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Changed my Differential Fluid today.

37679 Views 85 Replies 27 Participants Last post by  LeeRenfro
I dont have the pics uploaded yet however I changed my Differential fluid today on a buddies lift since GM says to do so in the service manual @ 1500 miles and WOW boy am I glad I did.

of course it is supposed to look milky grey after use of the rearend heating up breaking down the fluid. The Drain plug is a magnet on these cars I had not a lot but I guess a normal amount of shavings stuck to the drain plug.
I put my finger's inside of the fluid after it came out and it felt a litttle gritty.

I did this at a friends gear and axle shop so I had someone around to tell me if thats good or not he told me it was normal and will be good to get that trash out of the rearend :thumbsup:

I put NEW fluid in the rearend along with the GM additive that GM calls for to be installed with the fluid and she now runs much smoother.

Belevie it or not it does run smoother and you can feel it.

Total cost of this cost me about $26 thats for 1 quart of fluid and the addative. it actually takes 1.1 quarts but after the 1 quart of fluid the addative makes it 1.1 :thumbsup:

This is a simple task you could do in your driveway with simple house hold tools , jack and jackstands :thumbsup:

just 2 bolts ( drain plug and Fill plug ) I would recommend getting a piece of vaccum hose to stick over the nipple on the fluid bottle so you can reach over the exhaust and squirt it inside the rearend :thumbsup:

Also get some cardboard and stick infront of your exhaust pipe because when it comes out it will hit the pipe directly if that cardboard isnt there.

this task is so easy even Shunt could jump out of the trunk and do it :thumbsup: :lol:

took me 15 minutes tops :thumbsup:
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yea i felt a difference as well.

makes me wonder if it is necessary to do the transmission also. :hmm:
i used the Mobil 1 75w-90 LS differential fluid. it already had the limited slip additive included. and was cheaper than the royal purple
Wow, I'm surprised they recommend changing it at 1500 miles. Sounds like a good idea...
the book says if vehicle is intended for racing use, change the fluid at 1500 miles. :thumbsup:

racing recommendations in a vehicle owner's manual... that is AWESOME!
Change it to another type/version or change it in general?
Wonder what the rational is. People drive hard on the street as well :D
just change it in general.

a lot of people change it anyways and everyone has said that fine metal shaving have come out with the fluid.
At 1500 miles? I don't think mine's been changed yet! :eek:

Will call dealer now.
you can easily change it yourself for cheaper than the dealer cost.

just crawl up the rear of the car, unbolt the fill plug, put a oil drain bucket underneath, unbolt the drain plug, put drain plug back in after it stops dripping, use a 3/8" hose and connect it to the new oil bottle and squeeze 1.1 quarts in through the fill plug, put the fill plug back in and done!
if you can fit a 1/2" ratchet wrench into the plug, you can do it without removing the exhaust.
There is no reason you should have to remove the exhaust. You can fit my fist sideways inbetween my exhaust and the nut.

if you do have to remove exhaust it will be the muffler only however I dont see anyone having that problem.

i had that problem and had to remove my driver side axle back section :D
doesn't the borla axle back connect after the hangers behind the differential? the magnaflow connects to the stock pipe in front of the differential
Does anyone have the drain and fill plug torque specs? And thread sealant ID?

Thanks in advance!
i just hand tightened mine, and had no leaks!
where does it say that gm recommends changing the fluid after 1500 miles? i just turned about 2300 on mine and i guess if helps, i probably need it done.
its in the owner's manual. couldn't give you an exact page, but it does say "for racing purposes" change the diff fluid at 1500 ;)
well, since im a race car driver :lol: i should probably change it. my dealer said they would do it under warranty. their going to put royal purple in for me though. hes a great guy :thumbsup:
thats a great deal!

i bought 2 quarts of mobil 1 75w-90 LS fluid for $30 and did it myself one weekend.

wasn't too hard of a job, but hell if you can get it done for free, that's awesome!
page 8-17:
New Vehicle Break-In
Notice: Follow these recommended guidelines during the first 2 414 km/1,500 miles of driving this vehicle. Parts have a break‐in period and performance will be better in the long run.

. For the first 2 414 km/ 1,500 miles:
. Avoid full throttle starts and abrupt stops.
. Do not exceed 4,000 engine rpm.
. Avoid driving at any one constant speed, fast or slow.
. Do not drive above 160 km/h (100 mph).
. Avoid downshifting to brake or slow the vehicle when the engine speed will exceed 4000 RPM.
. Do not let the engine labor. Never lug the engine in high gear at low speeds. With a manual transmission, shift to the next lower gear. This rule applies at all times, not just during the break‐in period.
. Do not participate in racing events, sport driving schools, or similar activities
during this break‐in period.
. Check engine oil with every refueling and add if necessary. Oil and fuel consumption may be higher than normal during the first 2 414 km/1,500 miles.
. To break in new tires, drive at moderate speeds and avoid hard cornering for the first 322 km/200 miles. New tires do not have maximum traction and may tend to slip.
. New brake linings also need a break‐in period. Avoid
making hard stops during the first 322 km/200 miles. This is recommended every time brake linings are replaced.
. Should the vehicle be used for racing or competitive driving (after break‐in), the rear axle lubricant must be replaced before hand.
This is off the Mobil 1 site, so do I or don't I add the limited slip additive?:confused:

Mobil 1 Synthetic Gear Lube LS 75W-90 contains special friction modifiers designed for limited slip-type differentials. In most applications, the addition of special LS (limited slip) additives is not required. For axles requiring the highest level of limited-slip performance, OEM specific LS additives can be added to this fluid.
i used this gear lube when i changed mine... and you DO NOT need to add any additive. driven about 3,000 miles with the new lube and it never whined or broke :thumbsup:

plus it is cheaper than the OEM and royal purple, i paid $25 for 2 quarts and only used a little over 1 quart.
Thanks RJ, the guy at a local parts store tried to sell me the additive saying it HAD to be added. I didn't think so but wantd to make sure.
NP, i was sceptical at first as well, but the reason GM sells that stuff is because the OEM lube doesn't have it inside, so they can use the same bottle of lube on multiple cars that contain or do not contain limited slips.

most off the shelf lubes do like Mobil1, Royal Purple, and Redline; so no need for the GM additive with those.
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