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<p>Ah, one of our favorite 'religious topics.'</p>
<p>FWIW, I've used MT-90 for many years and probably at least 60,000
miles and swear by it (I ought to keep track of this, but
record-keeping is not my strong suit). I never bought the 'use
non-detergent oil so the sludge can build up in the bottom of the
case' theory (anybody want 'sludge' in their arteries?). Unless
you constantly grind gears there shouldn't be a lot of loose metal
in a gearbox/OD (IMO). When I do change out the Redline the only
metal particles in the oil are extremely finely ground
particles--you can't feel them if you rub the oil between your
fingers--of what appears to be brass (you can only see the
particles in bright sunlight). I presume the brass is from the
shifting forks wearing down; I expect using synthetic oil
mitigates--but can't eliminate--that. My OD screen with magnets
never has anything appreciable on it, and when I had the gearbox
out the bottom and side walls were spotless. A lot of
greases--e.g. molybdenum and lithium--are finely ground soft
metals suspended in oil, and brass is a soft metal.<br>
</p>
<p>I used 20W-50 dino oil for a few years/thousand miles but tried
the Redline hoping to get a little quicker engagement from a hot
OD. I wasn't expecting it, so no confirmation bias, but I swear
the gearbox shifts smoother*. Yeah, it's harder to contain but
that's a small price to pay IMO. I've gone through the gearbox
once already, and will be doing so again soon, and the gears
appear perfect so either type of oil is good as far as lubricating
properties. My OD has almost 200K miles on it and while I have it
out I'll probably check the accumulator rings and bore, and the
pump, and as I already have a new one I might change the solenoid,
but on the advice of this list I'll otherwise leave it alone. I
use MT-90 in my BJ8 and BN2, and Redline gear oil in both (75W-90
in the BN2, and 75W-110 in the BJ8, which quiets a mild whine a
bit). I'm contemplating going to a synthetic oil in the BJ8
engine eventually as the PCV has all but eliminated the leak from
the rear 'seal.'<br>
</p>
<p>Like our cars, most of us were 'manufactured' in the 50s and 60s;
if you follow the 'use what the factory recommended in 1959' trope
we should only allow doctors to treat us with medicines and
surgical techniques available then (no arthroscopic surgery for
you). Lubricants have come a long way in the last 60 years (one
possible exception is the reduction/elimination of ZDDP in engine
oil, but we have plenty of alternatives and I think we all
appreciate cleaner air).<br>
</p>
<p>Bob<br>
</p>
* When I bought my Mustang GT, I thought the shifting action was
rough and 'notchy.' I checked the Mustang forums, and got a
recommendation to use synthetic gearbox oil, specifically Royal
Purple Synchromax (the oil recommended by Ford is actually an ATF).
Sure enough, the shifting action improved and, supposedly, the RP
'conditions' the gearbox over time so it keeps improving. I can't
prove that, but I don't dispute it either.<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 8/8/2017 8:24 PM, Harold Manifold
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:C0B0D3204F1A4357ADD0F375C93DFADF@AllInOne">
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<div dir="ltr" align="left"><span class="343023002-09082017"><font
size="2" face="Arial" color="#0000ff">Mike,</font></span></div>
<div dir="ltr" align="left"><span class="343023002-09082017"></span> </div>
<div dir="ltr" align="left"><span class="343023002-09082017"><font
size="2" face="Arial" color="#0000ff">I am new to the Healey
world but I am an engineer with an automotive background who
recently had a BN4 transmission with an overdrive completely
rebuilt. I could not find a consistent answer on the
recommended oil for the transmission. The original Healey
manuals are not consistent either, the shop manual
recommends 20W50 and the Healey service bulletins from the
day recommend 30W. Coming up with the right oil is further
complicated by the design of a Healey transmission which is
two different transmissions with a common oil system. One
transmission is a traditional gear type with syncro rings
that are not compatible with the additives in modern gear
lubricants and the other is a hydraulic pump. I am sure
there will be much disagreement but these are the steps I
went through to select the oil I would use:</font></span></div>
<div dir="ltr" align="left"><span class="343023002-09082017"></span> </div>
<div dir="ltr" align="left"><span class="343023002-09082017"><font
size="2" face="Arial" color="#0000ff">1. The additives had
to be compatible with brass and other soft metals used in
