The Stovebolt Site Forums The Shop Area Engine Shop 66 rear axle interchange?

New-ish to these trucks, but I want to lower the rear end ratio on my '66. Not sure yet what ratio it is(4.10?orig. 6 cyl/3 spd.) but I'm taching almost 3,000 at 60 mph. With the current 350/4spd/245 tire combo I'm looking to bring it down to the 3.0-3.23 range. I'd like to retain the 6 bolt wheels for now so I'm curious what drum to drum rears interchange with the '66 trailing arm setup. I know I can get another R&P just looking for alternatives.

Any help or hints appreciated,
thanks,
Dave

The factory rear axle in the 10 Series trucks in '64-'66, was a 12-bolt with a 3.73:1 ratio. The 4.10 was in the 3/4 ton, Series 20 truck with an 8 lug rearend.

There are many opinions on engine/tranny/axle combinations, to attain more desireable highway speeds:

Swap 4-speed transmission for automatic transmission (350 or 400)
Swap 4-speed transmission for overdrive transmission (700R4)
Higher R&P ratio rearend (3.08:1)
Swap R&P in current rearend (3.08:1)

This topic has been explored, at great lengths, on this forum. Try doing a search for a tremendous amount of information, that will identify the pros/cons to help you make your decision.

Tony Smith

Swapping to a TH350 or 400 wil not gain anything over the 4 speed, high gear will still be 1:1 in either case. The TH700R4 with the overdrive or the gear swap will make a difference. '63-'70 will be a more or less bolt in swap. I do beleive that there is a slight difference in the arms and Panhard bar attachment, but nothing that can't be easily taken care of. You probably have the 4.10 gear, optional in the 1/2 ton, along with 3.08. The 3.73 was the std gear. Aftermarket gears are redily available, but you do need to confirm which carrier (the part the ring gear bolts to) you have to determine what ratios are availble to use without changine the carrier out.

Thanks for the info guys, I tried the search but I guess I didn't have the right keywords to match on.

Dave