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Gearbox/Overdrive - Help on Noise

To: "Triumph List" <triumphs@autox.team.net>
Subject: Gearbox/Overdrive - Help on Noise
From: "Brian Sanborn" <sanborn@net1plus.com>
Date: Sat, 6 Apr 2002 15:29:32 -0500
Hi guys,

I have been laying low lately... only answering when I have
something right on target to say.  The TR4... after 4 years of
intense work is just about finished. I am enjoying it immensely.
It's time for another car and restoration project... but I am 2
years from retiring and want to wait before starting again.

Last year I rebuilt a very beat up A-type overdrive I had found.
I mated it to my previously rebuilt gearbox and installed it in
the car and it worked perfectly.  I loved the car twice over for
that OD addition.  One problem was very apparent right away.  It
was leaking oil like crazy.  It would leave a large cookie size
spot on the cardboard under my car every time I drove it.  It
lost about a quart in 1000 miles... NOT GOOD.

There was so much oil leakage I could not tell where it was
coming from.  I ended up using a fluorescent dye and a commercial
grade UV light from Roger Colson of the List.  The leak showed up
like gangbusters.  It was leaking at the joint of the OD and the
adapter plate as well as the rear shaft seal. Is the seal
internal diameter different for an OD vs. non-OD...  the flange
is the same flange. I had tested the adapter plate for warp but
it leaked anyway.  My mistake was using the blue Hylomar on this
gasket.  These old cars never saw a CNC machine... so this time I
will use the good old fashioned lacquer based sticky stuff.  But
the Gearbox/OD had to come out anyway to get sealed up.

NOW FOR THE BIG CONSULTATION.  It seemed that when the gearbox
oil got lowish I could hear a sort of "UPS Truck" noise in the
drive train about at my hip or forward of that when I had the car
in 4th and down at 30-40 MPH.  By the end of the summer it I
could force it to happen in 3rd as well at a low RPM.  This is
the kind of subtle noise that only I can hear.  Doug Frank of the
list was in the car once and could not hear it when I could
plainly.  You know how it is... when you rebuild one of these
things... you listen for the slightest change in sounds.

I suspected a bad layshaft roller bearing... they have a tendency
to drift out for some reason.  I disassembled the gearbox but
found no smoking gun.  Everything is perfect.  The only thing
that I could call strange is a series of lengthwise scratch marks
on the layshaft... mostly at the forward end.  I am guessing that
this happened during the reassembly last winter.  The laygear
would not drop down and I tried to coax it a little... until I
figured out was in the way.  There are about 5-6 of these
scratches not scoring... just very light scratching... but I can
feel them with my fingernail if I really try hard.  Could this be
the cause of the "UPS Truck" noise.  The scratches would be
rolling over the roller bearings at the front of the laygear
where the input shaft gear transfers power to the laygear?????

I plan to replace the layshaft just in case.  Another suspect is
the universal joints in the driveshaft... they will get replaced
as well along with the differential front oil seal while I am
there.  I will also open the diff cover to see if there is any
damage apparent there.

Does anybody have any advice for me on this.  I don't want to
pull the gearbox/OD again.  I would be happier if I had found a
chewed up bearing.

TIA.... this the place for the best advice available on TRs

Brian Sanborn
'62 TR4  CT16260L-O - Groton, MA

My TR4 Restoration Web Site
http://www.net1plus.com/users/sanborn

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