Ranger-Forums - The Ultimate Ford Ranger Resource - How To: Change Rear Differential Fluids

Written By: dixie_boysles

Discalimer: Neither I nor this site takes any responsibility in any damage or actions resulting from this . When performing this, you are doing so at your own risk

In this how-to I will be showing you my method to replacing the gear oil in your rear differential. There may be other ways, but this is the way that I found best. This was for my 04' Lariat with 3.73 Limit Slip. The same steps go for a Ranger.

Materials needed:

- Gear Oil ( quantity and specs manual calls for)
- 1 Tube of TransX Friction Modifier (for people with limited slip only!!!)
- 1 tube of RTV Sealant (The gray kind if possible)
- 1 Can of brake cleaner
- Old Rags

Tools Needed:

- 3/8" Drive Ratchet
- 1/2" Socket
- Extension
- 1/2" wrench if needed
- razor blade or gasket scraper
- Hammer
- Oil Drain pan

Tips:

- Wear old cloths as you dont want gear oil or rtv sealant on you
- I wore medical gloves to keep the smelly gear oil off my hands (that stuff stinks)
- you should always loosen the fill plug before you start the job to make sure the plug will come out. You'll be in a tough situation if you pull the pan, drain the fluid, re-install the pan then find out you can't get the fill plug out.

Procedure:

Gather Materials:

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Put truck in park and apply brake. Place Oil catch pan under rear differential

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Using the 1/2" Ratchet or Wrench, start loosening all of the bolts

I took them all out but the top Two, used them to hold the cover so it wouldnt fall for the next step.

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Once that is done, it's time to break the seal. Using a combination of the screw driver and the hammer, try to pry away the bottom of the cover from the axle. dont force too much in one area.

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Then oil should start to drain

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When it drain all the oil then go ahead and remove the remaining two top bolts.

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Use the razor blade to clean both mating surfaces on the axle and cover

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Use brake cleaner to clean the gears and the back of the diff cover

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Once both surfaces are clean, apply RTV sealant around all the holes and a good solid bead around the perimeter of the cover

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Put cover on and hand tighten all the bolts, let RTV dry for an hour then tighten completely using a cross bolt pattern similar to tightening lugs for wheels.

Using the 3/8" drive ratchet, loosen oil drain plug

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Once loose, begin filling. I mixed my friction modifier with a qrt before putting it in. fill until the oil is level with the fill hole. Plug the hole. Done.