erratic speedometer

JMGNPD · #1 02-28-2007, 11:37 PM

I just did a boat load of work to my '95 F150 5.8 5speed(conversion) 4x4. I took it for it's first drive after the work, the list of which would exceed this block's word limiit, and the speedo became erratic. The needle jumped from what seemed to be an accurate speed to lower speeds. The needle jumped more as speed increased, becoming most noticeable above 65 M.P.H. The only problem was the needle, and nothing else seemed to be affected. My cruise control no longer works either, but that could be due to some harness wire jumping to eliminate the old auto's wiring and control. Any help much appreciated. I did change the speed sensor in the rear but not the one in the transfer case. Which one actually controls the speedo? I think the rear is just for the ABS.

Steve83 · #2 03-01-2007, 02:54 AM

Read this thread, then click my signature link & look in the 8.8" Axle album. Pull your ABS sensor, clean off any metal filings, & inspect the tone ring thru the hole. If you chock BOTH front tires front&back, lift at least 1 rear tire, & put the trans in N, you can spin the d'shaft and inspect the entire tone ring for damage or looseness. If there are a lot of filings on the sensor, you should open the rear cover & find out why.

If all of that checks OK, then it's probably the PSOM dying. They're known to occasionally. Just find a used one. If you can't find one locally, e-mail me. I have a few.

adrianspeeder · #3 03-01-2007, 10:03 AM

What did you get the transfer case from? There shouldn't be a need on the '92-'96 to have a transfer case speed sensor.

Adrianspeeder

JMGNPD · #4 03-01-2007, 11:29 AM

The transfer case is the original electronic shift BW 1356. The rear end speed sensor is brand new but it was one I had lying around for a while. I also changed rear oil. The old rear sensor wasn't that bad and there wasn't any excessive shavings on the sensor or in the rear. The speed sensor in the transfer case is also original and looks to be a little involved to change.

Steve83 · #5 03-01-2007, 11:56 AM

JMGNPD
Check it all anyway.

adrian
All ESOFs have a speed sensor (#20) embedded in the back cover of the t-case. It's what the 2 odd wires from the shift motor connector go to. Most people don't realize how easy it is to access, so they cut the wires when removing the motor.

adrianspeeder · #6 03-01-2007, 12:33 PM

Wow, never saw that. Course always had manuals in the fleet.

Adrianspeeder

JMGNPD · #7 03-01-2007, 03:55 PM

The truck originally was an auto. with push button 4x4. I swapped in the 5 speed. Ford never made a 5 speed with push button 4x4 so I'm guessing that the speed sensor on the transfer case has only to do with the shift on the fly push button. The service manual doesn't show a speed sensor on the manual shift tcase. I still have the push button. I just had to add a switch to the neutral wires on the old auto wiring to shift into four low.