Mileometer / Trip Meter Repair

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foggyjames
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Mileometer / Trip Meter Repair

Post by foggyjames » 12 Dec 2006 02:29 am

Howdy folks!

One of the insignificant but annoying faults which affects the 300 series is the two mileage counters failing. Here's my brief guide to fixing it...

The fix goes as follows. Remove the instrument cluster (see Haynes, swear at Haynes, work it out for yourself), and remove the speedo from the cluster (4x 5.5mm hex-headed screws). While the cluster is out, take this opportunity to run some light oil (3 in 1, perhaps?) down the middle of the speedo cable to help prevent 'needle waggle'.

Next, locate the hole in the rear of the speedo housing, and shove some blu-tack in there. Raise the needle to exactly 60mph (or another chosen number), and push the blu-tack in, fixing the needle in place. Now you can safely remove the needle (either by hand, or some like to use a fork) without messing up the calibration - although of course you need to put it back on right! We're doing this because there is 'preload' on the needle, so pulling the needle straight off, then sticking it back on at 0mph won't give the right result. At this point, you can remove the two screws which hold the facia on, and you have access to the mechanism.

Blu-tack Pictar!
Image

At this point in time, if you can be bothered, you can roll the mileage on simply by pushing the numbers around - starting at the 'lowest value' end. It's is usually easiest to turn the trip meter, as this is coupled to the mileometer, but is still rigidly mounted. See below...

Image

Now down to the 'meat' of the situation...
The problem is caused by the plastic housing of the speedo becoming worn (Figure A), and allowing the spindle which the main mileometer is attached to work loose and move. Eventually, it will work its way sideways, and the gear will be pulled clear of the worm-gear (Figure B), meaning the shaft no longer turns, and the mileometer stops advancing.

Figure A - Where the housing wears
Image

Figure B - Where the gear no longer meshes with the worm-gear
Image

Figure C - How it should mesh
Image

Once you're happy with the mileage, you just need to line the shaft up with the hole (ooh err) as in Figure A and push on the gear end to re-mesh with the worm gear, and start the mileometer turning again. Re-assemble, and you're done....Hurrah!

-----------------------------------------------------------------------------------

....Not quite.... :lol:

Thing is, that housing for the shaft is worn, right? So it'll just pull straight out again. We need to secure it somehow. Andy's method is to add a blob of solder to the end of the shaft (the end shown in Figure A), but that seems a bit too much like Ninja soldering to me, so I'm going to try an easier method.

I cracked out the drill and pop-riveter (I guess I have an unfair advantage there...), and got to work on the casework. Essentially, I riveted in place a small bar which prevents the gear from moving out of mesh with the worm gear. A picture tells a thousand words...

Image
Image

Then it's a case of putting it all back together, and going for a test drive :)

Hopefully that has been of some use...

cheers

James
VOC 300-series Register Keeper
'89 740 Turbo Intercooler
'88 360 Turbo Intercooler
'85 360 GLT
'81 343 GLS R-Sport
'79 343 DL
'70 164
...and some modern FWD nonsense to get me to work...

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340GLT
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Post by 340GLT » 12 Dec 2006 11:56 am

You know if you remove the pin on it foggy the needle moves back round and lines up with a mark on the face, so no need for blue tack? :P
I explained that in my 140MPH article!! lol
Adam
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foggyjames
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Post by foggyjames » 12 Dec 2006 07:07 pm

Yeah...but I have shares in Blu-tack PLC :-P I figured that instructing people to remove the pin might be risky, as I imagine it's more than a little delicate.

cheers

James
VOC 300-series Register Keeper
'89 740 Turbo Intercooler
'88 360 Turbo Intercooler
'85 360 GLT
'81 343 GLS R-Sport
'79 343 DL
'70 164
...and some modern FWD nonsense to get me to work...

pettaw
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Post by pettaw » 12 Dec 2006 09:26 pm

I can confirm that Adam's way works absolutely great :) There is a mark to line up with and the article explains exactly how to do it.
In fact, I feel a topic copy and paste coming on ;)

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foggyjames
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Post by foggyjames » 24 Jun 2007 12:03 am

Go on then, do the copy and paste :-D

Update...about a week later, the speedo cable snapped...it's doomed! sm56

I've also found a much easier way of adjusting the mileage. If you move the upper of the two 'bars' - the one which carries the small 'cogs' - out of the way, you can turn the number wheels freely.

Isn't it a bit risky, James, telling people how to 'clock' their cars?! Not really. Any 300 series enthusiast worth their salt knows mileage means approximately nothing to a 300 - nowadays it's all about the rust, and the quality of maintainance. Knock 50k the clock off if you must - we won't care, and we certainly won't give you any more money for your car sm56

cheers

James
VOC 300-series Register Keeper
'89 740 Turbo Intercooler
'88 360 Turbo Intercooler
'85 360 GLT
'81 343 GLS R-Sport
'79 343 DL
'70 164
...and some modern FWD nonsense to get me to work...

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foggyjames
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Re: Mileometer / Trip Meter Repair

Post by foggyjames » 28 Jan 2012 11:41 pm

Finally, after many PM requests, I re-uploaded the pictures to Photobucket.

Oh, and here's the section from Adam's "140mph speedo retro-fit" thread on lining up the needle without using the blu-tac method. The pics are of a 400 series speedo, but I assume the procedure is similar.
340GLT wrote:Assembly is simply reversal of unassembly.
When you come to put the needle on line it up with mark on the face of the gauge like this....
Image

Make sure you fit this first then the pin!!! The new hole for the pin will need to be redrilled i think it is 1.5mm or 2mm i cant remember. Check that with the existing hole!!
Next job is to fit the trip push!!! push through hole onto bar and twist square block. Push front piece on!!

You should now have something that looks like this!!!!
Image
cheers

James
VOC 300-series Register Keeper
'89 740 Turbo Intercooler
'88 360 Turbo Intercooler
'85 360 GLT
'81 343 GLS R-Sport
'79 343 DL
'70 164
...and some modern FWD nonsense to get me to work...

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