Magnet Inside Differential Came Free - Need Adhesive

electrak · March 6, 2008

I have a 2003 Avalanche 2500 with a 10.5" ring-grear rear differential. I'm in the process of replacing the rear cover and decided to clean out the bottom of the diff and noticed a 2-inch diameter donut shaped magnet near the bottom drain plug, with a fair amount of normal gunky-pasty magnetic material. Nothing big. I tried to clean all around in with small wooden sticks and managed to get it pretty clean while in place because it seemed to be attached by some means to the lower casting. I didn't know by what means it was attached so I was being pretty careful. However, as I was finishing up I noticed it came loose, so I removed it entirely and finished cleaning it up. It was then that I noticed it had been glued in place. Now that it is free I need to know what type of adhesive can tolerate being under gear oil - forever - without failing. I suspect that if the glue fails the magnet has a chance of coming free and destroying the entire diff. The ring gear gets to within 3/4 of an inch or so of the magnet and I suspect there are some pretty decent hydrodynamic forces that could peal the magnet loose if it is not attached well. Anyone have experience with reattaching one of these? Or maybe someone knows of a good magnetic plug I can replace mine with instead of using the donut magnet. I really don't even like the idea of this thing being in there. Sorry to be so wordy! Dave

facn8me · March 6, 2008

3m adhesive. The yellow stuff. Affectionatly known as gorilla snot. Is what I would recomend.

the hammer · March 6, 2008

That is something I worry about myself! I thought it was magnetically held on but I guess not. Since it came loose, I would actually try and get a really powerful magnet that will stick on the outside of the differential(if you can find one). The magnetism at that strength should hold particles together.

On a side note, I bet that this was your first time cleaning it, as the pasty stuff was in mine too (and there was a LOT at 30k) the first time. Afterwards when you change fluid there isn't a whole lot in there if any at all (I hope!)

electrak · March 6, 2008

3m adhesive. The yellow stuff. Affectionatly known as gorilla snot. Is what I would recomend.

I'll check at the auto parts store... Would I go to the Chevy dealer to get this? I know 3m makes a lot of adhesives but does anyone know if this yellow 'goilla snot' is rated for this kind of use? Also, I do realize I need to prep the area (and magnet) with acetone or a good quality degreaser before attempting to glue it on. Still looking for a magnetic plug as well if anyone has any advice. Also, someone mentioned putting the magnet on the outside? Being someone that knows something about permanent-magnet motor design, no, the magnetic field will not pass through the casing, it actually takes very little steel to capture 99% of the field. I appreciate the free-thinking though! Have a good one.

the hammer · March 6, 2008

My diff doesn't have a drain plug, but if you have one I would just get the magnetized drain plug. That is what I would prefer if I could do it.

facn8me · March 6, 2008

The only way to get a magnetic drain plug would be to drill and weld a bung on or get an aftermarket cover. As for the adhesive all parts stores will carry it. It dries hard so the oil wll not affect it. By the way my qualifications are ASE master medium heavy truck and automoblie. Ford school and GM. Plus a little electric vehicle training also. Not bragging or questioning your asking for more advice just throwing it out there. I currently run the fleet mant. Dept for TU.

Wingnut · March 6, 2008

The only way to get a magnetic drain plug would be to drill and weld a bung on or get an aftermarket cover. As for the adhesive all parts stores will carry it. It dries hard so the oil wll not affect it. By the way my qualifications are ASE master medium heavy truck and automoblie. Ford school and GM. Plus a little electric vehicle training also. Not bragging or questioning your asking for more advice just throwing it out there. I currently run the fleet mant. Dept for TU.

That's all great...But WHERE HAVE YOU BEEN LATELY?

facn8me · March 6, 2008

I still stop by and check up on ya 'nut. Been chasing women since you asked... No I haven't caught any yet.

electrak · March 6, 2008

The only way to get a magnetic drain plug would be to drill and weld a bung on or get an aftermarket cover. As for the adhesive all parts stores will carry it. It dries hard so the oil wll not affect it. By the way my qualifications are ASE master medium heavy truck and automoblie. Ford school and GM. Plus a little electric vehicle training also. Not bragging or questioning your asking for more advice just throwing it out there. I currently run the fleet mant. Dept for TU.

Thanks for the info. Looking at the next comment I can see that others have been wanting your advice also... Well I just completed making my changes. I bought a new drain plug from the dealer and drilled a 1/2" hole 1/4" into the backside of the plug. I then set a very stong rare-earth magnet into the hole and glued it in using a small amount of black RTV in the hole. The magnet is so strong that it takes about 40lbs pull to remove it, and that is before using the glue! I also took a couple of very strong magnets that came from an old hard disk drive and attached them into the bottom of the diff, adjacent to the drain plug opening. I'm not even going to glue these because thay are of such low mass / low profile that it would take about 100g's of force to get them to move! I am very confident any metal particles won't have a chance against these magnets and I'm betting they will never move. I'm glad I did not put the stock magnet back in because I have found several stories on-line about how the magnets have destroyed the gears when they let go, and my gut tells me the magnet is too large and too weak to stay in place, thus the adhesive the manufacturer uses. I never like relying on glue to keep me going... Have a good one! And thanks for the advice everyone.