Speedometer reading dropout

[ptallant]

The speedometer reading in my '92 auto, 4x4, ext. cab drops out after the auto shifts into overdrive. For example, I can accelerate normally to about 30 mph where the overdrive kicks in. Soon after, the reading will drop back to the 20s range -- and the auto will down shift to 3rd range. Once back in 3rd, then the reading will usually pop up to actual -- and the auto will shift into overdrive again. This irregular cycle can go on and on.



I've replaced the distance sensor and its adapter. I've also replaced the auto's thermo switch.



Comments, Ideas, fixes?

 

[ETOBICOKE]

Speedo

This is a very common problem, the electric speed sensor is in effect a small generator and it's output voltage varies acording to the speed at which it is driven. The two most common things that give trouble are the electrical connector on the speed sensor being dirty and the rear yoke on the transmission being loose and letting the gear slip. The other possibility is the angle drive unit sometimes comes loose where it is fastened to the transmission housing which allows the gears to come out of mesh. Check the mechanical part out first, if that doesn't solve the problem you will need a service manual. PM me if you need more help and don't have a manual.



Neil

 

[bflood]

I have a manual Getrag and just had this same problem. Eventually the nut on the universal yoke fell off and was rattling around inside the universal (sounded like a stone in a hubcap). The speedo would drop to about half speed whenever I let off on the throttle and sometimes randomly too. Had the nut reinstalled and properly torqued (280 ft-lbs) with loctite after washing off. The bad news is it may have damaged my new rebuilt Getrag which is now popping out of 2nd gear on the downhill. This, was done by a dealer last October while on a breakdown in Iowa. The dealer also put in the wrong oil (75W-140 instead of 5W-30). I'm having an impossible time getting them, or Chrysler Corp. , to accept any responsibility, but thats a whole other story.



I'm now in the process of upgrading to a NV4500. At least the transmission rebuilder, Midwest Transmissions in Zumbroda, MN. , has been very supportive. After this is all over I will share my experience on the forum.



I don't know what this problem, the loose yoke nut, will do to the automatic but you should look into it. If the nut is loose I wouldn't wait long to fix it.



Good Luck!

Bruce