Ok so Im sure most of us bought our Machs used as I did and its hard telling what mods were done before we bought em unless its obvious things like wheels, stripes, etc. My question today is about diff gears. When I was cruising the highway this morning at the comfortable clip of 75 down the highway (auto w/ OD on) I looked at my tach and its reading 2400-2500 rpms. Is that typical with stock 3.55's in it? With the OD off it jumps up to 3400-3500 which I expected of course. All I have to compare to is my trade in: A 2001 F150 Supercrew. It had the 5.4L, 4 speed auto and 3.55's but it cruised 70 around much lower rpm's. Obviously the transmission will be "geared" differently but maybe Im hoping for someone to tell me someone has put 3.73's in my car? Or is this just typical?

 

sounds closer to 4.10 to me but idk much about autos

 

That does seem a tad high even for an auto.
I too had the same question. At 2k rpms in 5th gear what speed are manuals at with stock gearing?

 

You have stock gears, 3.55s. The autos have a much shorter OD. Fiddle with the calculators in the tech sticky, though some are only applicable for manuals.

PROMETHEUS, 5spd. w/ stock gear..........2K rpm=70 mph, 75mph is approx. 2.2K

 

Exactly dead nuts 70 mph. I drove all the way to oregon at 70mph most of the way and remember it being at 2k rpms.

 

Wow! I'd hate to see what it'd rev at with 4.10's at 75 mph. There goes the mpg! Damn! Cant we have it all?

 

Yeah I figured it was stock gears but with an aftermarket griddle I was hoping..lol
Thanks for the replys and with an auto them RPM's should would be high.

 

Yeah definitely thanks for the replies guys. I agree. I was really hoping for some gears already installed. Guess that leaves me something more to do now but with it being my DD i cant see going beyond 3.73's ...for now.