Changing rear diff fluid.

[kaw550]

I am in the process of swapping the rear springs. I decided it would be a good time to change the fluid in the rear differential.

How hard is it to remove the third member to drain the fluid? Do I just unbolt it and pull it forward? Is the install the same?


I am also considering drilling out the housing to add a drain under the back of the cover or under the diff.


Any thoughts

 

[vintage bronco]

First off you have to pull the axles then unbolt the third member then slide it out, keep in mind you need a new gasket and its a good idea to get new copper washers for under the nuts holding the third member in.

 

[Steve83]

You can buy a siphon pump to remove the old fluid without any disassembly, but unless it's more than 10yrs old or you KNOW it's contaminated, there's no reason to change it.

If you decide to pull the 3rd member, it would be a good idea to add a drain plug. Either weld a bung into the housing, or buy a drain plug kit, or drill/tap the 3rd member. If you weld or tap, I recommend a fill plug from an '87-up 8.8" axle since it has a magnet.

.

 

[Zillacon]

Since the oil sits a little lower in the housing I welded in a 1/2" NPT pipe coupling cut down, ordered up a magnetic plug and then welded on a 1/4" thick mini skid plate to protect it from rocks on the trail.

 

[fungus]

Since the oil sits a little lower in the housing I welded in a 1/2" NPT pipe coupling cut down, ordered up a magnetic plug and then welded on a 1/4" thick mini skid plate to protect it from rocks on the trail.

I like it. Looks clean and very functional!

 

[kaw550]

Putting a drain on the bottom ay be over kill for me. I dont drive the truck that much and never go offroad.

I did find the thread where I had seen the back of the housing drilled.
Does the third member need to be out to do this?
http://classicbroncos.com/forums/showthread.php?t=154396&page=2

 

[Steve83]

Yes, any drain mod will require the chunk to come out.

 

[sriha]

Good pictures. I just took my 3rd member out today. Was defeated until I read about removing the brass/copper washers. After they were off then it popped out easily. Glad this thread came up. I ratchet strapped the 3rd member to my floor jack so the jack did the lifting and I just guided and pulled it out. Beats bench pressing and getting gear lube all over you.

 

[kaw550]

What's involved with removing the axles?
I assume I would need to change the rear axle seals after???

Right now I have the leaf springs are removed and the rear end sitting on jack stands. It is the time to do it but I really dont want to open a can of worms.

 

[DirtDonk]

You pull the drums, un-bolt the four bolts you can see through the holes in the axle flange. Then yank.
Sometimes they yank back, but you'll get 'em out. Sometimes they don't fight at all and pop right out.

Don't necessarily have to change the seals. As long as you're careful not to just drag the shaft across it all the way out, you should be good.
That said, it's not a bad idea to closely inspect them for wear, and the bearings too. They don't live forever, and now's the time...

Paul

 

[Bartonatl]

See recent post "rear axle seals" with pics and possible pit-falls. Changing the axle seals and bearings was not bad, inexpensive and like Dirtdonk said...now's the time. of course, this always happens. You were just changing the springs....then the diff. fluid, then add a drain, then the axle seals and bearings...etc..etc. There is so much that can be done. Careful what you start because that leads to other stuff. I had one leaky axle seal which lead to pulling both axles, changing bearings and brakes jobs. It will be nice when I get done , but remember when you choose one job it will lead to three others. Why?....because now's the time.

 

[broncotime]

You can buy a siphon pump to remove the old fluid without any disassembly, but unless it's more than 10yrs old or you KNOW it's contaminated, there's no reason to change it.

I bought one of these:

http://www.costco.com/Browse/Produc...ang=en-US&Sp=C&ec=BC-EC22577-Cat21277&topnav=

I have changed the front and rear differential fluid on both my broncos and it is much quicker than pulling the cover (or third member out) and cleaning everything off and resealing. It's a little slow, but I found if you apply some heat (I use a hot air blower) to the bottom of the case, it loosens the gear oil up a little. In any event, I use this gadget all the time for oil changes also (I have a couple of VW's that my wife and daughter drive and there's a cover over the drain plug underneath so this also saves a ton of time there as well). If you don't need to get inside to fix or inspect something, I'd go this route.

Good luck.

 

[trailpsycho]

Since the oil sits a little lower in the housing I welded in a 1/2" NPT pipe coupling cut down, ordered up a magnetic plug and then welded on a 1/4" thick mini skid plate to protect it from rocks on the trail.

NICE! Very clean. Hindsight, I should have done it this way.

I used a few large washers-because I had them on hand...drilled for the tap, welded one sized washer to create increased thread-space, then a larger washer outside of the tapped hole to pretect the plug. Works great, seals great...looks sort of like a pimple on the ass-cheek of my housing. Jack up the Pass side to get to the last drop...works good, provide protection and functional.

BUT, I really like the skid-plate idea that you did there. Very cool and nice welds!

 

[Maverick1701]

IIRC cant you pull the 3rd member forward just a little (enough for the fluid to drain out) w/the axles still in place?
I pulled the nuts but I cant break the third member free to pull it forward (just a little) to dran all the fluid out...any tips?

eventually Im going to add a drain plug too but not this time.

 

[DirtDonk]

Yep, you can do that too. I've done it and it works well, but won't get the last bit of gunk out of the bottom. Not a deal-breaker, but not the best way.

Your stuck 3rd member might just be the washers as was mentioned above. Can be the gasket seal as well of course, but the washers do their mechanical-lock thing pretty well.
Make sure all the washers are off the studs, everything is clean and free of burrs or bent studs or buggered threads, and if that doesn't quite do it, take a very small flathead screwdriver or whatever (scraper? putty knife?) and gently slip it in the gap there. I like to do it up top just in case I do manage to score the sealing surface. I figure that way it's less likely to ever be the cause of a leak.
So far I've never marred the mating surfaces, but it looks like a gouge waiting to happen to me.

Good luck.

Paul

 

[needabronco]

If you buy a cheap $2.99 fluid pump (the kind that goes on the quart bottle) you can hook the flexible line to the spout and pump, it'll suck the fluid out (at least mine does), I've used mine on several customer rigs and can litterally change fluid in both diff's in about 30 minutes..

HOWEVER if you have never pulled the 3rd member out or don't think the PO did either, it's a good idea to pull it now and clean all the soupy gunk out of the bottom of the housing. After that your good to just suck it out...

A drain plug will cost you about $5 and maybe $15 for the tap, and then you can easily change fluid anytime.

 

[armynavy17]

Instead of drilling through the bottom of the case and creating something to get ripped off on a rock, you could just knock one or two of the lowest studs out and tap them. Then replace the studs with bolts and its easy to drain and no more likely to spill all of your diff fluid on the trail than before.

 

[DirtDonk]

Now that right there is a stupendous idea. You done it? Does it work well?
And I wonder if you did the same to one near the top, if the drain speed would be faster, with the air "vent" at the top?

Paul

 

[Skiddy]

Now that right there is a stupendous idea. You done it? Does it work well?
And I wonder if you did the same to one near the top, if the drain speed would be faster, with the air "vent" at the top?

Paul

neat idea, i would be afraid the third member would leak though. hmmm but i guess you could use a bolt instead of a plug

 

[DirtDonk]

Yeah, that's what he's referring to anyway. Just replace the stud with a bolt (after threading the housing) if there's enough material for threads. Which there should be I would think.
The leaking is still a legitimate concern though. Maybe though, if you just make sure you continue to use the copper (or brass?) washers, they would still continue to seal enough to avoid any real issues.
I hate leaks, but would probably be willing to try this next time I'm in there anyway.

Paul