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speedo gear issue

themud

NAXJA Forum User
Location
Scottsdale AZ
I'm currently running 5.38's and 35's on my rig and my speedo is off by 5 mph across the board I orgininally picked up a 41 tooth speedo gear as thats what the charts were saying. I think this is what's causing me to run 5 mph fast on the speedo I do have a 40 tooth and want to know if i put that back in will that slow down my speedo to a more normal level... I can normally do the math thing but I'm too damn tired... help my hear guys...

themud
 
Lemme think for a minute...lol
***To speed up the speedo you need less teeth, and to slow down the speedo you need more teeth. Each tooth is 3% change approx.*** - Courtesy of GoJeep!
So a 42, 43.
Found this, you need a 43...
http://www.jeep4x4center.com/jeep-speedometer-gears/

I'm about to do a double diff swap to a HP44 FullSpool /Ford 9" Limited Slip with 5.13's on 35's. I currently have 4.56's in my D30/LockRight and 8.25:29/PowerTrax No-Slip.
How do you like the deep gearing with the 35's?
What axles are you running? -B
 
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Looks like I'll need a 43 tooth but sure as hell not for 109.00 ouch I guess Ill just mentally calculate for the faster speed I can live with that....

As for the gears I love em a little limited on top speed but I don't down shift anymore and it does great on the trail especially that I only have stock t case gearing and won't be going deeper on the t case due to money issues... It's a bit thirsty on gas at 70 all day long but I usally just go 60 and cruise away it's not that bad just have to leave a few minutes earlier.. I wouldn't have done the 5.13's as I planned to get 36's and have them now and want the extra turning power for the rubber....

In other words:thumbup::thumbup: for the 5.38's...
Im running 44's front and rear out of a ford pickup- the front is a hp44 out of a 77 f-150 and the 44 rear is out of a 76-79 ford f-150 or fullsize ranger 2WD only...
themud

ps anyone got a a short shaft 43 tooth speedo that wants to trade???
 
Just remember you are not 5 mph out across all speeds. You can only be a percentage out.
 
FWIW i use my Magellan Roadmate GPS mounted on the dash. It's a heads up display and very useful too. You can get a GPS fairly cheap these days and better money spent than on the speedo gear. Just a thought. -B
 
yeah I was going to correct my speedo but once I found out the prices I decided....yeah I'll just go with the reading off the GPS! Too rich for my blood.
 
FWIW i use my Magellan Roadmate GPS mounted on the dash. It's a heads up display and very useful too. You can get a GPS fairly cheap these days and better money spent than on the speedo gear. Just a thought. -B
Except for the models which rely on the speedo being correct for information going to the ECU and even the auto.
 
Except for the models which rely on the speedo being correct for information going to the ECU and even the auto.

As usual, very valid point GJ.
Here's a for instance:
Let's say i'm bee-boppin along the highway at 65mph GPS, but my speedo reads 58mph for a difference of 7mph. At what point or percentage does the speedo/GPS difference start to affect the ECU and AW4 in a detrimental way? What would the 'cutoff' be?
FWIW, right now i'm on the money, well 2 kph out. But when i change diffs with 5:13 gearing i'm guessing a speedo gear is in my future.
I'll check the prices out here for the speedo gears and see if they are any cheaper through CDN dealerships. -B
 
I think the most critical part is in the trans(auto) shift points.As with everything else,if your geared/tired correctly the XJ will drive better than stock.I tow my trailer with me for most runs and it really makes a difference!
 
I don't think the speedometer actually controls the shift points for the XJ and ZJ....a friend of mine had a 96 OBD2 ZJ and his speedometer and odometer haven't worked for quite some time, yet it still shifts fine.
 
I noticed a difference in the auto after fitting the right gear but have a 95 and the last year of the OBDI. I believe OBDII have there own pickup inside the auto which has nothing to do with the speedo.
Also prices vary a lot depending on if it is a common tooth count or not. The more you are away from stock, the more expensive they become it seems.
 
Sorry to hi-jack but didn't want to start a new thread for a question. I have an '01, I just got 4.88 gears and 35's. I know my speedo is off but my question is, will this effect my overhead gas mileage gauge? Also will it have an effect on odometor?

Thanks in advance and once again sorry for the hi-jack.
 
Yes, it will. They all operate off the same Vehicle Speed Sensor driven by the speedo gear, so they'll all be off.
 
It seems to me that speedo gears are different prices from the same vendor depending on the tooth number. Perhaps certain ones are more in demand and command a premium. I had to buy a 40-tooth gear this week for 32's/4.56's and had to fork over $90 for it ($105 shipped!). The same vendor had 39-tooth gears for $40.

And to add insult to injury, this is the second speedo gear I've bought. I had to buy a 31-tooth gear for 32's/3.55's when I first lifted my XJ.
 
I just got a 39 tooth gear for $30 - it is actually for chrysler 727 transmissions for older mopar cars-has the same length and shaft for the 231 transfer case-long shaft with speedo cable.:thumbup:
 
is this one close for you?
http://cgi.ebay.com/ebaymotors/MOPA...cfdQQitemZ370244193533QQptZRaceQ5fCarQ5fParts
even though it is the long shaft you can take a punch and tap it out from the bottom and do the same to yours - when you press the gear on the shaft just use some epoxy or super glue just to be sure it wont move on the shaft-it is a hard press to -
I just like to be sure it stays there- did that to my last gear- 6 years no issues.
 
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I believe this is a super old post but for anyone looking.................Parts Mike has what you need for great prices!!
 
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