Rear end suggestions...

[SlowYellow]

Hello all, I've got a 13' GT500 and I purchased it with about 8K on the odometer. I've had it for about a year and a half, and I'm done with the rear end. The previous owner replaced the gears with a set of 3.73's. I love the gears, however the install that was done by a "cert'd ford tech" I am assuming was done poorly. The gear whine is ridiculous. They are ford racing gears. Beyond that, he gave me no data. That was all that was done in the rear end, I do know that, i.e. no carrier or axle upgrade. I'd like to fix it, and while I have it apart go ahead an replace what needs to be replaced to make it solid. I have aspirations in the far future to make around 1k whp. But like I said, it's a long way away. The cars current mods are:

CJ TB
Metco Idler pulley
2.4" VMP Pulley
Whipple CAI with factory air box
Lund Tune

Soon to be installed:
Kooks LT headers
Kooks Catted H

I'd like to get the consensus on what I should do with the rear end. I'd imagine that I should go ahead and order new gears, because I'm afraid that the gears are going to be trashed when the cover gets removed. I'm open to suggestions, and I appreciate them in advance.

 

[dale.baker]

Hello all, I've got a 13' GT500 and I purchased it with about 8K on the odometer. I've had it for about a year and a half, and I'm done with the rear end. The previous owner replaced the gears with a set of 3.73's. I love the gears, however the install that was done by a "cert'd ford tech" I am assuming was done poorly. The gear whine is ridiculous. They are ford racing gears. Beyond that, he gave me no data. That was all that was done in the rear end, I do know that, i.e. no carrier or axle upgrade. I'd like to fix it, and while I have it apart go ahead an replace what needs to be replaced to make it solid. I have aspirations in the far future to make around 1k whp. But like I said, it's a long way away. The cars current mods are:

CJ TB
Metco Idler pulley
2.4" VMP Pulley
Whipple CAI with factory air box
Lund Tune

Soon to be installed:
Kooks LT headers
Kooks Catted H

I'd like to get the consensus on what I should do with the rear end. I'd imagine that I should go ahead and order new gears, because I'm afraid that the gears are going to be trashed when the cover gets removed. I'm open to suggestions, and I appreciate them in advance.

You can spend $3K on upgrading your 8.8" rear end with all the modifications known to man and at the end of the day you will still have whine and disappointment, guaranteed! I myself sold my rear end when the car was brand new and purchased a 9" from Moser Engineering with 4:11:1 gears. I love the rear end (see my signature). There is some NVH from solid Heim joints and the aluminum drive shaft but no annoying whine. I got 19.5MPG going from Pittsburgh to Myrtle Beach and never came out of 6th gear. 3:73:1 are a waste of time although it is an improvement over the 3:31:1 ratio. Don't fear the gear as Bimini would say. Again lots of opinions out there but take it from someone who has done every modification to one of these Shelbys and has not touched a wrench on my car in 2.5 years. Not bad for 1000HP car! Lastly 1000HP on 20" drag radials is not a recipe for success. There is not a 20' tire that will hold this kind of horsepower on the street. Go to an 18" or 15" and this will give you some sidewall to work with and provide some "give" to your axles and other parts in the reliability department. Hope this helps.

 

[PaxtonShelby]

Paging Dr J @biminiLX

 

[biminiLX]

Paging Dr J @biminiLX

Well, nothing really to add here that hasn't been said numerous times meaning:
1) if you're going for 1000hp, and may even try the drag strip once, go 9" as Dale mentioned above
2) if you'll just do street roll racing or top speed events, rebuild the 8.8 with best parts available AND grab a support brace
Still, when you mention 1000hp, that's enough for me to say save the $1000+ in building the 8.8 to go towards the $3000 9" bill.
By selling the sought after '13-14 8.8 even if whining, you're money ahead to just go 9" over built 8.8"
-J

 

[biminiLX]

And as Dale said, go 315/40/18 NT05R on 18x10-11" for good street traction/manners or the MT/Hoosier aggressive DRs for top shelf street traction but less manners.
I'll be going MT 315/50/17 on 17x11" beadlock Welds for the bling,but the 18x10.5" Darkstars with 325/45/18 Hoosiers were absolutely killer with 4.10s and 965rwhp. Hooking for second roll til 160 was mind blowing
-J

 

[NIXDSG]

M9, be done with it!

NIXDSG

 

[Bearbo]

If you have track pack car, can you still go Moser 9?

 

[Jam421]

[QUOTEif you'll just do street roll racing or top speed events, rebuild the 8.8 with best parts available AND grab a support brace][/QUOTE]
Bimini...what exactly does the support brace do for our rear ?

