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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