I've got a 61 f100 and just notice that the rearend is starting to leak.. I have no experience in the area and want to find out:

How timely and expensive it is to replace the gasket?

How do you replace the fluid that you lose and how do u tell when its getting low?

Would this be the cause of a thud that i would hear occasionally when stopping?

Thanks in advance
Any help would be appreciated

 

Don't know about the thud, could be lots of things including loose gears, an axle that isn't tied down tight, loose springs, loose brake shoes, shocks etc.

Depending on the differential, there are two ways of removing the fluid.

RULE #1 if you have to jack up your truck, use jack stands. I learned this the hard way, ruined a pair of my best undies.

Most of the diffs have a coverplate and gasket. This is usually easy to remove but a PITA to clean and put a new gasket on, not hard, just a PITA. What I do is get a wide drain pan and have it handy. Then I loosen the lower bolts on the cover almost all the way and the upper bolts just part way. Then you will probably need a wide flat screww driver or better yet a flat chisle or one of those painters handy dandy tools to pop open paint cans. Use the tool at the bottom of the pan and try to loosen the cover from the differntial, try not to bend the sheet metal as you do this. You might need a rubber mallet to get started. If you do this right, the bottom of the cover will pop open and the oil will drain out the bottom. If you do it wrong, not so bad but you may have a mess since the oil may come out the sides.

Once the cover is off, clean off all the grease and wire brush or scrape all the gasket material off the cover and the differential. Try not to get too much crap inside the diff. Use your finger or rag to scoop out as much oil as you can from inside the diff. Take a look at the magnet if you have one to see what kind of metal is sticking to it. Should just see a grey fuzz, any chunks bigger than a grain of rice may be bad. Look at the gear surfaces and teeth to make sure they are smooth and there is an even shiney patch in the middle of each tooth. Look at the fluid in the pan to see if there are any chunks.

Once you are clean and satisifed that nothing is wrong, get a good gasket sealer and glue the gasket to the cover and let it set. Put some sealer on the other side of the gasket or on the differential sealing surfaces, which ever is easier and less messy for you. Put the cover on and torque it up, I think most bolts take about 25 foot pounds or so, or hand wrench tight but not gorilla strength. Tighten in kind of a opposite side circular pattern, ie don't tighten bolts right next to each other, try to spread the pressure around.

I like to let the cover sit over night to set up. Then there should be a plug on the side of the diff housing in front of the axle above the centerline of the axle, that has a square hole in it, or maybe a hex bolt head. Use either the square extention on a ratchet or hex socket to remove the plug. Get yourself a pump and pump in 2 or 3 quarts or more of fluid, depnds on your truck. You will build up muscles while doing this part. You might need limited slip additive, depends again. Put fluid in until it starts to dribble out of the fill hole.

Put the plug back in, take it for a drive. I like to do some figure 8s in a parking lot to spread things around. Come back home and pull the plug and stick your pinky in there, you should be able to feel the fluid within half an inch of the hole.

If you have the other kind of axle, the whole job is much easier. there will be a fill plug, like above and a drain plug at the bottom.

An easy job, should take maybe an hour or two if you take it easy and inspect things. BTW while you are under the truck is a good time to crawl around and look for loose or missing things, wiggle stuff, check your parking brake cable etc.

Good Luck,

Jim Henderson

 

 

Thanks alot... very helpful. I'll start working my way to the rear end next week.

I'll let you know how it turns out.