todzilla

OK this is a really odd one that - in my previous 5 Porsches - I'[ve never encountered!

About a week after I bought my '86 951, I did the gauge cluster lighting 'refresh' and all went great. I always reset my trip odometer upon a refill to track my mileage and know not to press the reset button when the car's in motion. But yesterday - about a month after I did the gauge lighting job - I noticed the the 2nd digit in my odo's cluter (not the trip meter, but the actual recorded mileage counter) is rolling over at the same rate as the last digit! In otherwords, it goes from 145000 miles to 155001 to 165002 (as an example)....yes, I'm accumulating a hideous amount of miles alarmingly quick! Not good!

I hadn't looked to see if this happened just after I reassembled the cluster after I plugged in the 3 harnesses behind the gauges, or if it's a recent, unrelated thing. It would make sense that something happened while I was in there tinkering, but it all went smooth and other than those 3 harnesses behind the gauges, nothing elaborate or detailed is really tinkered with so I don't think I tweaked anything?

I did some searching and I've heard gear failures are fairly common but from what I can tell, it's 'working'...just in hyperdrive!

Anyone experienced this kind of thing?

Cheers

931guru

Yep, not uncommon problem with VDO speedometers. The bottom line is that the odo part of the speedo is a bit too loose on its spindle and one of the tumblers is turning in sympathy with the miles tumbler. Sometimes it's the thousands tumbler, sometimes it's the ten thousands, and sometimes it's the hundred thousands tumbler.

You might have to replace the speedo.

smz2ride

Had a similar issue with mine. The tumblers are loose on the shaft as 931guru pointed out. I just cut a small slot in a washer, pushed all the tumblers to one side and wedged the washer in onto the shaft to take up the slack. That was about 10k miles ago

william_b_noble

as others said, you need to add a shim to take up the end play in the ODO mechanism - a small washer of suitable thickness is what you need. I usually slide the shaft out and put the washer in place and then slide it back, you can use plastic or metal washer.

And, please note, it is absolutely FALSE that pressing the reset on the trip odometer at any time has any relationship to the gear failure - if you look at the mechanism and how it works this will immediately be apparent to you.

todzilla

Thanx guys! I knew someone here had such an experience =)

So is it easy to get to that shaft to do the shimmy thing? I've had the gauge cluster out, and I know once it is, it's about 12 (?) teeny screws to get the thing apart...but from that point, is it fairly apparent as to how it's screwed together, so to speak? last thing I want to do is make it worse!

Cheers

veleno

Be sure to take pictures of the process when/if you do it so we have a resource for others.

931guru

In order to split the speed into two parts, you have to remove the painted gauge face.

In order to remove the gauge face, you have to remove the speedo needle.

The speedo needle is VERY fragile, and, if you break it, it cannot be repaired.

Just sayin'.

todzilla

I think what I will be doing is just replacing the whole gauge cluster and being done with it. There's a friend here that has 2 clusters available so that is probably the safer approach. To be determined.......

william_b_noble

oh, come on - it is an easy fix, I've had about a dozen of these apart, just pop the pointer off, unscrew and disassemble - it's really not hard. don't be stupid, protect the face, use proper tools including a screwdriver that fits the screws and so on. If you are super clumsy I suppose you can break anything, I use a pair of dikes to leverage the pointer off.

todzilla

As I'm getting a cluster with a new odo gear installed thru a friend (thanx Rich!) - it's more cost effective to swap it out as opposed to take it apart. Were the gauge cluster pricey, I'd def. take your advice...but I'm getting a great deal =)

william_b_noble

you may be getting a deal, but you are learning nothing from it. But it's your choice.