[TR] Transmission internal pressure question - drilling for oil

[Mark Hooper]

Hmmm. I popped off the top of my A-type unit (not installed in the car) and
from a careful comparison of the photo you sent, I see that where they
actually put the breather hole is a bit different than I thought. There are
passageways for the 3 shifting fork rods at the very top front of the
transmission. Each has a "viewing hole" which probably serves to get
lubrication to the shafts (coals to Newcastle all things considered).  What
they did was just drill from the top into that space beyond where the reverse
rod is in it's normal placement. Oil would have to go up through the viewing
port, and then up to the little hole to get out. This allowed them to put the
hole right up at the front, away from the gears spinning the oil up from
below.

So, I can indeed drill that hole, but will have to pop the top off the car's
transmission to do it. Shouldn't be a problem, just have to remember what sort
of gasket material to use in re-sealing. The mechanic used something light
grey which I do not recognise.

Strangely, all the transmission shift towers have a vertical barrel of
aluminium on the right side which looks for all the world to be a space
prepped for a breather. However it is not drilled through. There is no
machinery underneath. I suppose in another model of car something fit there.

Mark
1972 TR6

________________________________________
From: triumphs-bounces at autox.team.net [triumphs-bounces at autox.team.net] On
Behalf Of Mark Hooper [mhooper at digiscreen.ca]
Sent: May 2, 2010 10:31 AM
To: Randall; triumphs at autox.team.net
Subject: Re: [TR] Transmission internal pressure question

Hi Randall & Ken :

Thanks for the replies. I have been all over the shift tower on my J-type and
my A-type units. I do not see a vent hole. Randall's attached image makes it
seem that the factory simply drilled a hole between the reverse and 3rd/4th
selector rods (leftmost and middle). The placement seems rather specific
since
the aluminium is thinner almost everywhere else. I assume the place was
chosen
to give a longer pathway to reduce oil slopping out the breather hole.

I am now thinking that when my mechanic made up my transmission, he did so
using a shift tower without a breather.

The cure would then be to pop off the tower and make like a US politician.

Now trying to get maximum detail on placement and routing of hole. (Thanks
for
that photo Randall, it gives me placement, but can't tell if it is a simple
vertical hole or something more complex.

Cheers,

Mark




________________________________________
From: triumphs-bounces at autox.team.net [triumphs-bounces at autox.team.net] On
Behalf Of Randall [tr3driver at ca.rr.com]
Sent: May 2, 2010 12:19 AM
To: triumphs at autox.team.net
Subject: Re: [TR] Transmission internal pressure question

> Is a TR6 j-type tranmission supposed to have venting, or
> internal pressure?

Well, both actually <G>

>  I see now that the
> transmission is
> weeping oil from the seals around the shifting rods

A common problem even without blocked vents.  The seals being sold today do
not fit the cavities in the cover snugly. Herman mentioned machining spacers
from brass to fill the gap, but I was able to source some Teflon backing
rings that did the trick for me.

> I think the fellow who rebuilt the transmission and put in
> the nice unit from
> Laycock Rebuilders used 80w90 gear oil. This I have been told
> is a no-no.

Hard to go very wrong with the factory-recommended lubricant!

> Is there a vent hole in the transmission somewhere that might
> be blocked up?

I believe there should be.  Not sure where it was on earlier gearboxes, but
by the time the J-type came in, it was on the top cover near the front RH
corner:
http://tinyurl.com/23kmev4

There is even a factory service bulletin about checking that hole, if the
rear seal is leaking.

> Certainly I used to use 20w50 in the a-type and did not have
> this leaking.

A-types have a big vent in the OD body.  I don't believe the J-type does,
instead it relies on the gearbox vent.

Randall