Upgrade OEM LSD with FRPP M-4700-C Carbon Pack?

AutoXRacer · Oct 26, 2009

OK, I am inquiring about the M-4700-C carbon clutch disc rebuild kit...

Has anyone gotten these installed?

I have a 2008 with only 23,000 miles on it...but the one wheel spinning action while trying to exit a corner is really annoying me. I ultimately will replace the t-lok with a Detroit True-trac.

For the meantime, I thought I'd save some money and just upgrade the stocker with the carbon discs.
It is my understanding that you can rebuild the pumpkin (LSD) while still in the car...without having to unbolt the carrier.

I have read that the carbon discs provide more lock... Is this true?

My only reason for rebuilding my stock is to get more lock while exiting corners...

Can anyone comment?

Thanks

SpartaPerformance · Oct 26, 2009

Yes the carbon clutches are more "grippy" but it's also one how you pack the shims. I unlike the instructions pack the diff with shims dry as opposed to soaked in gear oil, I find I can squeeze and extra shim or two..... You don't want it super packed but an extra 1 or two over stock doesn't hurt.

AutoXRacer · Oct 26, 2009

You mean one or two disks on each side...?

walter · Oct 26, 2009

I would have gone with a detroit truetrac unit. With a torsen unit the only maintenance you have to do is changing the fluid. No wear parts. In addition the lock is more progressive then a clutch type that makes it better for road racing and auto-x.

AutoXRacer · Oct 27, 2009

walter said:
I would have gone with a detroit truetrac unit. With a torsen unit the only maintenance you have to do is changing the fluid. No wear parts. In addition the lock is more progressive then a clutch type that makes it better for road racing and auto-x.

I will be going with a Detroit True-trac sometime next year...the carbon clutch packs would only be a hold me over till then.

walter · Oct 27, 2009

Atta boy. Coming from a Nissan where a damn LSD unit costs in the neighborhood of at least 900 bucks for a simple 2 way unit from Nismo you could imagine how pleasantly surprised I was to see that a truetrac is in the neighborhood of 400 bucks

AutoXRacer · Nov 4, 2009

I ended up ordering the Truetrac... Roush put them in their Trak Pak cars, so its good enough for me. The POSI is a little too aggressive, plus I don't want to be changing clutches every season or half season.

Roush is having some really good sales on these Truetrac and POSI units...that is until the inventory is gone!! $350 for either, that at least $100 off from anyone else online for the Truetrac and $150 off the POSI...

Get them now!!!

Anyway, I'll be installing mine in December... We'll see how this thing performs.

walter · Nov 4, 2009

Awesome!!! keep us posted.

metroplex · Nov 7, 2009

Every 03-04 Cobra, 05-up S197 GT, 07-up GT500 comes with the carbon fiber clutches from the factory.

As for the Torsen/True-Trac, they don't provide nearly as much torque biasing as the clutch driven LSD's. As for being stouter, it depends on the design. The 2-pinion TrueTrac kept breaking left and right on all Ford 8.8" applications. They've upgraded to a 3-pinion design, but in the end the torque-biasing units aren't exactly the best choice for a rear LSD.

The Traction-Lok is probably the best way to go unless you are doing dedicated auto-crossing. The clutches are easy and inexpensive to replace. I grenaded my TrueTrac and they wouldn't replace it, and it's not easily repairable.

AutoXRacer · Nov 7, 2009

metroplex said:
The Traction-Lok is probably the best way to go unless you are doing dedicated auto-crossing. The clutches are easy and inexpensive to replace. I grenaded my TrueTrac and they wouldn't replace it, and it's not easily repairable.

So I take it you don't like the Truetrac, regardless of what happened...?

Any details on your experience with it and what happened that it blew?

metroplex · Nov 7, 2009

AutoXRacer said:
So I take it you don't like the Truetrac, regardless of what happened...?

Any details on your experience with it and what happened that it blew?

The Torque-biasing/Torsen style differential is really suited for front differentials on FWD/4WD/AWD cars. It's been used widely in RWD applications but I feel that for normal driving / daily driving, it's not that useful as a speed-sensitive or clutch-driven rear differential. The clutch driven LSD's like Traction-Lok offer a lot of function and are easily rebuildable in your own garage.

My TrueTrac busted open in the Crown Vic. 3 of the 4 bolts holding the side plate just snapped and it caused weird stuff to happen, like keep my axles spinning together during a turn or not "lock" when I applied torque. They claim to have improved the design but I'd recommend sticking with a brand like Zexel/Gleason/Toyoda/Torsen (the FRPP Torsen as an example) or Quaife or just rebuild the Traction-Lok.

I like the stock carbon clutches in my 07 GT rear diff, no complaints from me. You can do the +1 clutch mod if you want.

Pop's · Nov 16, 2009

Could you explain a little more about the +1 clutch. I'm due for new clutches and as long as everything is opened might as well do all that's possible for traction. I do lapping during the season and would like to get as much traction as possible exiting corners.

Thanks

metroplex · Nov 16, 2009

The +1 clutch mod is an old trick used for the "B" clutches (the ones that Ford used since 1986 before the "C" carbon fiber clutches debuted in the 03 Cobra). Basically instead of following the clutch and steel plate arrangement, you tweak it a little and add an extra clutch per axle and remove some steel plates from each axle side.

Rebuilding Your Traction Lock Differential

UBB Error - Crownvic.net

The drawback is that you need 2 extra clutches that are in reasonably new condition. That may require buying another kit, or you could see if anyone has take-offs that you can use.

The alternative is to stick with stock, which isn't too bad.

I have the +1 clutch mod with the "B" clutches on my Crown Vic. My 07 GT still has the stock carbon fiber clutches.

Upgrade OEM LSD with FRPP M-4700-C Carbon Pack?

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