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Speedo gearz: which chart is correct?

HaleYes

HaleYes

NAXJA Forum User
Location
Clay County, IL
Definately go with the chart GoJeep supplies - the other one looks incorrect to me. I'm running 33" tyres with 4.56 ratios and went with the 39 tooth gear as per GoJeep's recommendation and it worked out perfect for me. So, with your 4.88 ratios and 33" tyres the 41 tooth gear sounds about right.
 
Have you guys checked yours and seen if it's accurate across the board?
 
Cant remember the exact nums right now but;

I have 4.10 and 32" (true) tires. Backed down to a 35 tooth and am about 3-4% off (low) on indicated speed vs. true (gps).

By my cyphering, I probably need another tooth down (34). IIRC, you get about 4% per tooth?

In any case, it looks like a 34 will work for my case, judge the charts from there. The one thing certain is I have a 35 in it now and a 36 will be incorrect.
 
When I re-geared my speedo to match my 4.88s, I was running 34s and I *think* I went with a 40 tooth. Now that I dropped back down to 33s, I imagine I am off a bit. I don't have a GPS to verify, but I need to find one.

When we were headed to Redbird on 41, my speedo was showing 65, do you remember what yours said Mike?
 
I used GoJeeps, to find I needed a 32 tooth gear for 3.55s and "31s" that measured to 30.5.


At 80 Im about 4mph off according to my GPS, and at 60 Im almost dead on. Hypothetically speaking of course, at 90 its about 6 off. I think.;)
 
IllianaXJ said:
When we were headed to Redbird on 41, my speedo was showing 65, do you remember what yours said Mike?
Click to expand...

Sure don't. :doh:
 
I used the GoJeep one and the speedo is right on, I checked it with highway markers over a 10 mile strip, its within .1 of a mile.

I'm running 31's with 3.73's behind an AX-15

~Alex
 
I used go-jeeps and at 65 it is off 2 mph by gps. I would use his, 33's with 4:10's
 
Starboard M said:
I used GoJeeps, to find I needed a 32 tooth gear for 3.55s and "31s" that measured to 30.5.

At 80 Im about 4mph off according to my GPS, and at 60 Im almost dead on. Hypothetically speaking of course, at 90 its about 6 off. I think.;)
Click to expand...

My XJ came as standard wih 16" rims and 225/70x16 tyres and OE fitment on the speedo gear was a 33 tooth. Later when I fitted 31" tyres, the speedo was close on being spot on with the GPS. The 32 tooth as per Go Jeeps chart will probably give that little margin of "safety error" that was built in at the factory (where the speedo reads slightly faster than true speed).
 
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