So as my trek into Jeep repair continues, I've got a new issue. Thespeedometer is wrong by like 10 or 15 MPH or so. Now, this Jeep (a '94Wrangler YJ) was in a pretty bad accident a while back, and had a lot ofrepair work done to it... after which, the speedo started readingincorrectly. I haven't learned anything about the speedometer system on aJeep yet, though I have seen that it's electronic, so I'm hoping the manual(when it arrives) will give me details on recalibrating it, but here's myconcern... it dawned on me that perhaps the rear end was swapped out as apart of the repairs (entirely possible), and that the new one that was putin, for some reason, had a different gear ratio and that's causing themassively incorrect speedo readings. Now if this is the case, that'd bejust fine unless the gear ratio in the front differential did not match,correct? It seems to me that if the front and rear differential gear ratiosdo not match up, engaging 4WD would quickly break something if you were todrive very far on anything but the loosest of gravel.I don't have a way to ask the repair shop if the rear differential waschanged out in any way, and the normal trick of rotating the wheels whilethe vehicle is elevated and counting the rotations of the driveshaft doesn'tseem to be working as the differential is a bit too loose for that and itjust spins the other wheel in the opposite direction (turning the driveshaftand counting wheel rotations isn't working either). Is there any sort oftrick to figuring out from casting marks or ratio tags on the differentialhousings what the internals might be? Or if it's the same assembly thatcame with the vehicle originally? Judging by the amount of yuck on thehousing I'm guessing it's the original, but then that doesn't explain thehuge speedo discrepancy. Maybe someone out there knows how the speedosystem well enough to explain how this could happen. Thanks in advance forany suggestions! Bryan

Tire size same? Did the transmission or transfer case get changed?There's a plastic gear that is changeable that drives the speedsensor... perhaps that gear is wrong now? You don't have acable drive speedo, do you? Later speedos are basically ameter movement; the computer puts out volts and the speedodisplays mph.__Steve.

That would be off the chart at:

Speedo wrong, but is that all?

Oct 02, 2003 22 Replies

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L.W.(ßill) 22 years ago

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Kevin 22 years ago

Use a GPS for your spedometer. Much more accurate.

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The Hurdy Gurdy Man 22 years ago

Probably not a street legal method of monitoring your speed in California, though... not to mention the price differential between a GPS unit and a speedometer gear!

Bryan

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