Gearbox Breather - Where is it?

[Nigel Triumph]

The gearbox and overdrive on my CP-series 6 leak copious quantities of oil. Whenever I remove the filler plug to top up, a 'whoosh' of air escapes, implying that the 'box is pressurised, so not breathing properly.

 

I've tried to find the breather to see if it's blocked. Searching the forum I found this thread, indicating the breather is a 2mm hole at the front of the top cover:

 

http://www.tr-register.co.uk/forums/index.php?/topic/31782-invisible-gearbox-oil-breather/

 

I also found this image online, with bent wire helpfully showing the location of the breather on a '74 TR6, which confirms the position:

 

 

I've wiped away the grime from the top cover of my gearbox and there's no hole in this position. Can the wise ones here please give any clues to where else I should look?

 

I'm fairly sure if I could find the breather and unblock it, there's a much better chance the oil will stay inside the gearbox!

 

 

Nigel

[RogerH]

Hi Nigel,

definitely put a hole in where the piece of wire is. I fit a split pin in there to keep it clear.

See the attached pic for the breather on the OD.

 

If you have leaks from the selector rods then you are not on your own. Consider fitting Q seals or Quad seals.

These are like four leaf clover in cross section and have twice the chance of sealing.

 

 

Roger

 

 

Edited May 26, 2017 by RogerH

[foster461]

I just checked a couple of TR4 gearboxes and they dont have a breather hole. Easy enough to remove the cover and drill a 1/16 hole if you have access to it.

 

Stan

[Nigel Triumph]

Thank you Roger and Stan.

 

I will drill a 2mm hole in the top cover. The selector rod seals don't seam to be leaking, most of the oil is coming from the inhibitor switches on the top cover and the overdrive cover. I've got new spacer/sealing washers for the top cover switches and will replace them and external gaskets and seals on the O/D.

 

My A-type overdrive has a square headed blanking plug where the breather is on Roger's photo. I'm familiar with that type of overdrive breather as one is fitted to the D-type on my GT6. Strange that my TR doesn't have one but I assume I can remove the blanking plug and fit a breather.

 

 

Nigel

[Robin Powell]

As the oil is common to both gearbox and overdrive I would have thought the breather on the overdrive would have been sufficient to releave the pressure?

[Nigel Triumph]

As the oil is common to both gearbox and overdrive I would have thought the breather on the overdrive would have been sufficient to releave the pressure?

 

Yes, I wondered that too.

 

Nigel

[RogerH]

Hi Nigel/Robin,

even with extra breathing holes the selector rods still appear to leak. It must be capillary action or something.

 

Roger

[BlueTR3A-5EKT]

My TR3 has a late Stag gearbox with the breather hole in the remote as pictured in OP, plus I have bored the top cover to accept a dipstick/filler as orig TR2/3.

Still leaks out the selector rods, so Rogers Q seal trickis on the horizon.

Peter W

[Litespud]

My gearbox cover doesn't have a breather in the position indicated above, but as others have mentioned, the A-type O/D has a relatively large vent that does the needful for both the gearbox and the O/D

[Nigel Triumph]

Thank you all,

 

I will fit the O/D breather and see if a hole is needed in the top cover as well.

 

 

Nigel

[peejay4A]

If you do drill the top cover, and I had to on my gearbox which has a J type O/D because they have no breather, make sure it's exactly in the right place and comes through into a baffled area of the top cover. Otherwise the oil splash in the box will find its way out through the hole, guaranteed. This is where I drilled mine and no more leaks, at least from the gearbox.

 

Whoops, wrong picture. It's on one of my early posts so not sure I can find it but from memory it's about where your picture has it.

 

You can just about see it here...

 

Edited May 26, 2017 by peejay4A