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Gearbox rebuild problem
https://www.ausmini.com/forums/viewtopic.php?f=2&t=85018		 Page 1 of 1
Author:  Curly [ Mon Mar 24, 2014 6:07 pm ]
Post subject:  Gearbox rebuild problem
I'm putting together a 4-syncro Cooper S gearbox for the Marcos I'm restoring. Unfortunately when it came to fitting up the mainshaft bearing retainer to check the bearing preload, the retainer wouldn't fit over the final drive pinion :evil: It appears that if you're going to fit a 3.1:1 crownwheel and pinion you've got to a enlarge the inside diameter of the mainshaft bearing retainer to clear the larger diameter of the physically larger final drive pinion.
I wonder if the later Rover Minis that ran the 3.1 ratio had a different bearing retainer, or whether all the rod-change boxes were built with extra clearance in mind?

Any ideas?
Author:  michaelb [ Mon Mar 24, 2014 6:52 pm ]
Post subject:  Re: Gearbox rebuild problem
I concur.
I had to grind out the inside of my bearing retainer with a dremel.
Little bit at a time until I had clearance.
Author:  slacko [ Mon Mar 24, 2014 7:07 pm ]
Post subject:  Re: Gearbox rebuild problem
I also concur
I have built myself a 4 syncro box with a 3.1 diff
I am probably not as subtle as Michael
I took to mine with the angle grinder
Don't own a dremell
Author:  TheMiniMan [ Mon Mar 24, 2014 7:11 pm ]
Post subject:  Re: Gearbox rebuild problem
The std issue (later A+) boxes have the lager Inner diam retainer , yes, factory item
Author:  kiwiinwgtn [ Mon Mar 24, 2014 7:28 pm ]
Post subject:  Re: Gearbox rebuild problem
Yep same problem with my 3.1. Got a friend to turn it bigger in a lathe
Author:  Curly [ Mon Mar 24, 2014 7:34 pm ]
Post subject:  Re: Gearbox rebuild problem
:lol:
So many different ways of enlarging the retainer - I used a barrel type of flap wheel sander mounted in my pedestal drill, it took a while but leaves a nice finish.
Author:  simon k [ Mon Mar 24, 2014 7:52 pm ]
Post subject:  Re: Gearbox rebuild problem
I used a half round file :D
Author:  michaelb [ Mon Mar 24, 2014 8:53 pm ]
Post subject:  Re: Gearbox rebuild problem
I used a half round file

Sounds a bit slow... :)
I'm too impatient :evil:
Author:  Curly [ Tue Mar 25, 2014 4:31 pm ]
Post subject:  Re: Gearbox rebuild problem - new developments !!
.... so I get the retainer to fit over the pinion gear, sort out a shim for the correct bearing preload, find a couple of new lock tabs and torque up the 4 bolts - all good until one felt soft and pulled the threads out of the alloy housing - BUGGER :evil:
That means tomorrow's job is to strip it all down again and helicoil the housing. Luckily I have nothing better to do with my time :roll:
Author:  drmini in aust [ Tue Mar 25, 2014 5:37 pm ]
Post subject:  Re: Gearbox rebuild problem
Don't helicoil it. More trouble than it's worth in that spot, the thread is very short.
You have stripped the hole, so it is now 5/16", = right size to tap it to 3/8" UNC. Then just drill out the retainer (and the layshaft lockplate, if that's the one that stripped (which is usual) with a 3/8" drill..
It won't strip again, the 3/8 thread is much stronger.

ps. if you pull the cluster and reverse gear out and are careful with some rags, you can do this job without stripping the rest of the box. As no drilling of the case is needed.
Author:  Curly [ Tue Mar 25, 2014 5:57 pm ]
Post subject:  Re: Gearbox rebuild problem
Thanks Doc, I'll follow your advice :wink:
By the way, it was the hole above the one that takes the locking plate that stripped out - at least it's probably the easiest one to get at :roll: .
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