Speedo question

[ARedetzke]

I guess I lied, I'm going to be a pain in the butt. Bear with me, this might take a while. I have been experiencing a problem with the speedo jumping. 1st time it happened, I found the VSS had worked loose from the gear ratio box on the transmission. Tightened it up, and it worked for awile, then quit completely. Replaced VSS, fixed it for a few months, quit again. 3 speed sensors later (O'Reilly's Borg Warner rebuilts every time, lifetime warranty) I kept getting the same results. It would fix the problem for awhile, and then it would quit. So last time I got a new (to me) speedo head unit from the junkyard, along with the VSS, and I cut out a splice that was in the line and put it back together with the heat shrink connectors, fixed it for awile but now the old familiar tick is coming back, and (now that I finally got around to fixing it) the cruise control jumps around to try and compensate for the tick in the speedo. My question is, what are the odds that I have gotten 4 defective VSSs in a row? Could it be that the reduction unit that plugs into the transmission is causing the VSS to die? I have no idea what else to replace. Tried recrimping all connections, even on the back of the head unit, and nothing seems to work. I searched the forums, but it seems like I've tried everything listed there. Changing the VSS fixes it every time, but only for a couple of months. In fact last time all I did was take it off and put it back on, and it started working again. WTF?????????

 

[Paychk]

I had a problem similar to what you are describing. The problem was in the VSS gear ratio box, it has a drive pin located between it and the speedometer pinion on the side of the transmission, it was stripped. I used JB weld to glue it in and It has worked since. Try looking there for your problem.

 

[ARedetzke]

JB the VSS to the ratio box, or the ratio box to the transmission?

 

[Paychk]

I believe if you take the gear box off of the transmission you''ll find a drive pin and it may be worn to the point of slipping. I used JB weld to fix the drive pin into the gearbox. I wouldn't recommend using JB weld to permanently attach the VSS to the gear box or the gear box to the transmission or maybe in your case the transfer case.

 

[dpuckett]

ARedetzke-



Take the truck end of the pigtail apart (the one the plugs into the VSS), and look at the female ends of the wires where they attach to the VSS. If they arent PERFECTLY ROUND, the thing will not work consistently, due to a bad connection. I straightened mine out with a pair of 7" Vice Grips and a soft hand. And dont worry about getting the wires back right; it is impossible to get them wrong. Has to do with the design of the VSS. IF you notice, when you go backwards, the miles add up along with telling you how fast you're going.



JB Weld goes on the speedo box, and the adaptor the is secured to the transmission tailshaft with the bolt (1/2" head; this adaptor has a gear on the end of it inside the transmission). I tried JBing it on the last 93 I had, and it didnt last 200mi. Ended up getting a "new" (to me) one from a junkyard.



Since it works when you play with the electrical stuff, I'd lean toward the wire ends not being quite up to par.



Daniel

 

[ARedetzke]

Thanks guys, back under the truck I go!

 

[JKurley]

Did you check the aluminum elbow coming off the transmission? Take it completely off, and look at the drive cable coming out of the transmission- it should be square, as should the hole in the elbow that it goes into. Thats the speedo drive cable (the green plastic gear usually doesent go bad). When I bought my truck, the speedo didnt work, and the culprit was the square drive cable- it had rounded, so there was nothing to catch, I wasted $65 at the s****** for a vss- ohwell, now I have a spare! Check that little cable.