Mg Midget 1275 gearbox rebuild

Discuss mechanical problems here.
Murrayminor
Minor Addict
Posts: 556
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Mg Midget 1275 gearbox rebuild

Postby Murrayminor » Wed Jun 24, 2020 8:43 am

I have recently bought a 1275 Midget box for my Minor project.
The box looks in remarkable shape, and the guy I bought it from who had a choice of 6 was kind enough to talk me through the pit falls of buying a gearbox and opened each one for me to inspect, and even showed me the bad box he had.

I then mentioned I would be rebuilding the box with new bearings and gaskets so he talked me through the process very quickly, he has built numerous gearboxes for the MG Midget race series.

Obviously I couldn't take everything in there and then so I set about looking for a guide and came across a PDF of the rebuild of a Morris Minor 1908 gearbox.

Would the process of building the Minor box be the same as the Midget box apart from the brass bushes and roller bearings as used in the Midget box?

I have a copy of the minor 1000 workshop manual which shows the majority of the process but again relates to the Minor box.

Here is the PDF I mentioned.

http://www.dorsetmmoc.co.uk/wordpress/t ... ebuild.pdf
Proud owner of my first Morris Minor

philthehill
Minor Maniac
Posts: 8142
Joined: Thu Jul 19, 2012 12:05 pm
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby philthehill » Wed Jun 24, 2020 10:54 am

That is a good guide and can be transposed to the 1275cc Midget box with out difficulty or problems.


Murrayminor
Minor Addict
Posts: 556
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Murrayminor » Wed Jul 01, 2020 12:45 pm

philthehill wrote:
Wed Jun 24, 2020 10:54 am
That is a good guide and can be transposed to the 1275cc Midget box with out difficulty or problems.
Thanks for that Phil, I have the box stripped and have bought all the bearings, gaskets etc.
I'm struggling with getting the indent balls into the first/second gear hub.

They are fiddly to say the least and I have had to retrieve them from under the bench twice now, I wonder if there are any tricks or tips to assist.

Up to now I have inserted the springs into the gear, put a blob of grease on the end of the spring, held a ball to the grease and then held it in place with some Duct Tape whilst I worked my way round the other two balls and the locating peg.

I then put a wide cable tie around the circumference of the gear and tightened it up ensuring the balls were held in under the cable tie and cut off the excess tape.
I then attempted to fit the gear over the balls but it gets to the balls and stops and won't engage.

Rather than hit it with something I walked away and heard the gentle twang of spring and ball so new balls and springs are on their way to me now. :D

Any help or advice much appreciated.
Proud owner of my first Morris Minor

philthehill
Minor Maniac
Posts: 8142
Joined: Thu Jul 19, 2012 12:05 pm
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby philthehill » Wed Jul 01, 2020 2:10 pm

This is the tool you want:-

https://www.ebay.co.uk/itm/Classic-Mini ... Swm6xdvGrP

Do it all inside a large clear plastic bag of which the neck is tied. Keeps everything together if it flies apart.


Murrayminor
Minor Addict
Posts: 556
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Murrayminor » Wed Jul 01, 2020 4:38 pm

Phil

Thanks for that, yes I have quickly learnt the plastic bag tip.
I have ordered the tool so hopefully I can get the box back together next week.

Thanks for your link to the tool.
Proud owner of my first Morris Minor

Mark Wilson
Minor Addict
Posts: 865
Joined: Fri Aug 26, 2011 12:42 pm
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Mark Wilson » Thu Jul 02, 2020 9:52 am

I managed without any special tools - but very difficult and if I'd know about this I'd have happily spent the £26!
Attachments
DSCF9184 (Medium).JPG
DSCF9184 (Medium).JPG (167.22 KiB) Viewed 632 times

Murrayminor
Minor Addict
Posts: 556
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Murrayminor » Thu Jul 02, 2020 12:23 pm

Mark Wilson wrote:
Thu Jul 02, 2020 9:52 am
I managed without any special tools - but very difficult and if I'd know about this I'd have happily spent the £26!
You are clearly a braver person than me, I was frightened to death of putting a mark on the main shaft and you have yours clamped in a vice and a G clamp as well. :D

Yes, if the tool works its worth every penny of the few pounds it cost.
Proud owner of my first Morris Minor

Chipper
Minor Addict
Posts: 738
Joined: Thu Apr 26, 2007 11:43 pm
MMOC Member: No

Re: Mg Midget 1275 gearbox rebuild

Postby Chipper » Thu Jul 02, 2020 3:38 pm

I found the cable tie method to work well when I rebuilt one.
Maurice, E. Kent
(1970 Traveller)

Mark Wilson
Minor Addict
Posts: 865
Joined: Fri Aug 26, 2011 12:42 pm
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Mark Wilson » Thu Jul 02, 2020 4:30 pm

