Yeah this is always what happens when we open this discussion. Someone reads 3.90 and
insists that their truck has one in it but they are always getting the half ton gear set mixed
up with the HO52/72 axles.
But the question was why JC doesn't up date his tech notes. Every newbie with a 3600 or
3800 that reads that note has this false hope that he's gonna be able to find on of those
new gear sets only to find after months of searching and 29 pages of us explaining that
there are no mo of those around and haven't been for a decade. I'm running a 4.10 in my
'50, 3604 and have been searching for a donor for my newly acquired '54, 3604. Even the
used 4.10 axles are getting almost impossible to find now.
Iin the six years that I've been back to the hobby I've yet to hear from anyone that has
ever had one of those new 3.90 gear sets for an HO52/72 axle.
Jerry I do have an early and a late pumpkin here and I had both of them apart next to each
other on the bench. I matched up the early and the late differential carriers and they are
the same dimensionally and they will interchange as do the spiders and I also swapped the
ring gears from one to the other, both were 4.57 ratios and I saw no difference between
them.
The problem comes in with the pinions, they are different. The early and late housing is
cast different internally in the way their pinion is supported and you can't exchange the
pinions.
Denny Graham
Sandwich, IL
Last edited by Denny Graham; 11/17/2011 11:00 AM.
