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MG TD TF 1500 - Gearbox and differential oil

Today I finally got around to replacing both the gearbox and differential oil with a 90w gear oil recommended on the forum. Not easy opening up the plugs!
I also installed Tom Lange's magnetic plugs so if anyone is looking for a non-magnetic gearbox or diff plug let me know.
My question is: how often should these oils be changed?
Geoffrey M Baker

Geoff,
You have e-mail (again). I can use your gearbox plug.
Check the WSM for change intervals.
Joe
Joe Olson

The WSM gives mileage data (change every 6000 miles).
This car hasn't done 6000 miles in 45 years. But that may well be the last time the differential oil was changed.
Do people recommend changing the differential annually, or less frequently, if you are not going by miles driven?
Geoffrey M Baker

Changing annually or biannually is a good idea since water (humidity) accumulates in the oil, particularly if the cars sits a lot, like most of ours do. If you run it to a full warm up run at least monthly that's not as much of an issue, IMHO.
Kevin McLemore

My 93 Chevy truck that I bought new, has 260,000 miles on it and the oil in the rear has never been changed. It doesn't leak, so the oil level remains the same. I do check it about once a year and it still feels and smells as it did when the truck was new. Now the engine is a different story, every three to four thousand miles it gets changed and still runs flawlessly. PJ
Paul161

I'm with Paul, I don't believe I have ever changed the diff in any of my vehicles and never had issues with any. I change my engine oils every 3000 miles.
rich40701

I'm going to start a vehicle log for Lily Christine IV. I'll peg changing the diff and gearbox oil at once every 2 years. Reason is, that it will be run once monthly at least to warmup, and I live in a very dry climate, so water buildup is less of a problem.
At any rate, two more long-deferred-maintenance items complete! Changing the gearbox oil was relatively easy (as others have suggested, I just put the oil in a small plastic drinking bottle, this allowed an easy pour in a confined space. The differential was more difficult (My stands don't lift the vehicle very high) but should be easier next time, and having installed a restaurant pan in the rear plywood did give a nice easy access area to work in. Again, filling from a small bottle made for a clean job. And with a set of magnetic plugs all around, I have greater peace of mind.
Geoffrey M Baker

Be clever to change it if you ever negotiate a water crossing or drive in snow, the breathers are not well sealed.
G Evans

I agree Graeme. The breathers aren't sealed on the TD & I guess not on the TF. The MGA breather mushroom is well worth installing. Cheers
Peter TD 5801
P Hehir

It's really a good idea to change the transmission and differential oil periodically. It does oxidize and its additives break down, just as with engine oil. The oil that came out of my differential and transmission was pretty disturbing when I restored the car; it was a sickly olive color. I admit that I have no idea how long it had been in there (probably quite some time) but still, it needed changing. Does it have to be done every 6000 miles? I really can't say, but I don't think I'd wait until it is clearly deteriorated.

S Maas

Modern oils are a different breed than oils of yesteryear. Example is my farm tractors, they all use hydraulic oil in everything, pumps, power steering, transmissions, front and rear final drives. It's around 20W and is quite efficient in protecting the gearing under sometimes tremendous loads, far beyond anything auto gears would encounter. Would I use it in auto gearing, yes, if the seals that are used in cars were designed the same. The TF gear box gets a stiff oil to help quiet it down, no other reason. PJ
Paul161

Yes, that 'olive color' is likely the result of thorough mixing of oil and water. I've seen it many times.
Kevin McLemore

It may be overkill but I do mine once a year. To me it's just cheap insurance.
Keith Yarbrough(TD 1275)

Living in dry Arizona, I don't think you need to worry about anything past the manufacturer's recommendations. If the car is rarely driven then I would change it out once every few years.
Steve Simmons

This thread was discussed between 12/11/2015 and 15/11/2015

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