Speedo drive gear r/r at home?
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Junior Member
Joined: Dec 2008
Posts: 94
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From: Cambridge, MA
Year: 1992
Model: Cherokee
Engine: 4.0L HO
Speedo drive gear r/r at home?
Hey guys, had this problem for a while, and googling the old speedo stuff was really enlightening. My speedo has been intermittently failing, and when it doesn't register the speed, it doesn't register miles on my odo. (duh.)
So looking through the tech manual I'm getting the following feeling about working this problem:
1 - It's probably *not* the sensor, because the failure is intermittent, and if it was the sensor it would just fail completely.
2 - This is not something someone who is only passable with mechanical work, and does not possess an off street location should get into. AFAIK only offstreet location I have to do work is the Autozone parking lot.
So, in the grand scheme of things, is this a big job? If I take it to a garage, am I going to be taken to the cleaners? If the speedo gear has to be r/r'ed, does the tranny have to be pulled out? I'm not completely clear on how it would be done, as the tech manual seems to make it sound like their approach is with the tranny off the car.
Would love feedback. Thanks!
So looking through the tech manual I'm getting the following feeling about working this problem:
1 - It's probably *not* the sensor, because the failure is intermittent, and if it was the sensor it would just fail completely.
2 - This is not something someone who is only passable with mechanical work, and does not possess an off street location should get into. AFAIK only offstreet location I have to do work is the Autozone parking lot.
So, in the grand scheme of things, is this a big job? If I take it to a garage, am I going to be taken to the cleaners? If the speedo gear has to be r/r'ed, does the tranny have to be pulled out? I'm not completely clear on how it would be done, as the tech manual seems to make it sound like their approach is with the tranny off the car.
Would love feedback. Thanks!
Seasoned Member
Joined: Mar 2010
Posts: 379
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From: Modesto
Year: 1993
Model: Cherokee
Engine: 4.0 high output straight 6
I am assuming you have a 4x4 and not a 2wheel drive. if that is the case the speedo gear is located on the tailshaft of the transfercase. it is held on with i think a 10mm bolt. easy to swap unless you mean the gear that drives the speed sensor gear.
Thread Starter
Junior Member
Joined: Dec 2008
Posts: 94
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From: Cambridge, MA
Year: 1992
Model: Cherokee
Engine: 4.0L HO
Ok, seriously, I've been reading the chrysler manual... how are they different?
Senior Member
Joined: Aug 2011
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From: Santa Rosa, CA
Year: 1996
Model: Cherokee
Engine: 4.0
Thread Starter
Junior Member
Joined: Dec 2008
Posts: 94
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From: Cambridge, MA
Year: 1992
Model: Cherokee
Engine: 4.0L HO
CF Veteran
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From: Salt Lake City, UT
Year: 2000
Model: Cherokee
Engine: 4.0L
they speedo sensor is held in with a 1/2" or 13mm bolt. unplug the sensor, Take the bolt off, slide off the tention clip. then pop the sensor straight out. you will see a gear at the end of the sensor it just pulls straight off. so just pop it off. check the teeth on the plastic gear when you have it out. Also a good time to correct the speedo if you have bigger tires.
Thread Starter
Junior Member
Joined: Dec 2008
Posts: 94
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From: Cambridge, MA
Year: 1992
Model: Cherokee
Engine: 4.0L HO
Sounds easy enough as well. Any gotchas that I should keep in mind when pulling that out? Also, think I should replace the sensor + gear, or just gear? (Based on the limited info provided.)
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CF Veteran
Joined: Sep 2010
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From: Salt Lake City, UT
Year: 2000
Model: Cherokee
Engine: 4.0L
hard to say. could be the gauge too. or a ground/wiring issue too. I would think its the sensor/gear. if the gear looks good the sensor would be where i would start. Get a new o-ring too, or it will most likely leak.
Senior Member
Joined: Jun 2009
Posts: 553
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From: West Texas
Year: 1991
Model: Cherokee
Engine: 4.0 L
Well sir, if your sensor attachment is differnt than mine then I would be hard pressed to correctly identify the issue at hand. However, on my 91, I had IDENTICAL symptoms as you describe several times over the course of ownership of Ol' Red, and the problem was VERY SIMPLE.
the "VSS" or Vehicle Speed Sensor is bad. like $45.00 from Rockauto.com or dealer or even autozone.
