Trail Maintenance: Driveline fluids, how and when to change them

The topic of oil in vehicles is the easiest way to spark a debate on the internet in the gear head world. To be honest I am not sure how, when or why this trigger developed, but I can say that it ultimately causes a lot of confusion on which fluids to use where and when to change them.

Having done an extensive amount of research on the subject of driveline lubrication for these 4Runners, I want to share what I have found and the regimen that I follow.

Note: These are my recommendations, and ultimately you should refer to the owners manual, or your local mechanic for exact specifications to suit your individual conditions.

Parts required

Crush Washers:

• Front axle: Toyota #90430-24003 (drain), Toyota #12157-10010 (fill)
  • 10mm hex bit socket (drain & fill)
  • Torque specs: 48 ft•lbf (drain) / 29 ft•lbf (fill)
• Transfer case: Toyota #90430-A0003 (drain & fill)
  • 24mm 6-point socket (drain & fill)
  • Torque specs: 27 ft•lbf (drain & fill)
• Rear axle: Toyota #12157-10010 (drain & fill)
  • 24mm 6-point socket (drain & fill)
  • Torque specs: 36 ft•lbf (drain & fill)

Gear Oil (as recommended by Toyota):

• Front axle: Toyota Genuine differential gear oil LT 75W-85 GL-5 or equivalent
  • 1.6 / 1.5 U.S. quarts (part-time 4wd / full-time 4wd)
• Transfer case: Toyota Genuine Transfer gear oil LF or equivalent SAE 75w
  • 1.1 / 1.5 U.S. quarts (part-time 4wd / full-time 4wd)
• Rear axle: Toyota Genuine differential gear oil LT 75W-85 GL-5 or equivalent
  • 2.9 / 2.8 U.S. quarts (with locker / without locker)

Service intervals (as recommended by Toyota):

• Differentials: 15,000 miles when heavily loaded, or with roof-mounted gear
• Transfer case: 30,000 miles when driving dirty or dusty roads

Both of those intervals assume that the vehicle is under those conditions constantly. Toyota recommends that under “standard conditions” fluids be replaced as needed based on levels and color. My personal regimen is to replace all driveline fluids at 30,000 miles. This is a reasonable interval for the weekend warrior to keep their driveline healthy.

Other items for driveline service:

• Shop towels
• Nitrile gloves
• Torque wrench
• Quart bottle fluid pump
• Degreasing fluid
• Oil drain pan/container

Differential gear oil options

Gear oil in differentials is a pretty straightforward choice. Stick with the manufacturer weights, and required additives and you’re home-free. For the 4Runner, Toyota recommends using 75w-85 GL-5 gear oil in both the front and rear differentials. Unfortunately, the options for this specific weight are limited including OEM and some third party products. For this reason, many DIYers will use a more widely available 75w-90 GL-5 gear oil as it easier to find in-store and is generally cheaper. This substitute is very heavily discussed on a number of online forums. To summarize, it’s a very popular swap and over the seemingly thousands of posts that I have read through there hasn’t been a differential failure that was pinned directly on the misuse of gear oil weights for the 4Runner. When choosing your gear oil (regardless of weight), be sure to use a full synthetic gear oil for optimal protection against wear.

Transfer case gear oil options

Here is where Toyota makes things more difficult, and where the controversy begins.

Toyota specifies their Genuine Transfer gear oil SAE 75w or equivalent as a proper fluid for the transfer case. The problem is that this weight of oil is very uncommon. So uncommon that the only 75w options available are the original OEM fluid, and Ravenol’s SAE 75w manual transmission fluid. To make things more interesting, Redline specifies that their 75w-85 is a substitute for SAE 75w weight oils (matching OEM specs). The one big caveat to these options, are that neither of them are a direct match for the OEM fluid. The reason for this is that Toyota hasn’t disclosed the formula for their 75w transfer gear oil, so third party companies haven’t been able to create an equivalent oil matching Toyota’s specs.

[Edit 12/28/2018]: Royal Purple Synchromax Manual Transmission Fluid is also recommended by Royal Purple as a suitable replacement for the Toyota Genuine Transfer gear oil. They also have a guarantee that states any defects or problems caused directly by the use of their recommended product will be covered for repair by Royal Purple.

