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Gearbox rebuild (new Q page 3)
https://www.ausmini.com/forums/viewtopic.php?f=2&t=87446		 Page 1 of 3
Author:  Kennomini [ Sat Oct 11, 2014 1:27 pm ]
Post subject:  Gearbox rebuild (new Q page 3)
I plan to fully rebuild a 4 sycro remote box. This box is for my 1360 BMW twincam build, it'll have a Quafie ATB diff with a 3.1 FD and the engine will be tuned for torque. So with all that in mind.
I'll have a heap of questions but for now I'll only ask five. Currently I have striped as much out as I can and I need some guidance with a few things.
(1) The drain has striped out so what are my options :?:
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(2) How do I and is it nessary to remove the speedo drive :?:
Image
(3) Should I replace the driveshaft output bushes (the bearing thingy) :?:
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(4) The top and bottom bushes in the diff housing for the gear selector shaft, the shaft seems to move around a bit in them. How tight/loose is the shaft meant to be, should I replace these :?:
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(5) cleaning up the threads on everything, what taps and dies do I need :?: And I'm assuming I leave all the studs in where they are correct?
Author:  Irish Yobbo [ Sat Oct 11, 2014 6:43 pm ]
Post subject:  Re: Gearbox rebuild
Kennomini wrote:
(1) The drain has striped out so what are my options :?:


You can get plugs for stripped drain threads here, but you will probably be better off with a helicoil. I have never used a helicoil, but i have one on my gearbox in the same place, and it works well.
Kennomini wrote:
(2) How do I and is it nessary to remove the speedo drive :?:


It should slide out from the side once you have removed the cover plate. You shouldn't need to touch it though.
Kennomini wrote:
(3) Should I replace the driveshaft output bushes (the bearing thingy) :?:


Only if they're worn, I'd say. I've never seen them wear down before, but they may well do.
Kennomini wrote:
(4) The top and bottom bushes in the diff housing for the gear selector shaft, the shaft seems to move around a bit in them. How tight/loose is the shaft meant to be, should I replace these :?:


They shouldn't be tight, but they should move freely with little sideways movement. I'm not sure what you would do to fix that.
Kennomini wrote:
(5) cleaning up the threads on everything, what taps and dies do I need :?: And I'm assuming I leave all the studs in where they are correct?

Can't say off the top of my head - I'm not good with thread sizes anyway.
Author:  Wombat [ Sun Oct 12, 2014 12:31 pm ]
Post subject:  Re: Gearbox rebuild
For the drain plug I helicoiled it - have some left over if you need it.
Author:  Mick [ Sun Oct 12, 2014 12:34 pm ]
Post subject:  Re: Gearbox rebuild
Irish Yobbo wrote:
(5) cleaning up the threads on everything, what taps and dies do I need :?: And I'm assuming I leave all the studs in where they are correct?


You can take the studs out, it makes cleaning the gasket surfaces easier. Its just time consuming.
You will need 1/4 and 5/16th and a 3/8 UNC finishing taps to bottom out the threads.

The studs will have UNC on one end, and UNF on the other.
Author:  drmini in aust [ Sun Oct 12, 2014 6:10 pm ]
Post subject:  Re: Gearbox rebuild
The 2 side cover bushes are usually worn- press new ones in then get them set up true in a lathe and machined to size for ~.001" clearance on your drive flanges or pot joints. If you leave them worn the seals won't last long before leaking.
These bushes are about .007" undersize when bought.

The 2 shift shaft bushes in the diff cover wear bad and should be replaced. I screw a 9/16" UNF tap in, then use a hammer and a bit of 3/8 rod to drive them out. You could also use a 14mm tap.
Author:  simon k [ Sun Oct 12, 2014 7:29 pm ]
Post subject:  Re: Gearbox rebuild
4/ you can just catch the side of them with a long drift, or use a slide bearing puller. Easy job
Author:  Kennomini [ Sun Oct 12, 2014 8:28 pm ]
Post subject:  Re: Gearbox rebuild
Thanks for the answers so far.
Can I use selector shafts and knuckle joint parts from a 3 sycro remote box? It's only the gear clusters that are different correct :?: Can you fit 4 sycro gears into a 3 sycro box, what is the difference between the two boxes :?:
Author:  drmini in aust [ Mon Oct 13, 2014 6:45 am ]
Post subject:  Re: Gearbox rebuild
The knuckles and shift shafts they attach to are the same.
The selector shafts in the bottom of the box are not.
The 4 synchro case is wider inside, and machined differently. Can't fit 4 synchro setup to a 3 synchro case. Go find a Mink K/1098 Clubby box..
Author:  Kennomini [ Mon Oct 13, 2014 5:58 pm ]
Post subject:  Re: Gearbox rebuild
Thanks Doc, also (I can never remember) can the gears out of a rod change be installed in a remote box :?: (I think the answer is yes but I want to confirm for sure).
Author:  mini_mad_matt [ Mon Oct 13, 2014 6:14 pm ]
Post subject:  Re: Gearbox rebuild
4 syncro gears are 4 syncro gears, doesn't matter what shift type
Author:  Scoop [ Mon Oct 13, 2014 7:29 pm ]
Post subject:  Re: Gearbox rebuild
Except reverse idle gear, thats different. NLA I believe
Author:  drmini in aust [ Mon Oct 13, 2014 8:00 pm ]
Post subject:  Re: Gearbox rebuild
Scoop wrote:
Except reverse idle gear, thats different. NLA I believe

Might be NLA new, but PM me if ya need a good s/h one.

The difference in the reverse gear is the groove position for the selector fork.
Author:  mini-dunger [ Sun Nov 02, 2014 6:43 pm ]
Post subject:  Re: Gearbox rebuild
I have just rebuilt a box now it's stuck in either 1st or 2nd? I can still select 3 , 4 and R ..... What have I done ?
Author:  Scoop [ Sun Nov 02, 2014 7:27 pm ]
Post subject:  Re: Gearbox rebuild
Did you line up all the bell crank levers putting the selector shaft in?
Author:  mini-dunger [ Sun Nov 02, 2014 7:32 pm ]
Post subject:  Re: Gearbox rebuild
Yeah I think so. I just had to replace 1st gear so I left all the selectors in.
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