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May 18, 2011 10:43 a.m. ReverendDexter SuperDork

Okay, the 5.0's starting to be a bit more one-tire-fire than I'd like.

Currently has the stock Trac-Lok.

I've got a rebuild kit for it up at my 'rents, as well as as set of 3.73s (which honestly seem like too much gear for a car that's done at 4500 rpm, but whatever, don't fear the gear, right?).

Is there a better option for an LSD that won't break my bank other than just rebuilding the stocker? Seems like anything I look at (Torsen, Detroit, Auburn) bumps this from a $2-400 project to a $1k project in a right hurry. If budget was not a concern, I think I'd want the Auburn that's both an LSD and an e-locker.

I've seen a Detroit snap a half-shaft, and I've heard Torsens only work if both tires have at least some traction. I'm not interested in a Lincoln-locker or spool at this point.

Car is mostly AX, but still street driven. Has seen some drifting, may see more in the future.

In short, what LSD is recommended for a Ford 8.8" that's not hella expensive?

Thanks!
May 18, 2011 11:05 a.m. e_pie New Reader

I've always liked torsen diffs, but I have no real reason for it other than personal preferance and I like how they work (no real wear parts compared to a more conventional clutch type diff)
May 18, 2011 11:43 a.m. Strizzo SuperDork

you could rebuild the 8.8 with the (i think from the truck version) heavier preload springs and two rebuild kits for a tighter diff if thats what you're wanting, even the stock clutch style lsd only has the spring preload when one tire is at zero traction.
May 18, 2011 11:57 a.m. pres589 Dork

Summit sells a Ford Racing branded Torsen for $535;

http://www.summitracing.com/parts/FMS-M-4204-T28

That's the one for 28 spline shafts, which I think your Mustang has. If it has 31's, there's this;

http://www.summitracing.com/parts/FMS-M-4204-T31

I've thought this might be a nice upgrade for my street SN95, possibly for next year (trying to find a way to get some serious suspension upgrades done first, budget isn't happy) and am curious how you've got a $1k bill on this, assuming you do the install yourself.
May 18, 2011 12:20 p.m. Javelin SuperDork

You can easily rebuild the trak-lok with more plates in it. Old drag racing trick that's been around forever.
May 18, 2011 12:56 p.m. ReverendDexter SuperDork

Strizzo wrote:

you could rebuild the 8.8 with the (i think from the truck version) heavier preload springs and two rebuild kits

Javelin wrote:

You can easily rebuild the trak-lok with more plates in it. Old drag racing trick that's been around forever.

Please sirs, tell me more.
May 18, 2011 1:24 p.m. PseudoSport Reader

I used a beer can to preload the worn out limited slip in my challenge car. I just traced one of the frictions on a beer can and installed my shim between the housing and one of the steel plates. This was good for 150 ft lbs of preload. Budget hit was $0.05 MA deposit.
May 18, 2011 1:45 p.m. Strizzo SuperDork

ReverendDexter wrote:

Strizzo wrote:

you could rebuild the 8.8 with the (i think from the truck version) heavier preload springs and two rebuild kits

Javelin wrote:

You can easily rebuild the trak-lok with more plates in it. Old drag racing trick that's been around forever.

Please sirs, tell me more.

http://www.angelfire.com/theforce/5ohcpa/cpa5ohtech018.htm

basically, instead of the factory order of shim, friction disc, two steel splined discs, friction disc, two more steel splined discs, friction disc and then side gear you replace some of the steel splined discs with friction discs and alternate them 1 for 1. so the order would be: shim - friction disc - steel - friction - steel - friction - steel - friction - side gear
May 18, 2011 3:38 p.m. ReverendDexter SuperDork

Okay, so, what sort of behavioral difference will this cause with the differential?

I'm not sure of the vocabulary to describe how "locked up" a differential is... I'm guessing that the differential allows a certain amount of slip before it "locks up" and then there's going to be a certain threshold torque that exceeds the holding capacity of the differential and it starts slipping again.

Looking at a clutch type, it seems like the differential is always locked until threshold torque, so by adding more friction disks, this would just increase the amount of torque it would take before you hit that limit.

