diff oil

I changed my rear end oil and put 3 quarts. I thought you needed to fill until it comes out of the plug in the back, but now I am second guessing myself? I changed it a few years ago but I don't remember what I did.

Also back in the day I did not know you needed some type of additive for the limited slip. What are the signs that you messed up something by not putting the additive in with the oil? I have been running for years without the additive and I don't see a problem. Maybe my limited slip does not work like it should? Oil was still very light brown.

I added the special stuff this time.

What are you driving?

the additive actually is to reduce chatter from diff when turning,
it actually creates slip.
Usually you only add as much as needed to reduce chatter.
Many people think the additive adds grip but it actually does the exact oppisite.
It's a friction modifier that allows the clutches and plates to glide smoothly over each other versus chattering
If your rear diff doesnt chatter dont worry about it.

It is a 2005 2500 HD. GMC Serria.

I was reading the bottle about what it is "suppose" to prevent. I have not had those symptoms in the diff. I think it is ok. Only thing that leads me to believe the limited slip does not work is when we get stuck at the boat ramp, but I think that is just how limited slip works or the ramp is so wet, one wheel just breaks loose.

Quote:

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Originally Posted by htrdlncn

the additive actually is to reduce chatter from diff when turning,
it actually creates slip.
Usually you only add as much as needed to reduce chatter.
Many people think the additive adds grip but it actually does the exact oppisite.
It's a friction modifier that allows the clutches and plates to glide smoothly over each other versus chattering
If your rear diff doesnt chatter dont worry about it.

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I hope I put in enough. I have to leave for work and the wife is gone.

if only one tire spins the posi is not working.
putting the additive only makes it slip more.
stock posi units arent that effective.
I rebuilt the one in my Xsport when I first bought it,
used kevlar clutches, heavier springs and used only enough
additive to stop chatter in normal turning,
there is a bit of chatter in tight parking which is fine.
After 65,000 miles it still spins both tires evenly on dirt,water,snow,dry,etc.
Just have to be real careful driiving on wet stuff as it gets sideways easily.

I spoke with the mechanic and he got me all squared away. It it working fine and I like 1/2 quart getting it full. He said my problem at the boat ramp is, when it is wet the wheel with less traction breaks loose. Like you explained stock limited slip is not so great. I have air on board, maybe I should install an air locker! I may have to do that if I ever move up to a larger boat. My truck will not handle much more at the boat ramp. Most of the time Brandon drives out at an angle across all lanes. People don't like that but what else can we do.