1999 xj, speedo has a problem at around 30 mph it reads 34 or so, and on the highway going 60 it reads 68 or so. I know because i followed my gf home on the highway and called her and told her to go 60 on the phone and mine was reading 67-68. Also used the speed traps that read your speed to you to know i was going 34 when it read 30. I first noticed it when i bought the jeep about a week ago on the ride home. It has 135k on it, and i know changing tire sizes can affect this but it has p215/75 r15 tires on it so those are pretty much stock size from what ive read. I'm not sure what the problem is.

 

I don't know what the problem is but 235's should make it about perfect.

 

Mine came with 215's & 235's seem to make it read slow. (I'm guessin' that's why it's off)
Does that sound correct? I'd like to swap the gear in trans but never figured out which one I need.

 

well mine is reading fast which doesnt make sense, and im pretty sure its not the trans where you need to change gears its in the speedo. Theres a tire size chart somewhere that shows which size gear you need and you just swap them out when you do your tires its cheap and fast.

 

Select it here:


Buy it here:
Speedo Gears

 

Nice part there CHEAP!

 

Still doesnt really help me though, like i said i have pretty much stock tires so any suggestions here?

 

YES IT DOES.
Go to your Transfercase or transmission. IDK what you have. Remove the gear and count the teeth.... THEN compare to above chart... There are also calculator you can google that will tell you which gear and what tire size might correct the issue.

 

ok so the gear size in my current trans is 34. My gear ratio is 3.55 and my tire is 215/75/15 which is 27.70'' tires (basically 28''). The chart says i should be using a 35 gear, could that 1 size up from the 34 to the 35 make that big of a difference? Also if anyone has an extra 35 tooth short gear pm me, $40 sounds like such a rip off for one of these.

 

Considering how vital a part it truly is, I wouldn't mind spending only $40, considering I paid almost $100 for my stock replacement (didn't know about that website that was mentioned....Dealer part). If you ever try and get a good mileage estimate, you'll never even get close since your speedo is so WAY off.

 

Well i just got the jeep and have been spending alot fixing misc parts etc, if i didnt try to get a deal on every part id be into the jeep for more than its worth. Its worth the try to ask around and see if someone has one sitting in a drawer they will never use.

 

Won't argue with you there, but anyone who has a Cherokee would say you'll ALWAYS be in them more than their worth. I believe that's the "Jeep Thing" you always hear about But anyway, it IS worth it to shop around, but the $40 is a good price.

 

For what it's worth, I just use a few samples from the county mile markers, compare that to the odometer, then figure what percentage I need to add or subtract. (for instance 4% under would mean adding 2 MPH at 50.), or 4 miles on each 100.

 

i know, i think its just more of a "used car thing" in fact im pretty sure jeeps would be up there in the cheapest cost to own if you ask me. Easy to work on, domestic parts and thousands of them littered in used auto yards and graveyards. Either way, just trying to take it easy on my pocket, ive owned a 3000gt, 2x subaru legacy's and an eclipse all used jap cars so happy to have a real vehicle for once. Although that 3000gt was definitely a good quality car by far.