just wondering if i could get a real world number for running 4:88 gears with 35" tires at 75mph. if any one knows i would also like to know how well the stock 4:10 gears pull the 35" tires. thanks for the help.

 

there are some calculators online and some tables, if I located them again, I'll post up here.

I've had my 35's on the Rubi since last Thur and with the 4:10s it runs fantastic, no issues going up bridges with 6th gear or anything. Not sure if you're auto or manual (manual) here and love the 4:10's. I'll probably do 4:88 or 5:13s one day but taking it offroad this weekend and climbing in 4L was barely different than with the 32s.

 

i'm running an automatic. i've seen the gear/tire ratio charts but not the gear-tire-rpm chart. mine feels like the parking brake is halfway pulled when i'm going up hills on the highway but pulls great at lower speeds with the stock tires. i just want to make sure i'm not going to have to lasso the winch cable to a diesel when going up hills on the interstate after the lift and tires. gears will be in the budget after tires, wheels and lift.
thanks for the help.

 

Mine is just over 2500 rpm @ 75. I had my gears before my tires, so I cant answer that part. The power seems to be about like it was stock (its a Rubi).

 

My numbers are about the same 2500 @ 75 35's 4:88's auto. I still find myself locking out the OD when I am on any kind of a hill. I would like to drive one with 5:13's to see if it is better. It is tons better than my stock 4:10's. Does great off road.

 

Not to hi-jack this thread, but I think this might even help the first poster out.

That's great that you posted this, because I think I've finally found my missing number...

I've been trying to derive the formula that is given in many gear catalogs: rev/min=[(mi/hr)*gear ratio*336]/tire size. I've been able to break everything down easily enough and found that the factor of 336 that they use is to make all of the units cancel out when the tire size in inches and speed in mi/hr is used so you end up with rev/min. They additionally used 1/pi to get the circumference into revolutions.

What confused me was I was getting a calculation of 3318.68 rpms for my 5.13 gears and 33.75" tires (measured) at 65mph. However, while driving I would read a speed of only about 2750 rpm's at 65mph. With your manual transmission ratio multiplied into the above formula, the rpms come out about right, 2788.53!

Awesome.