2004 Rear End Fluid Change

[scotty7676]

I have been searching trying to figure out how to change the rear end fluid in my 2004 XLS. I think it has a limited slip due to the grinding noise it makes around turns, and wanted to change the fluid to see if that helps. I found two plugs on the diff cover. Ones a huge one which is the drain I'm sure, and there is one above it that I am assuming is the fill plug. Both are facing the rear of the vehicle and are located in the cover. I have two questions.

1. What the heck size is that drain plug square? Where do I find a tool to fit that?

2. Is that really the fill plug above the drain on the cover? I took it out and fluid started pouring out.

Thanks!

 

[Hyper26414]

Get a 1/2" ratchet and plug it in if not that then 3/8" ratchet no special tools required. Yes the top one is the fill plug you want the fluid to be level with this when the vehicle is level meaning fill her up until it starts coming back out of the fill hole. If you want to put a little extra in jack the rear higher than the front. Go to town and good luck.

 

[scotty7676]

Thanks for the reply! The drain square is quite a bit bigger than my 1/2" drive, so I measured it out. It is a 3/4"! So I'll go out today and see if I can find a 3/4" breaker bar for a decent price. The fill plug came out ok, and it is a 3/8".

Thanks again.

 

[E.B. Cornburner]

Just go to your local Lowe's or Home Depot and get a 1/2" to 3/4" adaptor. Much cheaper than buying a whole new breaker bar for one task. If you can't get enough leverage with the 1/2" breaker bar, use a "cheater pipe"...Find a piece of pipe that slips over the handle, and use it to increase leverage.

If you have AdvanceTrac, then you don't have a limited slip diff. The AdvanceTrac acts as a 4-wheel LSD to some degree, and wouldn't function correctly if both rear wheels were locked. If you don't have it, an easy way to determine if you have a LSD, is to jack up one rear wheel and try to spin it. If it's locked tight, then you have a LSD. Or, if you have both rear wheels off the ground, spin one forward, and if the other spins the same direction, it has a LSD. If it spins opposite, then it's a standard open differential.

I'd definitely recommend a synthetic oil a bit heavier than the OEM 75W90 synthetic oil. I'd probably go with a 75W140 from Amsoil, Schaeffer, Redline, or any other top quality synthetic oil. This is especially recommended if you do any towing with it.

 

[scotty7676]

Thanks for all the helpful info. I went to Home Depot and Lowe's here, but the biggest size of anything they sold was 1/2". They did not have any adaptors to 3/4", and when I asked, they had no clue what I was talking about anyways. So, I ended up buying a 3' piece of 3/4" aluminum square tubing. I cut off 2" of it and stuck in the drain plug, then put a 12 point socket on the other end. It actually worked! So I took the drain out, jacked the front up and let it drain for a while. Then put the front down, cleaned everything and put some black rtv on the plug and screwed back in. I then filled with Mobile 1 75W90 like the manual says and put in friction modifier. I drove around in figure 8's a few times to get it all mixed in the clutch pack, but I still have a groaning noise coming from the rear end when turning under power. I think the clutch pack is just screwed or something. Oh well, at least I know I have fresh fluid in there now!

Oh yeah, and I know I don't have advance trac. I just have the cheap-o XLS, but it does have limited slip from looking at the tab on the rear end.