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Triumph Torque  /  Spitfire/GT6  /  Gearbox oil?
Posted by: phil866, January 8, 2008, 6:10pm
Sorry to ask but what is the difference between GL4 and GL5 gear oil? Which is ok for an o/d gearbox.  What is EP80W-90 GL4 and is it suitable??

Many thanks.
Posted by: CharlieB, January 8, 2008, 6:52pm; Reply: 1
EP80W-90 GL4 is a multigrade gear oil which has the viscosity of an EP80 when cold & the viscosity of an EP90 when hot. EP means it has "extreme pressure" additives for hypoid gears. The GL number signifies how much EP additives it has, GL1 none to GL5 lots. Some of the additives used in GL5 oils (sulphur compounds I think) attack yellow metals like synchros etc when they get hot so is generally not recomended in Triumph gearboxes or diffs.

EP80W-90 GL4 is ideal for your gearbox.

To complicate matters some modern synthetic GL5 oils eg Redline say they are fine with yellow metals, see: http://www.club.triumph.org.uk/cgi-bin/forum/Blah.pl?m-1198094218/s-4/highlight-/#num4
Posted by: phil866, January 9, 2008, 11:20am; Reply: 2
Many thanks CharlieB, thats exactley the info I needed. Cheers!
Posted by: G.in_Lux, January 9, 2008, 11:58am; Reply: 3
read the box carefully...

A lot say GL4 on the front then in the small print behind, GL4/GL5...

I ain't no oil expert, just careful (and untrusting)
Posted by: Mac, January 9, 2008, 12:20pm; Reply: 4
Only use GL4 in the diff, you can use GL4 in the gearbox too as recommended in the manual but modern (also synthetic) 80/90 GL5 is fine in the gearbox, overdrive too.
Posted by: rotoflex, January 9, 2008, 12:25pm; Reply: 5
I think the precaution regarding GL5-spec oils is that they degrade "yellow metals", i.e., like the brass synchros in the gearbox.  The gearbox is the LAST place I'd use GL5-spec oil.
Posted by: Mac, January 9, 2008, 12:35pm; Reply: 6
Well, I asked around when deciding which oils to use in gearbox and diff, and this is what I found.

Question
"is it now ok to use modern GL5 SAE 80/90 gear oil for the diff, gearbox and overdrive?"

Answer
"Would prefer GL4 in the diff, but not critical."

Online reference on the use of synthetic oil in Triumph overdrive gearboxes:
Use good oil in the gearbox/overdrive, it is worth the extra (particularly synthetics) as it is working very hard and changing it every 50000 miles is well worth the effort.

To add more fuel to the debate
**It is essential to use an EP (extreme pressure) oil to GL4 spec only for the diff and overdrive. DO NOT USE GL5. Virtually all oils now sold are to GL5 spec and will "melt" the copper washers in the diff. 80W90 GL1 is another great alternative. The GL1 can be found locally at Tractor Supply, farm stores or marine supply stores.
Mineral oils are usually EP90, semi synthetics etc can be EP75W90.
It is the sulphur and/or zinc based EP (extreme pressure) additives in the GL5 oil that can react with yellow metals above 200 deg. F and "melt" them.
The gearbox isn't so particular and any spec of EP oil can be used - as there is so little in there it is generally preferable to buy the most expensive as it will probably be the best.


Been running GL4 SAE90 in the diff and GL5 SAE 80/90 in the OD gearbox for about 7 thou miles now, no probs from the overdrive or gearbox, rebuilding the diff. Should I use GL4 in the gearbox too?
Posted by: CharlieB, January 9, 2008, 1:19pm; Reply: 7
I think it's a good idea when quoting advice to say where it came from, otherwise we don't know how authoritative it is.

I've decided to use Red line synthetic oil. Since they make GL4 & GL5 they have no vested interest in telling me to use the 'wrong' one. MT90 GL4 - gearbox & 75W90 GL5 (safe for yellow metals) diff. It may be a little OTT for a Spitfire but what the hell ;D
Posted by: Mac, January 9, 2008, 1:26pm; Reply: 8
Hi Charlie,
First question/answer is e-mails to/from a reputable Triumph dealer who sells both oils.

Online reference is John Kipping

Last web quote  is from triumphspitfire.com
Posted by: G.in_Lux, January 9, 2008, 1:39pm; Reply: 9
Incidentally...

I suppose it would be possible, eventually, and with a lot of mucky hands and elbow grease, to replace the copper elements in the transmission with steel ones, no?

I imagine that it'll soon be impossible to find GL4 spec oil... I was lucky to find an old batch and was told nobody (over here) stocks the stuff...
Posted by: Mac, January 9, 2008, 3:52pm; Reply: 10
Quoted from G.in_Lux
Incidentally...

I suppose it would be possible, eventually, and with a lot of mucky hands and elbow grease, to replace the copper elements in the transmission with steel ones, no?

I imagine that it'll soon be impossible to find GL4 spec oil... I was lucky to find an old batch and was told nobody (over here) stocks the stuff...


