[TR] GT6 gearbox progress

[Jim Muller]

Well, I've made some progress, learned a bunch never having done this 
before.  Got the rear extension and bell housing off.  Got the input 
shaft out.  Got the reverse idler shaft out, and the layshaft.

It's been interesting trying to follow the instructions.  I'm using 
the 3-rail gearbox section of the Haynes Spitfire book.  I checked my 
Bentley manual, which is for the 1500 only.  Sinlge-rail or 3, it has 
so little detail that it would have been mostly useless.  But the 
Haynes manual doesn't quite agree with my gearbox either.  Maybe the 
GT6 box is sufficiently different, or the box changed a bit from 
early to late 3-rail versions.  For example:

The manual says to remove the top by removing the eight bolts, and 
note which is the long one.  Sure, there were eight bolts but none 
was longer.  But there are actually nine holes, one being empty.

The manual says to lift the reverse idler gear out.  But the gear 
clears neither the gear behind it on the output shaft nor the cluster 
gear.  And anyway, it is too large to come through the hole at the 
back end of the gearbox shell, which I discovered after I removed the 
reverse idler shaft.

The manual did not mention a pin bolt on the reverse idler shaft, but 
there is one.  And I thought (I'm starting to forget what it says!) 
it said there was a pin bolt holding the layshaft, but there wasn't.

There were three springs through the front of the gearbox shell, held 
in place by the bell housing and apparently exerting pressure on a 
thrust plate at the front of the layshaft.  These were not mentioned 
in the manual.  The layshaft lifted out easily from the back.  I do 
hope it will go back in as easily!  Well, all those parts went in 
once before so it can't be too hard.

So far I see nothing untoward, nothing obviously broken, no broken 
input bearing visible on casual inspection, no broken teeth.  As I 
take the various gears out I expect to see a worn bearing at least on 
something related to 2nd.  That must wait for tomorrow...

Is there anything in particular I should be looking for?  Some 
measurement that is more critical that others?  Sure is some pretty 
brass in there.

Tanks!

-- 
Jim Muller
jimmuller at rcn.com
'80 Spitfire, '70 GT6+