To try to sort things out, forum members have contacted Redline directly asking for a recommendation on Toyota transfer case fluids. They consistently respond stating that they don’t have a recommendation because they don’t have access to Toyota’s specifications. In addition, the Ravenol fluid has been compared directly to the OEM fluid by submitting virgin samples to Blackstone Labs. The results showed a similar composition, however, the Toyota brand fluid contained a number of additives that supposedly are designed to help protect the specific transfer case components from excessive wear.

[Edit 10/2020]: Red Line Oil has developed a new fluid that is a direct replacement for the Toyota Genuine Transfer Gear Oil LF 75w. I contacted Red Line directly to ask them for an updated recommendation, and they state that the new MT-LV 70W/75W GL-4 Gear Oil is a direct replacement for the OEM fluid. I wouldn’t hesitate to use this fluid in your transfer case if you prefer their product.

Click here for the Red Line MT-LV 70w/75w GL-4 Gear Oil product page

Why the great debate? Why not go with the Toyota fluid? The biggest factors are cost and availability. Toyota Genuine SAE 75w Transfer gear oil is notoriously hard to find, and by comparison very expensive. When asked, some dealers can’t order the fluid directly. Thankfully online distributors make purchasing the Toyota fluid easier, and a bit more affordable. Most costs range from $60 to $90 per 1 liter can, depending on shipping and source. This is much more expensive than third-party alternatives which is why many people stray from the OEM “liquid gold” when changing their fluids.

There is one more alternative to add to this mix. It’s well documented that another popular fluid replacement for the 4Runner transfer case is the easy to find 75w90 GL-5 weight gear oil. Many have used this weight with no issues that have been a direct result of improper fluid weight. I personally used Redline 75w90 in my transfer case for approximately 30 thousand miles without any negative side effects. When researching the subject keep in mind that while some will tell you on a forum thread “if you use fluid other than the Toyota specified gear oil your transfer case will blow up”, there aren’t any specific examples of a transfer case failing due to improper fluid.

The Bottom Line

Depending on your specific usage, your intervals for changing transfer case gear oil will range from approximately 30 to 60 thousand miles. For that service interval, the cost of purchasing the more expensive Toyota fluid is worth it. Knowing that it’s exactly what the transfer case needs to perform at its peak makes the initial price easier to swallow.

Plug locations

Changing your fluids

Changing gear oil in these 4Runners is a very simple process. I will run through that process first, followed by some tips for the individual housings to make the fluid change easy!

Before changing the fluids, take a 5-10 mile drive to warm up all of the fluids in the drivetrain. Warm oil is less viscous and will drain quicker and more completely.

Draining

Both axles and the transfer case have a drain plug, and a fill plug. Each one of the plugs have their own crush washer (see the beginning of the article to see which one goes where).

To drain the fluid remove the fill plug, and after placing a receptacle under the housing, remove the drain plug. Removing the fill plug first will allow the fluid to drain freely and quickly. Let the fluid fully drain.

All of the drain plugs have a magnets that collects any metallic debris in the oil. These need to be inspected for any large chunks, and wiped clean during every fluid change. Some “metallic paste” is normal to see between fluid changes, so fear not if you have some to wipe off. Reinstall the drain plug along with the appropriate crush washer and torque to spec.

Filling

The fill capacities are simply as much as the individual housing will hold before coming out of the fill hole (actual specs above). You’ll want to fill them on level ground using a hand pump and a tube to keep spills to a minimum. When fluid begins to drip out of the fill hole, give an extra couple of pumps when you remove the tube. Let the excess spill out until it stops. Reinstall the fill plug along with the appropriate crush washer and torque to spec. Clean all of your housings with a good degreaser to keep an eye on possible leaks.

Front differential tips:

• Remove the skid plate first, providing easier access to the differential.
• Before reinstalling the skid plate, drive for about an hour and let it sit overnight to check for potential leaks.
• Make sure you have a few socket extensions on hand. It’s a tricky spot to work in, find the best combination based on your tools.

Transfer case tips:

• Use an old-fashioned can opener to open your Toyota gear oil can (if chosen). One with a pointed end. Then use your hand pump to pump directly from the can.

Rear differential tips:

• Remove the spare tire first to give you extra space while servicing the rear differential.
• Check your stock or aftermarket differential breathers while you’re under there to make sure they’re functioning properly.

Enjoy the miles you put on your 4Runner by making sure that it’s healthy and ready for the next adventure!