Author Topic: T35 speedo drive gearbox  (Read 2520 times)

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Offline yosemite

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T35 speedo drive gearbox
« on: 08 Oct 2018 at 19:38 »
On the return trip from Peebles yesterday the speedo on my T35 stopped working, have investigated and found the cabe is driving the speedo, although there is quite a bit of resistance and the speedo drive box output rotates when the wheelis spun but there is about 3/8 inch back annd forward movement on the output shaft,I suspect that the gearbox has started to fail, coupled with the high cable resistance, or indeed caused by, is the problem
I have removed the rear wheel, but cannot separate the speeedo drive from the wheel assembly, I have removed the nut wheel adjuster  and spacer parts 16, 41 and15 on plate27 in the parts manual but the drive will not come off. , thinking that it was pehaps a tight fit on the wheel spindle I tried using a gear puller but I didn't try ths to hard as it seemed solid and showed no sign of moving.
Is there something that I have missed,cant see any nut or circlip outboard of the speedo drive either on the wheel or on the partts diagram or are they just tight   and I need to use more force?

Offline eddie

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Re: T35 speedo drive gearbox
« Reply #1 on: 08 Oct 2018 at 21:41 »
The zinc alloy of the case has probably been squeezed enough that it has pinched onto the thread of the wheel spindle. Try unscrewing it off the spindle or just rotate the wheel spindle.

  Regards,
               Eddie.

Offline Doug

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Re: T35 speedo drive gearbox
« Reply #2 on: 09 Oct 2018 at 05:45 »
Same thing happened to mine. I had to un-thread it.

-Doug

Offline Neville Heath

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Re: T35 speedo drive gearbox
« Reply #3 on: 09 Oct 2018 at 09:23 »
See my Spannerama in July /August New Conrod magazine. There are photos and a full description. I suppose some people read it.
Neville Heath

Offline yosemite

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Re: T35 speedo drive gearbox
« Reply #4 on: 10 Oct 2018 at 18:33 »
Thanks everyone
the drive unscrewed once I realized, thanks to your information, problem with the drive was the inside square was "rounded " and was no longer driving the cable. made a small die and punch out of some scrap steel and reformeg the square around a broken end from an old speedo cable, also made a new spacer as Neville detailed in the new conrod article. My apologies to Neville for not recalling the article dont know why I  didnt,when i reread it  I remembered reading it when the New  Conrod arrived but for some reason it just didn't stay in mind
  Having rebuilt, ridden an repaired many British motorcycles over a 40+ year timespan the "extrusion" of the  speedo drive material into the  wheel spindle,   which seems to be fairly common on Douglas,(had a look at the mk 5 and that appears to be the same) does not seem in my experience  to occur on other marques.