Rear end drain plug stuck, could i fill it through the vent?

DarkknightGT · Sep 15, 2024

So when changing my differential gasket I made the discovery in place of my 8.8 was a 7.5 rear differential out of a 98 v6 mustang. Car is a daily so while I was a bit peeved I got the wrong gasket, I order another and snagged it. Long story short I tried to take the fill plug off and ended up stripping it. I know I'll need to get it off at some point, but I have been doing a bit of reading that you can fill it through the vent tube on the axle because it goes to the differential. Is this true? I'll still get the fill plug off I just wanna see if I can do that just to get 2 quarts of gear oil in the 7.5 so I can drive the thing again. Any help is appreciated. Thanks for looking

cobrajeff96 · Sep 16, 2024

Yes, you can. It'll just take you a long time. But be careful, you can overfill it this way especially since the fill plug can't be opened until you fix it.

My advice, buy a steel hex spacer tube, weld it to the fill plug (carefully). After a few minutes, take a propane torch to the fill plug as best you can for about 20 seconds, then unwind it.

DarkknightGT · Sep 16, 2024

cobrajeff96 said:
Yes, you can. It'll just take you a long time. But be careful, you can overfill it this way especially since the fill plug can't be opened until you fix it.

My advice, buy a steel hex spacer tube, weld it to the fill plug (carefully). After a few minutes, take a propane torch to the fill plug as best you can for about 20 seconds, then unwind it.

Sweet! I have the car already all buttoned up, I did it backwards, should have seen about taking the fill plug off FIRST instead of the other way around. First time jitters I guess lol, but I will definitely keep that in mind. I work at a parts store so I'm gonna see about getting a replacement and just using an extractor. Unfortunately don't have access to a welder at the moment. But that isn't a very bad idea.

DarkknightGT · Sep 16, 2024

cobrajeff96 said:
Yes, you can. It'll just take you a long time. But be careful, you can overfill it this way especially since the fill plug can't be opened until you fix it.

My advice, buy a steel hex spacer tube, weld it to the fill plug (carefully). After a few minutes, take a propane torch to the fill plug as best you can for about 20 seconds, then unwind it.

Also, would 2 quarts of 80w90 be enough? It's an open diff so no trac-loc (unfortunately) don't wanna overfill this thing

shovel · Sep 16, 2024

I've heard tales of people just putting ziploc bags full of oil into axles when they couldn't fill through the fill plug. Never done it myself but if you need ideas there's one.

cobrajeff96 · Sep 16, 2024

It's really not that big of a deal if you overfill. The excess usually just pukes out of the vent as vaporized oil. But then yea it kind of gunks up your rear bumper and tail lights until you wash it all off. Been a long time since I ran with a SRA but I seem to remember it taking more than just a couple quarts.

RAU03MACH · Sep 16, 2024

id be looking for an 8.8 rear end

cobrajeff96 · Sep 16, 2024

I do have one up for grabs, but alas it is in Germany at this time.

DarkknightGT · Sep 17, 2024

cobrajeff96 said:
It's really not that big of a deal if you overfill. The excess usually just pukes out of the vent as vaporized oil. But then yea it kind of gunks up your rear bumper and tail lights until you wash it all off. Been a long time since I ran with a SRA but I seem to remember it taking more than just a couple quarts.

True that. Tried a bolt extractor and unfortunately didn't work. I'm at a loss right now

cobrajeff96 · Sep 17, 2024

Clean it with brake clean or acetone, take it to a shop and have them (carefully) weld a nut onto the plug but not to the housing. I think it'd be difficult for a weld to actually stick to that iron axle but you never know. Or weld a bolt to the plug and that might work better actually, the hex head facing out of course. That should stand it off enough for you to get a socket or wrench on it and twist it right off. It's probably a 3/8 npt plug. You can buy those anywhere online.

Bronco2Fan · Sep 17, 2024

Why can't you just get another diff cover? Especially if you work at a parts store. Just asking.

cobrajeff96 · Sep 17, 2024

The fill plug for an SRA is actually on the driver front of the axle and is the true fill line. If you fill it up to the fill plug on most (or maybe all) aftermarket covers, that's a guaranteed overfill and gear oil vapor will spew everywhere.

weendoggy · Sep 18, 2024

cobrajeff96 said:
The fill plug for an SRA is actually on the driver front of the axle and is the true fill line. If you fill it up to the fill plug on most (or maybe all) aftermarket covers, that's a guaranteed overfill and gear oil vapor will spew everywhere.

There are several covers that have a fill plug in the correct position, plus a drain. You just have to search for them. Summit Racing has at least two to choose from.

Mustang5L5 · Sep 18, 2024

The bolt on my 8.8 stripped out a long time ago. Ended up just buying an aftermarket diff cover with a drain and fill port on the cover. That alone was worth the cost of admission as it's just a much easier time filling from the front.

Also, i like using the Lube Locker gaskets. No more RTV. Install them dry and i've had them on and off a few times without leaks. Really nice gasket. I have them on both my Mustangs.

cobrajeff96 · Sep 18, 2024

If the OP has OEM cover there is no fill port on it.

weendoggy · Sep 18, 2024

cobrajeff96 said:
If the OP has OEM cover there is no fill port on it.

I believe this is true, but, the OP already drained the oil and then found the stripped plug. So, all they need to do is replace the cover (that has a fill port) and then fill it.

Mustang5L5 · Sep 18, 2024

weendoggy said:
I believe this is true, but, the OP already drained the oil and then found the stripped plug. So, all they need to do is replace the cover (that has a fill port) and then fill it.

Yeah. I was in the same boat before. This was back when my Mustang was a daily driver and my only car. Took the cover off, drained it and then discovered the plug was stripped when I went to refill. Had to rush around to find a cover.

Needless to say, first step of any drain/fill I do these days is to verify I can access the fill port.

cobrajeff96 · Sep 18, 2024

I don't think there was ever a mention that OP had an aftermarket cover with a fill port. If the fill port from factory is stripped, then buy a cover for a 7.5 rear (if they exist, IDK if they do) can at least get it rolling again instead of having to go through the process of filling through a vent tube, lol.

weendoggy · Sep 19, 2024

cobrajeff96 said:
I don't think there was ever a mention that OP had an aftermarket cover with a fill port. If the fill port from factory is stripped, then buy a cover for a 7.5 rear (if they exist, IDK if they do) can at least get it rolling again instead of having to go through the process of filling through a vent tube, lol.

Or, just remove it and put one in. Yeah, that's the ticket!

DarkknightGT · Sep 19, 2024

Mustang5L5 said:
Yeah. I was in the same boat before. This was back when my Mustang was a daily driver and my only car. Took the cover off, drained it and then discovered the plug was stripped when I went to refill. Had to rush around to find a cover.

Needless to say, first step of any drain/fill I do these days is to verify I can access the fill port.

Yeah this was my first time doing it, so I did everything backwards. Next time I most definitely will.