What's the correct speedo gear?

[jfrabat]

Guys,

I am going to buy the new speedometer gear to correct for the 31" tires that my jeep came with, but I get conflicting reports from the different sites I have found online. I even ordered one speedo gear from quadratec, but it did not fit in my jeep!

First of all, a little background; my Jeep is a '94 YJ 2.5L. Transfer case is the NP231. Theoretically (there is no tag on the diffs) it has 4.10 gears (I am assuming the old owner never changed them!). Tires are 31" Bridgestone Dueler H/T (I plan to keep these for a while, so I will recalibrate for these, and when I change to 33" MT's, I'll recalibrate again).

According to http://www.jeeptech.com/javaAps/Speedo.html I need a 35 tooth speedo gear. According to the stealership, I need a 41 tooth one. According to the chart on quatrec's site (http://www.quadratec.com/jeep_knowledgebase/article-46.htm) I need 38 tooth.
According to Batty53 (http://monkeycage.island4x4.com/showthread.php?t=27104) and the sites he quotes (http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=257847, and to mdillon at http://www.naxja.org/forum/showthread.php?t=78159&highlight=speedometer) I should use a 36 tooth one. I am more inclined by the 36 tooth one to be honest, but I am not sure...

Also, do I need the short version, or the long version? I know sometime in 93/94 they switched from the long to the short one, and I suspect I need the long one because the one I got from Quadratec some months ago would not engage the wrom drive and actually fell in the well because it did not make contact...

Any help is greatly appreciated!

Felipe

 

[LGR]

I've found all the charts to really say differnt things. I ended up using quadratecs and it was pretty good as far as correct speed when driving next to a friends car.

Not sure about what version though.

 

[jfrabat]

OK, went out with my wife (she was in her car). At 60 mph (her car), the Jeep was reading 56 mph. I also got the gear that I have right now, and it is a 41 tooth gear.

So, (56/60)*41=38.27... Rounding it off, I need a 38. Now, the catch is that mine is the long gear, and I have only been able to locate the 38 tooth short one... I called Quadratec, and they said that the 3" gear (which is what mine measured from top to bottom) was the long one. But neither Quadratec nor 4wd.com had the 38 tooth long one.

Any other place I can get it from?

Felipe

 

[TwistedCU]

I doubt you'll get it much closer than 4mph @ 60 mph. If you're going to get bigger tires later then I'd wait.

You really should check it with an hand-held GPS rather than your wife's car. Too much room for error, you could end up changing the gear and being more off than beforehand :lol:

 

[jfrabat]

OK, so now I am back to thinking that I am needing the short version rather than the long one... I checked out the long ones on-line, and they just look too long. What do you guys think?

This one is lengthwise. Looks like the short one...

This one shows that it is a 41 tooth gear; the diameter of this one, however, is significantly thicker than the one I got last one (I'd like to say it was a 38 tooth one, but i do not remember for sure).

Twisted,

Actually, the size I need according to my calculations, is exactly what quadratec recommends. And since the tires are staying on for about 2 more years, I'd rather have the right speed on the speedometer, and distance showing in the odometer.

Felipe

 

[Bounty__Hunter]

You need the short gear, yours likely fell out because it had not been twisted enough in the housing to contact the mainshaft.

I got my last speedo gear from www.tacomaspeedometer.com , they were very knowledgeable and helpful.