Chevy]

the numbers you need wil be stamped on the very edge of the ring gear in plain view, may have to turn the gears a lil before you find the spot that they are stamped on on the gear.
the numbers of most importance will look like somethin like this: 41 - 9
and 3 - 16 - 72

if the 307 engine is wat truck originally came with then it will be 3.07 if with 4 speed or auto and 3.73 if with 3 speed manual without O/D


good luck

[JHickson6]

Another possibility would be to check the driver side axle tube for the stamped in axle code. Then take that code and find it on the chart below. This chart is off of www.americanclassic.com/paint.htm

1972 Rear Axle codes

Series Code Ratio Plant
1/2-Ton RAA 3.73:1 N/A
1/2-Ton RHA 3.07:1 N/A
1/2-Ton RHB 3.07:1 N/A
1/2-Ton RHC 3.73:1 N/A
1/2-Ton RHD 4.11:1 N/A
1/2-Ton RHG 4.11:1 N/A
1/2-Ton RHS 3.07:1 N/A
1/2-Ton RHT 3.07:1 N/A
1/2-Ton RHW 3.73:1 N/A
1/2-Ton RHX 3.73:1 N/A
1/2-Ton RHY 4.11:1 N/A
1/2-Ton RHZ 4.11:1 N/A
1/2-Ton RRR 3.07:1 N/A
1/2-Ton RRS 3.07:1 N/A
1/2-Ton RRT 3.07:1 N/A
1/2-Ton RRW 3.07:1 N/A

[Fast68Chevy]

pass side tube top front side of it about 4 to 6" from the edge of the cast iron center housing sleeve where axle tube enters, codes are also listed in the red book, which alot of us have handy
72 is the only 67-72 year with R codes, 70 and 71 are T codes, and 69-earlier are two digit codes

[JHickson6]

Sorry your right Fast68Chevy, the axle that i checked was upside down! Woops!

JHickson6