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ABS/Speedomoter

1K views 10 replies 3 participants last post by  Stephen Silver 
#1 ·
I am having trouble with my 95. The speedometer doesn't work and the truck doesn't shift until the ABS light comes on. This normally happens after the truck has been sitting for at least a few hours. I can't find this issue anywhere online, hopefully you guys can point me in the right direction.
 
#2 ·
Welcome to LR!:bigtu
 
#4 ·
I should have mentioned that before, but the original one was covered in metal shavings. It was the first thing that I replaced while trying to fix this problem. I also purchased a new cluster (new to me anyway) to see if that was the case as well. I had the same issues with that.
 
#5 ·
Did it work for a while after you replaced it???? pull it out again and clean it. Attach an AC volt meter to the terminals and operate the truck on jack stands and see if you are getting a low voltage AC signal from the sensor. If there are shavings on it again more than likley has a differential starting to fail.

Depending on what year and transmission combination, some also had a speed sensor on the tail-shaft housing of the transmission.
 
#7 ·
Did it work for a while after you replaced it???? pull it out again and clean it. Attach an AC volt meter to the terminals and operate the truck on jack stands and see if you are getting a low voltage AC signal from the sensor. If there are shavings on it again more than likley has a differential starting to fail.

Depending on what year and transmission combination, some also had a speed sensor on the tail-shaft housing of the transmission.

It actually did start to work better, but not for long. I have already taken the differential apart, cleaned everything, replaced the axles (which had been ground down to the point that the clips fell off), there was a lot of metal in there, but it was all axle. The actual gears look brand new. Could it be something else that is causing metal shavings? I will check the sensor when I get home. Also, its got the E4OD that doesnt have the sensor in it, it only has the one on the top front side of the differential.
 
#8 ·
Once the sensor is covered with filings it does not work properly, I do remember that happening back in the days when those trucks were new. As I remember, and that was a long time ago, it was the Carrier that got damaged, I want to say the side gears ate into the case// but I could be wrong. I don't ever remember having ring and pinion problems with anything except diesels. I would pull the carrier or at least the side gears and inspect the case, probably replace the side gears pinion gears pinion shaft and lock bolt Make sure you run something down the axle tubes. debris likes to set at the bottom of the tubes as grease doesn't really move there, just puddles. Make a big swab with a rag and with the axle bearings and seals removed clean the tubes very well also the low spot where the pinion is. Probably put some regular inexpensive gear oil in it run it for a few hundred miles and do a change to get any contamination out.
 
#11 ·
I seem to have found the major issue. Someone at some point had messed with the speedometer harness. After researching for a bit, I found that the wire that was tampered with was "Rear Anti-Lock Brake Signal Input to PSOM." We have already fixed that issues and it seems that my speedometer is now working properly. The next issue that I'm facing is that I was told that the PSOM constant is probably wrong. It is a bit more difficult that I originally thought it would be to calculate. Does anyone here have their constant? Everything that could be involved is factory except for the tires. I have replaced them with the same size (275/60r17.) Any help would be appreciated.
 
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