Murrayminor wrote:
Thu Jul 02, 2020 12:23 pm


You are clearly a braver person than me, I was frightened to death of putting a mark on the main shaft and you have yours clamped in a vice and a G clamp as well. :D
Only sat across the jaws of the vice, not clamped, and the tiny G clamp was gently tightened enough to stop the ring escaping while I manoeuvered the plunger in with a ground down screwdriver. No components harmed, but not good for the nerves! Good luck 😎

les
Minor Maniac
Posts: 7747
Joined: Tue Feb 12, 2002 12:00 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby les » Thu Jul 02, 2020 4:37 pm

No components were harmed in the making of this gearbox. :D


paul 300358
Minor Fan
Posts: 339
Joined: Thu May 11, 2017 8:23 pm
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby paul 300358 » Thu Jul 02, 2020 8:20 pm


newagetraveller
Minor Fan
Posts: 353
Joined: Wed Feb 13, 2002 12:00 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby newagetraveller » Fri Jul 03, 2020 1:57 pm

I used a big jubilee clip and three little screwdrivers to put this together.

pgp001
Minor Addict
Posts: 602
Joined: Sun Aug 27, 2017 6:05 pm
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby pgp001 » Sat Jul 04, 2020 12:08 am

I just found a cheaper version of the special tool.

https://www.ebay.co.uk/itm/Classic-Mini ... 2749.l2649

My offer of £10 and free p&p was accepted, so well pleased.

Phil

don58van
Minor Addict
Posts: 612
Joined: Sun Feb 01, 2009 6:24 am
MMOC Member: No

Re: Mg Midget 1275 gearbox rebuild

Postby don58van » Sat Jul 04, 2020 3:15 am

I just found a cheaper version of the special tool.
Well done Phil. I wish I had seen that.

Don

Murrayminor
Minor Addict
Posts: 556
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Murrayminor » Tue Jul 07, 2020 1:06 pm

Hi all
I have been taking my time with the gearbox rebuild, mainly because I have never opened a gearbox before and secondly I need this box to be right once finished.
I have a couple of questions to ask, and a couple of photographs which I will upload after this post.

Is there a thrust washer on the 1275 gearbox? my parts diagram (from Moss) doesn't list one for the 1275 gearbox but does for the 1098.
The picture below shows how there will be a space between the gear and the bearing if no thrust washer is fitted.
I can move the gear fore and aft which I think will interfere with the bearing if allowed to move so much.

Secondly on stripping this box down I found two shims the same diameter as the mainshaft bearing, but they were clearly damaged and looked like they were trapped between the bearing and housing.

Can anyone shed any light on these shims and where they are supposed to sit?

Mine were just rolling about on the mainshaft.
Proud owner of my first Morris Minor

Murrayminor
Minor Addict
Posts: 556
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Murrayminor » Tue Jul 07, 2020 1:09 pm

Photographs as promised.
Attachments
20200707_125847.jpg
Partially assembled main shaft
20200707_125847.jpg (1.88 MiB) Viewed 471 times
20200707_125658.jpg
Amount of movement without thrust bearing
20200707_125658.jpg (1.92 MiB) Viewed 471 times
20200707_125639.jpg
Missing thrust bearing?
20200707_125639.jpg (1.97 MiB) Viewed 471 times
Proud owner of my first Morris Minor

Murrayminor
Minor Addict
Posts: 556
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Murrayminor » Tue Jul 07, 2020 1:12 pm

Image of damaged shims.
Attachments
20200707_131108.jpg
Damaged shims
20200707_131108.jpg (1.81 MiB) Viewed 470 times
Proud owner of my first Morris Minor

Murrayminor
Minor Addict
Posts: 556
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Murrayminor » Tue Jul 07, 2020 2:49 pm

I have worked out the shims should reside behind the bellhousing bearing cover plate so I can now calculate the sizes for the new shims.

Just the thrust washer or lack of to contend with now.
Proud owner of my first Morris Minor

pgp001
Minor Addict
Posts: 602
Joined: Sun Aug 27, 2017 6:05 pm
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby pgp001 » Tue Jul 07, 2020 3:02 pm

This guy on Youtube has some good information. Here are a couple of samples, but there are lots more on his channel

https://www.youtube.com/watch?v=qmqCMxmLL1c

https://www.youtube.com/watch?v=l8wjrifuh44

Phil

Murrayminor
Minor Addict
Posts: 556
Joined: Mon Oct 15, 2018 9:47 am
MMOC Member: Yes

Re: Mg Midget 1275 gearbox rebuild

Postby Murrayminor » Mon Jul 20, 2020 10:32 pm

I had the gearbox on the bench this evening to see if I could get it back together.
Yes it all went back together, up to a point.

I was wary of attempting to select the gears as a trial run without the selectors in place so I waited until they were in before I slipped the box into first.

Then "PING" out fly the ball bearings from the first gear synchro.
I had fitted the 2mm brass spacer modification between the selector rod and the case to stop the over selection but clearly something was amiss the gearbox is now minus it's ball bearings on 1st/2nd synchro.

I'm annoyed but equally confused as to why it happened.

I now have to strip it out again which will entail yet another set of bearings, it would have been easier just to buy one already reconditioned.

These things are sent to try us, so I will look at it again tomorrow evening.
Proud owner of my first Morris Minor


Who is online

Users browsing this forum: No registered users and 7 guests