2wd speedo gear

[UNL1MTD]

I have a 2wd. I run 31s and since I had a D35 with 4.10s I put that in.

 

So 2wd Mj, with 4.10 gears, and 31" meats = 38 teeth speedo gear, my current tooth count is 30, its way off.

 

I order a speedo gear from 4wd hardware like I always do when I change tire sizes in my TJ. I knew about the long versus short metal shaft the speedo rides on in comparison to MJs/TJs so I was just going to swap them. Well I'm thinking its no dice. Hopefully someone can help.

 

The thing is the 2wd speedo gear is only 1 1/8"s in diameter whereas the NP231 gears are more like 1 3/8"s in diameter. I have 4 laying around and it hit me like a ton of bricks.

 

So I'm curious if anyone has regeared their speedo in a 2wd and how it was done? maybe I am just missing where to look to order them on various websites.

 

-Sean

 

ps- anyone need a 40,38, or 34 count speedo gear? :brows:

[JeepcoMJ]

I have a 2wd. I run 31s and since I had a D35 with 4.10s I put that in.

 

So 2wd Mj, with 4.10 gears, and 31" meats = 38 teeth speedo gear, my current tooth count is 30, its way off.

 

I order a speedo gear from 4wd hardware like I always do when I change tire sizes in my TJ. I knew about the long versus short metal shaft the speedo rides on in comparison to MJs/TJs so I was just going to swap them. Well I'm thinking its no dice. Hopefully someone can help.

 

The thing is the 2wd speedo gear is only 1 1/8"s in diameter whereas the NP231 gears are more like 1 3/8"s in diameter. I have 4 laying around and it hit me like a ton of bricks.

 

So I'm curious if anyone has regeared their speedo in a 2wd and how it was done? maybe I am just missing where to look to order them on various websites.

 

-Sean

 

ps- anyone need a 40,38, or 34 count speedo gear? :brows:

 

what is the equasion for figuring out the gear teeth?

 

and you have a 4 cylinder with np207 tcase right? those are different speedo gears...you have to order one by tranny and engine option...they are specific.

 

one for a np207 tcase would be the same

[UNL1MTD]

I have a 2wd. I run 31s and since I had a D35 with 4.10s I put that in.

 

So 2wd Mj, with 4.10 gears, and 31" meats = 38 teeth speedo gear, my current tooth count is 30, its way off.

 

I order a speedo gear from 4wd hardware like I always do when I change tire sizes in my TJ. I knew about the long versus short metal shaft the speedo rides on in comparison to MJs/TJs so I was just going to swap them. Well I'm thinking its no dice. Hopefully someone can help.

 

The thing is the 2wd speedo gear is only 1 1/8"s in diameter whereas the NP231 gears are more like 1 3/8"s in diameter. I have 4 laying around and it hit me like a ton of bricks.

 

So I'm curious if anyone has regeared their speedo in a 2wd and how it was done? maybe I am just missing where to look to order them on various websites.

 

-Sean

 

ps- anyone need a 40,38, or 34 count speedo gear? :brows:

 

what is the equasion for figuring out the gear teeth?

 

and you have a 4 cylinder with np207 tcase right? those are different speedo gears...you have to order one by tranny and engine option...they are specific.

 

one for a np207 tcase would be the same

 

The parts truck is a 4 banger with a 231, its got the larger diameter gears, I checked it before I posted. This truck is a 4.0L. Where do people order from? I havent found a place that I can order like that. Dealer maybe?

 

I'm not sure of the equation I just use the charts in the Quadratec and 4wd magazines, they have been dead on perfect twice now.

[JeepcoMJ]

 

The parts truck is a 4 banger with a 231, its got the larger diameter gears, I checked it before I posted. This truck is a 4.0L. Where do people order from? I havent found a place that I can order like that. Dealer maybe?

 

I'm not sure of the equation I just use the charts in the Quadratec and 4wd magazines, they have been dead on perfect twice now.

 

they should be the same. the gear diameter WILL expand with higher counts of teeth in my experience...try them?

 

otherwise, it has to come from internet or dealer.

 

what's the chart say for 31x10.50's with 3.55 gearing? if you could help :roll:

[Pete M]

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

[JeepcoMJ]

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

 

hmm...something is wrong here. my speedo gear is a 23 tooth gear. my speedometer is off by 2.7 mph, as clocked with a cop radar detector (by a mechanic who has one).

