how do you test that electronic doo-hickey that sits on top of the off set gear for the speedo?? (down on the transfer case)<br>What type of output is there from that unit? Variable resistance? open circuit with a momentary short?

 

Are you having a problem with yours? If so let us know what it is - I'm sure someone here can help.<br>Bob

 

Several years ago my speedo up and quit. On a whim I had replaced the (electronic doo-hickey what ever it's name may be)<br>all was well and I had been driving happily until last fall when the speedo was intermittent. I would be driving down the road with the speedo jumping up and down. Now when I have thought it had finally given it's last gasp and died, it starts working for a brief moment and has since died (again)<br>Having read other posts on this it could be one of three things<br>1.the off set gear attached to the transfer case<br>2. the electronic doo-hickey attached to the off set gear<br>3. a short in the wiring harness somewhere<br><br>I have visually inspected the wiring harness (as best I could) and have placed plastic loom over the harness in one spot.<br> with the off set gear attached to the transfer case I placed a small screwdriver in the end and gave with a twist to see if the gears were somehow stripped<br>the last thing I have not been able to do is properly &quot;test&quot; the electronic doo-hickey. <br>It is the intermittent part that has me reluctant to just replace it on a whim this time<br>thanks

 

That is exactly the way mine behave too.....<br>I don't have any idea what test values apply to the speed sensor (aka: doo hickey ) but all it took was a new one and I was good to go.<br>The speedo thrashing around is the giveaway on this one I think...<br><br>Bob.

 

It looks like both the wires connect to the input side of the computer and the output goes to the speed control or speedo. I kinda sorta think it is a magnetic pulse type sender. It should be a complete circuit with ? ohms resistance when checked. Aren't intermittant electrical problems a blast? I could do them all day long! : Jim

 

Thanks for all the replies. I think it's time for the parts store...

 

The 5 speeds had another problem especially the Getrags. Drop the driveline at the rear of the tranny and pull the nut off clean the threaded shaft - locktite is and torque that puppy down. I can get the exact torque if you need it. That nut acts as a jamb nut to hold the speedo drive gear from moving - that's the only thing that keeps it from moving. I had this problem and that's how I solved it. It might save you some $$$ if it works. Good Luck<br>Bob

 

Am I incorrect in my assumption that problem was only on the two wheel drive trucks?<br>All the speedo gears are in the np205 transfer case on my truck. (4X4)<br>Thanks

 

There was a TSB for 4X4's before the problem was found in 4X2's.<br>Bob

 

Well I finally bought a speed sensor, it repaired my problem. So... Mark one up for the electronic doo-hickey

 

Oooooo Baby,,, I luv it when a plan comes together.... ;D ;D ;D

bob.

 

I am glad the Spped Sensor fixed your problem. oweve on mine though it did not and I had to replace a faulty computer under the hood. So remember fella's that sensor sends a signal to the computer, then the computer sends a signal to the speedo unit in the dash. Bill