Diff oil was nasty after 500 miles

[babbage]

I was doing my henious billet control arms yesterday and decided to change the 80W-90 gear oil the LM dealer put in. Glad I did. It was very black and dirty looking. Couldn't see any golden color at all. I had new axles, bearings and new spider gears installed a little while ago.

Used my Amsoil pump and nifty girdle fill and drain holes. Flushed about 1/4 of a quart through the pumpkin till it came out clear and flushed out all the blackness... Put in 2.5 quarts of AMSOIL 75w-110.

Good to go. Was really suprised how dirty the gear oil was - I only did one real quick burnout to test the trak-lok after dealer install (yep 2 black lines 10ft long) and put about 500-600 miles on it since all rear end work was done.

Should have taken a picture. Cost me less than 1/2 tank of gas...

[RacerX]

After 500 miles??? Only thing I can think of is that the new fluid picked up crap off of the diff housing etc. and mixed with it. Should be good now though!

[babbage]

After 500 miles??? Only thing I can think of is that the new fluid picked up crap off of the diff housing etc. and mixed with it. Should be good now though!

Yep, strange too as I had all new clean parts. The clutches were new too, I didn't abuse it so It couldn't have been clutch material..

Just trying to take care of my new parts as best I can..

[RF Overlord]

babbage, good on ya' for changing it out. Most people would never think twice about it, and with a worn axle repair there will be wear metals floating around that should be flushed out.

I do have one question, though: are you sure the dealer put in 80W-90, because they shouldn't have. The Ford axle TSB changed the spec to 75W-140 synthetic.

I recently changed out the 75W-90 synth blend I had put in as a "flush" when I did the axles on Phoebe, and it came out almost as clean as it went in. I'm not sure how many miles were on it, but it was at least a couple of hundred.

I did spray down the interior of the housing with Brakleen and made sure the well at the bottom of the diff housing was cleaned out when I reassembled everything. I would hope your tech did that, too.

For the final fill I used Valvoline 75W-140 synthetic with the friction modifier already in. So far so good...no chattering on corners and it's nice and quiet.

*EDIT* That Amsoil SevereGear 75W-110 is supposed to be the ****z, too.

[babbage]

I think the 75w-110 is perfect for my 3.73's

re: oil-- I know I gave my LM dealer that TSB. I read the oil weight right off the service order after I got the car back. I could clearly see the 80w-90 in the part number for the oil... and they used a tube of Ford FM. Yep it was black, really black. Perhaps it was some of the RTV sealer/gasket maker that got on the inside.

I will change it again next year and see...

[Marauderjack]

I understood you to have filled it through the girdle fill hole??

If so it will be way over full unless you filled it to the OEM fill hole level ONLY!!

Glad you changed it.....you can never change fluids too often......as long as you can afford it!!

Have a good weekend!!

[Egon Spengler]

Maybe the shop gave you used oil figuring you would never check it yourself???

[babbage]

I understood you to have filled it through the girdle fill hole??

If so it will be way over full unless you filled it to the OEM fill hole level ONLY!!

Wow you'd better call trick flow and tell them!

Glad you changed it.....you can never change fluids too often......as long as you can afford it!!

Cost less than 1/2 a tank of gas.

Have a good weekend!!

Tankx - you too!

[babbage]

Maybe the shop gave you used oil figuring you would never check it yourself???

Yeah my upstanding Lincoln Mercury dealer installed all new parts on my rear end covered on my ESP and gave me a rental for 5 days - so they could put in used 80w-90 oil in my pumpkin when they were all done.

Yeah I'm totally sure that happened.