Same problem in Italy, really hard to find, go to a shop and they look at ya like you're from Mars or something ;-) ended up getting some for the diff sent over from the Uk

Definately interested in people's opinions on whether GL5 is ok for the gearbox or GL4 is better/safer as I'm about to refill the gearbox

Posted by: CharlieB, January 9, 2008, 4:33pm; Reply: 11
Quoted from Mac
Definately interested in people's opinions on whether GL5 is ok for the gearbox or GL4 is better/safer as I'm about to refill the gearbox

I would say use GL4 unless the manufacturer specifically says their GL5 is safe for yellow metals.
Some very recent production cars specify GL4.
Posted by: rotoflex, January 9, 2008, 6:11pm; Reply: 12
I didn't have a problem finding it on auto parts store shelves here, but I had to look on the back of several containers.

The GL4 I found seems like the packaging indicated that it was actually marketed towards trucks.
Posted by: KevinR (Guest), January 9, 2008, 7:05pm; Reply: 13
Most manufacturers formulations of GL5 (there are one or two exceptions, I believe Penrite are one exception, but check first) contain chemicals that attack and disolve phosphor bronze bearings and shims - and most of the smaller Triumphs use phosphor bronze components in the diff, and therefore require GL4 gear oil in the diff.  

Oil comes in various thicknesses and specifications

Thickness
EP is "Extreme Pressure" ie gearbox (and trunion) oil
80, 90, 140 etc is the viscosity, and if there are two numbers quoted, such as 80W90 then when cold it behaves as an 80 viscosity oil, and when hot as a 90.

Specification
There are two grades of gear oil generally available
API-GL4 which does not attack phosphor bronze
API-GL5 which normally destroys phosphor bronze

GL5 is not better than GL4, it is different, and has different properties.  The diffs on most (but not all) modern cars have been designed to work with GL5

According to the RimmerBros website, the correct oil for a T2000 diff is Unipart GGL190, which is a GL4 specification oil EP90 oil - they specify the same oil for the small Triumphs as well, so I guess that the T2000 diff also contains components that are destroyed by the additives in GL5 oil.

Checking the lubrication chart for a T2000 should confirm that a GL4 specification EP90 oil should be used.  If the chart says GL4, then DO NOT use GL5 unless the manufacturer guarantees that it is compatible with internal components of the diff (Penrite is the only GL5 oil that I think is compatible)  If GL4 spec EP90 cannot be obtained, the GL4 spec EP80W90 is fine.  Halfords sell GL4 EP80W90.
Posted by: Spitfire2500, January 9, 2008, 7:08pm; Reply: 14
Quoted from KevinR
(Penrite is the only GL5 oil that I think is compatible)


As correctly noted in a post above the Red Line synthetic GL5 EP gear oils are compatible.

Posted by: junkuser, January 9, 2008, 8:12pm; Reply: 15
"I suppose it would be possible, eventually, and with a lot of mucky hands and elbow grease, to replace the copper elements in the transmission with steel ones, no?"  G.

Bronze is used for the bushes, thrusts and synchromesh rings in the gearbox so could not be replaced with steel G.
Posted by: rotoflex, January 9, 2008, 9:42pm; Reply: 16
I have part of a bottle of the last I put in, a couple of months ago:

The brand is LubriMatic, product name is Gear Lube.   GL-4 SAE 85W/90 EP.
The part # is 11493

Web searches for Lubrimatic Gear Lube turned up a bunch of Lubrimatic Gear Lube products, mostly incompatible (GL-5, greases, etc.)

Lubrimatic is manufactured by Plews Edelman, & a search for part number 11493 on their site turned it up about halfway down this page::
http://www.plews-edelmann.com/brochure.cfm?brochure=1965&location_id=2630

It's not BP or Gulf or a similar big brand, but I believe the odds are good that it's as good as what might have been put out by those guys in 1972.

Web searches also showed Lubrimatic gear lube products turning up at a LOT of marine (boat) supply stores, so that might be a good place to search for an appropriate GL-4 gear oil on your side.

Going out on a limb:  Redline is very well thought of, & a lot of racers use their MTL & other products in their cars requiring non-GL-5, non-ATF, etc. oils in the transmission.  GT6Steve might nose around his crowd for clues.  However, if I couldn't find GL-5, I would go with what Redline recommends & feel like I've probably made the best decision possible.

I'm very cautious with the GT6, but not really averse to trying new things which may be improvements.  
Of course my position on that remains, as always, You Do It First.

Posted by: billspit, January 10, 2008, 5:25pm; Reply: 17
After reading several postings on web boards, I changed out the GL-4 in my Spitfire w/OD to 30w nondetergent motor oil.   I works fine so far.  I had a hard time finding GL-4, and  it was expensive.   I am using Redline MT90 in my Nissan truck diff and trans.  
Posted by: phil866, January 10, 2008, 5:58pm; Reply: 18
Well, for better or worse, I bought 5 litres of EP80W-90 GL4 mineral gear oil manufactured by Comma for 12.50.  http://WWW.commaoil.com
Posted by: cliftyhanger, January 10, 2008, 9:54pm; Reply: 19
Thats the stuff I have been using for years. Nothing to report, which must be good.
Hasn't stopped me destroying a few diffs though (2.5  and a very low first did that).
I suspect most oils of a given spec are pretty much the same, and modern oild do tend to be better than the old ones from the sixties. I think. Could be wrong!
Posted by: phil866, January 10, 2008, 10:41pm; Reply: 20
Thats a relief clifty, sometimes the old names just do the job!
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