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74 MGB gearbox main bearing

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74 MGB gearbox main bearing
#1
airmech953 Dave Jenkins
Melbourne, Australia   AUS
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1975 MG MGB MkII
I have stripped my 4synchro gearboxto replace the bearings and cure oil leaks. I ordered a new main bearing (Moss catalogue, page42 item13). My question is that the new bearing, part number 22B313 is a ball bearing yet the bearing in my gearbox is a roller bearing - what should I have?
My local bearing supplier can only supply the roller unit to special order and it would then have to have a circlip groove machined in at some expense!
Any advice as to the correct bearing would be gratefully received.
Dave - Australia

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Re: 74 MGB gearbox main bearing
#2
ErnieY Avatar
ErnieY Ernie Y
Albatera, Alicante, Spain   ESP
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1976 MG MGB GT
6K830 is the front bearing for all, 22B313 is for the rear for a 4sp and is a circlipped roller bearing as pictured below.

If you have a roller bearing without a circlip then it must be 22H283 which is for the OD box although Moss list it as NA.



Edited 2 time(s). Last edit at 2015-11-26 12:35 AM by ErnieY.


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Re: 74 MGB gearbox main bearing
#3
airmech953 Dave Jenkins
Melbourne, Australia   AUS
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1975 MG MGB MkII
The bearing that I am querying is the centre bearing which mounts behind the mainshaft reverse gear. On ny late '74MGB this is a roller bearing. Reference is made to a roller bearing in this location in an old American Moss catalogue, but it doesn't say when it was used. The bearing code is N306N, which indicates an N306 with an external circlip groove.
I am quite certain that the part fitted is indeed a roller bearing. My question is when this was used.


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Re: 74 MGB gearbox main bearing
#4
ErnieY Avatar
ErnieY Ernie Y
Albatera, Alicante, Spain   ESP
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1976 MG MGB GT
N306 - 1/N306N is the correct bearing for all 4 synchro non OD gearboxes and 22B313 is the Leyland number for it.

I've stripped several 4sp boxes for spares ranging from 1970 to 1980 (left overs from OD conversions) and never seen anything else.

If you have something claiming to be a 22B313 which isn't the above roller bearing then it's been supplied by mistake, what number is engraved on it ?

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Re: 74 MGB gearbox main bearing
#5
airmech953 Dave Jenkins
Melbourne, Australia   AUS
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1975 MG MGB MkII
The bearing I received from Moss
UK is in a box marked 22B313 but it is a ball bearing. I will check the engraving on the bearing itself tomorrow.
The American Moss catalogue lists both a ball bearing or a roller bearing in the main bearing location and that catalogue lists completely different part numbers for each.
Perhaps some of our American friends can shed some light on this.

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Re: 74 MGB gearbox main bearing
#6
ErnieY Avatar
ErnieY Ernie Y
Albatera, Alicante, Spain   ESP
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1976 MG MGB GT
Mystery solved I think.

http://www.jagspares.co.uk/Abingdon/partdetail.asp?partno=22B313

With 22B313 having been NA for a long time a ball bearing has been selected as a substitute.

Moss really ought to explain that to buyers though, or at least suffix the 22B313 part number with a letter which is the traditional way of flagging up non original or alternative pars.

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Re: 74 MGB gearbox main bearing
#7
airmech953 Dave Jenkins
Melbourne, Australia   AUS
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1975 MG MGB MkII
I have managed to acquire an N306 bearing and a snap ring groove is being machined.
I have also contacted Moss UK to clarify why they are supplying the ball bearing.
The question still remains why Moss USA listed both ball and roller bearings.

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Re: 74 MGB gearbox main bearing
#8
airmech953 Dave Jenkins
Melbourne, Australia   AUS
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1975 MG MGB MkII
Ernies comment has been confirmed by Moss. The original bearing was a roller type which Moss substituted with a ball bearing as the original unit became hard to source. Moss did put a suffix on the part number to indicate this substitution but the suffix was later dropped for administrative reasons. Moss USA has listed both types of bearing but has never stocked the roller type.
I have been able to buy an N306 roller bearing and then have the snap ring groove machined in. The cost here in Australia can be in the region of $100.
Thanks for the input Ernie.

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Re: 74 MGB gearbox main bearing
#9
ErnieY Avatar
ErnieY Ernie Y
Albatera, Alicante, Spain   ESP
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1976 MG MGB GT
Glad we got to the bottom of the mystery winking smiley

EDIT: The basic N306 bearing is readily available, it's the groove in the outer race which makes it special and is the reason it bears a different number 1/N306N



Edited 1 time(s). Last edit at 2015-11-27 03:26 PM by ErnieY.

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