Ok one of my friends got 3.73s in his car and he says anyways that his gas milage went up and he only runs about 2300 on the interstate at 70. Now he has a 02 3.8L V6 and like I said he says his milage went up.

I have always been sceptical of getting gears in my car because of the fear of losing gas milage and wearing my engine out ever so sligthly quicker.

So My point is I already have a Tlock and I was wondering if I should do some 3.73 or not, because they seemed to help his car quite a bit but, I was wondering how the 4.0's reponded to gears.

 

3.73s will help on take off and gets the engine
in its RPM power range faster.
But at 70, the RPMs will be much higher
with better throttle response but decreased
MPGs?

 

I got a t-lok and 3.73's installed back in October. My mileage hasn't changed at all. I don't really do a whole lot of highway driving though, just city. As far as response, it's amazing. No regrets at all.

 

When I put the 3.73's on I had about a 1-2 mpg drop. I do a lot of highway driving daily.

But your friend is BS'ing you - the engine is turning at higher RPM so it is using more gas. He may think that he is getting better MPG, but I bet he never changed his computer to know that he has something other than stock gears in the car. If I put my nitrous tune on the car to make the drive to the track I get amazing gas mileage - but that is because the nitrous tune reads the gears as 3.31 (I need to have my tuner unlock the parameters so I can set the gears to the 3.73).