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Real Speed Versus Speedometer

flash2pablo

flash2pablo

NAXJA Forum User
Location
Vancouver, WA
I just bought a 96 2 Door Cherokee.
I just took a little trip, and it felt like I was going rather fast, since i was passing everyone, but my speedometer said I was going the speed limit.

Yesterday I checked my odometer against mileage markers, for every mile of mileage marker my odometer only recorded .85 of a mile.

I have 30.5*9.5*15 tires.
I have two inch blocks in the back and probably about 2" spacers upfront, for a lift.

Would this size of tire really throw my speedometer off this much?
Gears are 3.07 Stock.

Thanks for any help.

PBen
 
Has the XJ had any transmission/transfer case work done before you owned it? If the t-case was swapped out, it may have the wrong gear in it.

30" tires shouldn't throw off the speedo much at all. IIRC, when I got my first lifted XJ, it had 32" tires and the speedo was only off 8 mph.

I'd suggest finding a friend to follow you on the highway, then when it's clear, have them drive right next to your XJ at 55 mph and find out what your friend's vehicle's speedo says - of course, that's assuming the friend is driving a stock vehicle with stock tires..... :D
 
Good call on the transfer case. I just put a used one in it a week ago.
It is an NP231 from a 96. I replaced it with the same.
My old case had a hole in the rear half of the case. I bought a used one

The only difference is that the "new case was from a 4 door, I think, becuase the shift rod was about 3 inches longer. I also noticed when I pulled what must have been the speedometer cable that it was a little smaller so I left it.
Should I change that, I know that the one from the old case is a little bigger?
Can i just pull it out of the transfer case and directly swap them?
 
I am a little lost. I tried to find what you guys are talking about, i searched and couldn't find a speedometer gear. :eye:
 
Thanks guys, I will get this fixed rigth away. I am thinking a 28 tooth.
 
28 is correct.

On the dealer computers, it isn't listed like that........but when you get it, make sure you look and read the number that is stamped on the gear. They go by tire size and year and model and trans and such.....you can't just walk in and request a 28 teeth speed gear, FYI.
 
Damn, i knew it sounded to easy to be true!!!!!!!!!
 
Blaine B. said:
$7.00 actually!
Click to expand...
Hmm..in Alabama, it was a special order part, and $17...:(
 
flash2pablo said:
The only difference is that the "new case was from a 4 door, I think, becuase the shift rod was about 3 inches longer.
Click to expand...

bobnoxious said:
FYI...2dr and 4dr have the same wheelbase. Same everything driveline and suspension-wise.
Click to expand...

I'm betting the donor was an automatic had an AW4. The xfer case linkage rod on the auto is 3" longer - 12" versus 9" as I recall from doing my swap. The AW4 tranny is 1" longer than the AX15 and the shifter pivot point is 2" further forward on the body bracket. This would also explain the speedo gear difference as the auto likely had 3.55 gearing and the AX15 had 3.07.
 
ChuckstrPT said:
Hmm..in Alabama, it was a special order part, and $17...:(
Click to expand...
it was 25$ here ;)
 
FYI:

84811662.gif
 
YELLAHEEP said:
30" tires shouldn't throw off the speedo much at all. IIRC, when I got my first lifted XJ, it had 32" tires and the speedo was only off 8 mph.
Click to expand...

at what speed? its not 8 all the time, its a ratio of how fast your goin, say for every 10 mph, it is 10% faster than what it is stock, 40 on speedometer = 44 real speed, 50=55 ect..
 
Just take the part number I list to any dealer and they will give you the right one no worries.
 
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