LSD vs Open Diff - FFCars.com : Factory Five Racing Discussion Forum
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post #1 of 19 (permalink) Old 04-09-2019, 03:14 PM Thread Starter
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Icon21 LSD vs Open Diff

While putting my axles back in on my 8. rear end, I managed to get the S shaped washers in wrong. A 1/2 mile later they popped out and got mangled by the ring gear. I cleaned out the debris, added new oil, and went for another short drive. I had just put in Wilwood brake kit front and rear. Really wanted to try the new brake(they are fabulous). I really didn't noticed the missing LSD. So, I went for a 300 mile drive. Worked great for open road driving even at a spirited pace on twisty back roads at 30 to 80mph. I guess I'm trying to convince myself to spend $1800 on a True Track diff. I never do drag starts. Motor is a 331 with heads and all that for about 350hp. Car did feel a little nicer when dive bombing into corners but no real problems coming hard out of corners. I know that depends on how much throttle is used coming out of the corners but I'm not trying to be Ricky Roadracer. Time will tell.


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post #2 of 19 (permalink) Old 04-09-2019, 03:31 PM
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Marty, for all out performance the LSD is probably the way to go, BUT the car is safer with an open differential. When the tires brake loose on hard acceleration this will keep the car from wanting to come around because both tires mostly likely won't spin, therefore one keeps traction and holds the back end from coming around. Not saying that it's impossible for it to come around, but more than likely it won't.

It sounds like for what your doing your never going to miss it.

Just my 2 cents.


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post #3 of 19 (permalink) Old 04-09-2019, 04:11 PM
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I love my Torsen. I fell in love with them on my old miata, it behaves very predictably, particularly in low traction like rain. I don't plan my car on perfect conditions, but on the worst case I want to drive, so this fits nicely.
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post #4 of 19 (permalink) Old 04-09-2019, 04:49 PM
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I am doing a wavetrac . I plan to track my car.

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post #5 of 19 (permalink) Old 04-09-2019, 05:27 PM
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In a low power, low traction car, absolutely won't miss it. In a cobra, I think you'll see some unpredictable behavior at times. 95% of the time, it'll just spin the inside or low traction tire. Then 5% of the time when you are expecting a one wheel peel, it'll spin both and the entire dynamic of the car changes. I never found a rhyme or reason. I also found it would sometimes switch from spinning one to the other just trying to pedal the car to catch traction again. That can make for a very unsettling feeling.
At least that's my experience, 88 mustang 2.3T, [email protected], open diff. So similar power to weight ratio.
Again, if you are just looking to cruise, the open diff is probably fine, but be aware they can behave unpredictably when pushed to the limit and beyond.

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Originally Posted by JimS View Post
Marty, for all out performance the LSD is probably the way to go, BUT the car is safer with an open differential. When the tires brake loose on hard acceleration this will keep the car from wanting to come around because both tires mostly likely won't spin, therefore one keeps traction and holds the back end from coming around.

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post #6 of 19 (permalink) Old 04-09-2019, 06:35 PM
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I don’t understand, was it not a ford trac loc LSD before your incident?
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post #7 of 19 (permalink) Old 04-09-2019, 06:55 PM
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I currently have an open differential installed in my GTM. I know it's apples to oranges but there are a lot of similarities. I'm not as concerned with acceleration as I am with how the car behaves under hard braking, especially on the track. With our sticky modern tires, we can hook up pretty well. Under hard braking, ie on the track, the car rear can get squirrely with an open differential and make the car unsettled. Time will tell, but I think that would be the reason I add a LSD if I do.

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post #8 of 19 (permalink) Old 04-10-2019, 12:19 AM Thread Starter
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It was a Track Lock diff but without those spring washers there is not enough pre load on the clutch packs to bring them in to play.

