Speedometer disassembly

[Thrasher]

I've searched the archives and re-read the tech articles for this one, but no luck:

I have the classic worn out odometer gear on my '84 coupe - electronic speedometer. I removed the gauge and got the bezel off, but Wayne's book and all the articles on this site refer to the mechanical speedo with "2 screws" holding in the "guts".

My electric speedo has 4 screws, plus 2 more for the wire mounting plate - which do I remove to get the guts out of my speedo for replacing the plastic gear?

Also, anyone with experience want to debate the necessity of removing the needle and face to do this on an electric speedo?

Thanks,

Craig

[Rot 911]

This has got to be the dumbest question anyone has ever posted on this board!

[Thrasher]

very funny Valentine.

Thanks for the free bump, though.

[caliber60]

Dumb? Not really. I don't understand what he is talking about. Picture would help.

[Thrasher]

Kurt was just yankin my chain because I asked him first and he said it was worthy of posting w/o looking like the newbie that I am.

So, I can post a pic later, but if you've been in there you'd know without a picture.

My question is: Once the speedo is removed and the front bezel and glass are out, how do I proceed on an electronic unit? There are 6 screws on the back, do I remove them all? There are two screws near the trip odometer on the front - do those need to come out as well?

I'd rather not mess with the needle removal because it necessitates recalibrating and opens the option of breaking the needle. The archives aren't clear on this, and Wayne's article and book refer to a mechanical unit.

Thanks,

Craig

[ausgezeichnet]

I ended up removing all the crews on the back of my speedo when I replaced my odometer gear on my 84. I seem to remember that I could have done it with only removing 4 but is was no problem getting all 6 back in. Just make sure you do not pinch any wires.

If you search the archive there is a reference to removing the odometer reset push rod and then rotating the face so the hole is over the 4 screws so you can remove them. I tired it but could not remove the push rod. I ended up snapping the needle off. Just sent it in for a $170 repair!

Here is what the speedo looks like with the face off.



When you replace the odometer gear you will have to remove two or three additional gears and then reassemble in the reverse order.

Good luck.

[Thrasher]

Thanks,

that helps - it sure seems like there's a fair amount of information lacking in the tech article on this one for the SC/Carrera crowd, especially for something so common and delicate.

Maybe I should volunteer to document this for an electronic speedo - provided all goes well.

I had read something about removing the reset push rod and getting access to screws - but how is the rod removed and what screws am I accessing???

I've had a few beers tonight watching the Packers smash our Rams, so I'll be waiting til tomorrow on this ;-)

West Coast Bumps away!!!

Craig

[Rodney Nelson]

I just did mine two days ago it was kind of a pain in the butt.

1. I could not get the odometer reset button out either. I was able to slide the metal pin out of the plastic clip at the bottom on the reset button, but I could not get the Plastic clip off. Therefore I could not remove the button. If I could I would have simply rotated the face around to access the four screws out that are under the face plate.

2. Carefully tilt the face to one side and get a small screw driver (sideways) onto the head of the screw and turn (if you cant get the odometer reste button off). Be carefull not to but to much stress on the needle. It takes a lot of time but you have to do this four all four screws. Once you get them all the way screwed out you need to use a small pair of needle nose pliars to pull the screw out.

3. I believe there are another two more screws on the back of the assembly that you have to take out as well.

4. You will basically have to remove all of the gears to get to the one that is bad. Two of the similar gears are held on via a clip on the metal pin. The two gears that are in the center fit together and are on a metal pin. Push the pin thru the hole and remove all of the gears.

5. Install the bad gear first then the rest.

6. When it was time to put those four damn screws back on under the face plate I simply got some powerful wire cuters and cut all of the screws in half, that way it took way less time to re-install them.

It is just a little bit time consuming. My advice is just to sit there for a while and examine how everything works then a big light will come on and before you know it you will save a $150 bucks by fixing it yourself.

Good luck.

[Thrasher]

Thanks Rodney - I'll dive into this tonight. It sounds very tedious, but I'm willing to try.

I assume the 4 screws you're referring to are the ones in Ausgezeichnet's pic above.

Anyone have any tips on removing the reset button so I can use that access hole?

[Gunter]

In order to get to the odometer gears, the face plate has to come off (2 screws) To get the face plate off, the needle has to be removed. When you get the needle off, the calibration is gone. When trying to get the needle off, you will break the tiny shaft that holds the needle, now your'e screwed! Been there, done that! North Hollywood Speedo will do it for about $100.00 if the needle shaft is not broken, otherwise $150.00.
NHS will repair, calibrate and give you a one year warranty. Does Pelican do speedo repairs? Maybe that's the way to go.

