91 dodge odometer problem

My brother in law has turned to me for help on his 91 Dodge pickup. His speedometer works but his odometer does not. He told me that he had the entire speedometer and odometer changed. It did not fix the problem. I was at the wrecking yard and picked up a complete dash gauge setup and still no dice.The mechanics at the local dealership don't even remember one this old. I was told that the speedometer and odometer may run off of different sensors. Does this sound right? One guy told me the speedo ran off of the rear end and the odometer ran off of the tranny. It has the drive coming out of the back of the tranny that converts to wires and feeds the dash gauges.

Not right, the differential sensor didn't start until 1998, then it ran odo and speedo as the VSS in the '91 does. It's been too long but since he's replaced both those things I'm guessing it may have a PCM problem?

Robert

Just googled it and it seems the 90-92 have a plastic gear that breaks and the speedo works but the odometer does not. Looks like I'm in for some repair work.

Those year clusters have 2 small plastic gears in the cluster that fail. You have to take the back off the speedometer and replace one or both. A common failure on these truck. Chances are you have enough to build a working unit.

My 91 stopped working over 10 years ago :-/
MPH works fine.

Please let us know what you find. I might try fixing mine someday

Ok. Made the fix today. The old unit I just bought at the wrecking yard has bad gears in it. Speedo worked but odometer did not. OEM gears were blue and they both had broken teeth. The new unit he got from dodge did not work on the odometer but speed worked. However the gears were white plastic and were not stripped. After several swaps we finally got the combination right and used the winding from the old odometer motor in the new housing with the new gears and got it working. Evidently he got a bad unit from dodge three years ago with a bad odometer winding at a cost of $500! They take your old one and change the mileage to the new one and destroy your old unit. Anyway, it's fixed. With new paint and interior, he's already had several people wanting to buy it!