Differential Fluid Change Question

[furgoon]

Greetings,

Today, I got off my lazy butt and actually changed the differential fluid in my 2004 Colorado with Amsoil 75w-90 Synthetic oil. Everything went well but when I took off the cover I noticed a grey paste like substance over the magnet. This is my first time ever changing a diff and was wondering what it was. To me, it didn't seem normal. I cleaned it off when I cleaned the cover to put it back on. Is this something that the magnet needs? I didn't notice any shavings in it. I have read many how-to's on the net and not any of the one's that I read mentioned anything about regreasing a magnet. Thanks for the help.

 

[JasonC]

Ive seen it on every diff Ive changed the fluid in. Nothing to worry about.

 

[JTK]

I had the gray paste coating on the inside of the rear diff cover and magnet on my 2005 Trailblazer at ~20Kmi as well. I used a rag and some mineral spirits to clean it. The diff oil was BLACK. The nicest thing about the job was the reusable rubber/metal diff cover gasket. Does your Colorado have the same thing?

Joel

 

[furgoon]

Indeed, it had the same gasket. I put a new one on since I had ordered it in anticipation of doing the job many months ago. The old one could have easily been used again. I saved it in case I ever need it again. Thanks for the advice, I did clean it off the magnet and took a test spin. No leaks. The oil was black which I guess is normal for 67,000 miles. I am the second owner of the truck and not much previous maintenance was ever done. The transfer case and front diff. are next. Those will be easier as each has a fill and drain plug.

 

[pickled]

That paste is fine metal fragments from wear. Some folks here on the board actually have a photo album of different magnetic shavings. You'll see this paste looking metal on every differential and every auto trans pan magnet. You did your truck a big favor today...it will thank you!

 

[JTK]

furgoon, definitely get that front diff oil changed. That too was nasty looking on my Trailblazer at only 20Kmi. The front diffs don't hold much and are often neglected or run low on lube after a seal leak, etc.. The magical expensive GM lube in the transfer cases seems to look good after many miles, but yours is due with that age/mileage. OT, but another thing you will want to do ASAP on your Atlas/Vortec 5cyl is [carefully] pull each coil over and throw some never-sieze on the looooong skinny bolt that secures each coil to the aluminum cyl head. These bolts snap easily at which point you are 'stuck' holding your coil in place with RTV, silicone or duct tape!

Joel

 

[furgoon]

Thanks JTK! I changed the plugs last year but never thought of doing that to the bolts. That will be my next maintenance "mod".

I am planning an AMSOIL Syncromesh change for the case as well.

Is there a magnet on the front cover for the diff? I ask because I was hoping not to pull off the cover as it has the drain plug and fill plug.

 

[JTK]

There is no cover on the front diff. They are a vertically split case. IIRC, the small drain bolt was not magnetic on my Trailblazer, but the fill plug was a HUGE aluminum threaded cap with an O-ring seal. The fill port was so big you could drop a golf ball in there. Yeah, if you got those coil hold-down screws out on that plug change, you'll be good to go. They tend to sick in place over time (steel bolt in an aluminum tapped hole)

Joel

 

[furgoon]

Well, I was motivated again and changed the oil in the front diff. The drain was very black at first and then the stream sort of percolated. After that the oil looked much cleaner coming out. Not sure what that means or if I am just becoming way too observant about oil. The front diff drain plug was magnetic and it was not very full of paste like the rear was. The fill plug had a plastic washer as well that I didn't notice until I cleaned it. The transfer case is next. This will complete my transformation to Amsoil all around.

 

[mechtech2]

Diff and trans magnets rarely have actual metal shavings like from the floor area around a lathe operator. They extremely fine ferrous particulate matter looks like black or gray sludge on the magnet.

 

[Triple_Se7en]

Does the Colorado owners manual specify the capacity size for both differentials and transfer case fluids?