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Speedometer not working after gear change

InOmaha

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Sep 26, 2019
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95
Location
Omaha
I tried searching but it always comes up gear change. I changed the gear and now my speedometer stopped working right.

My speedometer was off by 5 mph, so I changed it. Got perfect results, and now it's off 10-15 mph low and bouncing some.

What could this be?
 

Jerry Bransford

TJ Guru
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Nov 9, 2015
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Escondido California
You probably didn't rotate the speedometer housing far enough so the new speedometer gear is fully engaging the pinion gear underneath it. The speedo housing is on an eccentric so it moves the gear closer to or further away from the pinion gear as needed for different speedo gear diameters. It has to be able to do this since varying gear tooth counts cause the speedometer gear diameter to vary.
 
Last edited:
OP
I

InOmaha

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Sep 26, 2019
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Omaha
I took it out today and reseated it with the same results. It was spot on with my GPS after I installed it. I'll take it out and count the teeth to see if it's the wrong gear, but I got accurate results at first.

I can install the old one and see if it goes back to off but more accurate.

Maybe reset the PCM and check the wiring.

I have no codes, just a horrible speedometer compared to the one 5 mph off.
 
OP
I

InOmaha

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Sep 26, 2019
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Omaha
I bought a 32 tooth gear, installed it with the 32-38 in the 5 o clock position, wiggled it back and forth until the gear lined up and I could push it in, rotated it just enough to line up the lock, tightened it down, drove the car and checked the gauge with a GPS phone app.

Two days later I notice it's off 10 mph. I search around and only find how to change the gear. I'd suspect I installed it wrong too if it never worked. But it did for several days.

I'll check the install one more time, and try the old gear if needed. Then I'll have to move on to wiring, the sending unit, or the guage.

I need to order an ELM 327 type scanner. Then I could see what the ECM is seeing. That would give me and indication of before or after the ECM.

I'll let you know if I'm an idiot after i check it again, but GPS verification showed me it was correct when I put it in the first time.
 
OP
I

InOmaha

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Sep 26, 2019
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Omaha
I did install trailer wiring with a new ground back there a couple days after the speedometer. I wonder if the sending unit is confused about ground now. I'll pull the engine ground again and re clean it. Or unplug the wiring kt and see if that does anything.
 
OP
I

InOmaha

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Joined
Sep 26, 2019
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Location
Omaha
I cleaned the engine mount ground connection.

Then pulled the gear and counted teeth at 32. Made sure the housing was clean, installed like below. There is no other way to install it without leaving off the retainer and its fully seated on the lip. The gear looks good with no damage to it.

Same issue. I'll move on the disconnecting the trailer wiring I installed after installing the gear and check if that's my issue. I may try the old 34 tooth gear first.

2019-10-12 11.59.49.jpg
 
OP
I

InOmaha

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Joined
Sep 26, 2019
Messages
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Location
Omaha
I put the original gear back in and it worked fine. 3-5 mph off like before. I noticed it snaps in with about twice the effort and the ends are different. Original on the left. Much sharper pressed area on the metal end.

I may return it and try another or try this one again when I have time to mess with it, turning it as far counterclockwise and clockwise like I tried already once.

But I'll probably just get the speed fixer instead.

At least now I'm not doing 65 on the highway with it reading 50 and bouncing around. A steady 60 is much closer.

20191012_124017.jpg
 

dbbd1

go away...
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You can rotate the speedo gear housing to 0/360, 90, 180 and 270 degrees, depending upon how many teeth your speedo gear has. Look closely at the housing...
 

pagrey

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Apr 10, 2018
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Los Angeles, CA, USA
You can rotate the speedo gear housing to 0/360, 90, 180 and 270 degrees, depending upon how many teeth your speedo gear has. Look closely at the housing...
I'm actually a little confused by your comments. The OP described doing exactly this and posted a picture that is identical to yours that shows the numbers in the correct position. Are you saying that there is something else to do?

As far as doing something else you might do a self test on the instrument cluster to check and see if the gauge is moving freely. Simply hold down the trip reset and turn the ignition on and watch the cluster and see if everything works smoothly. Beyond that it might need a new VSS.
 

MallCrawlOnTons

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Joined
Dec 9, 2018
Messages
647
Location
West Georgia
You can rotate the speedo gear housing to 0/360, 90, 180 and 270 degrees, depending upon how many teeth your speedo gear has. Look closely at the housing...
900 posts and still can’t comprehend what the op has done in the thread with good detail...

To the op. Hope you figure this out.
What brand gear did you pickup?
 

MallCrawlOnTons

TJ Enthusiast
Joined
Dec 9, 2018
Messages
647
Location
West Georgia
I put the original gear back in and it worked fine. 3-5 mph off like before. I noticed it snaps in with about twice the effort and the ends are different. Original on the left. Much sharper pressed area on the metal end.

I may return it and try another or try this one again when I have time to mess with it, turning it as far counterclockwise and clockwise like I tried already once.

But I'll probably just get the speed fixer instead.

At least now I'm not doing 65 on the highway with it reading 50 and bouncing around. A steady 60 is much closer.

View attachment 119525
The new shaft looks worn on the top. Something ain’t right with it.
 
OP
I

InOmaha

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Joined
Sep 26, 2019
Messages
95
Location
Omaha
There is some adjustment possible with the retainer because it's slotted at the bolt. I rotated as far clockwise as possible, as far counterclockwise as possible, and in the middle; with the same result. I put the old gear in and it worked fine first time, just off 3-5 mph again because it's 34 instead of 32 teeth.

I'm going to leave it like that for now and get a speed healer. I'll probably make one using pagrey's thread on it.

I moved on to other things I want to check out before winter. Plugs, oil, hoses, coolant set up for -35F, installing a new rear window and some misc. parts the dealer agreed to before I would buy it, etc.

Just weird. Either a faulty gear somehow, or I'd have to rotate it to a position I can't use the retainer clip, or I rotate it to the 31 tooth position and see what happens.

Strange it worked fine for 2 days before getting squirrelly. If the original stops working in a couple days, I'll check the VSS and guages.