Improving Limited Slip lockup.

[Colt45ws]

So I had a situation last night, and its the second time this has happened, where I was on ice and the limited slip in my CVPI turned into an open differential and everything went to the driver side tire.
I has on an incline pointing downhill and was trying to reverse back up it. My friends car was parked in front of me so no going forward either. In fact, trying to work it out I slid into his bumper.
This happened before on flat ground too with ice where I was trying to back into my garage and got stopped on the ridge of ice at the garage door.
I rebuilt it with fresh clutches and steels about 10-12k miles ago. So I dont think they are worn out. I used only Valvoline Synpower. I didnt need to add any FM along with it to keep it from grinding in normal use.
There is a part number for a F150 clutch preload spring that is heavier than the car springs, but I don't know if it would actually make a usable difference. Any one have experience with the F150 spring vs the Car spring?
The other thing I was thinking about doing was fixing my parking brake. KCSO never used the park brake the whole time they had the car, so the cables are seized. Unfortunately they worked well enough once for them to get stuck ON shortly after I bought it and I smoked the shoes so I need to source cables and shoes to fix it.
I think that if I couldve tensioned it with the P. Brake, I mightve been able to get it to lockup better.
Thoughts?
Oh, I have Altimax arctics on the car.

 

[Andrew1972]

According to some RWD with winters is the bomb on this forum! One wheel drive sucks.

Given the situation likely rarely happens drive on and see if you actually encounter it?

My wife's Subaru with pure mechanical AWD and rear LSD acts similarly on pure wet ice on side and pure traction on the other. It barely kicks power over.

 

[buck91]

Firstly, you have to remember the Ford Trac-Lok isn't really a very good high performance LSD. It can work pretty well when fresh but there are certainly better options. In other words, its functional but don't set your expectations too high especially after a few miles.

You could put the truck s-spring in, but that really only will help in zero friction situations and low slip speeds. The most popular "mod" for these diff's is to use the alternating plate stack method, which is basically changing from the stock order (something like clutch-steel-steel-clutch....etc) to the alternate method (clutch-steel-clutch-steel...). This does require an extra clutch plate or two per side but many people just salvage the best looking ones from the old kit and reuse them. I did this on a '94 CVLX when installing a trac-lok and it worked very well for around 50k miles.

In my '96 GT I rebuilt the clutches about 30k miles ago, used the "Cobra" carbon fiber clutch kit as it is supposed to offer better lockup and durability... Used the stock stack method and its pretty much totally blown out at this point, but locked up wonderfully when fresh. I drive it hard, but its got about 10-20k miles of "grandma" driving on it this time around. FWIW that clutch kit came with a VERY strong s-spring, too. I plan to rebuild with the extra kit I bought at the same time and doing the alternating stack this spring or summer.

 

[Colt45ws]

Originally Posted By: buck91
Firstly, you have to remember the Ford Trac-Lok isn't really a very good high performance LSD. It can work pretty well when fresh but there are certainly better options. In other words, its functional but don't set your expectations too high especially after a few miles.

You could put the truck s-spring in, but that really only will help in zero friction situations and low slip speeds. The most popular "mod" for these diff's is to use the alternating plate stack method, which is basically changing from the stock order (something like clutch-steel-steel-clutch....etc) to the alternate method (clutch-steel-clutch-steel...). This does require an extra clutch plate or two per side but many people just salvage the best looking ones from the old kit and reuse them. I did this on a '94 CVLX when installing a trac-lok and it worked very well for around 50k miles.

In my '96 GT I rebuilt the clutches about 30k miles ago, used the "Cobra" carbon fiber clutch kit as it is supposed to offer better lockup and durability... Used the stock stack method and its pretty much totally blown out at this point, but locked up wonderfully when fresh. I drive it hard, but its got about 10-20k miles of "grandma" driving on it this time around. FWIW that clutch kit came with a VERY strong s-spring, too. I plan to rebuild with the extra kit I bought at the same time and doing the alternating stack this spring or summer.

Oh yeah, I forgot to mention I used the 'standard' clutches. Which, you can't even get a new unit with those clutches anymore from Ford Racing.
I didnt know the cabon fiber kit came with a new s-spring. What Im reading now is what I call a F150 spring is acutally a 31-spline spring and fits 28 spline axles but is included with 31-spline carriers by default, too, including Cobras of course.
I might just put the carbon pack in it then, if it includes a new spring. Ill have too lok at that. I once I pop the cover and pull the spring, thats like most of the battle of replacing the clutches, anyway.

