Tips needed for draining Ford 9 inch differential

Early 70’s Ford truck, Ford 9 inch limited slip differential. There’s no drain plug in either the housing or the carrier. I’ve drained it in the past by loosening the bolts that hold the carrier to the housing enough to pop the seal at the bottom, maybe 1/16 inch. The gear oil drains out, then I tighten the bolts and hope it doesn’t leak. So far it hasn’t developed a leak, but the gasket is nearly 50 years old, so I’m doubting my luck holds this time. My plan is to cross my fingers and do it the same way.

Posts on the internet say to remove the axles and the entire carrier, drain it out, and install a new gasket. This would allow for a better drain and clean, but that’s a big job, especially to do from under the truck in a driveway. Others say to drill a hole in the bottom of the housing, then tap it for a 1/2 inch NPT fitting. Sort of worrying to drill the housing though, given it is a structural member. Still others say to pump it out with a suction pump of some sort. Most who say they attempted this say their attempt didn’t work b/c they couldn’t get the suction tube to the bottom, due to the the limited amount of clearance…

Yays or nays to any of the above? Any other ideas to improve my odds of a successful 9 incher drain?

Drill and tap would be my choice. Do it on the rear of the banjo, not the bottom of the housing. It won’t weaken the housing.

??? … not sure what you mean by “banjo”

Why not do it as you been doing but remove the cover and install a new gasket?

I believe I’d do it the way you have been, except I’d remove the gasket and just squirt a bead of black rtv in there instead of the gasket. Use a can of brake clean to clean the mating surfaces real well before putting the rtv bead down.

I don’t have any experience with a 9”, but I’m assuming the mating surfaces are flat. I never use a gasket on differential covers (which I know a 9” does not have, but you’re still sealing the same thing, pretty much).

1 Like

9” is made different. No cover, removable gearset.

It’s between the fiddle and the redneck :joy:

I think he’s talking about what would be the bottom of the cover / inspection plate on a diff that had one.

Re: Why not do it as you been doing but remove the cover and install a new gasket?

I don’t think that’s possible without removing the axles. There isn’t really any cover that’s removable; the front of the third member is the cover. Ford 9 inchers are configured as removable carriers (third members). This is part of what makes them popular for race cars, b/c its fairly easy to reconfigure the vehicles rear axle gear ratios, the decision can be made at the track on race day.

Thank you I did not know that.

Good one. :laughing:

my 2 cents… you got lucky so far with a 50 year old gasket. might be time to do it right and replace it. either by you or a shop. plus you will get all the gunk out that lays on the bottom. also do as Mustangman said for the future.

1 Like

The big round part of the axle housing the ring gear carrier bolts into.

also since you have to pull the axels, change the axel wheel bearings an seals.


Do you have to pull the axles completely, or just slide them out a few inches?

slide them out about 6 inches


Ok, I understand. The thing that looks like a big pumpkin. That’s what I meant by the “housing” as it has the lowest spot I think.

Now that I think about this, I recall I actually removed the carrier about 20 years ago. I didn’t have to entirely remove the axles, just pull them out enough so they came out of the third member side gears. I put the third member in the trunk of my Corolla and drove it to work. A co-worker there has 9 incher expertise b/c he enjoyed building dirt track race cars for a hobby. I didn’t know if the backlash was correct or not, thought it might have too much and that was causing a clunk sound. Took him no more than two minutes of fiddling, he said the backlash was correct. Anyway, when I reinstalled the third member I’m sure I used a new gasket. So the gasket is actually only 20 years old.

Wonder what that carrier weighs? George, can you bench around 200? :stuck_out_tongue_closed_eyes:

Kidding. They make jacks for that. Although I have bench pressed a transfer case or two into place.

How many miles on the gear oil? If under 50k and the clutches aren’t grabbing or chattering…I might skip it if you don’t put many miles on it, honestly.

It has under 50K since I last removed the carrier, but the clutches are definitely grabbing, which is what is motivating me to do a drain and fill and adding some new slipperiness modifier.

OMG! It was really a challenge last time I did it. I used a jack to help get it out of course. Still, it’s not an easy thing to do, first b/c it isn’t easy to find a balance point to place the jack at, and second it is covered by about the most slippery stuff imaginable, so it is very hard to grab hold of enough to steady. It was definitely one of my three-stooges moments … lol …


Plus, you get to enjoy that funky gear oil aroma. I took a bath in it when I changed the oil in my dad’s 1950 Chevy truck as a teen. Mmmm…1950’s gear oil! Gear oil smell has kind of made me a little nauseous ever since !


The aroma of the gear oil is bad enough, but that slipperiness modifier is even worse.

Last time I removed the carrier, I recall I now that I also replaced the clutches while the third member was out. So hopefully just a drain a refill will do the job.