Gear oil change question.

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BAD97LSC

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i need to change my rear end fluid this week before i go to the keys. i have never drained and changed the gear oil in any of my marks, but with the trac loc, i am starting to hear a very faint hum from the rear end when i let off the gas and coast, how much does it take, derek gave me a whole bottle of rpyal purple gear oil, but im sure one isnt enough right? also would it be best for me to make an adapter for my shop vac and suck the fluid out of the diff? i need to do this quickly, like in the next 3 days, as well as my brakes too, i had my new rotors drilled today for my bolt pattern so i want to do it all in one shot. advice please, whats the best way to do the oil drain and change? thanks.
 
just buy a suction gun from the auto parts store for approx 10 bucks. suck it out. refill to proper level. i think you need to add Ford friction modifier too, but dont quote me.
 
like was stated, suck it out and refill it to the fill hole.
if it has a trac lok, you need the friction modifier.
 
Tip #1.

Wear rubber gloves and get ready for the most rotten smell your Mark can muster. :wrench
 
fwiw....i would take the extra time about 30min and pop the cover off...if your getting a slight hum on decel...it sounds like your pinion bearing is either out of torque or on its way out it has to be set to a preload and sometimes they back off a bit

i find permatex ultra grey is a good sealer for diff cover one you goto reseal it...let it sit for 30min or longer and fill...if you can wait i would let it set for atleast 12hrs...but i have filled them with as little as 30min setting time and never had a leak
 
I dunno about sucking it out, I've always taken the cover off and drained, then fill to the fill hole. The friction modifier stuff def. needs to be added to the fluid for a car with Trac-loc
 
accourding to royal purple you dont add friction modifier to their gear oil its already in it. if i pull the cover off i will have to support the diff housing right since i will have to remove the rear mount bolts to remove the cover? i have smelt gear oil many times, just never changed it in a mark VIII i was working in an auto repair shop when i was 16 so i have done many things to many cars! i remember putting sperm whale oil in my mustang gt rear end, that is far worse smelling than any gear oil!
 
YOU DO NOT NEED FRICTION MODIFIER! I've called Royal Purple myself when I was going to put it in my stang and they said Royal Purple already has friction modifier in it. If it's the same size as a 99-04 GT Jamie, they hold 2 1/2 quarts.

Do you have an aftermarket rear end cover (girdle cover)? If so there should be a drain hole and fill hole. If not I have no clue the process.
 
when i chandged mine i sucked it out....very easy to do if you got the right sucker....mine was horrible so it took alittle longer then expected.
 
i wouldnt stress supporting the housing with the cover mounts pulled off...it doesnt weight that much, axles and the front mounts will more then hold the weight with the cover off....royal purple does not require a friction modifier...and royal purple is not the be all end all for oil products either

pennzoil 75w140 is synthetic and does not require a friction modifer either.....also amsoil does not require it....
 
Jamie, what I would do as I am assuming the gears arent really that old, would just be first to stick your finger in there and see what the fluid looks like. If you can still see thru it you should be perfectly fine. Just use your judgement. As for getting the old fluid out, I would suck it out. You pulling the cover isn't really going to tell you anything, other than maybe what the wear patern on the ring gear looks like. If you are just wanting to change the fluid, I would suck it out. What I use at work is basically a big fluid sucker. Ours runs off of shop air, but you can also get some that look like they have a bicycle type pump on the side. You are going to need a pretty firm peice of tube to fish it down between the guts of the rear diff and the rear cover to get down to the bottom of the diff. The sucker I am talking about could probably be gotten from an oreily's or a place like that. You can also use it if you accidently over fill a trans, or use it for P/S flushes. I'd bet money that your fluid is going to look good, but going to a different brand of fluid, could help with the noise. Removing the rear cover is a lot of extra work, if you arent really doing anything to the rear end.
 
derek gave me some royal purple thats why i was gonna use it, its also what is in the rear end already, everything in the car was royal purple and still is except the motor oil is mobil 1 now. i am gonna suck it out, i dont have time to pull :q:q:q:q apart i barley have the time to do this gear oil change and put the new rotors on. i am leaving at 4 am friday morning so between now and then with a full time job i am not doing anything extra right now. i just want peace of mind with new gear oil, the oil in the car is 3 years old, thats how old the gears and trac loc are. it cant hurt to change it before i make a 14 hour round trip! i'll find out what they have at the parts store for a fluid sucker and buy one, thanks.
 
It'll take you longer to go to the store and get one than it will to pop the cover off most likely. ;) It's two bolts in the rear mount attached to the cover and the cover bolts. You'll be able to see any sludge or crap in the bottom, or marks on the ring gear this way too. Only thing you'll have to wait for is the rtv to tack up (15-20min)...
 
True, lol... either way is fine, but I'd personally rather see how the insides are fwiw ;)
 
well i'll wait till after my trip like i said i dont have time to make this a production, what if i do find something wrong then i wont go on my trip, i'll take my chances and go now, look later, i drove it home to florida from connecticut in january and drive it daily and havent had anything go wrong yet so....!!
 
jamie97lsc said:
well i'll wait till after my trip like i said i dont have time to make this a production, what if i do find something wrong then i wont go on my trip, i'll take my chances and go now, look later, i drove it home to florida from connecticut in january and drive it daily and havent had anything go wrong yet so....!!
Click to expand...

Jamie advanced will price match internet sites now, tell them american muscle sells it for $12.99 with no tax and free shipping.
 
Less than 2 quarts, fill until it runs out of the fill hole, with the car level.
 
your gonna spend more time pissing around trying to suck the gear oil out....and you wont know if its all out and fwiw, that cover would be off i would clean all the sludge that sits in the bottom not to contaminate the new gear oil clean gasket surface, apply silcone do your rotors, then refill diff at the end....

but if you think 30minutes of work is a production, then you are not the mark viii specialist and dont deserve that podium everyone puts you on lol
 
Ya Jamie your a dirty dick mother :q:q:q:qer for not doing more work than is necessary. Some members here don't realize that people that work on cars for a living don't LOVE working on their cars when something breaks. Its not a big deal for me to change my spark plugs or do a suspension overhaul. Some people that have desk jobs or work in a completely non mechanical field get a woody when they get to pull out their no name tools and get to rip something apart. For me, and I love my car, its just another broke down car. What would be the use to remove the back cover? Find that hammer that has been missing and is rattling around inside the diff? If there is a problem, it will get addressed later if the noise becomes worse. If fluid fixes it, what was the point of pulling the cover? And at worst case, a cup of old fluid is in there, it mixes with the new fluid, and you will hardly notice a difference in the fluid color. This isnt a Diesel truck with 100k miles on it.
 
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