Draining front pumpkin

[KRB64]

Finally getting around to checking/changing fluids in the B-3 for the winter.

My front differential fluid is looking more brownish than it should so I was going to drain and re-fill with 90W but it doesn't have the little drain at the bottom like the rear. Do you just pull out the lower bolt to drain instead? I hate pumping out.

And if I remember correctly, the closed knuckles take 140W right? Isn't there a recessed screw in it to fill with? I couldn't find any references in the manuals last night.

Thanks,

[Charles Talbert]

Knuckles take grease (approximately 3 pounds of NLGI #2 in each one), not oil of any type. If you have oil in the knuckle housings, your inner axle seals have failed, a tear down is required for replacement. The diff housing should have a small 1/8" NPT plug at the bottom of the front side of the housing, it's small & could easily be hidden by dirt, paint, etc. I would search for it, likely it's there. If not you can drill & tap a hole for an 1/8" plug, look at the rear housing plug carefully, drill & thread the front identically. Plugs are easily available, I recommend steel rather than brass or cast. The correct oil for the diff is a premium name brand 80-90 gear lube. A straight 90 grade will not perform well at start up in cold weather.

[KRB64]

Many thanks!
I cleaned/wire brushed the diff and it doesn't have the 1/8" plug like the rear.
Thanks for the tip on grease in the knuckle, don't know where I got the 140W idea.

[KRB64]

The diff housing should have a small 1/8" NPT plug at the bottom of the front side of the housing, it's small & could easily be hidden by dirt, paint, etc. I would search for it, likely it's there. If not you can drill & tap a hole for an 1/8" plug, look at the rear housing plug carefully, drill & thread the front identically. Plugs are easily available, I recommend steel rather than brass or cast.

I see the spot where the plug should be. I'll tap that out as soon as I get a chance. Do I just drill straight into the dif or is it angled? The rear looks to be straight.
Thanks,

[Charles Talbert]

The drain holes are straight through. There isn't a lot of clearance in the immediate hole area from the interior bottom of the housing, it needs to be right in line with the interior surface so the unit can drain completely. As long as you center punch correctly, drill carefully & straight in accordance with the housing angle, all should go smoothly. Remember when you start to tap the threads that they are tapered. Tap carefully & be sure you don't go too deep with the tap. If you go too deep your plug will go in past the outside of the housing before it tightens. The plugs are so short that too deep threads can really be a problem. Tap a little, try the plug, if too shallow, tap a little deeper & try again etc, attention paid here will prevent problems & achieve the perfect plug depth.

[KRB64]

Many thanks, I'll pick up a plug from NAPA today.

[defdes]

Glad I found this posting, it was a bit dark in my shop this eve and the undercarriage is a bit rusty, but it looks as if these npt plugs have an inverted square hole, can anyone confirm that? Would a #3 square driver be the tool if that is the case?

[Charles Talbert]

Glad I found this posting, it was a bit dark in my shop this eve and the undercarriage is a bit rusty, but it looks as if these npt plugs have an inverted square hole, can anyone confirm that? Would a #3 square driver be the tool if that is the case?

1/8" NPT plugs are available with various head or drive designs; so there are any number of designs that could have been used. You'll have to work out removal tool needs in accordance with the type you have.

[defdes]

1/8" NPT plugs are available with various head or drive designs; so there are any number of designs that could have been used. You'll have to work out removal tool needs in accordance with the type you have.

Thanks, yeah... it looks like one of those 5 minute operations that's going to turn into a 2 hour project. The socket looks quite worn and like it hasn't been removed in 20 years, might need to drill it out.

[defdes]

The old gear oil was coming out and standing up like a sand castle, I think it could use a good flush. Could I pour kerosene into the filler hole to loosen any sediment at the bottom up?

[Desoto61]

My concern would be how readily you could get it to evaporate/dry out before adding the new grease. Otherwise it could thin and compromise the new lubricant.

[Charles Talbert]

Clean it out, and check it out

My suggestion would be to pull the unit from the axle housing for a good clean out. It sounds as if there is a lot of debris in that drained oil, perhaps a result of previous component failures or you may well have some failed thrust washers that have broken down and need to be replaced. Any time you see debris such as you describe, it is vital to check out what is going on. If you leave it there, add new oil and continue operation; there is a high likelyhood more costly problems will follow close behind.

[defdes]

Hi Charles, sorry for the confusion, it wasn't debris per se, just very viscous and dark oil which "mounded" as it very slowly flowed out. It wasn't warm in my shop, about 40* which could account for some of the viscosity, but it looked like it could stand a flushing out.

[Charles Talbert]

Hi Charles, sorry for the confusion, it wasn't debris per se, just very viscous and dark oil which "mounded" as it very slowly flowed out. It wasn't warm in my shop, about 40* which could account for some of the viscosity, but it looked like it could stand a flushing out.

Unless you know history for certain; checking and cleaning is still the way to go.

[gmharris]

The differentials are heavy. Be careful if you pull them out. Also, when they go back in, they need to be at exactly the right angle. For both reasons, you will probably need some kind of a transmission jack.