My truck is a 94 4x4 with V6. As the title of the thread says, when I'm driving down the highway (or anywhere) and I put on my turn signal to switch lanes... that's when my speedometer needle drops to zero... and then it immediately pops back up to the appropriate speed. The issue isn't consistent, but intermittent. It's enough to bother me. Anyone know where I should begin to troubleshoot this and maybe repair it?

Any advice is very, very appreciated!

 

I would venture it has something to do with the fog light install.

 

It's almost certainly a failing VSS1; the electronic speed transducer in the back of the transfer case. It will slowly get worse until it fails permanently. That will take out your cruise control and one of the signals the ECU uses.

Replacing it is not difficult, and RockAuto has them. You probably need the ~$250.00 one. There is a way to test them, but it is difficult, and since you have an intermittent problem that only makes it harder.

At least one member on this site reports successfully cleaning the inside of their transducer, but there's no telling how long that lasted.

 

Haha! Nope. This was an issue prior to the fog light install. :-)

Well this isn't good news. And $250 for a part... ugh.

 

How about http://www.aliexpress.com/item/speed...990446149.html ?

Or

 

$27 is much more reasonable. If I bought this thing though, I have no clue where or how to install it. Can I get a lil guidance?

 

It's the only transducer in the back of the transfer case. It's held in by one bolt, as you can see on the various photos. Get under your truck and take a look.

The gear is removable; these transducers don't usually include one (because there are different sized ones to accommodate different rear-end ratios). You may have to use the old gear.

Don't forget: aliexpress specializes in selling Chinese "after-market" parts. Many Chinese-made products are excellent. But for $27, you may be taking part in a simple experiment.