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Discussion Starter #1
First: I would like to keep this limited to XJs only, preferably those with automatic transmissions. If you have a manual you may participate, but please state that you have a manual trans.

Other models please refrain from posting, thank you.



I am curious as to what other XJs run on RPMs on the highway. This will be a serious thread with serious replies only please. Research and experimentation are the purposes for this thread, so specific info may be required. However, I would like to keep this simple.

Please answer the questions, and state the following:
-transmission (manual or auto)
-axle gear ratio
-lift height
-tire size
-anything in particular that stands out as possibly creating more drag or less aerodynamics
This is to keep the participants similar, and make sure each case is understood.


What RPM does your Jeep XJ run at 70mph? 80mph?
(No comments on "my Jeep doesn't go that fast..." etc.)

Mine runs at 2000rpm at 70mph, and 2500 at 80mph.
I have a 2001 with AW4 auto with 3.54 gears on 235/75/R15 tires. I have 4" lift in the front, and a roof rack with externally mounted tools that i know create drag.

Thank you for your participation and understanding.
 

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92 xj 4wd.
1990 aw4 with power/comfort switch.
3.73
Roof rack empty no air dam on front.
Home brew 3" PVC snorkel on drivers fender up pillar to roof. Forward facing 4" intake on it.
Winch bumper large brush guard.
8.5" rustys la
35/14.50/15
65 MPH 2200 rpms
70 MPH 2650 rpms
Anything faster is too dangerous
It should be known that this is with a 4.8 stroker

89 xj
Aw4
3.54
33/12.50/15 bfga/t
6.0" lift
70 MPH 2100 rpms
80 MPH 2750 rpms
 

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Discussion Starter #5
I am not at all concerned with differential calculations here guys. Sorry.
 

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1996 XJ 4.0 HO With 703 injector upgrade
AW4 with NP242
3.55
215/75/15 on stock (sagging) suspension.
tires are around 6 32nds
Stock roof rack
Mud flaps

68MPH at 2100 RPM,
(NOTE- After replacing my dash, my speedometer is off about 7 mph, according to the local speed minders. So at 75 on the gauge it's actually 68).
 

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Marshmallow
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3,780 Posts
1991 XJ Manual AX15, 4.0L with 3.5" lift and 31's, roof rack with axe and shovel. There's probably another 500# of crap inside.
65 mph - 2300 RPM
70 mph - 3000 RPM
 

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Yup, just me.
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"01 Sport, AW4, NP231j, 3:55, 235 75 R15. Light bar with 6" lights, custom front and rear bumpers. Front is 3" lower than rear so pretty good rake to body. Front fenders trimmed above flair mounts.

60 mph sits at 2000 rpm's.
 

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97 sport, Aw4, NP231, 3.55 gears, approximately 5in lift

55mph in 4th I'm at like 1500-1600 RPM Does NOT like to climb grades.

at 65-70mph it sits around 2100-2200 rpm. Much happier here
 

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2001 sport
-auto
-negative 4 inch sag in the rear
-2wd not 4x2
-Thule rack with either my snow board or bike on it
-235/75/15 Goodyear wranglers
-3.55 gears on a Dana 35

60mph holds at 2000 rpm
70mph around 2200 rpm
80mph is 2500rpm
90mph holds at 2600-2700rpm
100mph it's pushing 2800-2900rpm
110mph is a hair below or above 3000rpm
 

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Marshmallow
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3,780 Posts
I just picked up my gauge cluster for my 2K XJ today and will put it in Thursday. I will then have a Tach so I can find out what the RPMs are on it.
 

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1991, 4.0L, auto, 231, 6-8" lift, 315/75/16 (35X12.5) tires, 4.88 gears, roof rack with a highlift in it, and the Jeep weighs 4340 lbs.

The following numbers are in overdrive with the torque converter locked up.

70 mph - 2550 RPM
80 mph - 2950 RPM

As a note I threw the Jeep on jack stands when I got home and ran it up to the 70 and 80 mph mark. The numbers were almost the same, maybe 20 RPM less. I think this makes sense as the torque converter being locked takes all of the slip out of the trans.
 

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Marshmallow
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Now that I have a tach:
2000 XJ, 4.0L, AX4, NP231, 3.73 gears, 31x10.5R15's, custom bumpers, no lift yet.
65 mph - 1900 rpm
75 mph - 2250 rpm
 

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Test drove the mj project today
Waggy 44
Dana 70 dually
no rear fenders yet
4.88 gears
8.5 long arm
Aw4
Stock 4.0
Handyman bed
33/12.50/15 bfg a/t
55 - 2000 rpms
65 - 2600 rpms
75 - 3000 rpms
 

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XJ Superman,

Is all of this for AW-4 comparisons? What are you hoping to see from this data?
 

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Discussion Starter #18
I was just hoping to see some info between XJs, mostly about the highway cruising. I know I kinda set it up for some giant informational reveal, but its really nothing important. I just wanted a simple comparision between RPMs at cruising speeds and how some different setups worked. I was a little worried about my setup and aerodynamics affecting mpgs.

Obviously it does, but not enough to bother anything.

I would like to see this continue, just for others later though. It is pretty interesting to see how lifts and tires and gears change it.
 
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