Speedo Cable Flutuating and differential spinning question:

[Ducer]

Hey guys,

I have a couple of questions.

1. My tach does seem to work, but it fluctuates up and down.  What does this mean? Must I grease the ends?  Note: this car probably has not been running for years, until i bought it.

2. I had my 260z on jackstands and drove the car in the air, the rear driver side wheel spins freely as I am in all gears, the passenger wheel seems to want to spin but hardly moves and only skips.   Do I have an Open Differential? VLSD? or fluids in the pumpkin is bad? Note: The fluids probably never been changed in years, but why would only one wheel spin? or will the other wheel catch only when there is friction as a VLSD.

And do 260z come with VLSD ?

Thanks.

[Ducer]

Hey guys,

I have a couple of questions.

1. My tach does seem to work, but it fluctuates up and down. Does not go smoothly.  What does this mean? Must I grease the ends?  Note: this car probably has not been running for years, until i bought it.

2. I had my 260z on jackstands and drove the car in the air, the rear driver side wheel spins freely as I am in all gears, the passenger wheel seems to want to spin but hardly moves and only skips.   Do I have an Open Differential? VLSD? or fluids in the pumpkin is bad? Note: The fluids probably never been changed in years, but why would only one wheel spin? or will the other wheel catch only when there is friction as a VLSD.

Thanks.

[PZG302]

To quickly answer your questions,

The tacho is an electronic instrument, if standard, and so the jumping about would generally due to fluctuations in the signal being received by the tacho. There should be plenty of info here as to what can cause the jumpiness and how to fix it.

As for the diff, what you describe is standard behaviour for an open diff, so nothing wrong with it from that description. If it hasn't been used for a while it would probably be worth changing the diff oil, just use a good quality oil suitable for an open diff.

[Linton]

what  he said
your tach is electronic and does not require lubrication so I assume from the header you are referring to the speedo, you could pull out the inner cable and give it a light coating of grease, but also check for sharp bends or kinks, they wont run smooth if bent.
up in the air you will most likely see one wheel spin, the diff is not a LSD just an old plain jane conventional type if lsd is fitted both wheels will spin, if you want to confirm it ajust the brake on the spinning side so that you can just rotate the wheel by hand try it again in gear, if the other side takes off and it doesnt bog down its conventional diff. just just run it too hard up in the air
HTH Linton

[RB30X]

His title says speedo, but his post says tacho. I reckon he means speedo cable.

[Ducer]

OOps, I apologize, I mean "Speedometer" fluctuates.  Tachometer/rev is fine.

Okay, I got it guys, the speedometer signal is off the coil.

As for the Transmission, I did put some Synchromesh and 80/90, I'll change the diff oil.

Thanks gents. i SHALL look up the speedo in FAQ

[jamo240]

Hey Ducer

My speedo (73 240Z) also fluctuates and bounces around a bit....i don't know if oil has worked its was up the cable over the years and trace amounts have made it into the head unit to upset the pickup arrangement, causing it to bounce around.

You just kinda put up with it a bit...when I am crusiing at a steady speed it's fine...it's more an issue when accelerating...it tends to overshoot then bounce back down before settling down at a steady speed.

Cheers

Jamo