 

yet it's telling me i need a 32 tooth gear for my application...9 teeth would make a HUGE difference...i had a 34 tooth in before and was off by 17 mph low! so at 55mph i was doing 72 mph.

 

what gear type is that applied to? there's gotta be a change in type here...

[summerinmaine]

I just use a GPS for my speedo/odo. No gears/no problems. :D

[Eagle]

I have a 2wd. I run 31s and since I had a D35 with 4.10s I put that in.

 

So 2wd Mj, with 4.10 gears, and 31" meats = 38 teeth speedo gear, my current tooth count is 30, its way off.

 

I order a speedo gear from 4wd hardware like I always do when I change tire sizes in my TJ. I knew about the long versus short metal shaft the speedo rides on in comparison to MJs/TJs so I was just going to swap them. Well I'm thinking its no dice. Hopefully someone can help.

 

The thing is the 2wd speedo gear is only 1 1/8"s in diameter whereas the NP231 gears are more like 1 3/8"s in diameter. I have 4 laying around and it hit me like a ton of bricks.

 

So I'm curious if anyone has regeared their speedo in a 2wd and how it was done? maybe I am just missing where to look to order them on various websites.

Well, you've thrown a bunch of variables at the problem, but 2WD vs. 4WD isn't one of them. They use the same speedo gear. What you are overlooking is that the "quill" into which the speedo gear fits, and which in turn is bolted into the tranny (transfer case, for a 4WD) has to be rotated to a different orientation depending on how many teeth are on the gear. That's how you adjust for the different sizes of gear.

 

Since I ran 31x10.50/15s for some time, I'll start be pointing out that 31s with 3.73 gears works out to exactly the same final drive ratio as stock 225/75 tires with 3.54 gears as came from the factory with all 4.0L automatics. Assuming you have an automatic, your stock speedo gear should have had 33 teeth. (If your OEM tires were 215s, that would have been 34 teeth.)

 

Okay. 33 teeth stock automatic. 33 teeth also good for 31" tires with 3.73 gears, but you're running 4.10s. So you need more driven teeth to make the speedo read slower for each revolution of the driveline. The difference in percent is (4.10 - 3.73)/3.73 x 100 = 9.92 percent. So you need a speedo gear with 9.92% more teeth than the original 33 teeth. 33 + 9.92% = 36 teeth. Which just happens to coincide with the number shown in a table of speedo gear selections I printed out several years ago, from a web site that no longer exosts, when NAXJA was in its infancy.

 

Now ... about that quill clocking: Take a close look at the quill. You should see three small bars, and between the bars you should see numbers stamped/cast into the metal. The numbers correspond to the tooth count. There is a small index mark/boss cast into the housing below the hole the quill fits into, at about the 6:00 o'clock position. You need to rotate the quill untill the numbers of the range in which your speedo gear fall are aligned above the index boss. In the illustration in the old FSM they show only two sets of numbers, 32-38 teeth and 39-45 teeth. My fuzzy recollection is that the quill on my '88 MJ actually had three sets of numbers, but it doesn't matter. Whatever the tooth count, align the range into which it falls with the index mark.

 

One other point -- if you get it to within 2 to 3 percent, stop fighting it. You won't get any closer. There's that much difference between tires of the same nominal size from different manufacturers, or from different inflation pressures. My wife's 2000 XJ speedo reads 2-1/2% faster than actual speed (verified by running through the police radar trailers more than twice) with the original factory tires. Most vehicles come from the factory with speedos that read slightly faster than actual ground speed.

[Eagle]

hmm...something is wrong here. my speedo gear is a 23 tooth gear. my speedometer is off by 2.7 mph, as clocked with a cop radar detector (by a mechanic who has one).

 

yet it's telling me i need a 32 tooth gear for my application...9 teeth would make a HUGE difference...i had a 34 tooth in before and was off by 17 mph low! so at 55mph i was doing 72 mph.

 

what gear type is that applied to? there's gotta be a change in type here...

Yeah, there was a change. Are you asking about the 86 with a 207 transfer case? Different animal.

