Correct speedo gear

[chicofuentes0224]

If I'm running 31 x 10.5 x 15. Where's a good place to get one. Oh it's 3.55 gears. AW4

[BLHTAZ]

According to my calculation, you need a 32 tooth gear, but they have been discontinued through Chrysler. The part number is J3212732.

 

I can still get a 33 tooth, but that is likely going to be off by about 3 MPH.

 

Found this on a little Google search... http://forums.off-road.com/jeep-mid-siz ... -help.html

[xjcrazy09]

How did you do the calculations? Cause i would like to know what tooth gear I need for 35's and 4.56's. Thank you

[maddzz1]

How did you do the calculations? Cause i would like to know what tooth gear I need for 35's and 4.56's. Thank you

 

here's a link to a chart:

 

http://gojeep.willyshotrod.com/HowtoSpeedoGears.htm

 

It looks like you need 37 teeth.

[comanche87]

i also got a question. i run 235/75/r15 in the winter. and will be running 225/75r16 in the spring/summer and fall. the rear end is a dana 35 with i believe 3:55 gears.what would be the best speedo gear to get. right now my 16s have 215/70r16 but the 225 is the size i want. any sugestions? thanks.

[chicofuentes0224]

According to my calculation, you need a 32 tooth gear, but they have been discontinued through Chrysler. The part number is J3212732.

 

I can still get a 33 tooth, but that is likely going to be off by about 3 MPH.

 

Found this on a little Google search... http://forums.off-road.com/jeep-mid-siz ... -help.html

 

Taz, I don't care too much about the MPH. I'm just trying to get it right so I can figure how many miles I'm getting to the gallon. If we went with the 33 tooth, do you have any idea how far my calculations would be off for MPG?

[Eagle]

Taz, I don't care too much about the MPH. I'm just trying to get it right so I can figure how many miles I'm getting to the gallon. If we went with the 33 tooth, do you have any idea how far my calculations would be off for MPG?

Keep in mind that the factory typically lists each speedo gear for two or three tire sizes, so they usually aren't exact. My wife's 2000 XJ is absolutely stock, but the speedo reads 2 MPH fast at around 40 MPH, which translates to a 5% error. I've checked that multiple times going through those police radar trailers they like to use around here.

 

Okay, you need a 32-tooth but you can only get a 33. The gear we replace is the driven gear. 32 teeth *should* be one revolution but yours needs 33, so it will read slower than actual speed by 1/32, which is approximately 3 percent.

 

In other words, when you have gone 33 miles your odometer will only show 32. When you're driving 33 MPH your speedo will show 32. At 66 MPH your speedo will show 64. That's actually closer than my wife's XJ, but in the other direction, so you should keep the needle pretty close to the posted limit to avoid tickets. I always prefer to have the speedo read a bit fast rather than a bit slow.

[BLHTAZ]

:agree: Yea...what he said. :D

[chicofuentes0224]

Ok eagle and TAz, thank you very much for the explanations and help.

 

Taz, can ya get me a 33 tooth one and PM with total price w/ shipping?

I'll send ya the money 2morrow.

Thanks again :cheers:

[BLHTAZ]

PM sent... :D

[xjcrazy09]

How much are the tooth gears?

[BLHTAZ]

How much are the tooth gears?

It depends on which one you need, but they are typically in the $16 - $18 range.