speedo gear tooth question

[JofCore]

I'm putting 31's on my XJ ('91, auto, 4.0L) and I've figured out from searching the forums that I need a 32 tooth speedo gear to make my speedo read accurate after the new tires are on. However, from what I've read, there is only a 30 tooth and a 33 tooth available. Someone suggested the 33 will be close enough.. The question I have is will the 33 make the speedo read high or low? I would rather not have it read low and be speeding all the time...

thx!

 

[FrankNBrew]

A 32 tooth gear is available. Part # is 52067632. I know it exists because I am looking at one sitting on my desk. It's black in color, and has the number 32 stamped in the plastic.

On my 99 XJ with 3.55 gears and 31x10.5 BFG A/Ts the speedo was almost perfect (within 2%).

 

[NHextremeXJ]

Here's a question....if your speedo gear is off calibration does that change how your odometer reads the mileage? :shhh:

 

[Jeffro600]

Here's a question....if your speedo gear is off calibration does that change how your odometer reads the mileage? :shhh:

Yes...if it reads slower than your actually going, your odo will read less miles that what youve really traveled and vice-versa.

 

[JofCore]

A 32 tooth gear is available. Part # is 52067632.

I think that one only works on newer XJ's though... from what I understand, the '91 needs a "long shaft" part. I missed the part you mentioned since I wasn't looking @ those numbers. According to the chart here: http://jeepsunlimited.com/zj/speedo/speedo.htm, a '91 needs a long shaft part, and there isn't a 32 listed...

So I'm thinking I may need to use the 33, but I don't know enough about it to tell in "which direction" my speedo will be slightly off. I don't want to be speeding and not knowing it. I'd rather have it read higher than my actual speed than lower.

thx

 

[canadianwheeler]

I think that one only works on newer XJ's though... from what I understand, the '91 needs a "long shaft" part. I missed the part you mentioned since I wasn't looking @ those numbers. According to the chart here: http://jeepsunlimited.com/zj/speedo/speedo.htm, a '91 needs a long shaft part, and there isn't a 32 listed...

So I'm thinking I may need to use the 33, but I don't know enough about it to tell in "which direction" my speedo will be slightly off. I don't want to be speeding and not knowing it. I'd rather have it read higher than my actual speed than lower.

thx

The shafts come apart so it doesnt matter. I made the mistake of ordering a long shaft when i needed a short shaft. I just took a pair of vice grips and pulled on the shaft and it came out, installed my stock.

 

[JofCore]

The shafts come apart so it doesnt matter. I made the mistake of ordering a long shaft when i needed a short shaft. I just took a pair of vice grips and pulled on the shaft and it came out, installed my stock.

Hmm, so from what you're saying, I should be able to get the 32 tooth short shaft, and then extract the shaft and use the current stock shaft... interesting.

 

[canadianwheeler]

Hmm, so from what you're saying, I should be able to get the 32 tooth short shaft, and then extract the shaft and use the current stock shaft... interesting.

yup.... thats what i did.

 

[lawsoncl]

$7.18 plus shipping from http://www.chryslerpartsdirect.com/

Search on part number 2538932
Old Partnumber: 2538932
New Partnumber: 52068154

 

[JofCore]

$7.18 plus shipping from http://www.chryslerpartsdirect.com/

Search on part number 2538932
Old Partnumber: 2538932
New Partnumber: 52068154

Awesome! I think I will go ahead and order it from that site you specified, looks like exactly what I need

I got the tires and rims mounted on my XJ this weekend, BTW. It's awesome, completely changes the look of the jeep (before/after pix here if anyone's interested: http://www.hanser.org/gussie-tires)

Since I haven't fixed the speedo yet... does anyone know: Do bigger tires make my speedo read high or low? (I can never remember the math that explains how to figure it out...)

thx!

 

[KSXJ]

http://www.kcjeepclub.org/info/tech/calculators.php#spedo

this will help you calculate your speed

 

[JofCore]

http://www.kcjeepclub.org/info/tech/calculators.php#spedo

this will help you calculate your speed

awesome! thanx!

 

[ccflexj]

so what would the correct toothing for 4:88's and 33" tires?

 

[lawsoncl]

so what would the correct toothing for 4:88's and 33" tires?

Try this calculator and select 87" Wrangler. Gives you a 40-tooth. Ideally though, you'd measure your error using GPS, check what tooth you have and figure out how many you need. Not all 33" tires are exactly 33" and speedos aren't that accurate.

 

[TheNerd]

Since I haven't fixed the speedo yet... does anyone know: Do bigger tires make my speedo read high or low? (I can never remember the math that explains how to figure it out...)

Bigger numbers (speedo gear teeth OR tire size) = slower speedo display.

I.e. 33 tooth speedo gear will show a slower speed than a 32 tooth, just as 33" tires will show a slower speed that 31" tires.

...until you regar your speedo, it is showing a slower speed that you are really going.