My recent rebuild of a Moss box for my '62 Plus 4 yielded some
interesting options and opinions:
1) Yes, the synchro rings ARE integral to the gears and they ARE
available for some heavy coins (Linda at Morgan Spares was very
patient with my waffling on whether to buy or not). In the end I was
able to have mine 'freshened': The synchro faces have two types of
grooves (big axial and tiny circumferential), mine had the
circumferential grooves completely worn off but we cut them back in
and adjusted the gear location so the synchro would engage with the
proper clearance to the next gear. This means the gear itself is
moved almost 1 millimeter off the ideal axial alignment to the cluster
gear but it will still work just fine. Not a job for the amateur
rebuilder however.
2) Fred Sissons Bedside Reader has a VERY good bit of info to start
with. There are all sorts of subtle differences that you will start
to find in the gearboxes if you are observant or have a knowledgable
gearbox man handling it. I had a spalled layshaft which we replaced
with the layshaft out of a non-synchro Jag Moss box but some other
parts were not useable.
3) The spline on the 'constant input shaft' IS different between a
typical Jag Moss box and the Morgan Moss box. It is conceivable to
use a Jag box and change the constant input shaft to the Morgan type
(especially if your existing is in decent shape). The input shaft is
another heavy coin item (and rare).
4) One very intriguing alternative that was suggested to me (and I did
not follow up on) is to convert the gearbox to that found in the Volvo
122 series vehicles. It is compact, rugged as all get out, generally
available, and can be found with an overdrive that just might fit as
well! I don't know of anyone that has actually tried it (yet). If I
were rebuilding a car to be a more regular driver without concern for
historical accuracy, I would seriously investigate it. Set up
properly however, there is nothing wrong with the Moss box and it'll
last a lifetime with casual touring use.
5) With more modifications to the chassis and such, there are other
gearboxes that might be dumped in. I don't know who has tried one of
the Toyota Supra conversions but I expect there are a LOT of changes
necessary. I've heard of a Borgward transmission being fitted but
that sounds like MORE of a problem than the Moss box.
Send me an email if you want the name and number of the guy that did
my Moss box. He has a passion for early Jags and was very helpful in
knowing what to do and what not to do.
Adam Selene wrote:
>
> I have a 62' Plus 4 with gearbox problems. Even with double
> clutching, it's almost impossible to downshift from 3rd to 2nd
> without grinding gears. I've had two different fixes suggested to me,
> neither of which sounds very attractive.
>
> One "expert" suggested replacing the Moss Box with a later model
> Jaguar Moss Box with full synchromesh.
>
> Another said this was not possible as the Moss Box fitted to the +4,
> while looking similar from the outside, is actually different from
> the Jaguar Moss Box internally in that it has a different diameter
> input shaft and different ratios. This "expert" said that on the
> Morgan Moss Box, the synchro ring on 2nd gear is integral with the
> gear itself and therefore cannot be replaced. When asked if I
> couldn't simply get an entire new 2nd gear with synchro ring, he said
> that they were no longer available anywhere.
>
> If anyone has anything to add to this I'd appreciate hearing from
> you. I'm looking for any reasonable fix to this problem. Driving the
> car with the gearbox in it's current condition is simply not an
> option.
>
> Thanks
--
"Entropy Happens!"
Michael D. Miles, PE Consulting Design Engineer
(503) 292-1234, FAX: (503) 292-1105
email: mdmiles@mdmpe.com
http://www.mdmpe.com/
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