[Nobbc] Update on Tech Session

[Greg Tatarian]

Tim,

With respect, I would not look towards the layshaft or layshaft bearings 
as the first most likely cause for gear clashing. This is based on the 
noise commonly associated with worn layshaft bearings or layshaft, 
present either in one or two gears, or sometimes in all. Also, synchros 
will generally wear more rapidly than the layshaft or its bearings, 
unless the 'box was run low on oil.

While I agree with your observation that a worn layshaft or bearings 
will cause gear misalignment, Mark did not cite those symptoms, only 
gear clashing between 2nd and 3rd. I'm not sure that an MGA 'box is 
immune to this in the first place; the Alfa gearbox is known for early 
wear on 2nd gear synchros and constant need of slow and stately shifting 
in order to save the synchros. My experience with MGB's is that they 
synchros never last that long anyway. It might simply be that Mark's 
'box is not really defective, just a typical 50k mile MGA box that's 
getting a bit worn... hopefully Ron or someone else can weigh in on this.

It is always possible that a change in gear oil can minimize clashing (I 
bought myself a few months by switching to Redline MTL before finally 
yanking and rebuilding the 'box in my Lotus). If the 'box does have 
problems, I'd still lean towards worn synchros first, but not discount 
the other possible causes I mentioned in my earlier email. I do agree 
with you that if the 'box is truly in need of synchros, it doesn't make 
sense to fix or replace only those parts, which are readily available 
and not that expensive. A full rebuild can be a painfully costly 
exercise for some gearboxes; my Alfa 'box bearings cost 4x more than 
those for the Lotus - not to mention the synchros and other parts! I can 
do a full rebuild on a Lotus/Ford 2000E box for a few hundred $ in 
parts, while the Alfa has me in for $1,000 and I'm not even done yet!I'm 
not a professional gearbox mechanic, but I've built 7 of them now, and 
have disassembled about 11, and I've found many symptoms to be pretty 
diagnostic.

Feel free to correct me, Tim if your experience is more extensive than 
mine - I'm always trying to learn more about everything!

Cheers,
Greg




Tim Thresh wrote:
> Mark,
>
> Sounds as though you may have a worn layshaft /bearings. It could also 
> be the synchro cones. You have to strip the box to fix both matters so 
> do them all at once. At a certain point the wear will result in a 
> mis-alignment which will prove fatal (ie no engagement in any gear). 
> Mine stuck in neutral luckily but I am not sure that is guaranteed.
>
> Perhaps the group has a recommendation for a good tranny shop if you 
> do not wish to do it yourself or become a project day!
>
> Tim
> 1958 MGA
>
> --------------------------------------------------
> From: "Mark Darley" <markdarley at mac.com>
> Sent: Monday, March 08, 2010 6:07 PM
> To: "North Bay British Car Club" <nobbc at autox.team.net>
> Subject: Re: [Nobbc] Update on Tech Session