Originally Posted by frank-id
There are several methods of changing gear ratios. The easy way is to find a truck over/under drive gear box. These are hard to find but a great device for having all the good desirable gears. Find a overdrive unit to bolt to rear of current transmission. Finally, your vehicle is a very new type bus, so the parts needed could be available from a truck salvage place. I do not have any cost information. New gears to change ratio are easily available. Now the big decision will be..... rear gears ratio wanted/needed. Not all roads are steep nor flat. My goal is for more top speed and economy. My choice was 3:55 and currently my bus is 4:10 ratio. Changing the gears does require some mechanical skill. The most important part of the task is setting up gears for preload and gear pattern
in relationship to gears contact. Maybe a truck mechanic can be recruited for the fine adjustments. The gears are heavy and require a floor jack or trans jack to lift. A salvage gear set assembly will merely need some inspection by a mechanic, and probably no adjustments. Be sure to check the gears and lube carefully. If the donor is a wrecked truck, yea!!!!! The results are very rewarding. Maybe some one will need the old assembly. Frank
For my Ford, I'm changing the gears from 4.88s to 3.7somethings by buying them from Arvin Meritor. Here's the link:
This isn't cheap either. I have a reliable mechanic that's done this for decades. The total bill will be near $2K. Obviously not for everyone. However, for our needs it works in the long haul (pun intended). The intention is to get Big Max to cruise at 65 mph more or less and keep the fuel economy. I'm not concerned about acceleration, Big Max never had any neck-snapping G-forces in this department to begin with.