adjustable final drive ratio
 

This thought occurred to me today: Has anyone ever tried to create a vehicle with an adjustable final drive ratio?

I know you may be thinking that it's silly (just build a better transmission with more gears). I'm just thinking along the lines of a pickup truck that is sometimes heavily loaded, and sometimes empty. It may need a 4.10 rear end for hauling, but not for highway cruising.

Of course, the mechanics of temporarily disengaging the drive shaft would be complicated...I'm just thinking theoretically right now.

Kind of like a CVT?

A CVT will have a maximum and minimum ratio just like a manual or automatic. There used to be two speed rear axles, may still exist. Better to add an overdrive gear to the existing transmission and then you can choose the higher gears that match your load.

My 92 F150 had a .79 overdrive and a 2.73 rear axle. Overall that would be the same as a direct 4 speed and a 2.13 rear axle.

My design has the capability to make the overall drive ratio practically anything you want including the wheels spinning faster than the engine. That way you can change the overall drive ratio and lower engine speed while increasing the load regardless of the vehicles speed, load, or grade.

regards
Mech

I always thought this was a great idea and wonder why it was not further developed...

Mitsubishi Super Shift transmission - Wikipedia, the free encyclopedia

My m/t Tempos have a 4 speed transmission and 2 final drives; they could have opted to give me a twin stick shifter (4 speeds with hi/lo option for each one) but only gave me the high final drive in 5th instead.

http://upload.wikimedia.org/wikipedi...rshift_001.JPG

http://upload.wikimedia.org/wikipedi...t_3_d_1982.jpg

I actually drove one of these once! Probably right around the time I got my driver's licence.

A DIY vehicle with a "multi-range" gearbox (2 gearboxes, actually):

http://ecomodder.com/forum/showthrea...odel-t-92.html

Speaking of multi-ratios, the school busses I used to ride on had 2-speed rear axles. And my auto shop teacher in H.S. told us about a pickup he installed two manual transmissions back-to-back in.

I know someone that had one and he used to drive me to school in it sometimes. It was fun when we figured out it had two speeds in reverse too. :-)

Ok, so a CVT with the maximum and minimum ratios higher and lower, respectively, than you will ever need. :thumbup:

I used to have a s10 pick up that had a 4.3L , 4 speed auto, & 3.08 gears. Added a gear vendors overdrive to that combo, it would turn some real low rpms. If I remember correctly is would turn 2000rpms @ 70mph stock, turning on the GV od brought it down to 1450rpms or so. The truck was light, the engine was kinda torquey, so it would never really lug the engine. The slowest I could go was around 52-53mph in the tallest gearing mode, the truck handled that just fine even w/ the a/c on. It was turning 1100 rpms & would get 33mpg in the summer.