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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Differential breather

My TD just has a small hole in the tube near the case for a breather. I note that the MGA had a regular breather valve.

I would think it would be a good idea to add a regular breather. The Moss one for the MGA is plastic. I was thinking the Dorman metal axle vent would be more durable. https://www.dormanproducts.com/p-74931-924-262.aspx

Any reason not to add a breater?
Bruce Cunha

Hi Bruce

I have that breather on my TF. It came with the diff rebuild from Dave Clark.

Tom
'54 TF

T Norby

I fitted the same type to mine - MGA/B part.
Dave H
Dave Hill

Looks like the Dorman unit may have a larger diameter threaded connector !
Mel Pascoe

Hi Bruce. The addition of the MGA breather is recommended by Carl Cederstrand in his book on the gear change. The only reason not to do it would be if you were going for a 100 point car.

Butch
R Taras

Well. I doubt I will hit 100 points, but am trying to bring it back as close as I can to what it may have been from the factory (that is a tough one as we still do not know exactly how they came from the factory).

The MGA cap used by others is plastic and knowing me, I would break it. Since you have to drill and tap the hole anyway, if I decide to add it, I probably will go with the metal one.
Bruce Cunha

Don't tap the axle tube. Take out the filler plug and drill and tap that.
I simply made a pigtail breather out of spare brake pipe and soldered that into the plug.
Ray TF 2884
Ray Lee

I used the plastic MGA mushroom but drilled and tapped the existing hole when the reassembly was being cleaned before it was fitted with the 4.3 conversion. Didn't want to risk getting swarf into the axle tube so obviously this was the best time to do it. Not original I know but I wont tell anyone if you don't.. Cheers
Peter TD 5801
P Hehir

Good day to all,
I have my newly installed differential with the small hole in the tube. I am not crazy about the open hole and wanted to add a breather, but since the rear end is already finished, I do not want to tap the existing hole. Is there any reason not to just drill a hole in the fill cap like Ray mentioned and put in the one from Abingdon Spares? Is there room there for the mushroom breather there just mounted on the cap? My TD is down to the frame, so I am not sure where any interference might be there. Then I could just seal the breather hole in the tube.
Advice?
Jim TD17744
JV Smith TD17744

I made one using a carriage bolt..the head of which made a nice metal mushroom “cap”.

Regards, Tom
tm peterson

I use a brass one. It has a 1/8" BSP thread and will easily fit in a tapped filler cap. It is a much more sturdy breather than the cheapy plastic ones and certainly does not look out of place. Anybody wanting one let me know as it might be worth my while ordering a small batch of them.

Regards
Declan

Declan Burns

Count me in for one.

Jim B.
JA Benjamin

My brake line strap covers the vent in my TF axle tube. Probably keeps out most dirt and water. Diff can still "breathe." (Recommended in the archives.)

Lonnie
TF7211

LM Cook

What sort of pressure are we talking about? Couldn't a pressure relief valve such as the Festo one way control valve GRLA-1/8-PK-6-B be used? I have no affiliation with the company -just Googled relief valves.
JK Mazgaj

JK,
No need to go to all that bother. They are very simple to make. All that is inside is a steel ball that covers a small hole, You could make one up from contemporary fittings and a piece of brass stock.

Jim B-noted
Regards
Declan
Declan Burns

Thanks Declan.
JK Mazgaj

Hi Guys,

Just some useless information and opinion which might be significant.

I think the MG Y-Types just had a small hole towards the right-hand side of the axle tube.

Many years ago, in my racing TC Special, I had a small hole and tube (perhaps 2 or 3 mm I.D.) looping up to the roll bar, assuming that it would easily handle any breathing requirements. At the same time I had issues with oil in the back brakes despite various efforts to solve the problem. When I modified the breather to a much bigger size (can't remember what it is now ... perhaps 6 mm I.D.) I suddenly had much less oil finding its way into the back brakes. I am only guessing that under extreme conditions, the temperature can rise rapidly enough to require more breathing than I had imagined?

Bob
R L Schapel

I have the same type that T Norby has, which also came from my Dave Clark rebuild. PJ
PJ Jennings

I too had oil on back brakes but a new bearing totally fixed that! My TD's breather hole has no tubing at all!
Ed
efh Haskell

Yes, I agree. The TD breather hole is in the left tube, under where Lonnie's strap is. That open hole just kind of bothers me and I was looking for a way to allow the differential to breathe without the open hole to trap dirt and water. I don't want to tap that hole because the new rear end is already finished and I don't want shavings in my tube. I like the idea of drilling and tapping the filler cap.

My assumption is that we wouldn't want a one-way ball type breather because you want the differential to freely breathe in both directions as the differential heats and cools.

Jim
JV Smith TD17744

When I had my 4.3 gear set installed by Rick Smith (a long time ago) there was no thought about the breather. I should have installed one when I put the Jerry Austin half shafts into the axle. The idea of installing the breather into the filler cap is great. I'll order one tomorrow. Anybody happen to know what the thread is? TIA. Bud
Bud Krueger

Jim,
The ball and hole is not an issue as the ball bounces around with the diff and only settles when the car is stopped. It is not a check valve!
Regards
Declan
Declan Burns

Got it, Declan...Thanks

Bud, I found several online with 1/8" threads. I was just going to tap the filler cap to fit the breather. However, the ones I looked at were just simple breathers with a filter, not a ball valve type that Declan mentions.

Jim

JV Smith TD17744

The one that I've ordered from Abingdon Spares is the OEM one from MGA/MGB's for $8. It's Moss' #267-040. Should be easy to install in the filler plug. Bud
Bud Krueger

Bud,
Oh, I see it. Abingdon spares didn't have a measurement, but Moss looks like the thread is about 1/4".
Thanks,
Jim
JV Smith TD17744

Is it helpful/necessary to fit one in a TC?
JK Mazgaj

How about --- To install a breather after the fact could be done by using JBWeld then would not be necessary to drill tap and get filings inside
Michael Balahutrak

Michael, the thread on the breather measures .373" in diameter. Attached is a photo showing the breather hole on the top of an axle and the corrosion on the half shaft directly below the hole. The hole is only about 1/8" in diameter. The car had been sitting for some 20+ years. Bud

Bud Krueger

Bud

Thank you for this info -

this corrosion photo is very interesting - would not have thought it would cause such corrosion.

Michael
Michael Balahutrak

This thread was discussed between 27/03/2018 and 25/12/2020

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