In my quest to "baseline" the G320 since purchasing it last May, I have been methodically going through it to change all fluids and ensure they are proper and of the right specification.
After some research on the topic, I determined that I would go with RedLine fluids for the transfer case and the front & rear differentials on my G320. I didn't know what fluids had been installed, and it turns out that it was a good thing that I changed them.
I found good and bad news: the good news being that all fluids appeared to be very fresh and very recently changed. The bad news was that the same gear oil appeared to be used on all three items -- which is bad because the differentials require a different specification (GL-5) gear oil than the transfer case does (GL-4).
Research among experienced G-wagen owners has shown that the RedLine MT-90 (GL-4 spec) and 75W-90 Gear Oil (GL-5) has carried a very good reputation. Both of these oils are "pure synthetic" and are much cheaper (and probably of better quality) than MB's own oils. Furthermore, the GL-4 oil that MB specifies, which is used for the transfer case, is only available in 5-gallon containers, at a price of over $300. Thus, because only three quarts of this oil are used at a time, having to buy 5-gallons is an extremely expensive proposition. The change interval for the transfer case fluid is 60,000 miles, FYI.
Changing the oil in the differentials is exactly like doing it in the rear end of a car: you loosen the top "fill" plug to ensure it can be removed, and then you loosen, remove the bottom drain plug from the differential. Then you drain the diff, and replace the drain plug. Then remove the "fill" plug and pump the specified amount of oil into the differential.
In the case of the front differential on my G320, it was 1.4 liters. For the rear differential, it was 1.8 liters.
Here are some photos outlining the process. I'm not going to caption the photos, as they are fairly self-explanatory given the above description. All plugs for both the differentials and the transfer case use 14mm "hex".
The first few photos are just overviews of the fill and drain plugs. There was a little dampness around the upper fill plug.
Breaking the upper plug loose, and then loosening and removing the lower drain plug in preparation for fluid drain....
Draining the diff, and inspecting the drain plug.
Re-installing and tightening up the drain plug to the requisite 60 Nm of torque.
Fill plug removed, and pumping new RedLine juice into the diff. The rest is a matter of buttoning the diff back up and cleaning things off with a few quick shots of brake cleaner.
The second part of the job is the transfer case. Now, the transfer case on a G-wagen is probably the most important part of the entire drivetrain, and it MUST be taken care of. The transfer case is a large box that is mounted directly aft of the transmission, and is connected to the transmission output shaft via a short drive shaft. The TC also has twin output flanges, one of which leads directly to the forward differential to drive both front wheels, and the other that leads directly to the rear differential to drive both rear wheels.
So, it's a very complicated box, and it is really important that the very best lubricant be used to keep it in good running order. Like I said, the change interval for the TC is 60,000 miles by MB specification. I will shorten this to 50,000 miles just to be on the safe side. The TC drain plug also contains a small magnet to catch metal particles that are in the TC.
One way I could tell that my fluid was fresh (the dark green stuff) was that there was NO metal or other particles on my drain plug magnet - it had probably been cleaned off after the prior fluid was changed. In any case, I was glad to change the fluid since it was the same exact oil that was used in the differentials - and these units require oil of a different specification.
Same process, so I'm not going to go through it here.
The Transfer Case "Fill Plug" is located on the front right of the transfer case. The Transfer Case "drain plug" is located on the bottom of the case. Again, you break loose the fill plug, and then proceed to drain things, then replace drain plug and refill.
Here's my pictorial overview. The Transfer Case utilises just about 3 quarts of GL-4 specification lubricant -- in this case, the RedLine MT-90, which is specifically designed for manual transmissions and transaxles.
Here are a few "orienteering" photos to show the fill and then the drain plugs on the transfer case.
Breaking loose the top-most "fill" plug, and then loosening it by hand.
Then, loosening the drain plug, and proceeding with fluid drain.
Examining the drain plug. Notice the aluminum washer. Since I didn't have any spares on hand (and these are often omitted - I was glad that my G-wagen had them) I re-used them. The close-up of the inside of the drain plug shows the small, embedded magnet.
Replacing the drain plug...
And loosening/removing the fill plug, and pumping new MT-90 into the transfer case.
