Syncro Vanagon Speedometer Drive Gear Replacement

As usual at this time of year I start thinking about getting the westy trip-worthy. One of the items was getting the speedo and odometer working again.

The van has been without a speedometer and odometer for the last year. I got by using the miles-per-hour gauge on the ScanGauge2. (As I have a Bostig Zetec in my vanagon I can connect the ScanGauge to the OBD port.)

scangauge2

I had diagnosed the issue to be a problem with the speedo drive gear in the front differential: when I spun the speedo cable from the differential end the speedometer moved and when the front wheels were turning the speedo output on the side of the differential was stationary unless I gave it a bit of a twist manually, in which case it would turn about ¾ of a turn and stop again. Seemed like a few teeth were worn off the drive pinion gear.

There is a great thread at https://www.thesamba.com/vw/forum/viewtopic.php?t=482112 so I read that before attempting the job of replacing the drive gear. It was very helpful.  I then prepared for the task by getting an inexpensive set of roll-pin punches and purchasing a new speedo drive pinion gear from T3 Technique in the states. (previously this was only available from the UK.)

t3technique-website

There is an aluminum ‘sleeve’ held into the side of the front differential housing by a roll pin and as mentioned on that thesamba thread if you ‘extend’ your punch with a socket drive extension (I used an 10”, ½” drive extension and a 10 mm socket which fit perfectly over my roll-pin punch) it is a good set-up to drive the roll pin out.

roll-pin punch

roll-pin punch2

Once the roll pin was out I used a similar method to the one described on thesamba to remove the aluminum sleeve from the diff housing (but used an old nut and part of a ball bearing as a spacer).

speedo-drive-gear-assembly

Exactly as I suspected, a few teeth were worn off the plastic pinion gear.

speedo-drive-gear-assembly-missing-teeth

Next step was to make sure the new bronze gear from T3 had the same number of teeth as the old plastic one (they both have 19 teeth – well the plastic one maybe had 16 ½  left but started life with 19)

speedo-drive-gear-old-and-new

I then removed the old plastic gear with a hacksaw, cleaned the shaft and new gear with brake-clean, coated the knurls on the shaft with loc-tite 680 and pressed the shaft into the new gear.

speedo-drive-gear-assembly-gear-removed

speedo-drive-new-gear-pressed

According to the loc-tite website, 680 takes 24 hours to cure so I’ll put everything back together tomorrow. Looks like that should be an easy task. What I was most worried about on this job was the roll pin being stuck and possibly damaging the diff case like happened to one of the fellows on thesamba thread.

UPDATE: everything went together nicely and I now have a functional speedometer and odometer. The speedometer is a bit jumpy at low speeds though (below maybe 25 kmph). If I would have had a 10mm reamer I would have reamed out the housing the speedo pinion gear shaft fits into as there was a little resistance to turning there. I may still do that in the future, now I know this all comes apart fairly easily.

 

 

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6 Responses to Syncro Vanagon Speedometer Drive Gear Replacement

  1. stuart black says:

    I am going through the same process with the little white speedo gear (1986 syncro, North American model). I found a replacement white gear at Small Car Performance but after it arrived I realize it is different from the original. Both have 19 gears, but the original has a hole in the end which aligns with the dowel pin in the front differential, that I assume holds the gear and shaft in place above the ring gear. I used my iPhone to video inside the speedo hole and saw the dowel pin and the ring gear inside the front differential.

    I wanted to ask if you know if the hole in the end of the white or brass gear fits onto the dowel point?

    Either way, my options are: a) hope the nylon gear will stay in place, b) drill a hole in the end of SCP’s gear, c) see if SCP will refund my money and buy the T3 brass one.

    Incidentally, thanks for posting the hacksaw method as I was wondering if there was an easy way to get the old gear off the speedo drive shaft. I tried soaking it in boiling water, putting it in a vice and twisting it with a wrench on the shaft and vice grips on the gear. My next thought was to hacksaw the gear in half. But I didn’t want to damage the shaft.
    Stuart

    • edbee says:

      Hi Stuart,

      regarding “hole in the end of the white or brass gear fits onto the dowel point?” No idea as I didn’t see the dowel pin you are referring to. How tight a fit on the shaft is the new gear? The originals sure weren’t going to come off as they were on there very well. Did the white gear come with any glue? Is your video something you could put online and then I could see the dowel pin you are referring to.

      Best of luck with it in any case and if you can post the video, please put the link to it here.
      Ed

      • stuart black says:

        Hi Ed,
        Thanks for the quick reply.
        I plan to tackle hacksawing the old gear off the shaft today. I first wanted to find out if I needed a gear with a hole in the end (thinking that SCP might give me a refund and I would have to order the T3 brass one). But I just got an email from SCP saying that the hole is not used. They said to install on your original drive shaft by heating the shaft to 400deg F and inserting into the new gear.

        After I hacksaw the old one, I plan to soak the shaft in boiling water, spread some blue lock-tire and slip the new gear on.

        I will try to tidy up the video and post a link. It was difficult to shine a headlight and point the camera down the shaft and focus on the dowel pin. But I can send you the stills where you can see the dowel pin and internal gear if you zoom in (stuartblack at shaw dot ca).

        Ps. I see you were up at Brohm Ridge in 2012. I try to get up there a couple times a year (summer and winter). The forestry road on the left before Cat Lake is better than the road you took. But it gets rough near the top. On one trip, the trailing arm gave out and I wore out two tires just to get down to the Cat Lake road. I since upgraded to 16″ rims and a set of BF Goodrich AT tires, which makes the road seem easier.

        Ps. Sorry to hear they are logging in the Walbran again.

  2. stuart black says:

    Incidentally, do you know what caused your speedo gear to stop functioning? Yours looked to be in about the same shape as mine. Mine stopped functioning after getting hauled out of a snowbank at Cypress. As a I started driving down the hill, the speedo needle shot up to 100 and then dropped down to zero. After seeing how the drive is put together, I figure the pressure of the snow on the cable must’ve pushed the shaft enough to jam the white plastic gear against the internal metal pinion gear.
    After I finish this, I will use your advice to tackle my jammed diff lock. The vacuum servo works fine when taken apart, so it must be a seized diff lock shaft.

  3. edbee says:

    Hi Stuart,
    I think my speedo pinion gear failed due to the van being parked for maybe 6 months over winter. I suspect what happened was for some reason the speedo cable got stuck in the sleeve it runs through (from front diff to the actual speedometer) so when I first drove the van the plastic gear was being driven by the internal gear in the diff but the shaft couldn’t spin as it was being held stationary by the speedo cable, so the teeth just came off. I think if that happens again the brass gear will be stronger and force the shaft to turn which will then force the speedo cable to spin, overcoming any resistance from the speedo cable sleeve. (which reminds me, I should grease the cable the best I can to prevent it from sticking in the future.)

    • edbee says:

      PS – glad you found the diff lock posting. I now have another vanagon with that same issue so I am going to have to go through that process all over again. Did I post about Brohm Ridge, That was an amazing drive but I can’t find that post… strange…

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