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speedometer issues

trust

trust

PITA
City
White Rock
State
NM
So my speedo quit, I went to replace the cable assuming it had broken, wrong it was fine.... I got a new inner cable and cut it slightly longer, installed it and even though I can turn it by hand and get movement freely to the dash the speedo still doesnt work, so I put in another slghtly longer again to be sure both ends were engaged, spin by hand and it all works fune, button it up and nada.... thinking th esquare drive where it goes into the back of the speedo is hogged out maybe? any ideas? Any suggestions how to make the dash end slightly larger to see if I can drive the gauge?

thanks gurus
 
trust said:
So my speedo quit, I went to replace the cable assuming it had broken, wrong it was fine.... I got a new inner cable and cut it slightly longer, installed it and even though I can turn it by hand and get movement freely to the dash the speedo still doesnt work, so I put in another slghtly longer again to be sure both ends were engaged, spin by hand and it all works fune, button it up and nada.... thinking th esquare drive where it goes into the back of the speedo is hogged out maybe? any ideas? Any suggestions how to make the dash end slightly larger to see if I can drive the gauge?

thanks gurus
Click to expand...
Put a cordless drill on Tranny end and you should be able to tell if speedo is good or gear in tranny is smoked maybe
 
thanks, when I started I did spin it by hand and got an indication on the speedo, I neglected to mention that, sorry. I think I'll try your idea though anyway as this thing has me confused. The speedo end is sticking out of the dash through the factory radio hole and isnt spinning so I figured it must be the speedo drive from the speed sensor since it runs ok, so I ordered a new one, put it in today in the snow and still no spinning cable in the cab, I didnt hook it back to the seedometer itself but shouldnt the shaft be spinning? If its the drive gear in the transfer case is not driving the speed sensor and thus the cable shouldnt it run poorly if at all? I used to be a decent mechanic but this has me stumped and I really dont want to take it to a shop for something as simple(?) as a speedo....
 
trust said:
thanks, when I started I did spin it by hand and got an indication on the speedo, I neglected to mention that, sorry. I think I'll try your idea though anyway as this thing has me confused. The speedo end is sticking out of the dash through the factory radio hole and isnt spinning so I figured it must be the speedo drive from the speed sensor since it runs ok, so I ordered a new one, put it in today in the snow and still no spinning cable in the cab, I didnt hook it back to the seedometer itself but shouldnt the shaft be spinning? If its the drive gear in the transfer case is not driving the speed sensor and thus the cable shouldnt it run poorly if at all? I used to be a decent mechanic but this has me stumped and I really dont want to take it to a shop for something as simple(?) as a speedo....
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Sometimes the plastic gear inside tranny slips on the shaft ya have to remove the output shaft on back of tranny to get to it mine did it so i used some red locktite on it been working great for 3 years now they don’t reproduce the part anymore
 
Speedo gear is in transfer case, just don’t want ya tearing into the trans trying to fix it. :giggle:
 
hmmm I had the speedo drive gear out and thought it was ok, I guess I will have to pull it back out and see if the gear is slipping on the shaft. Im not clear though how it runs ok without the drive gear driving the speed sensor if that is in fact the issue, the speed sensor is responsible for alot of the FI changes as you drive and the vehicle speed changes etc.
 
Do you have a digital speed sensor with a mechanical pass thru?

Like this:
AAE5D64A-F7E5-4C01-A264-32A4BF948A36.gif
 
I believe that is a standard dodge dakota speedo adaptor with a machined bushing on the output to convert to the cj speedo cable threads.

Are you sure you are getting rotation on the output of that?

Rockauto, 1990 dodge dakota, 5.2l, electrical, speed sensor. Standard Motor Products, SC1l08. $48.79
 
I wish I had tried the Dakota unit, its 1/3 the cost of the hesco, of course..

Today I hooked up my drill to the input of the speed sensor and had steady readout on the speedometer in the cab. To me that implies everything from the T case to the readout is ok, or am I over simplifying? I then removed the drive gear from the t case and it appeared to be perfect, the input drive on the speed sensor fit into the shaft on the drive gear just fine, I couldnt move the gear on the shaft at all nor did the drive cable slip in the drive gear shaft. The only thing I can think now is that whatever drives the speedo drive gear has no teeth left.... That makes no sense though as the EFI SEEMS to work fine and if the speed sensor isnt being driven shouldnt the EFI be impacted?
 
Could be going into a "limp home mode" and running in open loop mode.

Next test is to thread the speedo end of the cable into the cab where it can be viewed while driving. Not connected to the speedo.

See if the cable is spinning while driving.
 
I had the speedo end loose in teh cab through the radio slot and drove it so I could observe rotation, there was none, Im down to thinking it has to be the drive gear in the tcase, maybe it looks good because all the teeth have been shaved down the same?
 
Without carefully reading through the thread, have you checked to make sure the gear housing is properly aligned when you're putting the gear/gear housing back in the t-case? It has an oblong internal shape and you'll notice there are numbers on the housing corresponding to the gear size you have, and a notch. That notch needs to line up with a corresponding notch on the t-case. Roughly, anyways. You can try rotating the housing slightly (clockwise, I think) to see if you can get the plastic gear to mesh with the internal metal gear and drive it properly.
 
As Walkerhoundvm says, the eccentric gear carrier must be clocked to correct position for the gear to engage properly (correct position varies depending on the tooth count of the gear being used). FWIW, you can still get new drive gears from a Mopar dealer if you can't locate them from an aftermarket source.
D300 eccentric.JPGSpeedometer gear housings.PNG
 
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well I thought, clearly incorrectly, that I had it properly clocked for the tooth count but after taking it apart to check the tooth count and paying close attention to the clocking it now works!! YAY! thank you all for the help! NOw why did it pop out last time? must have gotten loose? Anyway, I how have a functional speedo again, thanks gents!
 
Great!

Sometimes it is the “simple” things. Glad it was not a stripped gear in the output housing. Though I doubt that would happen without obvious signs on the plastic gear.
 
amen! I wish Id thought to check the alignment before spending the monty on numerous cables and the speed sensor, oh well... the fact that the drive gear was ok was a red herring, or a clueI guess, anyway, glad its fixed and again, thanks all for the help
 
Most people have a few spare parts just hanging around in their spare parts bins. Just the way it is with a CJ.
 
trust said:
well I thought, clearly incorrectly, that I had it properly clocked for the tooth count but after taking it apart to check the tooth count and paying close attention to the clocking it now works!! YAY! thank you all for the help! NOw why did it pop out last time? must have gotten loose? Anyway, I how have a functional speedo again, thanks gents!
Click to expand...
I'm rarely helpful, so glad we tracked this one down :)
 
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