John ~
Here is what Jim Carter has for info:
****Ring And Pinion
One series of the famous "drop out" GM differentials was used between
1946 and 1972 on 3/4 and 1 tons. The complete assembly (often called a
pumpkin) will interchange during these years with no alteration.
The highest gearing in this series is the 4.10 ratio and is found in
most 1967-72 3/4 tons with automatic transmissions. Therefore, those
"low gear blues" often associated with 3/4 and 1 tons during the late
1940's and 1950's can be greatly improved with no visible exterior
changes. Originally these older trucks had a ratio of 4.57 in the 3/4
tons and 5.14 in the 1 tons.
Once a 4.10 pumpkin is located (usually in a local wrecking yard) it is
a basic interchange requiring little more than new gaskets and gear
grease. Your truck's personality is now changed!
For those wanting a new 4.10 ring and pinion, production was begun again
in April 2000 (at this time they also produced a 3.90 ratio). In order
to use these assemblies in the 1940's and 1950's truck, they must be
attached to the differential carrier from a 1964-72 3/4 ton. Only then
can the complete pumpkin be installed in the older truck.
The only negative to this changeover is if you are hauling a ton of
gravel up a mountain road with the original smaller six cylinder!! In
this example a lower geared differential is best.
****This page and all of its content are the property of Jim Carter
Antique Truck Parts.
I recently paid about $300.00 with shipping for a 1970 Chevy C20 3/4 ton
4.10 third member. As you probably know I am also running a 5 speed
Chevy S10 T5 tranny so the 4.10 should be OK. If not I will get the
3.90 gears from Jim Carter.
Tom
Tom Poterack
Moline, IL.
Z49 Chevy Pickup Retro Rod
Inliner #3511 V8's R not INLINE
http://community.webtv.net/TOMPOT/TOMS1949CHEVYPICKUP
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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