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Driveline service by Bulldog and Atrac

Servicing the driveline is very similar for all platforms. This write up was done using the 4Runner V6 and V8 as examples. Differantial and transfer case fluid change was done and driveshafts were greased. Please remember the 2WD models DO NOT have front differential and transfer case, the driveshaft is also sealed and can not be serviced.

Tools and supplies required:

  • 24mm socket for rear diff and transfer case plugs
  • 10mm hex “key” (socket) for front diff plugs
  • Breaker bar for first time service (plugs can be very tight)
  • 2 Grease guns with flexible hoses and universal tips
  • Large drain pan
  • Lots of cheap terry towels (it can get messy)
  • Gear oil pump for easy final filling
  • Gear Oil (80W-90 for diffs (4.5 qts) and 75W-90 for transfer case (1.5qt)) ( I use 6 qts of Mobil1 75W-90 for all)
  • NLGI #2 Molybdenum Disulfide Lithium Based Grease for slip joints (Refer to manual to validate)
  • NLGI #2 Lithium Base Grease for U-Joints (Again refer to manual, I use Mobil 1 grease as it is pink)
  • Good supply of latex gloves to keep grease and oil of your hands
  • General tools
  • First drive around for a couple of miles to heat up fluids for easier draining, good time to go get those supplies or tools you need. Park on level surface with ample room to move. If the vehicle is not lifted it might be a tight squeeze, you can put it on 4 stands or a lift (however make sure it is level).

    Drain the rear diff first. First loosen the fill plug (blue circle) using 24mm socket, then position the drain pan under diff. Then undo drain plug (red circle also 24mm). Once the drain plug is completely removed, remove the fill plug. This way you can regulate the flow somewhat, but it can also lead to the oil squirting out. If you want you can catch some fluid in a cup to inspect or have analyzed.

    Replace rear diff drain plug and torque 36lb/ft (factory spec). Then add new oil. The rear diff takes about 3 qts, so squeeze the oil in with the bottles first. Then add the remaining fluid with a gear oil pump, which can be bought at auto stores and is normally by the gear oils itself. Keep filling till some oil comes out of the fill hole, so it is a good idea to keep the drain pan in place. Remove oil pump tube (be careful it tends to spill oil). Check fluid level with you finger, the ideal is for it to be slightly below fill plug hole. Screw fill plug back in and torque 36 lb/ft. I didn’t replace the crush washers on the plugs, probably a good idea after a few changes.

    Now do the transfer case. Use the same procedure as with the rear diff. It also uses 24mm sockets. Drain plug is marked with red circle and fill plug with blue circle. The torque spec for the transfer case is 27 lb/ft for both plugs. Be careful while draining as the drain plug is on the side and the oil can spout quite far.

    Undo the rear portion of the front skidplate, by removing the 4 retainer bolts and pushing it backwards for the rear bracket to unhook from the frame.

    Clean the hex plugs before using the 10mm Hex sockets to remove the plugs. Again use the same procedure as with the rear diff. Drain red and fill blue. There is also a fill plug on the front of the diff, but it is difficult to get to without removing the front portion of the skid plate, so I just used the side plug.

    Now you are done with the diffs and transfer case. Do not put the skid plate back yet. Below is some of the old rear diff oil in a cup. Also on the paper is some dabs of the fluids. In order left to right top to bottom, V8 rear, V8 transfer, V8 front diff, V6 rear, V6 transfer. The V8 had 20k miles on the fluids (all Mobil 1), as can be seen the rear diff takes the most beating on the V8 even with full time AWD. On the V6 the front diff and transfer case will do even less than the V8.

    Time to grease the driveshafts. Start with the front first. V6 owners will be lucky as you can move the front driveshaft by hand as it is disconnected. Position the driveshaft so you can clearly see the grease zerks. Clean the properly before applying the grease gun to it. The V6 crossflow pipe has a heat shield above it to protect the driveshaft, this only makes the task slightly more difficult. On the V8 you will have to undo the e-brake and put the transmission in neutral. Then move the vehicle by pushing on a wheel, it is a lot easier to control the movement while looking under the vehicle (Be careful if the vehicle is on the ground and not on a lift or stands).

    The blue zerk is for the slipjoint (apply moly grease to it) and the green the U-joint (normal Lithium grease). There is 3 zerks on each drive shaft (front and rear) (one slipjoint by transfer case side and 2 U-joints). On the U-joint keep pumping grease till you can see the new grease coming out of the u_joint then wipe clean all the excess grease. This is why I like the pink Mobil 1 grease as it is easy to spot.

    On the slip joint be careful not to over grease and only give it 3-5 good pump with the grease gun. If you notice the slip joint pushing out on the driveshaft, undo the zerk and put pressure on the vehicle to pump some excess grease out. This is not a problem if you only add 3-5 pumps with a large grease gun.

    Put back the front skidplate and you are done.