repacking rear gears

[63Stepside]

Greetings all. As you can tell from my user name I'm the proud owner of a 1963 Chevy Stepside. In a effort to extract the best possible gas mileage from my straight six I plan to install the most fuel efficent rear end set up. My question is: Can you pack 3.07 or 3.38 gears into a transfer case that once housed 4.11 gears? If so,It will cost $200 for a new ring and pinion and $300 to install. I would much rather go this route than buying a 40-45 year old complete rear end and installing it myself. If you can offer some advise please email me at andy_824@windstream.net (that's an underscore between andy and 824)

[Fastrucken]

You will need a spacer that goes inbetween the carrier and the ring gear to place a 3 series gear on a 4 series carrier. other then that no issues. this is assuming you have the 12 bolt and not the eaton rear end.
Graham

[greg64]

Howdy from BC! Typically, the carriers that hold the ring and spider gears are capable of handling a certain range of ratios. This is to accommodate the differences in pinion gear diameter. What type of rear end do you have under your truck? I wouldn't be surprised if your 4.11 carrier can accommodate 3.07, but I'd want to check to be sure.

[billydonn]

If it's a truck twelve bolt, the dividing line for the carrier change is 3.73, I believe. This is based on shopping I've done for new ring and pinion sets.

[kdrodworks316]

just my opinion, but why not update the whole rearend? maybe a 12 bolt or a dana 44 out of a 73-92? would require a little fab work, but should be cheaper and easier than rebuilding your existing one. not to mention the 44 would be stronger and have more gearing options.