Board logo

Gear oil - have I damaged my diff?!?
ed_crouch - 6/1/07 at 10:59 PM

Help!

I've just read that GL5 spec gear oil isnt suitable for my diff as it corrodes copper.

Shoulda used GL4, which doesnt have the suplphurous compounds in it!

Its been in there for a couple of weeks, and I wonder if I can get away with just changing the oil, or whether the damage is done!

Any ideas?

Ed.

wilkingj - 6/1/07 at 11:07 PM

If its only corrosion, the effect of being in there for two weeks should not do any real harm.

I would flush it out, run it on fresh oil for a few miles or so, then flush again and use new oil.

After all how much copper is there in a Diff??
I believe the problem is minimal, and a couple of good flushings will sort it. Anyone disagree?

PS.. I buy my EP 80 in 25 litre drums, which costs out at about £1.20 per litre, rather than the £3.95 per litre when bought in Litre tubs from people like Half Fords and the likes of.

Peteff - 7/1/07 at 10:34 AM

That's a lifetime's supply then, I think I've used probably half a litre in the last six years. As said, where's the copper in the diff? I'd just change it if it's worrying you.

JoelP - 7/1/07 at 11:02 AM

he owns a land rover, need to keep it topped up

02GF74 - 7/1/07 at 11:19 AM

quote:
Originally posted by ed_crouch

I've just read that GL5 spec gear oil isnt suitable for my diff as it corrodes copper.


firstly as has been said, how much copper is in a diff? Inside english axle it is 0; and I suspect that is the same for majority of diffs; gearboxes may contain brass (whcih is copper alloy?) bushes.

And I would suspect the time scales would be m any years before any oil will disolve a metal - probably a scaremongering myth by manufactureres to ocver their bums.

so in aswer to your questions, you diff will not have been damaged and to put you mind at reat, drain and fill with ep 90 (or whatever is specified).

wouldn't bother to flush as the amount left behind of the old stuff will be a few teaspoons (drive the car to warm the oil, drain and leave overnight).

britishtrident - 7/1/07 at 11:30 AM

I think you have misunderstood the oil recommendations.

Leave the oil in it is a high spec EP gear oil perfectly suitable for an Escort hypoid final drive. Using a non EP oil in a hypoid axle will cause excessive wear on the flanks of the gears. Because of the combination of extreme pressure and rubbing hypoid gears need very high levels of EP (extreme pressure) additive.

The warning on fretting corrosion of bronze applies to
all EP Hypoid gear oils which makes them unsuitable for use in those RWD gearboxes that have bronze synchromesh baulk rings.


General rule is all rwd axles after about 1958 have hypoid final drives and must use EP "Hypoid"gear oils which have very high levels of EP additive -- for this purpose GL5 spec is better than GL4 which was the best around when Ford spec the oil for the english axle in the late 1950s



[Edited on 7/1/07 by britishtrident]

ed_crouch - 7/1/07 at 01:38 PM

Cheers, fellas!

The diff I am talking about is a Triumph GT6, and it has copper thrust washers in.

Ive since found out that the Comma GL4 spec oil has the same sulphur compound in it as th GL5. This sulphur compound, as Britishtrident said, is the "elixir of Extreme Protection" required to prevent hypoid gears wearing out doublequick.

I put a spare piece of fresh copper brake pipe into a cupfull of GL5, and as with every pointless Chemistry experiment at school, its sitting there doing f*ck all. If its not affected the metal in a months time, I think we have our answer!

Im probably going to strip the diff and possibly the gearbox at the end of every sprint season anyway, as the GT6 diffs need to be in top condition to put up with 120+ BHP abuse up a hill/round a track.

Ta.

Ed.

NS Dev - 7/1/07 at 09:21 PM

you've said it yourself, but yes, most diffs have bronze thrustwashers for the planet gears and side gears, so there is quite a bit of copper in there one way or another!