Quote:
Originally Posted by Clarke
This doesn't answer your question, but I thought it would be appropriate to share. With my original 4.56 I was getting 9 mpg (mostly highway). After switching to 3.54 it improved to 11.3 mpg (same highway driving). The only reason I made the gear swap was due to the amount of highway driving I do and didn't want to beat the engine up keeping up with traffic.
|
David's reply reminded me of an experience I had when I first bought my '67 K model. I traveled from Medford, OR, down to LA (about 700 miles) to buy it. With the 4.56 rear gears it was a long, slow trip home burning lots of gas. I have a long (2/3 mile) steep gravel driveway, so I always use 4WD going up to keep from tearing it up. I got a big surprise when I shifted into 4WD and the truck wouldn't move. Having had the same experience a few years earlier though, I knew right away what the problem was. After shifting back into 2WD and proceeding up the driveway, I discovered that some previous owner had switched out the front gears to 3.73. Needless to say, I had the rear gears switched to 3.73 to match the front, and now enjoy better gas mileage and quieter freeway driving.
Coincidentally, the '62 Suburban I bought several years before that (from Jimjaz, sometimes on our forum) in the Phoenix area had the same problem. It still had the original 3.92 gears in the rear end. When I tried to go up my driveway in 4WD after the 1100 mile trip, it wouldn't go. The front gears had been swapped for 3.54 gears. So I had the rear changed to 3.54 and added a Powr-Lok while I was at it.
So, to answer the original question "Is it worth it?", for me it may never pencil out as a cost savings since I don't put a lot of miles on any of my 4 trucks. But to me it's worth it for peace of mind knowing that it's easier on the engines not to turn so high rpm's. Quieter running and saving gas are just added bonuses.