75W-90 API GL-5 vs API GL-4 for transmission, transfer and others...

[Msolano]

Guys,

This past weekend I serviced my GV 2006 with 50K km on the counter. I changed all the fluids and I used the API GL-5 75w90 for all following parts:

- Differential front and rear oil
- Manual Transmission oil
- Transfer case oil

Reading on the manual and the forum, I found that I had to use the GL-4 75w90 for transfer and transmission. I googled the "NORMS" (see link) and I found little difference between GL-4 and GL-5 in terms of application.

So my question is: is it OK to leave the oil for the transfer and transmissión with GL-5 instead of GL-4? Will be there any problems because of using different norms?

The "NORMS":
Norms

[annfan]

I'm not a Lubricants Engineer, but from what I understand the major difference between GL-4 and GL-5 gear lubes is in the lubricity or "slipperyness" of the oil and the ability to work properly under extreme pressure. GL-5 is more slippery and holds up under the very high gear pressures found in differentials.

In fact, GL-5 is too slippery for the syncros to work properly in most manual transmissions. That's why GL-4 is used and is still manufactured. Some older transmissions even use engine oil for the same reason.

I think Suzuki calls for GL-4 in its manual transmissions so the syncros work properly and continue to do so. If GL-5 was acceptable they would say so. You may not notice a difference at first by using GL-5 but you might find shifting (especially downshifts) become harder and harder as time goes on. I would also expect the sycros to wear faster with GL-5. I can't see Suzuki honouring a warranty claim if you've used the wrong lubricant in the transmission.

I realize its a real pain, but I would remove the GL-5 from both the transmission and transfer/extension case and replace it with the correct GL-4.

[Max]

Yep, concur. Change back to the recommended grade / type SOON before you damage anything.

[JimD]

I used red-line synthetic GL-4 in the transmission and GL-5 in the extension housing (mine is 2WD) and the rear end. I got it mail order from JEGs. Wasn't that expensive. Shifts might be slightly smoother with the synthetic, and wear/heat/noise is also supposed to be reduced. Can't say I really see a big difference but it still seemed like a good idea.

Might be a way to do more than just change out GL-5 to GL-4 - upgrade to synthetic.

Jim

[Msolano]

Thanks everyone who responded, specially annfan. You were right, it is important to follow the service manual. For transmission and transfer use 75w-90 GL-4 and for front and rear differential use 75w-90 GL-5. The reason? the additives (EP) present in each type. Have a look to this PDF (hope it is online):

http://www.stealth316.com/misc/pennz...oilsummary.pdf

It seems the GL-4 has half the anti rusting additives of that GL-5. The GV 4x4 transmissions and transfers has "yellow" parts that could be affected by the additives of GL-5, but not the differentials.

I followed JimD advice and poured some PENNZOIL® SYNTHETIC SAE 75W-90 GL-4 (each quart $13.20). I hope to forget about this for the next 50,000 km.

[fordem]

Originally Posted by annfan

I'm not a Lubricants Engineer, but from what I understand the major difference between GL-4 and GL-5 gear lubes is in the lubricity or "slipperyness" of the oil and the ability to work properly under extreme pressure. GL-5 is more slippery and holds up under the very high gear pressures found in differentials.

In fact, GL-5 is too slippery for the syncros to work properly in most manual transmissions. That's why GL-4 is used and is still manufactured. Some older transmissions even use engine oil for the same reason.

I think Suzuki calls for GL-4 in its manual transmissions so the syncros work properly and continue to do so. If GL-5 was acceptable they would say so. You may not notice a difference at first by using GL-5 but you might find shifting (especially downshifts) become harder and harder as time goes on. I would also expect the sycros to wear faster with GL-5. I can't see Suzuki honouring a warranty claim if you've used the wrong lubricant in the transmission.

I realize its a real pain, but I would remove the GL-5 from both the transmission and transfer/extension case and replace it with the correct GL-4.

This has nothing to do with "slipperyness" and GL5 oils are no more or less slippery than GL4 oils.

GL5 oils are intended for use in differentials with hypoid gears, which have more of a "wiping" type of contact and as such contain higher levels of extreme pressure additives.

Sulphur was commonly used as one of these additives in older GL5 oils and will attack the bronze synchros used in transmissions.

Newer GL5 oils are formulated with different additives, and depending on the oil you choose may be safe for transmissions containing bronze synchros - look at the bottle or the manufacturers spec sheet, if it says the oil is safe for "yellow metals" or "copper and it's alloys", it can safely be used in the transmissions & transfer case.

Depending on where you're located it may be impossible to find a GL4 oil - this has been my problem and as a result I have been using Exxon Mobil1 full synthetic 75w90 GL5 in a Suzuki transmission for over ten years now with no ill effects.

[Kootenanny]

As I understand it, the difference is that GL-5 lubricants may contain additives which attack "yellow" metals such as brass or bronze, which are commonly used for bushings and synchro parts--as others have already said.

I did not realize what fordem is saying, that some GL-5 lubes may be OK for yellow metals--I'll have to check this out, as GL-4 lube is becoming hard to find.

[fordem]

Originally Posted by Mobil 1

Excellent rust, staining and corrosion protection of copper and its alloys

This quote is taken from this page on the Exxon mobil web site.

Brass is an alloy of copper and zinc, bronze is an alloy of copper and tin

[mirageman]

check out this link, simply put by the Mobil 1 "techs"

GL-4 Gear Oil