Kolbjorn S

It's amazing, my car is on its 3rd speedometer unit after the odometer gear on the first two broke and stopped counting. Today, this one stopped as well. Digits were misaligned as well (what a surprise). I fixed the same problem on the 993 following this post on how to fix a broken odo. However Jeff at Odometer gears explained the Euro-spec 928 odogear could have 30, 32 or 34 teeth (US spec has 21, go figure) - so I guess it needs dissecting first to find this out. My "Gulf spec" car (option 150) is often a mix of Euro/US specs so it could be anything I guess.
Just appaling how bad quality Porsche odometers are . I remember my old 928S once started counting thousands instead of kilometers so by the time I got home I'd put on a good fifty thousand or so....

heinrich

Dude, mine have been excellent, over several Porsches. better than my Ford or Chevy ones. And they took a lot more miles. The only bad thing (agreed) is the jelly gear. You can replace that with a hard plastic one aftermarket (I did this in my 911).

Garth S

Ha! ... with cheap gas and the wide open roads of Oman, you probably lost track of time ... and distance
Interesting - there was another recent post about the first odometer digit 'jumping': this also happened on my '80 last year, when it advanced from 112K Km to the first digit being caught between 3 & 4 .... and I was only gone 30min.
What I did notice (seriously) was that a small brass screw holding the odo gear set to the dial face had loosened: in my case, I've done nothing as the odo otherwise works normally, and the first digit remained stable; however, the possibility is that if these screws loosen, the gear train becomes misaligned .... causing the drive gear to break, etc. Perhaps something to verify in your next 'surgery'.

jpitman2

My 83 spent 9 years in Saudi - up to 120F temps, and the gear is still fine.....but still under 50k miles. Mind you, I dont tempt fate by resetting trip while moving.
jp 83 Euro S AT 49k

Neil Warwick

Just remember, these odo's aren't made by porsche, they're VDO units. And they are a b.nuisance. My australian unit (for the S2) required one of the "variant" gears, worked well ~6/12 then stpooed again....the gear's fine so I think it's an alignment / meshing problem. Still, at least the digital system in my S4 is reliable, even though both over-read by the requisite 5%!

NeilW

hinchcliffe

Don't reset the odo when you're driving or rolling, only when you are stopped.

Kolbjorn S

True! In fact we had a backroad fun-run this morning, not a camel nor trooper in sight And thanks for the tip, I'll look for any loose screws in the assembly.

Good point not to reset the trip meter while moving, I try not to. I think mostly it's the humidity and heat killing it. I recon 3/4 of all older Porsches here suffer from this.

Rich9928p

Porsche doesn't make displays - if you look, it is a VDO display. VDO makes the displays for many marks of automobiles, including Mercedes Benz. So if you have a grip, take it up with VDO. I'm sure that Porsche didn't spec the composure of the small plastic gears.

928FIXER

True...VDO makes the unit.But to who's specs?My 928's only go 65-85k miles before they stop working.My benz on the other hand has over 400k on the speedo and its never needed fixing!

Kolbjorn S

This was the sad state of the odometer gear:

Note that this shows the front side of the gear with the standard 20 teeth, of which 4 are missing in my case. On the back side of the same yellowed gear sits a tiny wheel with either 29, 30, 32 or 34 teeth (and other variations perhaps?). In my case I had 29, but unfortunately Jeff at Odometer Gears LTD only manufactures from 30 and up.

His gears are apparently made from Celcon, a hard automotive plastic very unlike the original soft Urethane plastic.

Jeff sent me a 30 and a 32 gear to be on the safe side - before I had paid! No affiliation etc, but I find such trust these days to be beyond what is expected, particularly if I dear say between the "west" and Middle East! Hats off for such superb customer support Needless to say I returned the 32 gear to him.

I ended up using the 20/30 teeth gear, and got the mileage adjusted to correct reading and it now works great!

Flint

I replaced my gear with the better aftermarket version. It didn't work. Then the car sat for 10 months, wherein I took it out and cleaned it better. It still didn't work. Eventually after a few hundred miles, it started working intermittently, then normally. I have no idea why, nor am I tempting fate.