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1971 F100, flatbed, been used hard. I want to do this because I just got the truck and WOW, it's been an amazing, OMG bonanza of jury rigged repairs. It now starts and stops and I just want to make sure it has fluids, etc, before launching into any serious work. I am leaning towards either just drilling and tapping a small drain plug somewhere near the bottom of the diff, or possibly even welding a bung to the housing. The truck is currently a roadblock in the shop and I can't tie up much more time before someone drags it out - kidding but I AM inconviencing other folks.
At this point I either just top it off or manage a quick drain install.
Best location? Specifics tips for just drill and tap? Can I weld a bung with the oil still in it? Are there weld on kits specifically for 9"ers?
I added one to mine. The housing is thin like 1/8"-3/16" which is not enough meat to put in a large drain plug. Gear oil is heavy and does not flow real well so you want to use a large plug. I would recommend a min of 3/8" NPT, 1/2" NPT better. They sell drain/plug kits for this to weld in. I made my own using o-ring seal, so I don't get any seepage when using Syn gear oil. I used the 1 on the right. Requires a pin spanner to remove as less as loosen the allen locking set screw.
I ended up with a *******ized 9" unit myself
I removed my pumpkin and drilled and tapped the 9" case where a factory fill plug would have been
I then installed a pipe plug in the tapped hole
Some previous owner Yofus blew up my rear end and left all the chunks in the axle tubes
I had to pull an axle out to check it for gear oil, found the chunks and decided to remove the carrier
Wish they had a drain plug but I don’t have a welding outfit.
Bought a cheap “fluid extractor” off amazon, I’ll be doing my own gear oil changes from now on.
You can always pull an axle. Use a cheap HF hand pump and some hose to suck out as much as you can, then fill it back up. Most units hold 1.5 to 2 quarts.
