Drive gear for speedo

[Southern75]

Hi

Has anyone heard of a speedo drive gear which is made of bronze or something like that?

I have had a few issues with the plastic ones and as it is in a track car something that didn't get heat affected i think would be a good idea?

Any ideas?

[colcol]

There is a Sprint owner in Bendigo who knows about these, have a look at an earlier thread in the Sud\33 forum, a Sud that i knew did a lot of track had no trouble with these, what is the problem you are having with yours?, Colin.

[Southern75]

oh just done a couple in a short period of time ... and don't really like the idea of plastics gears ... i suspect it is the heat generated in the gearbox on old brittle components

[colcol]

Do you have an original twin carb Sud or Sprint with the long speedo cable?, if yes, this could be the problem, for Australian ADR's, they ran the speedo cable into a "box", that measured the road speed, then ran another cable out of this box up to the speedo, when its new it works ok , but get a bit of a sharp bend or kink or lack of lubrication and the poor old speedo gear in the gearbox has to do a lot of driving, the solution is too straighten any kinks and sharp bends and lubricate the speedo cable with light oil, also the thick gearbox oil works its way into the cable and acts like a lubricant, NO - NO, its too thick and creates too much drag for the gearbox speedo pinion to push around, Colin.

[colcol]

I saw some brand new Alfasud gearbox drive gears for the speedo cable on a Italian ebay site for spare parts for Italian cars, and i purchased some bits i had been chasing, Colin.

[Southern75]

Thanks Col

[colcol]

Some good Alfasud and 33 bits on those Italian ebay sites, and even though its in Italian, with the pictures you can work out what it is, Colin.

[Frank Musco]

Slightly off topic, if its strictly a track car, l suggest you will be faster if you leave the speedo gear out. On the track if you have time to look at the speedo your not going fast enough. Data acquisition should be used to 'look' at things like speed.

I use no speedo in the track car, I use lights for oil and temp, a rev limiter, and a big tacho which is almost useless! and I say that because its very difficult to think about what the revs/speed mean with respect to lap times while your trying to drive flat out. The only place you can read speed is once you get the car onto a straight, but I cant read how fast the car gets to, because I'm looking for the braking point.

If you drive the car during the week, I appreciate you need to know the speed, so I'll suggest you remove the gear just for the track days, maybe get yourself another one of the metal part which holds the speedo gear and block it up and use it as a replacement plug for track days. But this will not save the gear if there is a problem!, and considering you say you had a couple fail in a short period, you definitely have an issue somewhere.

After you immediately changed the plastic gear, did the speedo constantly flicker from as soon as you began driving, and get quicker as you drove faster? This suggests the metal drive gear on the drive hub may have a bad tooth? OR does the speedo read normally until a cetain speed and then it begins to flicker? which suggests you have a cable problem.

Also, like Colin mentioned, I also used to have the speedo working in the track car and have never had a failure, as well as every sprint I've owned and currently still daily drive, so check the cable and if that looks and feels good I would remove the drive hub from the gearbox and check the metal gear hasn't been damaged from previous work.

[colcol]

And as previously mentioned, take the cable out every few years, and lubricate it with some engine oil, the grease that people put in it and the gearbox oil that works its way into the cable is too thick, and the poor little plastic gear has too much work to do, coping with all that friction, Colin.

[Southern75]

Frank just reading you post.

As for having a few fail in a short space of time ... the first one i think was just a natural 'old age' failure.

The second one came our of a gearbox which was in a race car so who knows what sort of state that was in.
Since then (not that i have been on a track recently) i have not had any problems ... just running as per normal.

My car is still registered so i really need it to be there ... if it were strictly a track car i would probably take it out and go down the data logging path.

And yes frank you're right .... i shouldn't be looking at the speedo on the track.

Yes i will get in a lubricate the cable now ... good time as my cluster is not in.

Quick question ... would there be a better lubricant than engine oil ... perhaps something teflon based like bicycle chain lube or something like that? ... usually has less friction due to the strate viscosity that it is

[colcol]

You do have the single cable, and not the 2 piece that runs into a box so that the pollution gear knows what the road speed, if you have the 2 cable system, then dump it and put in a single cable, give the outer and inner cable a good clean, and lubricate it with silicone spray, that won't attrack dirt and dust, Colin.

[colcol]

Or for less friction, and no speedo cable to break you could always adapt a 33 speedo and electronic pickup, Colin.

[Southern75]

nah have the single cable one ... just going to lube it up today... still not keep on engine oil though

[colcol]

If its a race car that gets driven to the track, and sometimes used during the week, you could leave the speedo in for legal reasons and use a GPS as they are more accurate, the Sud i used to drive had a flickering needle that used to drive me mad, the speedo in the 33 is much more steady, [when its working], but not as accurate as a GPS, Colin.