aliass24

I have a 2013 fx4 eco with 4.10 rear and my rpms are ~ between 1950 and 2000 at 65 does that sound about right?

scap99

What size tire?
What gear?

aliass24

I have stock tires 275/55/20 with 4.10 gears.

BRUTE448

[MENTION=12562]ali[/MENTION]ssas is that spec order I've never seen a fx4 w-4.10's

aliass24

Special order with max tow.

scap99

Sounds right to me.

aliass24

Thanks.

RobertEvans

thats about what mine is but i can double check

spotterjoe

Using the formula that I wrote, it should be 1935 RPM, based on a tire diameter of 32" (actually 31.909"). Here is the formula that I wrote. Rear end ratio (4.11) x Transmission ratio (.69) x speed (65) x constant (336) / tire diameter (32").

Probably your speedometer is a little off as they usually are about 2-3 mph slower than indicated to insure that your not breaking the speed limit. I recalculated using 67mph and the rpm shows 1995.

Hope this helps & good luck on the new truck

aliass24

thanks again guys, I just thought that my rpms were a little high compared to others.