Changing rear diff oil (on my 60 and 79 4x4 plow truck)

[Zack1978]

Hey everyone,
I want to change the rear diff oil on my 87 fj60 and my 1979 4x4 Toyota 4x4 pu. I have never done a diff oil change before, so I need some help. Is it as simple as taking the drain plug out and letting it drain, then filling it by the filler plug? I guess I need to buy a pump to get the oil in the filler plug? Do I fill it till oil runs out the filler plug? On the plow truck the drain and fill plug is 24mm, is it the same on the 60? Any help or tips would be great.


Thank you,
Zack

 

[magFJ60]

I just changed the front and rear diff oil on my 85 fj60 today. Yes, it is as simple as removing the drain plug, letting it drain, replace drain plug, remove fill plug, fill until fluid comes out of the fill hole, then replace fill plug. Check the used oil to see if there is any debris. A pump helps to fill the diffs, but I just used the 1 quart bottles and poured as much in as I could and then used a large syringe to fill when the bottles wouldnt work anymore. Its hard to get a good angle with the oil bottle, so the syringe helped alot.

The drain and fill plug on my front diff were both 24 mm...on the rear diff, the drain plug was 24 mm and the fill plug was 18mm (I think the original plug was replaced).

PS - Does anyone know what grayish color diff fluid means? My front was gray and kind of milky, but the rear was still pretty clean.

 

[lovetoski]

Hey everyone,
I want to change the rear diff oil on my 87 fj60 and my 1979 4x4 Toyota 4x4 pu. I have never done a diff oil change before, so I need some help. Is it as simple as taking the drain plug out and letting it drain, then filling it by the filler plug? I guess I need to buy a pump to get the oil in the filler plug? Do I fill it till oil runs out the filler plug? On the plow truck the drain and fill plug is 24mm, is it the same on the 60? Any help or tips would be great.


Thank you,
Zack

You got it straight Zack. One thing though - please remember to remove the fill plug first. You don't want to drain the diff unless you are sure you can refill it. If the fill plug is frozen, there are ways to remove it. A search will show you this is a problem from time to time.

If your fill plugs are a little rounded, or rough, a bit of fine sand rubbed on them will help with grip when you go to loosen them.

One more thing - use a 6 point socket. 12 point is more likely to slip and round the plug.

 

[lovetoski]

PS - Does anyone know what grayish color diff fluid means? My front was gray and kind of milky, but the rear was still pretty clean.

This might not be good. There is an inner axle seal that separates the grease in the knuckle from the oil in the diff. The seal eventually fails and the two contaminate each other. Almost all higher milage cruisers have not had this done by the first or second owner...

One thing to check is to remove the square plug on the front top of the knuckle. Then fish a long zip tie down into the knuckle housing. (Don't drop it in there!) What comes out should be thick grease. If it's runny, then the gear oil has contaminated it, and the inner seal has failed.

When this happens, you need to do a front axle rebuild. It's not hard, but is time consuming. Parts are a few hundred. Paying somebody to do this job is $600-1200 per side.

You can usually put this off for awhile...but not too long. Do a search for front axle rebuild or knuckle rebuild or birf rebuild. Lots of posts...

 

[Zack1978]

You got it straight Zack. One thing though - please remember to remove the fill plug first. You don't want to drain the diff unless you are sure you can refill it. If the fill plug is frozen, there are ways to remove it. A search will show you this is a problem from time to time.

If your fill plugs are a little rounded, or rough, a bit of fine sand rubbed on them will help with grip when you go to loosen them.

One more thing - use a 6 point socket. 12 point is more likely to slip and round the plug.

On the plow truck I cracked both lose, for the reason you mentioned above. I was amazed that they both broke free, the oil has NEVER been changed in that truck. It only has 37,000 miles on it but I thin it's time for a change. I will try to see if they will break free on the 60 in the morning.

If it is frozen, how do I get it opened? Or what do I search under?

Thanks,
Zack

 

[PAFJ]

Does anyone know what grayish color diff fluid means? My front was gray and kind of milky, but the rear was still pretty clean

Yeah I just did mine too, front was milky. It seemed to take more then the recommended amount of oil to fill it up to. Time for a knuckel rebuild.

 

[magFJ60]

This might not be good. There is an inner axle seal that separates the grease in the knuckle from the oil in the diff. The seal eventually fails and the two contaminate each other. Almost all higher milage cruisers have not had this done by the first or second owner...

One thing to check is to remove the square plug on the front top of the knuckle. Then fish a long zip tie down into the knuckle housing. (Don't drop it in there!) What comes out should be thick grease. If it's runny, then the gear oil has contaminated it, and the inner seal has failed.

When this happens, you need to do a front axle rebuild. It's not hard, but is time consuming. Parts are a few hundred. Paying somebody to do this job is $600-1200 per side.

You can usually put this off for awhile...but not too long. Do a search for front axle rebuild or knuckle rebuild or birf rebuild. Lots of posts...

I had both sides of the front axle rebuilt about a year ago. This is the first time I've changed the diff fluid since then, but I've been through some water since that time too. I'll do what you suggested with the zip tie and check the grease.

Thanks

 

[zcruiser]

Good stuff! I'm planning to change my diff fluid soon, so will be good to know what to look for...

Hey, Zack, with all this good help here, and 372 posts, you need a star!!!