Hi all new to the forum, just bought a 2001 cherokee with 113k, auto 2wd all stock. My question, where is the rpm supposed to be while cruising at 60-65? mine is at like 2000-2200. Also it seems like im going faster than the gauge says, I have 235/75/15 those shouldnt throw off the guage, could the speed sensor be bad? thanks guys

 

Those tires are 2% taller than stock so the speedo is indicating less than actual speed. RPM seems about right but the taller tires effect that also.

 

I have the build sheet on my 01 Sport and it came with 225/75/15 if that helps.

 

My 2000 Cherokee Sport has a 3.55 rear end and it turns almost 2200 rpm at 65/70 mph.

 

The RPM is about right at 65 MPH in overdrive

 

I have 3.73 gears and that sounds right. Usually shifts to second at 10-ish mph, to third at 25-30, and fourth at 40-45. On the highway at 65-70 its usually 2250 rpm or so.

 

You are going faster with the 235 tires. I looked it up on some site that calculates the size tire with the speed and going from 225 to 235 tires you are going 3.2 ish mph faster at 70 mph.

 

thanks for the help guys i guess my tranny is workin fine

 

the 235 in the tire size refers to the WIDTH of the tire, not the diameter....

 

just to explain, they depend on eachother.

Width Aspect Wheel Diameter Section Width
225/75 15 = 28.3 8.9
235/75 15 = 28.9 9.3

The above numbers are computed values and some rounding has been done on the computed values. The actual tire sizes can and will vary depending on the tire manufacturer.

notice how the first # (width) changed but it also changes diameter. the second number (side wall height) is calculated off the first #. equation is-

HEIGHT = ((width * aspect-ratio * 2) / 2550) + rim size

WIDTH = (width / 25.50 )

For example, a 235/75R15 tire is ((235*75*2)/2550)+15) = 28.8 inches of tire height. The tire width is figured by 235/25.5 = 9.21

Metric tire sizes are stated as three numbers. The way it reads is:

width / aspect ratio R tire rim size
235 / 75 R 15

But staying on topic what your describing sounds normal to what mine does in OD, 2200 rpm +/- 50 ish rpm

 

2000-2200 RPm at 60-65 mph... I think you rig is doing good... Its above average...