Topic: Speedometer Issue

[northwestjet]

Hey, first post; gotta start with a tough one. Have actually used some info from these forums in a build-up of my '95 YJ and I appreciate you all being here.

What I'm looking at now is a speedometer problem. I have installed a JB Conversions super-short SYE, with a tone ring and electronic sensor. Due to 33's and 4.88 gears, I required a Dakota Digital SG-5A signal converter. I am able to calibrate the signal fine, but under acceleration, the speedometer drops to zero. When I let up on the accelerator, the speedometer comes back to life. I understand there have been problems with a spinning tone ring caused by under torquing the output pinion nut, but, (1) I have added torque twice and am way over torqued already, (2) I drove the Jeep with the SYE without the signal converter for a couple hundred miles with no speedometer problems, and (3) I would expect intermittent tone ring slippage to cause a more erratic speedometer reading than I am getting. The speedometer goes quickly from the correct speed all the way to zero and back to the correct reading, which means that the tone ring is either completely stopped or spinning at the same speed as the output shaft, but no speed in between. This seems unlikely.

I just don't know what electronically could cause the signal to drop out only under acceleration? Ideas?

[Bounty Hunter]

I've installed  a SS SYE and wondered how the speedo worked since the tone ring spins freely on the shaft.

I would contact both the SYE and the signal box manufacturers.

[northwestjet]

Yeah, the way I understand it, what keeps it from freely spinning is being compressed between the yoke and the shoulder on the output shaft. They had thought about changing it to have a dowel pin or some other way to lock it to the shaft, but they said it is a good indicator of proper torque on the yoke nut as it is now. That's from an article I read. I have a call in to JB, but I haven't talked to them yet.

[Elyod]

I think i read the same article, the speedometer malfunction was suposedly a warning sign of improperly torqued bolts.  But you did everything right so I don't know.

[northwestjet]

Wow! I finally figured it out. Determined that the tone ring was not slipping with help from John at JB Conversions...thanks.

Now what? Well, I had used a voltmeter to search for a 12V supply for the Dakota Digital module, rather than a wiring diagram.
Turns out the one I selected was the air conditioning compressor relay supply (I don't have air,) and I remembered that many vehicles
shut off the A/C compressor during acceleration via the PCM, so I changed the 12V source and all is well.

Thanks for those that put thought into this problem.

[Elyod]

Wow.  What a coincidence that you picked the AC supply.  At least you figured out that everything was working correctly. 

[Jeffy]

That's a weird one for sure.

[Bounty Hunter]

I never would have called that one.

[jeepheap]

ok....random.