Author Topic: ZB 32 gearbox  (Read 489 times)

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Dennis49

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ZB 32 gearbox
« on: 26 May, 2020, 20:51:38 »
I am having problems with selecting 2nd gear both up and down through the box. I have checked all the springs and pawls and they look ok and move freely. I took off the front cover today as the gear pedal would not move, I think it was whilst trying to find second. The quadrant appeared to be stuck. I discovered this after removing the clevis pin from the link for. I now have all the shafts and gears out of the box and nothing looks to be obviously wrong. I aim to rebuild it in the next few days. Any suggestions of what to specifically to look for would be appreciated. The 1st 3rd and 4 th gears all change nicely.
Dennis

Jim S

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Re: ZB 32 gearbox
« Reply #1 on: 27 May, 2020, 04:16:45 »
Hi Dennis
Have you separated the 3 shafts? You should look for wear on the fork faces and wear in the groove of the 1st/2nd dogged wheel. I had to replace a dogged wheel on my gearbox and weld repair and machine the corresponding fork because of excessive galling caused by poor alignment and rubbing of the fork and dogged wheel.
Also ensure the fork bodies slide smoothly along the gear selector shaft and there is no binding of the pins in the fork body grooves. If you feel any binding you can do some filing or very light blending to remove any raised areas that may be causing hang up of the pins in the grooves. Look for wear on the pins and grooves also. If you see any issues you may need to drive out the pins on the gear selector shaft to remove the forks.
Check that the dogs on the dogged wheel engage nicely with those on the face of the 2nd gear. The dogged wheel should also slide freely on the shaft.
See Service Sheet 608. I think it says the assembly should be in 4th gear when you stuff the 3 assembled shafts into the gearbox housing.In 4th gear the 1st/2nd shifter fork and dogged wheel should be mid way between the 1st and 2nd gear. If not you may need to add or remove a shim.
Push the inner cover into place including the gasket and install a couple of bolts. Try shifting gears while spinning the rear wheel or output sprocket. Everything should turn freely with no binding or resistance in all gears and in neutral. Spin the main shaft in neutral to feel for binding. If you feel binding, you may have a bent fork or slight misalignment. I had slight binding on my repaired fork which I corrected by light blending of the fork face. This took about 6 iterations of removing and reinstalling the gear train/shifter assembly.
Check that the shifter shaft doesn't have excessive axial movement. I don't know what the limit is but my gearbox had 0.015 in. axial movement and it works fine.
My gearbox also had a chipped tooth on the ratchet lever which I believe caused the ratchet mechanism to skew and jam. I had the tooth built up with weld and refiled the profile.
After you install the outer cover, ensure you install a c clip on the gear selector splined shaft. Otherwise you can have ratchet misalignment.
These are the points I can remember when working on the gearbox in 2018. I hope it helps.
Let us know how you get along.
Jim



Dennis49

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Re: ZB 32 gearbox
« Reply #2 on: 01 June, 2020, 19:48:20 »
I have taken the box out of the frame and stripped it completly. The selector for for 2nd gear is burred and shows signs of getting hot. The 2nd gear drive dog was tight on the shaft. There is damage to the selector fork groove and it seems debris has burred the shaft preventing free movement of the selector dog. Cleaned up the shaft and am waiting for a new selector shaft and selector forks.

Blackthou

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Re: ZB 32 gearbox
« Reply #3 on: 01 June, 2020, 21:28:44 »
Well done Dennis. Best way and often the quickest to get to the bottom of a problem - bull by the horns as they say.

Hope your bits don't take too long to materialise.

Dennis49

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Re: ZB 32 gearbox
« Reply #4 on: 07 June, 2020, 14:59:47 »
Well the spare parts arrived,is shaft complete with 2 selector forks. The forks are too thick and don't fit the sliding cogs. The shaft is shorter too. I can use the selector forks but need to thin them by 1.03 mm and they are hard. Will talk to a few people tomorrow to see if any one can grind off the excess. I will have to use the old shaft which is ok. Just have to drift out the drive pins, then use my new modified selector forks.

Dennis49

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Re: ZB 32 gearbox
« Reply #5 on: 17 June, 2020, 18:13:28 »
All sorted now,once I ordered the correct selector fork☺ Set the end float on each shaft and fitted the spacer that was missing on the selector shaft. Quick job it aint, however it is now good.

Jim S

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Re: ZB 32 gearbox
« Reply #6 on: 17 June, 2020, 20:00:38 »
Hi Dennis
Where did you buy the selector forks? I had to have mine repaired because I couldn't find any.

Jim

Dennis49

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Re: ZB 32 gearbox
« Reply #7 on: 17 June, 2020, 21:09:02 »
I got mine from dragonfly, had to reuse the pin as they were out of stock. The gearbox works a treat. Thanks for your very detailed guide. Took all weekend but worth the effort.Part number is 65-3292. I ordered a complete shaft with selector forks,part number 66-3288. Which was too thick between the forks. Dennis