98 XJS

I bought my XJ tonight and on the ride home I was hitting 2300 rpms+ at 55-60 mph.... It must not be dropping into high gear. what rpm should I be looking for with a stock rear on 31's? its a 98' I'm thinking it should be living around 1500

thanks

Zab243

that would be amazing for 1500 at 60-70

mine runs 2200 at 60 and 2500+ at 70

so your rmps are fine

98 XJS

yeah I guess you're right, 1500 would probably be dreaming, but I'm still not confident that its dropping into OD

no rdplz

Well, start being confident. 65mph should be about 2000 rpm's with 31's and 3.55 gears.

SeriousOffroad

http://www.grimmjeeper.com/gears.html

Use the pull-down menus to select your tranny and transfercase, enter your gear ratio, click on the Calculate button.

cj's99xjsport

i am at about 2100 doing 70mph....Is this normal

SeriousOffroad

Use the link I provided....

cj's99xjsport

[QUOTE=FrankZ;811056]Use the link I provided....[/QUOT


just saw that, you must have been posting it when i was writing my question.

Rock Toy

You could always just us the formula to get the rpms.

Speed x ring & pinion ratio x 336 / tire height x top transmission ratio = rpm

Example: 60 x 3.55 x 336 / 31 x .75 = 1731.48 rpms
70 x 3.55 x 336 / 31 x .75 = 2020.06 rpms

The AW4 transmissions OD ratio is .75. The AX15s OD ratio is .79.

The tire height must be the real height not what is stated on the sidewall.
If it said 31 and they are really 30.4 inches it makes a difference.

TrekkerJmm

RPM's should drop by 500 around 40-45mph if your not ON the gas too hard...Tj

jlv

I have 33's nd stock gears nd i am at 2000 at 60 so ur about right

98 XJS

thanks guys! I was out again today and counted the shifts and it is dropping into OD. For some reason I thought the revs were higher yesterday too but they are about 2000 - 2200. I feel a little more at ease now, thanks

sheepdog

i have stock 235/70/15s on mine and im going 68 on the speedo and exactly 2000 rpm's. im about to put on a 4 inch lift and 31's....by getting taller tires, technically shouldn't my rpm's lower because in one turn of the wheele my tires are moving me farther because of the enlarged outside diameter? its a 5 speed manual, really tall gearing, i think its the highest gearing they put in these...not completely sure, but i think so

ChileRedBateman

yes and no, if you change the speedo to reflect tire change the rpms will show lower, no otherwise but you're right you will be going faster because of distance traveled per rev of tire is farther. so 68 on the speedo will be about 72 realtime but same 2000rpm... so 64.5+/-mph would be 68 real mph and less rpm

sheepdog

ok cool, cuz right now, for some reason, my speedo is off. i had my dad (a highway patrolman) radar me, and at 65 on my speedo, im going 62-63, so 31 inch tires should just about make my speedo right on