Differential Plug Stuck, Stripped

Messages
34
So yesterday I attempted to change the rear differential fluid on my 15 Forester for the first time, at 85k miles.
So, I ordered the appropriate hex/torx socket attachments, etc. and watched a bunch of YouTube videos, read a bunch of forum posts, and felt ready. What I was not ready for, however, was six years of corrosion and pressure making the fill plug impossible to move. I got the 10mm hex on there with an extension and a cheater bar and gave it my all, but could not get the **** thing to budge. I read all sorts of helpful forum posts on ways to get the stuck plug out, and went outside to try them today. However, it seems that I inadvertently rounded the fill plug. So now I’m stuck.
This just adds to the problem, and the most popular way of dealing with it seems to be to weld a bit on the end of the bolt, which I am unequipped to do. I feel like I have come up with a workable solution, though, and thought I’d run it by the folks here to confirm that it is not a totally idiotic idea.
Basically, what I’m thinking is that I will take off the rear differential cover, thus draining it of old fluid. While the cover is off, I will either: a) try to use a grabbit, or some other sort of stripped fastener remover, to get to the plug, or plugs, out. Or, b) drill a new hole, and tap that to make a new fill plug.
If either of these failed to work, I would simply go to the dealership down the road, and buy a new differential cover. Even purchasing a new cover, with new plugs/gaskets, the hex sockets, and gear oil will be cheaper than having the dealer do the change for me.
Is this a reasonable course of action, or am I missing something? Thanks for your help
 
Messages
4,689
Location
Ohio
Take it to a shop and pay them to remove the drain plug and do the fluid change.

How much does an OEM cover cost ?
 

Chuck61

Thread starter
Messages
34
Take it to a shop and pay them to remove the drain plug and do the fluid change.

How much does an OEM cover cost ?
If I plan ahead and order online, $47. If I’m impatient and need it right away, $88.
I guess I could take it to a shop, but I like working on my car myself.
 
Last edited:
Messages
496
Location
Long Island, N.Y.
Do you have straight access to the bolt (bolt isn't located "Up and In" under the chassis) ?
How about using a simple Drill-out Bolt extractor?

https://www.harborfreight.com/screw...ent=&msclkid=abe67e3f4cb0105e323f21c412b9fe87

Purchase a new bolt from the Dealership and your good to go!

EDIT: So after re-reading thread, that was one of your first recourses......shouldn't need to remove diff cover though......Just Saying!!!
 
Messages
4,689
Location
Ohio
If I plan ahead and order online, $47. If I’m impatient and need it right away, $88
Wow, that's cheap. I'd probably go this route. Why would you be impatient or need it right away ? It's fine like it is until you replace it.
 

Chuck61

Thread starter
Messages
34
Do you have straight access to the bolt (bolt isn't located "Up and In" under the chassis) ?
How about using a simple Drill-out Bolt extractor?

https://www.harborfreight.com/screw...ent=&msclkid=abe67e3f4cb0105e323f21c412b9fe87

Purchase a new bolt from the Dealership and your good to go!

EDIT: So after re-reading thread, that was one of your first recourses......shouldn't need to remove diff cover though......Just Saying!!!
I guess it’s worth a shot to try it without taking the cover off. If it won’t come out, I can just take the cover off like I’d planned.
 

Chuck61

Thread starter
Messages
34
Wow, that's cheap. I'd probably go this route. Why would you be impatient or need it right away ? It's fine like it is until you replace it.
Good point. I think I’ll just get the replacement cover to be safe, and still try to salvage the old one. I can always return it if need be.
 

JC1

Messages
5,793
Location
Oshawa, Ontario Canada
Any way to take a picture of the cover and damaged plug? If you are lucky when you get the cover off you might be able to back the bolt off using vice grips from the inside of the diff cover if the bolt is long enough. I would also heat it up if you can and spray penetrating fluid on it.
 

JC1

Messages
5,793
Location
Oshawa, Ontario Canada
Does your diff cover look like this one?

I would give the plug 2-3 solid wacks with a hammer it may get it to budge. You could cut a slot with a grinder and the 3 o clock position and use a chisel to get it moving. (Hammering the chisel from 3 o'clock to 2 o'clock to get it loose.
 
Messages
6,940
Location
MIchigan
I used WD-40 pretty liberally after I couldn’t get it off the first time, but at that point I’d basically rounded it beyond repair.
At this point I would buy a new plug and get some Liquid Wrench and spray it down good...then take it down to a muffler shop/mechanic and have them remove the plug. Then take it home remove the cover and change the fluid. DO NOT remove the cover before you remove the fill plug.
 
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