High RPM's?

93redzj

93redzj

Well-Known Member
Joined
Aug 29, 2005
Location
Albemarle
My girlfriends jeep TJ has always gotten horrible gas mileage, its a 4.0, I know not to expect anything in the 20's but lately it just seems ridiculously low, I havent calculated exact numbers but it doesnt take long for it to drink a tank of gas. However, the other day while going down the interstate at 60-65mph I noticed the RPM's were at around 2300. The jeep itself has 80xxx on it, a budget boost and 31" mud dawgs. Is it typical for the RPM's to be this high?
 
google "gear ratio calculator" and try out a few...knowing your setup, you can easily calculate what your rpm's "should" be.

what's your 4th/5th gear ratio ... .70/.75?? What's your axle gearing??
 
sorry, forgot to mention it is an auto, not sure on gearing, its stock I know that, ill have to see if the tag is still visable/readable on the differential cover.
 
VortecJeep said:
The torque converter may not have locked up.
Click to expand...

That's what I was thinking. The bigger tires are keeping it from being able to lock up on the highway. Here's a question. If you're cruising on flat ground, about 60, and slowly let off the throttle, do the rpms eventually drop, like one last gear shift?
 
sometimes the converter wont lock until the fluid is warm.
My truck does it now that it is getting cold in the mornings.
 
catfishblues said:
That's what I was thinking. The bigger tires are keeping it from being able to lock up on the highway. Here's a question. If you're cruising on flat ground, about 60, and slowly let off the throttle, do the rpms eventually drop, like one last gear shift?
Click to expand...
never really noticed, next time I get it on the hwy, ill check that out, Thanks.
 
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