Bullet-proofing the rearend

[HwyCruiser]

I smoked my Ford limited slip at the track Sunday. One-wheel peels all day.

My supercharger guy is pricing up a rearend kit group buy on mm.net (limited slip or locker, with or w/o axles, install kit), I'm looking at the 31-spline Eaton limited slip / Moser c-clip style axle kit he's putting together to try and beef up the rearend.

I talked to a local about rebuilding the Ford limited slip and rebuild kit + labor is about $300. I don't think I'm going to go this way just to have to do it again next year.

For the guys that do their own work, on a scale of 0 (novice) to 10 (SAE cert tech), where does this job fall in? How many hours would it take for someone that knows what they are doing to swap limited slips and axles with new bearings & seals? Just trying to ballpark labor.

[p71towny]

about 6 if you have to set up everything again. I'd suggest a girdled cover plate to tighten up the housing. At any rate its gonna be $$$.

[Blaze86Vic]

I would suggest not getting a clutch based limited slip unless you get a race version. But either way you go, if you get a clutch based limited slip, it will ware out again. If you are completely drag I would go with a locker. If you drag, and daily drive or autocross, I would suggest some sort of torsion differential. I have detroit TrueTrac, and someone else here has a T2 Torsion differetial as well. The advantage to his is that it is what I have as well as a clutch helper to increase the bias. Either one is far better than clutch based versions. Holding bias of the TrueTrac is far greater than that of an Eaton LSD. Also, torsion diffs do not do a 50/50 power distribution. They destribute power to the wheel with the traction, opposite of an open diff. But the ability for the wheels to spin independantly under low power means that daily driving is going to be undisturbed unlike a locker or clutch shudder.

[HwyCruiser]

Thanks, I'll start researching the True-Trac 31 spline.

[N A]

I'm surprised no one told you to have the axle tubes welded to the pumpkin.

[HwyCruiser]

I emailed Detroit Locker last night about the TrueTrac since the Marauder isn't specifically listed in their application guide. I included my hp & tq specs and the fact that I occasionally race it on drag radials.

I got a response from the aftermarket sales manager today and his concern was running it in a Ford 8.8" rearend and how much force it was going to have to handle on a hard launch. He said there are Lightning guys running their 9.75" carrier in the 10's and 11's, but the 8.8" carrier isn't as stout as the 9.75".

He said there are Mustangs doing quite well with the 8.8" and they haven't heard of any breaking since they redesigned it last year, but I might be on the edge with a heavier car pushing 400+ rwtq through shorter gears. Maybe too much for the carrier to handle? He suggested that I look at upgrading to a 9.75" rearend. Not something I'm looking at doing at all right now.

So it looks like I'm going with an Eaton and hope it holds up for a couple of years, and then rebuild it when the clutches go. There's a lot of Marauders that have switched to the Eaton after the traction-loc took a dump, so that seems like the safe bet.

[SLYDAWG]

beefed rear

" I'd suggest a girdle"

I must agree here. In addition to a girdle, like the ones built by TA, replace the end cap bolts with studs. The 8.8 rear is pretty stout and will take a lot of abuse. A/Trans soften the blow a little at launch. The Stang guys are launching at 5000 rpm+ on slicks. They are tearing up the T-5s, but not hurting the 8.8

If you think you may get into the mid 11s, may as well plan on C-clip eliminators as required by NHRA at 11.49.

I think your solution will be a non clutch type posi unit, 31 spline axles, and a girdle.

[N A]

I'm surprised no one told you to have the axle tubes welded to the pumpkin.

Don't forget my post. Have the rearend removed from the car and checked to make sure it's straight. Then have them weld the axle tubes to the pumpkin. Put in the 31-spline axles, the Eaton diff, etc. It ain't going to break.

[HwyCruiser]

I already have a Ford Racing girdle and the caps have been studded.

I'm not planning on running any more boost or going with a higher gear than my 4.10's any time soon. I'd like to see a 11.9x sec timeslip and I've got a 100 octane tune just itching for the new diff though. After that, I might race occasionally at meets.

With the uncertainty of a gear-driven diff actually holding together under a hard launch (from the advice of the manufacturer), I'm going to chance burning up a clutch. At least there's something there to give loose. Like I said, the Eatons are holding up well and even seem to be the diff of choice with the Impala SS guys.

[HwyCruiser]

OK, screw it. I decided to go with the 31-spline TrueTrac after hearing Trilogy #1 laid down a 1.5 sec 60 footer on slicks with one. I'm also most likely going to a 4.30 gear during the upgrade since this is the most opportune time to correct that mistake of long ago.

N/A, I'm hearing you on the axle but I'm going to continue to run with the percentages on this one.

One 11.9x timeslip on the stock motor is all I ask, then she's retired to cruising and car shows until the forged motor debuts. And the band plays on...

[N A]

Just do it right the first time, don't skimp on your rearend. You don't want to break at the track. Find a good rearend shop. Have the 8.8" removed from the car. Have the axle tubes welded to the pumpkin, install 31-spline axles with 5/8" wheel studs, 4.30:1 gears and the Truetrac diff.

[Blaze86Vic]

You will not be dissapointed with the TrueTrac.

[HwyCruiser]

Well the 4.30's, Moser axles and TrueTrac diff is in.

I'm taking it easy for the first 200 miles or so but I've noticed a slight clicking noise against a high curb or another vehicle while braking. I don't think it's the gears because it's the same guy that set up my 4.10s.

I've heard that the TrueTrac's click on coast, something about the side gears overrunning the pinions on a no-load condition. It's not loud and I can't hear it with the windows up or on an open road. Maybe it'll go away once everything is broken in good.

[N A]

Sweet!!! Keep us posted with your results.

[Blaze86Vic]

Mine hasn't made any noise what-so-ever since day one....if it doesn't go away in a couple of tanks of gas, I would positivly diagnose where that noise is coming from.