[TR] Transmissin and rear diff oil for a TR6

[Randall]

> I am getting ready to change the trans and diff oil in my 74 TR6. It has a
> J type overdrive. My question to the list is what is the best oil to use?

That's a topic we debate from time to time, with no clear consensus.  

I use Redline MT-90 in my Triumph gearboxes (both A and J ODs).  Doesn't
seem to make much difference to OD operation, but it makes a noticeable
difference in the main gearbox, IMO.  Easier, more positive shifts; makes it
seem somewhat less "agricultural".

I use Valvoline Synpower 75W90 gear oil in the differentials.  It is GL5
rather than GL4; but does not use the additive that can attack copper
alloys.  (The Triumph diff uses brass thrust washers behind the spider
gears; and some gear oils use an additive that, over time, can attack and
degrade the brass.  Synpower doesn't use that additive.)

> Also, when draining the trans does it completely drain the OD? 

No.  You'll get more oil out by removing the 6 bolts and sump plate on the
bottom of the OD.  That still won't get absolutely all of the oil out, there
will still be some trapped in the passages and pistons, but it should be
close enough.  You should have a new gasket on hand.

> Anything to
> watch out for? This is the first time I have done this and want to get it
> right.

If you have the stock square head drain & fill plugs, I strongly recommend
buying an 8 point socket in 1/2" drive.  I got mine at Sears, don't know if
they still carry them or not.  Here is one on Amazon (just to show what I
mean) https://goo.gl/26QNyf
The plugs are soft and the head rounds off easily.  If you don't have one
already, a big breaker bar is a good investment as well.

I prefer to replace the stock plugs with hardened "hex socket" plugs; with a
magnet in the drain plug.
https://i.imgur.com/1TnOAg1.jpg
I get mine from McMaster-Carr (double-check the size, though)
https://www.mcmaster.com/?m=true#1072a22/=19w8upj

When you fill the gearbox, it takes some time for the oil to run back into
the OD.  Some go as far as driving the car a bit and then rechecking the oil
level; but IMO it isn't nearly that critical.

I use Teflon "pipe dope" on the drain & fill plugs.  The more common tape
will work, but if you use too much, there is a chance that it can break off
inside and possibly plug up a passage.

There is a pickup screen visible once you remove the plate from the OD.
Usually it can be just rinsed off in solvent and reused.  But if there is a
significant amount of crud on it, you might want to remove and clean the
high pressure screen, which is above one of the plugs with the two holes.
If you scroll down to "High Pressure Filter" in the article at
http://www.buckeyetriumphs.org/technical/jod/JOD1/JOD1.htm
There is a nice photo of the plug and screen.  The next article in that
series shows one way to make the tool to turn the plug:
http://www.buckeyetriumphs.org/technical/jod/JOD2/JOD2.htm
The one I made was simpler, just two pins (I used hardened dowel pins rather
than split pins) in a length of bar stock (concrete form stake from Home
Depot).  Unfortunately I don't have a photo handy.

One of the little hand oil pumps makes filling the gearbox much easier.
Usually available at Walmart or most auto parts stores; here is one on
Amazon:
https://www.amazon.com/Sta-Lube-SL4344-Fluid-Oil-Pump/dp/B000CPIOBA

I'm sure I'm forgetting something, but that should be enough to get you
started.

-- Randall