How do i repair the mileage counter, the speedometer works?

If it has a speed sensor in the transmission that sensor may have failed.

if the speedometer is working but the counter is not - then the counter gear is broken.
it is not worth trying to fix -- just buy a new gauge and install it.

c...

if the odometer qorks but the speedo dont then you have a bad guage.look online for speedometer or instrument cluster repair places they will probably be cheaper but you will have to change it out yourself. the dealer is the best place to go for such things though.

Probbably a bad body earth, Check allyour body earth connecions!
Hope this helps.......Bruce

Sounds like the clocks have been tampered with if the speedometer is still working, You can try running the miles backwards with a drill on the cable, and then forwards again past the number where it jammed, run it back and forth a few times and once it gets past the stuck number youre sorted... it may happen again in 1,10,100 or 1000 miles time... and if so youre best with a new or scrapyard speedometer - write down the original mileage when you change the speedometer - maybe on a panel under the bonnet so you have something to go off to decide when to service the car - EG old mileage + new mileage = actual mileage. hope this helps.

Not to sure, but i think its cable. Loosen the nut that holds the cable to the speedo drive on the gearbox. check if the inner cable is broken.

Regards
Phillip

Change speedo senser at gearbox.

You will need to pull the speedometer out and have the odometer (u call mileage counter) repaired, the little drive gear that comes off the speedometer to operate the odometer has failed or broken.

Expect to spend $350.00 for the P/S pump.
At 100,000 miles, I would not be surprised that it would need a timing chain replacement, in addition to the front seal. It's common for them to be worn out around 100K miles...
Expect to spend about $700/800 dollars there.
The speedo/odo is probably a cable, 70/80 dollars
Tach - A new one is $495.00

Offer this guy $750.00; that is all it is worth.
I hope this helps you out.

vetsr,
I believe there is an "amplifier" box, as you described, for the digital dash, I think under the dash towards the center console. Check out http://www.z31.com/ or call your local Nissan parts counter for exact location.. They should be able to tell you.
I don't know about the miles counter. If your speedometer works, it shouldn't be the speedometer cable. Sorry I can't help you on that.
My parts counter guy has always been helpful in trying to troubleshoot many issues. At least you should know his name.
Also, check out your local Z club. http://zcca.org/ and maybe
http://www.zcar.com/forums/
Good luck and happy motoring,
AlwaysRight