So i have a 12 bolt in my 71 and it has 3.73 richmond gears with a limited slip posi, when i first got the car about a year ago, when i spun the tires i had both going, and now with a new engine with more power, I only have one tire spinning, I was going to take my car to rear end specialties but then i realized that i had a drip of oil on the bottom of the rear end housing, so im hoping the fluid is low, my dad said there's a limited slip additive that loosens up the springs, should i use the additive or just put rear end oil in there?

and where the heck is the plug to fill it, and is there a dip stick or anything to let you know when its full? I'm not familiar to this at all and i've never done any work on a rear end so tell me everything you know please. thanks

you'll want to use a good gear oil and the limited slip additive(which can be purchased at any GM dealer)
Good luck

You have a plug on the right side of the reareand(drive direction). You fill untill it starts to run out from the plug then itīs full.

Marcus

is the plug in the rear side or on the front side of the differential?

The plug is on the right side of the center casting just in front of the right axle tube. It is probably covered with dirt or grease. If it is only spinning one wheel then there is something wrong with the posi, and changing the oil won't fix it. The additive is used to reduce the noise from the clutches slipping. It makes the clutches slip easier, which is just the opposite of what you need right now. You need to inspect the posi to see what is wrong with it.

how much would it cost to get new springs and clutches and can you get a more aggressive setup or are they all universal?

Clutches are $90 and springs run from around $40 to $90, depending on which ones you get. The Eaton posi is tunable, so you can set it up for mild street use or all out drag racing.

should i buy the springs and clutches and then take it somewhere to get it done or should i just let them get them for me and have it done and set up?

How do you want this set up? Do you want it for street use, street/strip or just for racing? There are 4 different clutch types and 3 different preload springs for the Eaton. You need to know how you want it to work before you have any work done to it. If the shop that you take it to doesn't know the difference then you might not be satisfied with the results. They also need to know how to shim the clutches for the proper preload.

I want it set up for street/strip... all i got to do is tell them that and they'll get the right clutches and springs or should i go get them?

I'd use the 18 disc steel clutch set with the 400 pound springs. This will give you a little more grip than the stock 200 pound springs without too much chatter when turning corners. Use the Ford limited slip oil additive.

should i just tell the rearend place that? and they'll know what to do?

Ask them what they think. They might already know what to do, or they may have a different idea of what would work best.

thanks man i appriciate all the help...

Brian