 

Example: From the old FSM. For the 228/229 transfer case (and the 231), 3.54 gears and 225/75 tires calls for a 33-tooth gear. For the 207 transfer case, 3.54 gears and 225/75 tires called for an 18-tooth gear.

 

You're going to have to run the numbers to calculate the right speedo gear for the 207 gearsets. In general, assuming NO change in axle gearing, a jump from 215 or 225 OEM tires to 30x9.50s represents about a 5% to 6% jump. Going from the same stock tire sizes to 31x10.50s is a jump of about 10% to 11%.

[tjbliley]

I have had good success with www.newjeepparts.com . they have good deals.

[Pete M]

I just use a GPS for my speedo/odo. No gears/no problems. :D

 

 

I use the tach in my 88. :D

[UNL1MTD]

I have a 2wd. I run 31s and since I had a D35 with 4.10s I put that in.

 

So 2wd Mj, with 4.10 gears, and 31" meats = 38 teeth speedo gear, my current tooth count is 30, its way off.

 

I order a speedo gear from 4wd hardware like I always do when I change tire sizes in my TJ. I knew about the long versus short metal shaft the speedo rides on in comparison to MJs/TJs so I was just going to swap them. Well I'm thinking its no dice. Hopefully someone can help.

 

The thing is the 2wd speedo gear is only 1 1/8"s in diameter whereas the NP231 gears are more like 1 3/8"s in diameter. I have 4 laying around and it hit me like a ton of bricks.

 

So I'm curious if anyone has regeared their speedo in a 2wd and how it was done? maybe I am just missing where to look to order them on various websites.

Well, you've thrown a bunch of variables at the problem, but 2WD vs. 4WD isn't one of them. They use the same speedo gear. What you are overlooking is that the "quill" into which the speedo gear fits, and which in turn is bolted into the tranny (transfer case, for a 4WD) has to be rotated to a different orientation depending on how many teeth are on the gear. That's how you adjust for the different sizes of gear.

 

Since I ran 31x10.50/15s for some time, I'll start be pointing out that 31s with 3.73 gears works out to exactly the same final drive ratio as stock 225/75 tires with 3.54 gears as came from the factory with all 4.0L automatics. Assuming you have an automatic, your stock speedo gear should have had 33 teeth. (If your OEM tires were 215s, that would have been 34 teeth.)

 

Okay. 33 teeth stock automatic. 33 teeth also good for 31" tires with 3.73 gears, but you're running 4.10s. So you need more driven teeth to make the speedo read slower for each revolution of the driveline. The difference in percent is (4.10 - 3.73)/3.73 x 100 = 9.92 percent. So you need a speedo gear with 9.92% more teeth than the original 33 teeth. 33 + 9.92% = 36 teeth. Which just happens to coincide with the number shown in a table of speedo gear selections I printed out several years ago, from a web site that no longer exosts, when NAXJA was in its infancy.

 

Now ... about that quill clocking: Take a close look at the quill. You should see three small bars, and between the bars you should see numbers stamped/cast into the metal. The numbers correspond to the tooth count. There is a small index mark/boss cast into the housing below the hole the quill fits into, at about the 6:00 o'clock position. You need to rotate the quill untill the numbers of the range in which your speedo gear fall are aligned above the index boss. In the illustration in the old FSM they show only two sets of numbers, 32-38 teeth and 39-45 teeth. My fuzzy recollection is that the quill on my '88 MJ actually had three sets of numbers, but it doesn't matter. Whatever the tooth count, align the range into which it falls with the index mark.

 

One other point -- if you get it to within 2 to 3 percent, stop fighting it. You won't get any closer. There's that much difference between tires of the same nominal size from different manufacturers, or from different inflation pressures. My wife's 2000 XJ speedo reads 2-1/2% faster than actual speed (verified by running through the police radar trailers more than twice) with the original factory tires. Most vehicles come from the factory with speedos that read slightly faster than actual ground speed.

 

Your completely right, I was overlooking the quill clocking. I knew about it but havent had to do it in the past. The tranny is a manual and the stock gears were 3.07s. So the stock speedo gear is a 30 tooth count. The other MJ has a 40 in it. I'm pretty confident in the 38 tooth count going in, and if its close it'll work. Currently I'm reading high by about 12 mph at 60mph.