Coming off the highway today our 1997 Blazer 4dr 4x4 did not want to move. Here is what I have noticed. If in OD & the ABS light is on it will not shift. I can manually shift it as far as 2nd. Sometimes the speedo will come off 0 right around 2300 rpm in 2nd. At that time I can put it in OD & it will shift into 3rd & then 4th normally. Everything worked just fine prior to today. No ABS light, speedo was fine, trans acted normally. I am thinking it is probably the VSS but was looking for opinions from Blazer gurus. Ideas guys? A search here brought up the VSS is usually the culprit with ABS light issues. It would make sense if shifting is controlled by speed input.

 

Definitely sounds like a VSS issue to me. Make sure you check the connections before replacing the sensor. 4x4's have a short extension to relocate the VSS to the transfer case, I had one where the connection to the extension went bad and still acted like a faulty VSS.

Now whenever I replace a VSS in a 4x4 I usually go and solder those wires together and shrinkwrap them so it can't fail.

 

Something to add to this. After letting the truck sit for 2 hrs everything worked as normal. Could the VSS react to heat as old Ford ignition modules would. Get hot & quit working. Cool down & all is good again till it gets hot or could I be looking at the module under the hood just behind the battery?

 

Sounds like it got locked into limp mode and reset while the ignition was off. But, seeing as it seems intermittent there's no real way to really tell via interwebs.

 

I'd start by checking the wiring and put a continuity meter on both sides of that connection, especially since it doesn't cost anything.

 

Same problem on my 1997 LT 4x4. It was the vss on transfer case. Put over 300 miles since repair. No more abs lite and no more shifting down. Runs great.

 

Sorry for the late reply but I put a VSS in the truck & problem solved.