[sammyg2]

I've done two now, didn't really have any problems with either one. Unfortuately I did them over a year ago and my memory is foggy about the details. I did have to take the needles off and I didn't break them although i was nervous about it.

[dfink]

Does opening and working on your own odometer without recertifying the mileage mess with value of the car. Don't you get some sort of certification to keep with the car when a professional shop does the repair.

[Thrasher]

seems like there are two distinct opinions on whether this one is worth the hassle and risk.

I'm already "in" the gauge, and several have said it's doable with patience, even without removing the needle. I'm willing to give it a try.

Anyone have any tips on removing the reset knob? That seems to be the key to getting at the other screws that allow access to the gears w/o removing the needle.

[schleg79]

Justification for spending a few extra bucks and having a pro do this is that they bench test the entire unit, electronics, gears, and all. This is done to get to the "real" problem. Often, a "worn" gear is a result of a deeper drive problem, etc.

Just a question - how much are the gears costing you?

I, too, had my gauge completely disassembled, found the problem and still decided to send it to NH Speedo. Cost me $110 2 mos ago.

[Thrasher]

I'm still not ruling it out, but as long as I've got the case opened up, I'm curious to see what's going on in there.

This seems to be a very common problem - 20 years ago the VDO factory put some lube that reacts over time on the plastic gear on the reset mechanism. It works fine until that gear simply dissolves and renders the odometer useless until replaced. '

If I get in there and see that's the case, I'll proceed. Otherwise, I'll send it to NH myself.

The gear was $25 from www.odometergears.com

[schleg79]

Are you talking about the soft, almost rubber-like gear? If so, that's the same gear that failed in mine. NH speedo tells me that gear is designed as the "weak link" for a reason (same principle as a fuse or cb). It is the first gear to disentegrate so that other gears don't chew themselves up in the case of a drive problem.

I'm sure also, as you said, that these gears disentigrate over time in a perfectly operable speedo. Sounds like you've got it figured out - just wanted to share with you what I came across..

btw - thanks for the link; the same guys I almost purchased from - the $25 for that 1/16 of a nano-ounce part pushed me over the edge to sending it in.

[Thrasher]

yep, it's falling apart

I'm still wondering how to remove the reset mech to use that as access for the screws. I don't want to go pulling on things haphazardly.

Anyone recall how to do this?

[robs]

I recommend removing the needle. At first I tried to pull the needle, but it didn't move. Instead I pulled the black push rod off the trip reset (this is dangerous, the push rod is attached very firmly and can break, do not pull it!). Then I turned the face plate to reach the screws through the holes. But the face plate was still in the way when I wanted to disassemble the gear set... So I carefully twisted the needle counter clockwise (against the internal stop of the axle) to break it loose, and that worked for me. Remember its original position when you put it back on.

PS: my odometer gear was the ROW version with 29 teeth. I didn't find this part in the U.S., but I found two dealers in Germany who sell the original VDO part. I paid approx. 15 US$.

[Thrasher]

Rob, thanks for the advice - I'm still considering removing the needle.

I've finally taken some pics of what you can expect to see if you crack open your electronic speedometer when your odometer quits working..

For the record, mine did stop working as a result of using the reset - but I was still at the gas station, standing still, with the motor off . The gear can be seen missing several teeth near the worm gear - the ones on the top of the gear dissolved when I lightly touched them with my finger, but were in place before that.






So, back to my question about the reset knob - here it is to refresh some memories for anyone who's done this.




- is there a good way to remove this, or should I follow Rob's advice and just pull the needle? I would think it should be easy enough to replace the needle in the approximate location - mine is already optimistic by about 7 or 8%, so I could even try to adjust for that mechanically by removing and reindexing a tad lower.

[david914]

OK, I just did this for a friend of mine. Yes, you can do this without removing the needle or the reset button, but it is a bit of a PITA.

First, remove the two small screws holding the gauge face on. This won't do anything but get you a little more clearance to remove the four screws underneath.



Next, (this is the fun part) take something flat that will fit between the loose gauge face and the white frame that houses the gears, and loosen the four slotted screws that you see here (I used the back side of an X-Acto knife)



(side view)


Once these are removed, you need to remove the motor that drives the odometer by removing this screw


Now you should be able to get to the C-Clip that holds the small white gear in place that is preventing you from removing the broken gear (also held in place with a C-Clip).

Of course, installation is the reverse of disassembly! Good luck!