el es tu

has anyone tried to change the diff's slip tendencies by adjusting the amount of additive or adding in more non additive gear fluid to the premixed stuff from gm? Im interested to find out if this may be a way to adjust the way the rear end works without going to an adjustable differential.

Thanks!

CHJ In Virginia

I have run several different fluids (M1, Redline, dino oil) with and without GM addatives in my diff over the years. Can't tell any difference in driving characteristics between any of them. What are you trying to accomplish ??

froggy47

Yes you can start with a fluid that has zero additive and then blend in your additive to your liking. I would call Redline tech support & ask them about it, it's a little hit/miss with the proportions.

Autox guys have done this for years, so many tight turns onto short straights.

They (Redline) sell it with or without the additive.

el es tu

froggy - thanks for the advice!

chj Id like to try making the diff to start connecting a bit later and/or with less force - in other words I want the limited slip to keep slipping just a bit more.

This seems like something cheap and easy enough to do repeatedly and take notes on to get the car to work exactly the way you want it.

Solofast

In my experience, once limited slips start to slip some, they very quickly become unlimited slips and you have to rebuild them. I've found that if you keep them tight the car powers out of corners better, but you have to build you setup around it, and use the exit power smoothly so you don't get power oversteer.

Once all the weight is on the outside wheel, the inside tire isn't doing much anyway so it doesn't matter if it's working like a spool or not, you just can't be heavy footed or you'll get serious power oversteer. That also means that you have to plan on trail braking to take the weight off the inside tire on turn in or it won't turn in worth a darn.

The reward for that is that if you build it tight and keep it locked up, it will last a lot longer between rebuilds.

I had a new set of clutches put in and used a noted synthetic lube and in about three events the diff was loose again.. Redid the clutches and used the factory fill and additive and it lasted three seasons.

fatbillybob

What's a loose diff? Wheel off ground breakaway torque less that how many foot lbs?

Solofast

I've always used less than 70 or 75 lbs "rebuild time" since I like to stay on the tight side.

I did a search and here is what Anthony @ LG Motorsports said...

el es tu

very useful info!

Han Solo

With Mobil 1 fluid I ran no additional additive in my Z06 and it worked fine.

In my Mustang I shim it tight and run synthetic blend Valvoline 85w90 with no additive. I also leave out the spreader spring so there isn't any breakaway to measure. It freewheels like an open diff when not under a load so it turns in better if I am coasting. Running a preload spring induces understeer if you coast into a turn. Not that I coast in that much or that often but I do coast a little after letting off the brake before getting on the throttle full. As soon as I apply torque with the throttle it starts locking both wheels.

In my F150 I have to run extra additive and sometimes have to add as it seems to loose it's capability or it will chatter just going around a turn from a stop. I think it must have the carbon disks in it.

C5ZEE06

I need to do this. Can anyone describe the procedure for checking break-away torque ?

Solofast

Jack up one side of the rear of the car so that the rear tire is just off the ground. Block the front opposite wheel. Leave the car in neutral. Get a torque wrench (a bending beam is better than a clicker for this) and put it on a lug. If the lug is at the top center, you want the torque wrench to be horizontal. If the lug you are cranking on is on the horizontal center line, you want the wrench to be vertical. If you put the torque wrench along a radial line you have to correct the value for the increase in arm length. If you put it the way I've described, you don't. Measure the torque it takes to start to rotate the wheel. That is the static breakaway torque.

fatbillybob

Os giken first and quaife second are the hot LSD's. Custom shimming stock OEM LSD's are getting you how close to these front runners and how much is the rebuild costing you? Are you guys doing them yourselves or favorite shop?

C5ZEE06

Thank you !
So check both left and right wheels in this manner ?
Direction of rotation (cw or ccw) - is not important ?

Solofast

Just one side will do it, you can do it either way, I do it so that you are tightening the lug, but I don't go over 100 ft lbs if it gets that high.

0Anthony @ LGMotorsports

Kind of....

You need to have a socket on the axle nut....putting it on a wheel stud moves the pivot point slightly.

Also you can put a stake so to speak between the rotor and the caliper of the other wheel, and have someone hold that in place to lock the other side.


Yes you need to use something other than a click style torque wrench, the new digital ones work awesome.

Solofast

Not kind of, torque it torque. It's the force along a line of action times the distance of that line to the centerline of rotation.

So long as the force is kept at a right angle to the wrench, whether the nut is offset or not doesn't matter. If the wheel rotates, just make sure you keep your pull at a right angle and the torque will be the same. You don't need to use the axle nut, and most folks don't have a socket that big. Go ahead and try it yourself, the numbers will be the same as long as you keep the wrench perpendicuar to the radial line defining that lug nut.... Can't be any different...

0Anthony @ LGMotorsports

We are splitting hairs here...but no it would change because you are changing the lever arm. Of course this all depends on how accurate the tool is you are using to measure it with as well.

Solofast

Come on Anthony, you're supposed to be an engineer...

Think about it...

So long as the wrench is at a right angle to the radial line, the wrench length is the same as the moment arm and the wrench reads the right torque about the axle centerline. If you screw up and don't have it at right angles or if you push at some funny angle, then no, but so long as you do it as shown the wrench is reading the torque, it's just the force x the distance and the distance is the same.... It's not kinda and not close, it's the same...

Shaka

You don't know what you are talking about , friend.

Shaka

The desired properties of a limited slip diff are designed into it and the lubricant can only optimise the design. Torque sensing LSDs respond to driveshaft torque and a torque wrench used as described below can't tell you anything useful other than clutch preload. Big deal.

The more driveshaft input torque present, the harder the clutches, cones or gears are pressed together due to spider gears trying to unmesh themselves. The number of clutches and ramp angles of spider gears determine %tage slip.

The preload clutch pack/s assist in low torque situations and that is why off road applications use clutches for high torque and locking devises for low. (trailing throttle/%tage slip, neutral or driveshaft input require different design inputs. The amount of preload (hence static coupling) on the clutches or cones are affected by the general condition (wear) and by how tightly they are loaded. A lubricant can't help here. I is possible to have your Vette stuck in the snow with one back wheel spinning at engine idle and nothing wrong with it.
There are many methods to limit slip. Rally cars and F1 require the most complicated electronics and mechanisms to control their diffs and diff design is the most important consideration in the design of a race chassis or high performance car. Lubricants are important for their correct functioning.