Need to build rear end....need laymens terms

2003gt · Aug 21, 2004

i need to build my rear end, due to DR's and lots of HP......please help

2003 gt 400hp, 425lbs TQ nitto 555r 315/35/17's

stock rear end

i need specific suggestions......i don't want any Professional every day drag stuff, just something that will support the power

thanks

2003gt · Aug 24, 2004

can anyone help me......

4.6_02_Black_GT · Aug 24, 2004

Eaton 8.8 posi diff with 31 spline $500
Ford Racing 4.10 or 4.30 ring and pinion $160
31 spline axles $250 per set
Mac Diff cover(ribbed and has studs to pre-load diff) $120

You'll be good for up to....1000 hp in street trim.

scalder · Aug 24, 2004

Spool that bad boy...and no more worries!

trents99 · Aug 25, 2004

4.6_02_Black_GT said:
Eaton 8.8 posi diff with 31 spline $500
Ford Racing 4.10 or 4.30 ring and pinion $160
31 spline axles $250 per set
Mac Diff cover(ribbed and has studs to pre-load diff) $120

You'll be good for up to....1000 hp in street trim.

Ditto that and pick up a set of upper control arms and lower control arms. They range in price so go check out places like Maximum Motorsports, Steeda, X2C, UPR and so on. May also want to look into some subframe connectors.

Playa · Aug 25, 2004

i am running on:
Auburn pro Differential:
the thing that the axles connect into, and the drive shaft connects to this(kinda)
Moser 31 Spline axles:
stock is ?28?, the extra splines help to reduce slipping where the axles meet the diff(if it were to happen)
Ford Racing gears:
depending on your setup, 4.10 or 4.30. you will need to do that research. but do not buy any other gears than FMS, IMO.

and i dont have one, but a Differential cover. alot stronger than the stock stamped peace.

also, make sure you get new berarings and all that for the "rebuild".

stallion98gt · Aug 25, 2004

SVO (ie TA performance) differential cover with longer studs. Moser 31 splines.Eaton posi.
MM arms.

white99gt · Aug 25, 2004

A eaton and 31 spline axles will do you fine depending on how hard you race it..Ive bent two sets of axles.SO i went to a 33 splined spool setup..

2003gt · Aug 27, 2004

can I do any of these in turn, like by the axels (install) then buy the other pieces 1 at a time.......or what can i buy first to install, then upgrade slowly ???

thanks for all the help !!!

forpit2000gt · Aug 28, 2004

if you switch to 31 spline axles, you must switch the carrier to 31 spline at the same time. To save on labor, you need to get axles , carrier, and gears , then install at once. With drag radials, your stock axles will last pretty well. You can damage even 31 spline with a lot less hp than you have depending on launches and traction. I bent 31 spline Strange axles and destroyed the spider gears with just 235 rwhp and a 6000 rpm launch. Save up or just buy a piece at a time until you have it all. UCA, and LCA will help with traction, but can be added at any time.

jbrown · Aug 28, 2004

4.30's or even 4.10's seem like too much gear for a supercharged 400hp car

2003gt · Aug 28, 2004

i have been told probably to go with 3.73's

fastback brian · Aug 28, 2004

2003gt, your engine/exhaust setup is basicly the same as on my 99, the power is a bit off, maybe you dont have a bullit intake. Anyways, I have had good luck with my "stock" 03 cobra posi, superior axles, and 4.30 motorsport gears. I run only on MT tires on the street so I dont have much of a traction problem from a roll. lots of miles on the setup, four sets of ET streets and no problems.

2003gt · Aug 28, 2004

sweet....thanks......ya, my car is completely stock except for the blower (and obvious upgrades) and full exhaust...i wanna fortify my bottom end more than anything right now....but i think i'm going to save up slowly for all this rear end stuff.........

fastback brian · Aug 28, 2004

The rear axle upgrade is worth every penny, I understand how most on here will say that 3.55-3.73 gears are what you should run, Ive been there and tried them, but my car is way faster even while spinning a 315 radial with the 4.10' and now the 4.30's. You may wanna go with the 4.10 gears utill the engine gets upgraded to handle more rpms and power. Eaton posi's seem to be the best choice right now.

2003gt · Aug 31, 2004

alright....i heard that if I can find a older "high" end model Explorer, it has an 8.8 posi differential, with 3.73 gears in it..... I don't know if its true, but if it is.....can I use this ? and just buy some strong new axels to go with them ???

thanks

Cobra Jay · Aug 31, 2004

2003gt said:
alright....i heard that if I can find a older "high" end model Explorer, it has an 8.8 posi differential, with 3.73 gears in it..... I don't know if its true, but if it is.....can I use this ? and just buy some strong new axels to go with them ???

thanks

That is correct. It's an optional up grade. I'm not sure what years to look for in junk yards, but I can find out for you if you'd like. The upgrade is an 8.8 with 3.73 gears. It's an IRS, but you can use the carrier and gears(that's what I'm assuming you're planning on doing). You can also add to that list some Rangers,Explorer Sport Tracs, & Mountaineer's. Also believe it or not, there are quite a few F-150's, Expedition's, & Navigator's that come with 8.8's rears and 3.73's. Most are 3.55's though, but they all come with 31 spline carriers and shafts. Also all the FRONT axles on the 4x4 models (F-series,Nav,Exped.) are an IRS 8.8 and will have the same gear ratio as the rear axle. I guess it just depends on which one you can get cheaper.

For axle shafts, I'd go with the Mosers'. I got mine $274.95 delivered to my door. That was with studs and mounts for the ABS exciter rings installed.

crew_dawg16 · Aug 31, 2004

2003gt said:
i have been told probably to go with 3.73's

I was going to say, for a supercharged car, you want a little bit wider gear, 3.73s or 3.90s would be just right.

2003gt · Sep 1, 2004

GT JAY said:
That is correct. It's an optional up grade. I'm not sure what years to look for in junk yards, but I can find out for you if you'd like. The upgrade is an 8.8 with 3.73 gears. It's an IRS, but you can use the carrier and gears(that's what I'm assuming you're planning on doing). You can also add to that list some Rangers,Explorer Sport Tracs, & Mountaineer's. Also believe it or not, there are quite a few F-150's, Expedition's, & Navigator's that come with 8.8's rears and 3.73's. Most are 3.55's though, but they all come with 31 spline carriers and shafts. Also all the FRONT axles on the 4x4 models (F-series,Nav,Exped.) are an IRS 8.8 and will have the same gear ratio as the rear axle. I guess it just depends on which one you can get cheaper.

For axle shafts, I'd go with the Mosers'. I got mine $274.95 delivered to my door. That was with studs and mounts for the ABS exciter rings installed.

So, I could find a used 8.8 posi with 3.73 from an explorer, (would this bolt right up to my car ?) and then buy the axels with the right spline ?

04DarkShadowGT · Sep 1, 2004

I prefer the Auburn Pro for two reasons, they have a deal where you can send the diff in when the cluthces go bad and get the whole things replaced for the same price as other companies clutch pack kits. Much better deal IMO.

And the biggest reason. THey are made in Auburn, IN where I am from

Im going Auburn Pro, Moser 31 spline axles, 4.10 gears, weld tubes, weld torque boxes, LCA, and Diff cover.

Need to build rear end....need laymens terms

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