older transmissions.</font></span></div>
<div dir="ltr" align="left"><span class="343023002-09082017"><font
size="2" face="Arial" color="#0000ff">2. The oil should be
designed to work with gears and have some level of EP
protection. Note very few engine oils meet gear oil
specifications.</font></span></div>
<div dir="ltr" align="left"><span class="343023002-09082017"><font
size="2" face="Arial" color="#0000ff">3. The oil should have
a viscosity similar 30W engine oil which was recommended in
an Austin Service bulletin in 1960 replacing 20W50.</font></span></div>
<div dir="ltr" align="left"><span class="343023002-09082017"></span> </div>
<div dir="ltr" align="left"><span class="343023002-09082017"><font
size="2" face="Arial" color="#0000ff">The oil that best fits
all of these requirements is a 70W-90 GL4 gear oil. Red Line
MT-90 meets this specification as does Pennzoil Synthetic
70W-90 GL4. I picked the Pennzoil as it costs less than the
Red Line but both should work well. Do not use a GL5 as the
additives are not compatible with brass. I looked into why
Austin switched their recommended oil from 20W50 to 30W and
concluded it was for a lower viscosity at lower temperatures
i.e. when the transmission is cold. Viscosity is another
important consideration. 70W-90 GL4 has the same viscosity
as 30W engine oil above 35 degrees C and a better low
temperature viscosity. The only downside I have seen with
Pennzoil Synthetic 70W-90 GL4 is that it can get through
even the smallest openings and cracks and the transmission
may leak a little more but that is evidence the oil is
getting every where it should. I have heard Red Line MT-90
doesn't leak as much as the Pennzoil.</font></span></div>
<div dir="ltr" align="left"><span class="343023002-09082017"></span> </div>
<div dir="ltr" align="left"><span class="343023002-09082017"><font
size="2" face="Arial" color="#0000ff">For those that may
doubt the viscosity claims please note that engine oils and
gears oils are classified differently and should be compared
by looking at the numbers on the can. See the attached
viscosity curve.</font></span></div>
<div dir="ltr" align="left"><span class="343023002-09082017"></span> </div>
<div dir="ltr" align="left"><span class="343023002-09082017"><font
size="2" face="Arial" color="#0000ff">I trust this helps but
I want to emphasize this is the oil I use and I recommend
you reach your own conclusion.</font></span></div>
<div dir="ltr" align="left"><span class="343023002-09082017"></span> </div>
<div dir="ltr" align="left"><span class="343023002-09082017"><font
size="2" face="Arial" color="#0000ff">Harold</font></span></div>
<div dir="ltr" align="left"><span class="343023002-09082017"></span> </div>
<div dir="ltr" align="left"><span class="343023002-09082017"></span> </div>
<br>
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<hr tabindex="-1">
<font size="2" face="Tahoma"><b>From:</b> Healeys
[<a class="moz-txt-link-freetext" href="mailto:healeys-bounces@autox.team.net">mailto:healeys-bounces@autox.team.net</a>] <b>On Behalf Of </b>Michael
MacLean<br>
<b>Sent:</b> Tuesday, August 08, 2017 5:47 PM<br>
<b>To:</b> Healey List<br>
<b>Subject:</b> [Healeys] Russ Thompson<br>
</font><br>
</div>
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york, times, serif; COLOR: #000; BACKGROUND-COLOR: #fff">
<div id="yui_3_16_0_ym19_1_1502237499620_134651" dir="ltr">
Through a reference from the list I am having Russ Thompson in
Northridge, California rebuild my BN2 transmission. It is a
low mileage (10,000 mi. approx) transmission, but I wanted to
be able to put it in and not have to take it back out again.
Good thing I took this precaution. Russ found the overdrive
stuck and would never have worked. Today he showed me the
accumulator piston. The smaller center piston was scored from
dirt or crap in the oil. Russ replaced it with a one piece
piston from a Triumph overdrive. There was a huge spring
below it. Anyone heard of this? He said engagement will be
real positive now. Even with the low mileage, the number 2
synchro was toast and will be replaced. The other two were
fine and will be re-used. All the gears showed very little
sign of wear. The reverse gear had some surface rust on the
teeth, but that can be blasted and it will be fine. Getting
closer to having the drive train is the car.</div>
<div id="yui_3_16_0_ym19_1_1502237499620_134884" dir="ltr">
I know I am going to start a discussion, but Russ recommends
using 40wt motor oil for the transmission. Anyone know what
weight Redline MTL is?<br>
</div>
<div id="yui_3_16_0_ym19_1_1502237499620_134867" dir="ltr">Mike
MacLean<br>
</div>
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