Here's what things look like, all buttoned up. Ready to rock and roll!
Thanks and regards,
Gerry
After some research on the topic, I determined that I would go with RedLine fluids for the transfer case and the front & rear differentials on my G320. I didn't know what fluids had been installed, and it turns out that it was a good thing that I changed them.
I found good and bad news: the good news being that all fluids appeared to be very fresh and very recently changed. The bad news was that the same gear oil appeared to be used on all three items -- which is bad because the differentials require a different specification (GL-5) gear oil than the transfer case does (GL-4).
Research among experienced G-wagen owners has shown that the RedLine MT-90 (GL-4 spec) and 75W-90 Gear Oil (GL-5) has carried a very good reputation. Both of these oils are "pure synthetic" and are much cheaper (and probably of better quality) than MB's own oils. Furthermore, the GL-4 oil that MB specifies, which is used for the transfer case, is only available in 5-gallon containers, at a price of over $300. Thus, because only three quarts of this oil are used at a time, having to buy 5-gallons is an extremely expensive proposition. The change interval for the transfer case fluid is 60,000 miles, FYI.
Changing the oil in the differentials is exactly like doing it in the rear end of a car: you loosen the top "fill" plug to ensure it can be removed, and then you loosen, remove the bottom drain plug from the differential. Then you drain the diff, and replace the drain plug. Then remove the "fill" plug and pump the specified amount of oil into the differential.
In the case of the front differential on my G320, it was 1.4 liters. For the rear differential, it was 1.8 liters.
Here are some photos outlining the process. I'm not going to caption the photos, as they are fairly self-explanatory given the above description. All plugs for both the differentials and the transfer case use 14mm "hex".
The first few photos are just overviews of the fill and drain plugs. There was a little dampness around the upper fill plug.
Breaking the upper plug loose, and then loosening and removing the lower drain plug in preparation for fluid drain....
Draining the diff, and inspecting the drain plug.
Re-installing and tightening up the drain plug to the requisite 60 Nm of torque.
Fill plug removed, and pumping new RedLine juice into the diff. The rest is a matter of buttoning the diff back up and cleaning things off with a few quick shots of brake cleaner.
The second part of the job is the transfer case. Now, the transfer case on a G-wagen is probably the most important part of the entire drivetrain, and it MUST be taken care of. The transfer case is a large box that is mounted directly aft of the transmission, and is connected to the transmission output shaft via a short drive shaft. The TC also has twin output flanges, one of which leads directly to the forward differential to drive both front wheels, and the other that leads directly to the rear differential to drive both rear wheels.
So, it's a very complicated box, and it is really important that the very best lubricant be used to keep it in good running order. Like I said, the change interval for the TC is 60,000 miles by MB specification. I will shorten this to 50,000 miles just to be on the safe side. The TC drain plug also contains a small magnet to catch metal particles that are in the TC.
One way I could tell that my fluid was fresh (the dark green stuff) was that there was NO metal or other particles on my drain plug magnet - it had probably been cleaned off after the prior fluid was changed. In any case, I was glad to change the fluid since it was the same exact oil that was used in the differentials - and these units require oil of a different specification.
Same process, so I'm not going to go through it here.
The Transfer Case "Fill Plug" is located on the front right of the transfer case. The Transfer Case "drain plug" is located on the bottom of the case. Again, you break loose the fill plug, and then proceed to drain things, then replace drain plug and refill.
Here's my pictorial overview. The Transfer Case utilises just about 3 quarts of GL-4 specification lubricant -- in this case, the RedLine MT-90, which is specifically designed for manual transmissions and transaxles.
Here are a few "orienteering" photos to show the fill and then the drain plugs on the transfer case.
Breaking loose the top-most "fill" plug, and then loosening it by hand.
Then, loosening the drain plug, and proceeding with fluid drain.
Examining the drain plug. Notice the aluminum washer. Since I didn't have any spares on hand (and these are often omitted - I was glad that my G-wagen had them) I re-used them. The close-up of the inside of the drain plug shows the small, embedded magnet.
Replacing the drain plug...
And loosening/removing the fill plug, and pumping new MT-90 into the transfer case.
Here's what things look like, all buttoned up. Ready to rock and roll!
Thanks and regards,
Gerry
