Another speed sensor dilemma

[trexterra]

I have been having a problem with my speedometer not getting an accurate read. I already tried replacing the gauge cluster and I get the same problem. The speed bounces from 10-30mph regardless of how fast i'm going and occasionally the speed drops to 0mph and the CEL comes on making me believe that the supposedly new speed sensor is failing. About a month ago or more I pulled out my speed sensor to check the condition and see if it had any visible concerns before I wanted to bother installing a new speed sensor. Upon pulling it out I noticed that the pinion gear on the end was warped on the inside of the fitting allowing for a lot of play/slack/not a tight fit on the speed sensor as well as looking banged up on the ends of the pinion like it was catching on something. It is also blue (may be important?). There was also no c-clip holding it on. So I call up courtesyparts and have them send me a new gear based off my VIN #. Part shows up and it is Red, bigger diameter, and shorter in length. So I took off the old, put on the new and it is a really really tight fit but eventually I get it to go in, put the bolt back in, double check the pigtail connection, and fire up the truck. Now I get no speed whatsoever it just sits at 0mph with no CEL. So I pull out the speed sensor completely and try the extra new speed sensor (Beck/Arnley Part#0905002 for extended cab 4wd auto trans 95 hardbody pickup) that I had just in case and try to install that one with the new pinion. Still sits at 0mph with no CEL. I also tried to fit the old pinion on the new speed sensor and it won't fit because apparently the new speed sensor I bought has a shorter stem than the old one. So right now i'm just letting the new speed sensor sit in there with the new pinion wondering if resetting the ECU is required? maybe something else is wrong? maybe i'll have to concede and take it to a dealer? I can't think of any other details to include but if there is any other detail that might help troubleshoot feel free to throw it out there. Thanks again for all the help in the past/present/future that I get on these forums.

Edited August 28, 2012 by trexterra

[trexterra]

drove around for a few miles and the CEL popped up. but disconnecting the battery to reset the ECU didn't accomplish anything

[Slartibartfast]

If you've gone through three sensors and two clusters and still have the problem, I suspect neither of them is at fault. Sounds to me like either the wiring is making intermittent connection or there's something wrong with the gear in the transmission that the speed sensor engages. If the sensor gear looked chewed up, this may be the case.

 

Also I think the blue speedo gear and the red speedo gear are about two teeth apart... which to use depends on what tires etc you're running.

[trexterra]

well I ordered the red one direct from nissan based off my vin so at this point I have to assume it's correct. I figure the blue one must have been beaten up because it's the wrong diameter so only parts of the gears were catching? I'm just going to have to take it in to the shop at this point I believe.

[trexterra]

took it to a mechanic today, he was able to determine that it's an internal problem by hand spinning the speed sensor while another guy was in the cab watching the speedo with the ignition on. Luckily this mechanic is also willing to do the fab work for my front bumper