here it comes! stupidest question ever

has anyone in any manual transmission replaced their over drive gear?

im looking at a transmission picture of just a traditional 5 speed manual and was curious if exchanging the over drive (5th) for a smaller gear would lower your cruising rpm's? if so how feasible or practical is it?

and i know it might seem like a stupid question but its something i have kind of always wondered and please im not really in the mood for sarcastic responses unless its a really good one thanks

 

put up the picture you're looking at.

 

http://static.howstuffworks.com/gif/transmission-5speed-gears.gif

 

Its not really a stupid question.
You could change the overdrive gear, but you would also need to change the idler, or final output gear to compensate for the difference in gear diameters.
I doubt that a gearset would be available from the factory, even from other model vehicles. So that means that a gearset would have to be custom made. You would need to figure out the tooth count for both gears, helix angles of the gear teeth, as well as material and heat treat properties.
In a nutshell, it would be more trouble that what its worth.

 

Wouldn't changing your rearend ratio be a better idea???

 

Changing the final drive ratio at the differential would be more straightforward and probably cheaper, though it wouldn't have exactly the same effect.

 

ya i guess^

to the rest: i want to do 4.56 when i get some 295/75 and all i want to do is change overdrive. i dont want to put <4.10 in my diff cause then the truck will turn into a doggg (even moreso than it is). im not looking to change all characteristics just that of the overdrive

changing the gears in the diff to < 4.10's would make my highway rpm's lower but then around town would suck, therefore changing the overdrive gear would only affect that, overdrive? is that right?