built 8.8 rear?

95PGTTech · Sep 7, 2007

The wife needs a rear in the 98, it's official. Here's the problem: she can't want any one thing. It's our daily driver, it sees 10 passes a week, and now she's hardcore into autocross and spirited country driving. So it has to be bullet proof, the fastest I can ever see it going is 11's but it needs to be able to hold up to burnouts and slicks, and it needs to not be a straight-line only car (there goes my easy answer...spool or locker).

Even reading up on the Torsens (who cares about price, if I only have to pay once and not each time she breaks it it's actually cheaper!), the cast iron case is not designed to deal with the shock-loading of dragracing. grrrr.

My best guess:

some kind of diff!
Moser 31 splines
4.10s or 3.73s - leaning towards 4.10s...would go 4.30 but the autocross...
welded axle tubes
ARP studs
FRPP girdle
FRPP stud kit

19mustang95 · Sep 7, 2007

c-clip eliminators..i would just use a ford 31 spline t-loc since you need it for daily drivign and cornering and such.

95PGTTech · Sep 8, 2007

Why use c-clip eliminators and will I have to worry about shock-loading the diff?

I saw this at Summit but the description is VERY vague...DTL-913A561

Eaton Detroit Truetrac Differentials
Differential, Eaton Detroit Truetrac, Limited Slip, 31-Spline, Ford, 8.8 in., Each

Get more power to the ground.
These Eaton Detroit Truetrac differentials use a patented design of parallel-axis planetary helix gears to provide a quiet, automatic splitting of torque. They perform like an open differential under normal driving conditions, automatically transferring torque to the wheel with better traction when ground conditions warrant.

I understand what you're saying though - use an OEM-type clutched differential - now if I could only find one I don't have to worry about blowing up.

ripper · Sep 8, 2007

No need for c-elim. unless you plan on makin 600hp. Tru-Trac with moser 31 spline axels. They do make noise though. But unless you have a stock exhaust you wont notice it. Never do another rear again :banana:

Paul · Sep 8, 2007

Here's the combo I've seen used to run 130+ mph trap speeds, be driven on the street all the time, and abused mercilessly:

F150 (31 spline) Trac-Lok with carbon fiber clutches
Your choice of decent 31 spline axles
Ford 3.73s
Your choice of a girdle
New seals, bearings, etc...

Welded axle tubes would be nice too, but I'm not sure it's actually necessary in this application.

C-Clip eliminators are unnecessary and suck on the street, plus they tend to leak.

Another option would be 9" ends with custom axles.

Paul.

95PGTTech · Sep 8, 2007

what year(s) F150 can I pull that out of, and where did you source your clutches from? Thanks for the heads up!

Paul · Sep 8, 2007

I believe FRPP sells the clutches, but you'll have to do some digging on the years for the F150 diff.

It's a great setup - I have two personal friends that run this exact setup. Both have trap speeds >130 mph, both drive them on the street all the time, and neither have any problems.

Paul.

uncltrvlnmatt · Sep 9, 2007

Pull the 8.8 and put in a 9 inch. Use a nodular housing, traction lock, 31 spline axles and 3:91 gears. Or you could have 2 pumpkins and swap them out for a quick ratio change depending on your aplication.

ripper · Sep 9, 2007

Good info on the 150 dif Paul. Im gonna look into that. O0

I havent done my rear yet and when Kevin was tuning my car the trac lok was working. He said it could have just been the heat from so many hard pulls was makin the clutches work.

I got a friend who owns a junkyard so gettin a F-150 diff will be easy for me.

Slow95Cobra · Oct 3, 2007

i personally dont recommend the moser axles.. they were a PAIN in the ass for me.. 2 sets of axles were rong for the abs rings, and then when i pulled the rearend apart for the gear, re-built the diff... put the new axles in, then the pin... BOOM, the axles are to long. had to grind the pin down to make it all work.. several people i know had this problem.

id go with a eaton diff. personally....

95PGTTech · Oct 3, 2007

what axles would you suggest for a 31 spline then?

ripper · Oct 4, 2007

Dont use Strange. They are too brittle for street use.

Passenger · Oct 4, 2007

Slow95Cobra said:
i personally dont recommend the moser axles.. they were a PAIN in the ass for me.. 2 sets of axles were rong for the abs rings, and then when i pulled the rearend apart for the gear, re-built the diff... put the new axles in, then the pin... BOOM, the axles are to long. had to grind the pin down to make it all work.. several people i know had this problem.

id go with a eaton diff. personally....

I'm not saying you done this, but, More than likely, the axles being too long comes from the fact that 99-04 cars are roughly 3/4" wider between the rear wheels than our sn95s. Just like sn95s are about the same (3/4" wider) than a fox. You must be specific with them!

If for some strange reason any of you ever need another stock axle, keep in mind that V6 cars, and GT's use the same axle shafts. There is NOTHING different about them. Local Mustang salvage yard wanted $100 for a stock axle, yet they're only ~$84 new from your local Autozone/Advanced!

Slow95Cobra · Oct 4, 2007

i know the 99 ups are a inch wider rearend... that wernt quite that far to long... i checked the part number 400 times, it was rite, i even called moser and asked them... they said thats how they made them. i was really ticked them.. i dont see how hard it is for someone to measure a factory length axle and make it the same... they never gave me a straight answer...lol. a guy i work with, his brother bought 31 mosers for his fox... same problem. on both of them we ground the pin down level with the 2 flat spots mine in the pin... then it all worked

Spd0lit · Oct 8, 2007

i'm doing the same thing right now.
Moser 31 spline
Detroit trutrac
welded tubes
FFRP Girdle
3.55s(planning on supercharger)

I'm done quite a bit of research and everyone has said it is almost bullit proof