And it is located right where the other guys have said.
simple, simple simple, remove and replace.
just dont over tighten or it will crack the 1" nut that secures it to the transfer case.
your existing one might even be loose, get under with a wrench and check it.
best of luck sir!
cpnwrench
Thread Starter
Junior Member
Joined: Dec 2008
Posts: 94
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From: Cambridge, MA
Year: 1992
Model: Cherokee
Engine: 4.0L HO
So Drive gear =/= driven gear. Which is good to know.
cpnwrench - when you bought the vss did it come with a gear? judging from a couple pics above, I'm feeling pretty good that someone like myself could get in there and do it. I'll need to check the old gear, and then deal with the sensor. IF that doesn't fix it, replace the speedo cable, if that doesn't place it, take it to a shop. I need a tuneup and a safety/emissions yearly check as well. Thanks for the pointers.
BTW, I was going to be brewing an amber tomorrow, looks like I have to do this instead!
Thread Starter
Junior Member
Joined: Dec 2008
Posts: 94
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From: Cambridge, MA
Year: 1992
Model: Cherokee
Engine: 4.0L HO
Extra question:
Anyone know where to get information on the stock speedometer driven gear teeth count, and the speedometer drive gear teeth count? Anyone know the part code from jeep?
I can't find it anywhere, and after a few phone calls to advance and napa no one knows what the part is or what I'm talking about.
Anyone know where to get information on the stock speedometer driven gear teeth count, and the speedometer drive gear teeth count? Anyone know the part code from jeep?
I can't find it anywhere, and after a few phone calls to advance and napa no one knows what the part is or what I'm talking about.
Senior Member
Joined: Jun 2009
Posts: 553
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From: West Texas
Year: 1991
Model: Cherokee
Engine: 4.0 L
data......the VSS does NOT come with a gear.
you can order one (a gear set, depending whehter you have a lift or not, etc.,etc.,etc.,)
several links out there for those.
but you can try rockauto.com, discountautoparts.com, quadratec.com, jeep4x4center.com....etc etc google on the part and you can probably find what you are looking for.
I think though if you replace the sensor, your problems will go away.
the speedo gears hardly ever go bad, if they do, you probably would hear some chatter in your tranny as you are driving.
and there is no more speedo cable its all electronic.....fyi
good luck!
cpnwrench
CF Veteran
Joined: Jun 2010
Posts: 2,117
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From: Ohio
Year: 1998
Model: Cherokee
Engine: 4.0 stock
I hope this helps... just so happens I replaced my speedometer gear recently...
10/8/2011: Received and replaced the NSS. I hope I don't have to touch it for another 150k miles 
I replaced the speedometer gear also. Here is the chart I used...
According to the chart the 31 tooth gear would work. I looked around and jeeze... places wanted almost $80 for it! I found one on Parts mike for half that price.
First to change out the speedometer gear you will need a 1/2" socket, O ring and the new gear
Here is the housing you will remove. The 1/2" bolt that holds the retainer clip is what you will remove.
Note on the housing there are 4 notches. This enables you to "clock" the housing to install the smaller gear.
Here are the two gears side by side note the physical size difference.
This clip and bolt is what holds the housing in.
For my application I had to clock the housing 180* from it's last position. I checked my speedometer Vs. GPS. The speed is accurate within 3mph. I have to say... what a difference just a speedometer gear makes! The MPG has gone back up due to the odometer being accurate. Also it seems the transmission is shifting at a lower RPM due to the more accurate speedometer... but that could just be me...
I replaced the speedometer gear also. Here is the chart I used...
According to the chart the 31 tooth gear would work. I looked around and jeeze... places wanted almost $80 for it! I found one on Parts mike for half that price.
First to change out the speedometer gear you will need a 1/2" socket, O ring and the new gear
Here is the housing you will remove. The 1/2" bolt that holds the retainer clip is what you will remove.
Note on the housing there are 4 notches. This enables you to "clock" the housing to install the smaller gear.
Here are the two gears side by side note the physical size difference.
This clip and bolt is what holds the housing in.
For my application I had to clock the housing 180* from it's last position. I checked my speedometer Vs. GPS. The speed is accurate within 3mph. I have to say... what a difference just a speedometer gear makes! The MPG has gone back up due to the odometer being accurate. Also it seems the transmission is shifting at a lower RPM due to the more accurate speedometer... but that could just be me...
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