The Stovebolt Site Forums The Shop Area Engine Shop 68-72 pumpkin ID

I'm heading to the Turlock swap meet next weekend and I was wondering if there is a way of identifying a 4.11 pumpkin out of a 68-72.

I'm thinking of using it to swap out my 40 3/4 ton rear end. If not, I'm conidering a 9" sitting at the local junk yard.

Any thoughts?

Hate to see your post not get answered. Bump.

I had a 1958 5.13 pumpkin and a 1971 4.11 pumpkin setting side by side. Just looking at dimensions (from the outisde) I couldn't tell any difference. The new pumpkin had LOTS more casting marks all over the sides. Especially around the adjustable pinion support area.

Count the teeth on the ring gear & divide by the # of teeth on the pinion gear. Brian

In My..I don't think that 9" will be 8-lug configuration...are you running a stock front axle?...My '53 3/4 has a '68 F*&d Dana 60 3.73..pretty good fit..still heavy duty,still 8-lug.

INYOUR40's
1) Like fleetside said, you can count the number of teeth on each gear (i.e. 41 Ring gear teeth & 10 Pinion gear teeth =41/10 or 4.10 ratio) or
2) The number of teeth should be stamped on the end of the pinion gear shaft, which is visible from the inside of the differential-bring a flashlight & you may need to reach in and clean off the end. You'll see a bunch of numbers but some will read something like "GM-7-32" which would mean 32 ring gear teeth/7 pinion gear teeth =4.57 ratio. This method is easier.

It's easy to tell the gear ratio of the pumpkin (just count the teeth). But how do you tell if it's a pumpkin from a 68-72?

I don't know how.

jhaa_lives are they stamped H072?

I've been looking around and I found this description of a GM rear end.

I can't tell if it was the same for Chevy, but the GM was use from 50-72.

Can you let me know if there are any part numbers on yours?

jhaa_lives,

A '68-'72 would be a coil-spring setup, so look for the round spring perches and brackets for trailing arms. However, I know '67 is also coil spring, and I think the previous model ('60-'66?) was also. Is there a reason it has to be from a '68-'72?

Paul

'60-'72 are for the most part coil spring, though some do have leaf spring, mostly 1 ton and 3/4 ton Camper Specials. The reason that you'll want to look for a late ('67-'72) rear is that they are more likely to have the 4.10 ratio. Most of the earlier diffs are either 4.56 or 5.13, depending on wheather they were 3/4 or 1 ton.
InMy40s-the diff pic you have linked in is a Chevy diff, most GMCs from '60-'72 use Spicer 60 or 70 diffs. There is also little difference between the HO56 and the HO72. Mainly it's just the original application, the 56 was used in 3/4, the 72 was 1 ton.