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MG TD TF 1500 - Gearbox Drain Leakage

I've reactivated a 2007 thread that fits this.

I've finally discovered why my garage floor keeps getting a coat of oil - it's coming from the gearbox. About a year ago I went through a miserable project to replace the front crank seal while lying on my back. In the same project I decided that I'd replace my gearbox drainplug with one that contains a magnet. The new drainplug doesn't have the machining of the OEM plug as discussed in the 2007 thread (http://www.ttalk.info/picture_this.htm#Gearbox%20Drain%20Plug). It came with a solid copper washer. Eventually, the project got finished and the engine oil leakage virtually stopped.

However, I found that I was still getting a messy floor under the car. Decided that the new plug wasn't doing what I wanted it to do and RedLine MT90 is too expensive to waste. I r/r'd the fluid and reinstalled the OEM plug, but with the solid washer, since I had lost the bifurcated one and wouldn't have reused it anyway. Didn't do much driving this past year due to problems getting the new xzx tires balanced.

Lazarus is now back on the road. The oil mess has been frustrating. I've concluded that the OEM system was the best, i.e., the machined plug with the split ring and the bifurcated washer. I've ordered a couple of washers from Abingdon Spares and should see them next week. I'll let you know if they cure the leak. Bud
Bud Krueger

Hey Bud, try annealing the copper washer; heat to cherry red and plunge in water. The soft copper should seal much better.
rich40701

Bud
Back in '07 did you write up your work to "replace the front crank seal laying on" your back? I just did a quick look at T Talk and did not see it. That miserable job in on my list

Regarding the drain plug, I bought a magnetic plug in 2016 from one of our contributors. It came with a copper washer. It might seep a bit, but does not drip.

Tom
'54 TF
T Norby

Rich, I tried that with the washer, but it didn't seem to be of any help.

Tom, it wasn't that long ago when I did the 'on my back' routine the first time. I'm afraid that I didn't write it up. Both times were miserable. The first time I was doing it in an unheated garage during a Massachusetts winter. Bud
Bud Krueger

You don't need to quench the washer after annealing, copper does not have any intermetallic compounds which embrittle ferrous materials. Quenching can help to remove any oxide. If you can, use a reducing flame not an oxydising one.
Ian Bowers

Hi Bud,

It may pay to check the flanged surface area of the brass plug upon which the copper washer sits. Any burr or aberration in that surface can cause
leakage.

Also,the area where the copper washer is pressed up against the Gearbox
housing may need careful examination. Again, any imperfection in the surface here can cause leakage.

I always use a new copper washer to good effect after replacing the Gearbox oil.

Additionally, I use Hylomar (Blue) sealant applied carefully and sparingly to both sides of the copper washer. I think Rolls Royce developed/used
Hylomar in their Factory.

After going through the motions of the above, Invariably no leaks then emanate from the Gearbox plug.

Are you running the Gearbox on the standard type Gearbox mineral oil or a synthetic such as Redline MT 90 ?

Cheers
Rob Grantham
TF3719("Aramis"),TF9177("Athos").
Rob Grantham

Hi Bud,

Just noticed in your Post that you are using Redline MT 90.

Cheers
Rob Grantham
Rob Grantham

Rob, I think that I have been using RedLine MT90 for over 10 years now with zero leakage when using an OEM plug with a bifurcated gasket. When I rebuilt the gearbox I gave special attention to the sealing surfaces. Were I using a solid copper washer I would probably give it a dab of Hylomar. Bud
Bud Krueger

Ok, I know I will get a bit on this one, but at John Twists rebuild class, he had us put a small amount of clear silicon sealant on any bolt that does into the case. It is put on the base threads so the sealant does not get into the transmission.

Same applied to the drain plug.

Have had no leakage since that rebuild.
Bruce Cunha

Reactivating --

I've noticed the drip under Lazarus by the gearbox is still there. Drained the gearbox and measured the amount that was left in it -- 450ml out of 710ml installed in October 2018. Covered 1400 miles since then. This time I reinstalled the OEM drain plug with a bifurcated washer with a small dab of blue gasket goo (hylomar). RedLine MT-90 at $20/qt is too expensive to soak up in kitty litter. Hope the goo does the trick.
The death of SEMGTR has just about ended Lazarus' mileage. Just joined Peachtree MG Registry. Meetings via Zoom.
Bud Krueger

There'd still be residual oil (and whatever else) left in and on the gearbox. If you got the gear oil hot (cold drains aren't as good) and left it dripping out over days then took the gearbox out of the car and laid it on each edge and drain each time for a day each time I'd guess you'd still find oil inside on a strip down.

I change the gearbox oil on my wife's modern (5.5 years old, 38k-miles) the other day and strangely I got more out (hot drain), from presumably a factory fill, than I could get back in.

On having the car driven for a couple of days and left to settle down I checked the fill level on ground I was even more sure was flat and level in all directions just to be sure it didn't need topping up and when I removed the filler plug some oil dripped out the box.

The oil that dripped out then was discoloured darkish brown from its fresh light honey colour showing possibly how much residual oil was left in from even the hot drain and/or how contaminated/dirty the box remains. I should really use the oil that's in the box now as a flush and hot drain change with new again soon but I won't, it's good enough, not concours-clean but well lubricated and protected, plus most of this type of car never get a g/box oil change in their entire life.

I did consider using Redline but decided to stay local and use a Millers product.

My wife said she noticed an improvement, and she wouldn't say so just to keep me happy, so again confirms changing the oil in gearbox and back axle reasonably regularly does help.

Changing the axle oil in my 1973 midget does quieten the whine from it a bit, but not for long, but does suggest something has happened from the changing of the oil.
Nigel Atkins

Try a Dowty washer instead of copper. Gives a compression seal on the metal + the nitrile insert centers the washer as well as providing extra seal.
Cheers.
Dave
D Moore

Dave, I'd love to, except that I can't seem to get one in that size to cross the ocean. Bud
Bud Krueger

Bud,
I have loads of them. I can send them to you no problem-as many as you want.
Regards
Declan


Declan Burns

The same Dowty washer also fits the filler cap-same thread.
Regards
Declan
Declan Burns

Declan, you have mail. Thanks, Bud
Bud Krueger

All I know is the Scottish in me kept trying to reuse these washers (specifically the sump drain). Now I know they are a one and done.
Christopher Couper

This thread was discussed between 06/10/2018 and 30/04/2021

MG TD TF 1500 index

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