 

[Lapham3]

I haven't had any reason to do other than fluid R+R in many years, but used to horse around with setting up the gears and rebuilds. Very good and informative post

 

[meep]

Is this short lifespan typical of clutch-based LSD? All of these examples seem extremely short lived.

 

[rslifkin]

The stiffer spring will give more lockup under light throttle and off-throttle, which will help in the slick stuff. It'll always tighten up more as you apply more power though. So the soft spring may work well for launching on dry pavement, but may not be enough in the snow.

 

[Colt45ws]

Originally Posted By: rslifkin
The stiffer spring will give more lockup under light throttle and off-throttle, which will help in the slick stuff. It'll always tighten up more as you apply more power though. So the soft spring may work well for launching on dry pavement, but may not be enough in the snow.

Yeah, [censored], when I first bought it it would lay both tires with a brake stand, that was with clutches so worn I could move the axle shafts 1/8-3/16" in and out. Getting to the point where I was worried about losing a c-clip while driving.
I dont think it takes much to lockup on dry ground, at least with stock 4.6L power.
I can get the Carbon clutch kit for around $100-110 which includes the heavy S-Spring which is $27 on its own. The Standard clutch kit is about $60-70 so the cost of the carbon clutches is actually about nil.
Ill pick it up when I get some money in my Paypal from selling parts from the '04.

 

[pcoxe]

The clutch pack will tighten more under torque. Setting the parking brake to where it drags kinda heavy will work to increase the torque loading to get both wheels moving. Just remember to release it once you get moving. I used this trick a couple of times on my old positraction equipped El Camino to get moving on ice.

 

[SZR48207]

Originally Posted By: pcoxe
The clutch pack will tighten more under torque. Setting the parking brake to where it drags kinda heavy will work to increase the torque loading to get both wheels moving. Just remember to release it once you get moving. I used this trick a couple of times on my old positraction equipped El Camino to get moving on ice.


Was gonna say this. It's my understanding that the experienced offroaders can use the 2 foot method (brake and gas) to limit wheelspin and get out of risky situations.

 

[Nick1994]

If you need brake parts can't you swap over from your other Crown Vic?

 

[supton]

Originally Posted By: Colt45ws
when I first bought it it would lay both tires with a brake stand, that was with clutches so worn I could move the axle shafts 1/8-3/16" in and out.


You can get "posi" on an open diff. If both wheels have the same amount of traction, then both will spin. It's once the traction gets unequal that one will spin faster than the other. Dissimilar road surface, or torque reaction of the car twisting in response to the engine causing one wheel to unload.

 

[Colt45ws]

Originally Posted By: Nick1994
If you need brake parts can't you swap over from your other Crown Vic?

Nope! When they changed over in '03 to the hydroformed front frame rails and the aluminum #2 cross member with wishbone suspension and coil-over shocks; they had to go to the high-offset wheels which meant the rear axle had to widen as well to match.
So they moved the shock absorber outboard of the frame, which precludes swapping the whole axle assembly and all the brake parts subtly changed; like the mounting bracket for the brake backing plate is welded 90 degrees off (its rectangle bolt pattern) and it went from solid disc to vented disc.
I know, that was far more in-depth than it needed to be.

 

[asand1]

Change the gear oil out for one with no friction modifier. You will get maximum traction at the expense of some binding and popping in tight corners.

 

[mlatour]

Originally Posted By: asand1
Change the gear oil out for one with no friction modifier. You will get maximum traction at the expense of some binding and popping in tight corners.


This would have been my suggestion as well,
perhaps too much friction modifier used.

Drain / refill and only add enough so dry pavement / warm weather operation doesn't chatter excessively.

 

[Colt45ws]

Since we are not allowed to delete anymore, this remains as a testament to my mistake.

 

[another Todd]

Originally Posted By: pcoxe
The clutch pack will tighten more under torque. Setting the parking brake to where it drags kinda heavy will work to increase the torque loading to get both wheels moving. Just remember to release it once you get moving. I used this trick a couple of times on my old positraction equipped El Camino to get moving on ice.


This.