Is that anywhere in the ballpark?
May 18, 2011 5:26 p.m. a401cj Reader

honestly RD, and don't laugh me off the board for saying this, either spool it or put in a Lincoln Locker (welded spiders). I run ARB's in both ends of a CJ and for the heck of it have left the rear locked whilst driving around town. It will bark the tire when turning sharp. Otherwise, there is not one adverse effect of running it locked. Not one.
In theory it could be disadvantageous on the Auto-X course but I think you might be surprised. While I haven't (for obvious reasons) AX'd the CJ, I do remember reading in Mark Donahue's book The Unfair Advantage that a locked rear was always faster during testing. He may have been referring to a Detroit Locker but those are 100% locked anytime you are on the gas AND they tend to lock / unlock at weird times. I can't imagine a spool would be worse
May 18, 2011 6:43 p.m. jimbbski Reader

ReverendDexter wrote:

Okay, so, what sort of behavioral difference will this cause with the differential?

I'm not sure of the vocabulary to describe how "locked up" a differential is... I'm guessing that the differential allows a certain amount of slip before it "locks up" and then there's going to be a certain threshold torque that exceeds the holding capacity of the differential and it starts slipping again.

Looking at a clutch type, it seems like the differential is always locked until threshold torque, so by adding more friction disks, this would just increase the amount of torque it would take before you hit that limit.

Is that anywhere in the ballpark?

I've done this on 2 of my Mustangs at least 3-4 times. Really all you do is reverse the order of the steel plates and friction dics. Where you had 4 dics and 3 friction plates you now have 4 friction and 3 dics. The other thing is to use shims thick enough that just allow you to install the "C" clip and then the spider gear crosshaft. I have sanded some metal off the end of the axel shaft so that i could install the crosshaft. Also you do not need two kits if you reuse 2 or your old friction plates. Also do not use the friction modifiyer it defeates the purpose of the diff rebuild. Yes it may be a little jerkey around tight turns but what do you want? Better traction or ?
May 18, 2011 7:30 p.m. Will HalfDork

I like the Eaton True Trac. I have two in 8.8s and one in a 9-inch.
May 18, 2011 7:31 p.m. dj06482 Reader

In addition to the different stacking orders of the plates, Ford Racing has a rebuild kit with carbon fiber plates that's supposed to be a slight upgrade, as well:

http://www.fordracingpartsdirect.com/product_p/m-4700-c.htm
May 18, 2011 8:56 p.m. BobOfTheFuture HalfDork

Heh heh heh. Must be nice having differential options unter $700.
May 18, 2011 9:50 p.m. Maroon92 SuperDork

BobOfTheFuture wrote:

Heh heh heh. Must be nice having differential options unter $700.

YOU AIN'T KIDDING! 1400 is twice what I paid for the WHOLE CAR!
May 19, 2011 9:04 a.m. ReverendDexter SuperDork

BobOfTheFuture wrote:

Heh heh heh. Must be nice having differential options unter $700.

It's the reward for putting up with a Mustang
May 19, 2011 11:25 a.m. RossD SuperDork

BobOfTheFuture wrote:

Heh heh heh. Must be nice having differential options unter $700.

You mean under $500: http://www.ringpinion.com/ProductDetails.aspx?ProdID=1907&Part=TT_912A562&...
May 19, 2011 11:33 a.m. Ranger50 HalfDork

I've done the additional clutch disc swap and installed a PITA F-series S-spring. No driveablilty issues doing that.

Also, as much as the truck motor 5.0 operates like a truck motor, I put in 4.10's in my 89GT at the time and couldn't have been happier, 275/50r15's at the time too. I launched it at about 2k on the strip, shifted at 5400 3 times, and the shift light came back on about 3' before the finish line stripe.
May 19, 2011 1:49 p.m. ReverendDexter SuperDork

The... strip? :blank stare:

I'm more curious why you ran yours out to 5400 rpm. Put mine on a dyno, peak torque is 3k-3500, after which it drops off pretty rapidly. Peak hp is only 4200, then it drops off like a rock. Seems to me like running that motor out past even 4500 is a total waste.
May 19, 2011 2:21 p.m. Ranger50 HalfDork

You can't race dyno's. Or can you?

The RPM drop with the T5 shifting at 5400 brought it back to about peak torque and through peak HP on every shift. That is how. If you are in one gear all the time, I would stay racing the exact way.

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