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MT-90 is actually a 75W-90 gear oil, equivalent to a 15W-40 motor
oil (motor and gear oils use different viscosity indexes, and 20W-50
motor oil was approved in later Healey shop manuals, like the
Bentley version). MTL is a thinner gear oil from Redline, and
equivalent to 30W motor oil. I've used ND 30W motor oil, 20W-50
motor oil and MT-90 and prefer MT-90. MT-90 is <i>specifically</i>
formulated for gearboxes, so I don't believe foaming is an issue,
but it's well-known that synthetic oils are more prone to taking the
easy way out of an engine or gearbox. I've put well over 120K miles
on MT-90, and have had no issues attributable to the oil, and all of
my gears in my 205K-mile gearbox were in pristine shape at overhaul
a couple years ago (the layshaft was, typically, worn at the ends).
Note MT-90 is also formulated without extreme pressure additives,
usually used in hypoid gear (GL-5) oils, which supposedly can
degrade brass or bronze components. Note also the 'W' stands for
winter--i.e. cold--viscosity, and not 'weight.'<br>
<br>
<a class="moz-txt-link-freetext" href="https://www.redlineoil.com/mt-90-75w90-gl-4-gear-oil">https://www.redlineoil.com/mt-90-75w90-gl-4-gear-oil</a><br>
<br>
My guess is Jim's new solenoid is defective, assuming it was
adjusted properly (measuring the lift of the operating valve). The
solenoids have two sets of points: one is a 'pull-up' set that
allows higher current to actuate the solenoid, and the other is a
sustaining set, which allows a lower current to hold the solenoid in
the activated position. If the pull-up points stick, you would
likely blow a fuse, and/or overheat and destroy the solenoid in
short order; this is also the reason the OD circuit has a slow-blow
fuse, as the initial current draw would blow a standard fuse every
time. The fact Jim's OD will operate with an assist on the lever
tells me the accumulator is OK. I did hear there were some defective
solenoids going around a few years ago.<br>
<br>
Bob<br>
<br>
<div class="moz-cite-prefix">On 6/13/2021 4:49 PM, Henry G Leach via
Healeys wrote:<br>
</div>
<blockquote type="cite"
cite="mid:7c404890f4d4400745846c563a794268ed9bffe5@webmail">
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Hi healeymanjim -there a few statements you made that trouble me
about your overdrive.
<div><br>
</div>
<div>1-why was there 90W oil in the trans? Was there an attempt to
get more pressure with heavier oil?</div>
<div><br>
</div>
<div>2- if you can manually engage overdrive with the lever on the
right-the overdrive is working and pressure has been built up
enough to switch from direct to OD (overcome spring pressure).
However you should probably measure the pressure with a gauge
and insure that it is over 400lbs.(photo)</div>
<div><br>
</div>
<div>3-the mainshaft should have nothing to do with engagement</div>
<div><br>
</div>
<div>4-if the solenoid is good, and if properly adjusted, it
should shift into OD if the switch on the dash is in OD. My
guess is that the adjustment is not by the book. Measure the
solenoid and if it draws about 8 Amps, it is defective.</div>
<div><br>
</div>
<div>5-you can follow the procedure in the workshop manual to
remover the accumulator, remembering that a huge spring is
pushing on the solenoid case and must be eased out. You should
have the correct replacement parts-piston rings or o-rings and
any gaskets-and a proper puller before you pull it apart, as
just examining it and replacing it won't give you an answer,
unless you see major scoring or broken piston rings.</div>
<div><br>
</div>
<div>6- I would never use 90W oil in that gearbox. It will foam
and cause problems in the overdrive and when cold adds
additional problems with gear engagement. Use the 30 ND (won't
foam)</div>
<div><br>
</div>
<div>Take particular care in disassembly, as this is an involved
mechanism, and must be handled correctly to achieve successful
operation. Regards, Hank<br>
<br>
<p>-----------------------------------------</p>
From: "healeymanjim via Healeys" <healeys@autox.team.net><br>
To: <a class="moz-txt-link-rfc2396E" href="mailto:healeys@autox.team.net">"healeys@autox.team.net"</a><br>
Cc: <br>
Sent: Sunday June 13 2021 3:33:31PM<br>
Subject: [Healeys] overdrive problem<br>
<br>
is there such a thing as a stuck accumulator in the overdrive?
a
few weeks ago we changed the gasket on the side of the<br>
case that houses the solenoid and arm. have been unable to get
o/d
to engage electrically ever since. the solenoid is new<br>
and works perfectly as long as the overdrive mainshaft is not
turning. it tries to move the arm but is unable. pushing on<br>
the right side shaft lever for a second or two will engage the
o/d
and it will stay in o/d until the o/d switch is returned to<br>
normal. it is like the accumulator has no pressure and does
not
give the boost to engage the o/d. can the accumulator be<br>
removed without damaging it? it had MT 90 oil in it which we
replaced with 30ND hoping to stop any more leaks but can<br>
put it back in if it would help. any assistance welcomed.<br>
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