OP: As stated there's opposite opinions gears and all are valid as per the driving and some say the install. I had 3 sets of 373's installed ..2 different shops...on 2 different GT500's and they always whined....some sooner as in the first hit after 500mile break in some later. On my '13 the 410's with taller 305 MT's (3.90's) do not whine.

I have aspirations in the far future to make around 1k whp. But like I said, it's a long way away.

Not nearly making the power some of these guys are producing but I've also backtracked my mods too many times throwing too much money down the drain. You are making the right decision trying to do it right the first time and unless "far future' is years down the road & you go 410's as a bridge....perhaps you could consider the 9" rear.

 

[Catmonkey]

If one were to go 9", what are the options for a bolt-in unit that uses the factory provision for control arms, shock mounts, brakes and suspension springs? I see BMR has an upper for a 9", but it doesn't say who's and only shows for 07-10.

 

[SlowYellow]

Thanks for all of the suggestions, and I think that I will just save the pennies for the M9, seems to be the smartest choice. The thing that terrifies me about this car, and I'm not sure if it's just because I got used to the IRS in my old Cobra, but when I go on my "drive" it's down a small two lane road, and when I cross over and really get on it to pass someone, the rear end gets SUPER loose. To the point that I have to back out of it. I know that the mods that I listed were all power mods, but I have the additional:

BMR upper mount and upper control arm
BMR lower control arms
BMR panhard bar and brace

All of those things are poly end/spherical end bars, no major NVH to talk about.

I thought that that would fix my "walking" issue with my rear end, and it did not, at all. It feels like the rear end is shifting, followed by SEVERE body roll and for sure a wreck if I didn't back out of it. I'm wondering if I'm spinning, I have new MT DR's on it, but they are 20's. My cobra always had those on it, and it never spun, even when cold and I was running about 650 WHP with that one. Not nearly the torque that this one is running, they really are two different beasts though. But the tires are the exact same tires, just 18's on the cobra and 20's on the GT500. As far as gear recommendation, I feel like the 4.10's would be overkill. I'm sure that I could be talked into them though, lol. Again, thanks for all of the feedback.

 

[biminiLX]

I just bolted in my Strange Cobra Jet housing tonight.
BMR UCA and all other suspension bolted right up, no headaches I was expecting.
Hell the driveshaft may even work with a different yolk.
True you're looking at $3000 but it's a foundation you'd never need to worry about.
If you intend to keep the car for years and drag race it even semi regularly, the 9" is the best option.
-J

 

[KENS96M6]

Would be very interested if the stock CF DS could be made to work. Its a shame to part with such a nice factory piece. I agree about the 9'', I have one in another car and it is probably the only thing I will not outgrow.

 

[SlowYellow]

I just bolted in my Strange Cobra Jet housing tonight.
BMR UCA and all other suspension bolted right up, no headaches I was expecting.
Hell the driveshaft may even work with a different yolk.
True you're looking at $3000 but it's a foundation you'd never need to worry about.
If you intend to keep the car for years and drag race it even semi regularly, the 9" is the best option.
-J

biminiLX, any ideas on the rear end walk described in my above post?

 

[tomshep]

biminiLX, any ideas on the rear end walk described in my above post?

OEM Goodyear tires. Big HP. Skinny road. Right foot being planted to floorboard instead of easing into easily.

Tom

 

[SlowYellow]

OEM Goodyear tires. Big HP. Skinny road. Right foot being planted to floorboard instead of easing into easily.

Tom

I thought that that would fix my "walking" issue with my rear end, and it did not, at all. It feels like the rear end is shifting, followed by SEVERE body roll and for sure a wreck if I didn't back out of it. I'm wondering if I'm spinning, I have new MT DR's on it, but they are 20's.

Please see bold quote...

 

[biminiLX]

Find a completely flat road and roll on at high speed as my guess it’s MT softer sidewall.
Why I run Nitto NT05R street and MT or Hoosier strip.
-J

 

[Bytor]

I just bolted in my Strange Cobra Jet housing tonight.
BMR UCA and all other suspension bolted right up, no headaches I was expecting.
Hell the driveshaft may even work with a different yolk.
True you're looking at $3000 but it's a foundation you'd never need to worry about.
If you intend to keep the car for years and drag race it even semi regularly, the 9" is the best option.
-J

Why did you choose the Cobra Jet housing instead of the 05-14 housing Strange offers? I started looking at Strange options this week. Lots of options to choose from.

 

[biminiLX]

Note it's minor changes, really just 1" relocation to allow 15" drag wheels, saves from buying relocation brackets. Might also be reinforced a bit more, but easy just to call and talk to a tech my guy wasEdwin.
-J