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post #9 of 19 (permalink) Old 04-10-2019, 03:08 AM
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Well, I saw LSD.....but you guys …….whoa! Flashback....gotta go
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post #10 of 19 (permalink) Old 04-10-2019, 12:08 PM
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If open diff doesn't bother you then it is fine. I absolutely wouldn't want one though. I strongly would not recommend a TrueTrac. I had one and it was great in autocrosses but not on the street. A characteristic of them is they add in extra drive line slop. Another is that they wear out and no internal parts are available. Ford has a carbon fiber clutch plate version of their standard lim slip and Summit sells it for a bit under $200. That is what replaced my TrueTrac. Well things have changed.
https://performanceparts.ford.com/ca.../Differentials
It may now be $400. They do offer a rebuild kit that includes the S spring though.


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post #11 of 19 (permalink) Old 04-10-2019, 09:03 PM
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Without the posi going around a slow corner (like the bank drive-thru) loses a lot of it's panache....

I'd have finished a long time ago if I knew they were this fun!


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post #12 of 19 (permalink) Old 04-13-2019, 02:45 PM
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I ran a spool, however that was a car that ran into the [email protected] mph at 2800 lbs ..My street cars ran lockers at low [email protected] mph full weight 1300 lb through the exhaust.

My Cobra is going to have the Mustang IRS and still haven't decided which differential I'm going to use. But it will have 800ish big block which will see autocross, the road course, and the drag strip.

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post #13 of 19 (permalink) Old 04-14-2019, 12:41 PM
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I put this style torsen in my car and absolutely love it! No chirping of the one tire around a corner and no sliding sideways around a corner when the road is wet.

https://www.powertrax.com/product-in...action-system/
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post #14 of 19 (permalink) Old 04-14-2019, 07:34 PM
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Quote:
Originally Posted by Marty D View Post
It was a Track Lock diff but without those spring washers there is not enough pre load on the clutch packs to bring them in to play.
This is partially true. If you have one wheel totally up in the air, yes, it will be open.

However, both wheel on the ground, the spider gear load will lockup the clutch pack. That’s why you are not missing the LSD, you’re not open. Maybe not as thight than with the S-Spring but still LSD.
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post #15 of 19 (permalink) Old 04-14-2019, 11:21 PM
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Quote:
Originally Posted by totem View Post
This is partially true. If you have one wheel totally up in the air, yes, it will be open.

However, both wheel on the ground, the spider gear load will lockup the clutch pack. That’s why you are not missing the LSD, you’re not open. Maybe not as thight than with the S-Spring but still LSD.
Is Trac Loc a decent system?
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post #16 of 19 (permalink) Old 04-15-2019, 11:13 AM
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I would not put an open diff in a car with this much power. You need both wheels driven to help traction. Buy a Ford trac lok, they are great for the street. I had one in my track cobra for years. Levy had a trick to install more clutch plates to make the diff tighter. A stock 8.8 trac lok is perfect for the street.

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post #17 of 19 (permalink) Old 04-15-2019, 08:12 PM
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Ditto what Trevor said. I bought two rebuild kits and then used the High Performance stacking method alternating the frictions and steels. You only need two frictions out of the second kit but you can easily sell the leftovers. Works like a champ.
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post #18 of 19 (permalink) Old 04-15-2019, 10:18 PM
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Quote:
Originally Posted by selo View Post
Is Trac Loc a decent system?
I think it is just fine. There are some fine points to a torsen type system when you get to that last 5% at the very tip of the high performance cornering behavior. But there are some drawbacks to some (see my post above) and different drawbacks to other versions. The Ford clutch type Trac Loc works very well and has no drawbacks. As mentioned above, it can even be somewhat tightened up w/ alternate assembly techniques. And parts are available pretty inexpensively if you were to ever wear one out.
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post #19 of 19 (permalink) Old 04-16-2019, 12:15 AM
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It's been a long time since I rebuilt my traction-lok but I think that I used an S-spring for a pickup truck. Much stiffer and was a bear to install.

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