Rearend strength

[SGT/SC#0471]

So how much hp can the stock rear end take? Is it the same unit that is in the GT500? Thanks for any info you have ....

[07SHELBY GT]

I'll try and say that an exact number is a little tough but plenty have seen 5-600 RWHP with out failure.A lot depends on how it is treated also,Obviously.The GT500 and Bullitt have a slightly different rear axle assembly.The carrier bearings have more surface contact area than the Mustang/Shelby GT.The 8.8 can benefit from a rear cover support system,But the ones to fit an S197 are a little different thanks to the panhard or locator bar.Slicks and a stick shift will be worse than slicks and an automatic,You get the idea.

[LuLu]

I'm not sure there is any difference at all between the Mustang GT and the GT 500 rear axle assemblies. The reason I'm not sure, is Ford's tech manual, the trusty Big Red Books.

 

I've been using them since 1997 and I get a set for every Ford product I own. Normally these books are very detailed and leave no stone unturned. In other topics, I find seperate sections for the Mustang GT and the GT 500 when parts/features differ. That seperation is absent in section 205-02B, and I scoured all 58 pages. Taking this as a clue, apparently there is only one 8.8" axle assembly, and it's a Traction Loc assembly as well. The only difference is gear ratio, and this is confusing to say the least.

 

So...I turned to my Ford Racing catalogue for some assistance, and found the same thing. FRP offers two 8.8" rear end assemblies for the '05-'08 Mustang. M-4006-S197 is a complete kit hub to hub, but you add the gear and differential of your choice, assembly required. M-4001-A355 is a fully assembled rear end assembly ready to bolt in. 3:55 gears and Traction Lok included and installed, see page 152 of the '08 catalogue.

 

With regard to durability, I trashed two 8.8 rear ends on my '03 Marauder before I wised up. That car weighed 4500+ pounds and delivered 550 RWHP/502 RWTQ. I found it's limitations the hard way, but I fixed them with an Auburn Pro 31 spline differential, FRP 4:10 gears and internals, Dana 60 stud kit, Moser 31 spline axles and the FRP girdle. Then it stayed together.

 

IMHO, the stock 8.8 differential is quite durable up to 500 RWHP, but I wouldn't push it any higher in it's stock form. Moreover, if you intend to race your SGT and plan to use slicks or drag radials, do yourself a favor? Have the axle tubes and lower control arm brackets welded in place. The axle tubes are steel and only sweated in place, and the LCA mounts need reinforcement. Hard launches with good traction will twist these weak spots into pretzels.

 

Happy motoring, gents.

[zdle]

I'm not sure there is any difference at all between the Mustang GT and the GT 500 rear axle assemblies. The reason I'm not sure, is Ford's tech manual, the trusty Big Red Books.

 

I've been using them since 1997 and I get a set for every Ford product I own. Normally these books are very detailed and leave no stone unturned. In other topics, I find seperate sections for the Mustang GT and the GT 500 when parts/features differ. That seperation is absent in section 205-02B, and I scoured all 58 pages. Taking this as a clue, apparently there is only one 8.8" axle assembly, and it's a Traction Loc assembly as well. The only difference is gear ratio, and this is confusing to say the least.

 

So...I turned to my Ford Racing catalogue for some assistance, and found the same thing. FRP offers two 8.8" rear end assemblies for the '05-'08 Mustang. M-4006-S197 is a complete kit hub to hub, but you add the gear and differential of your choice, assembly required. M-4001-A355 is a fully assembled rear end assembly ready to bolt in. 3:55 gears and Traction Lok included and installed, see page 152 of the '08 catalogue.

 

With regard to durability, I trashed two 8.8 rear ends on my '03 Marauder before I wised up. That car weighed 4500+ pounds and delivered 550 RWHP/502 RWTQ. I found it's limitations the hard way, but I fixed them with an Auburn Pro 31 spline differential, FRP 4:10 gears and internals, Dana 60 stud kit, Moser 31 spline axles and the FRP girdle. Then it stayed together.

 

IMHO, the stock 8.8 differential is quite durable up to 500 RWHP, but I wouldn't push it any higher in it's stock form. Moreover, if you intend to race your SGT and plan to use slicks or drag radials, do yourself a favor? Have the axle tubes and lower control arm brackets welded in place. The axle tubes are steel and only sweated in place, and the LCA mounts need reinforcement. Hard launches with good traction will twist these weak spots into pretzels.

 

Happy motoring, gents.

 

 

I installed a Fays 2 Watts link in my SGT ................It is a great improvment in handling on the race track (Willow Springs) , and ride especially with 20" wheels. But I did notice how the rear axel tube of the rear -end looks like it would take all of the torsional loads imparted by the Watts Link.

Could welding the tubes as you suggested ,help that , and do you have any pictures or locations of hhow the lower control arm brackets should be welded?

Zale Schuster

[LuLu]

I installed a Fays 2 Watts link in my SGT ................It is a great improvment in handling on the race track (Willow Springs) , and ride especially with 20" wheels. But I did notice how the rear axel tube of the rear -end looks like it would take all of the torsional loads imparted by the Watts Link.

Could welding the tubes as you suggested ,help that , and do you have any pictures or locations of hhow the lower control arm brackets should be welded?

Zale Schuster

Zale...I've only seen pics of the Fays 2 Watts link, but I tend to agree with you. This supplemental suspension will go a long way in deflecting injury away from the rear end assembly by reducing twist.

 

Sorry, no pictures yet, but the weld points are rather simple. Weld the axle tubes in place where the steel tubes meet the cast iron center section (often called a "pumpkin"), and reinforce the LCA mounts where they meet the axle tubes. This is not difficult or tricky welding, if you have to go to a pro, he shouldn't charge more than 100 bucks.

[Sharp GT500]

The GT500 and Bullitt have a slightly different rear axle assembly.The carrier bearings have more surface contact area than the Mustang/Shelby GT.

I have read this too.

[LuLu]

I have exhausted all the resources at my disposal, and I cannot find any support for a difference in rear end housings (where the hardened bearing races reside) between the GT 500 and the Mustang GT. My FMC parts guru has provided the following 411.

 

The last update to the rear axle housing as a repair part is dated 4 Dec. 2006 (note: production line part numbers are coded differently). Don't know the cause for the update, perhaps just share the hardened bearing races across the S197 platform? Again, I don't know more, and I presume this applies to the Bullitt as well.

 

The repair part number 7R3Z-4010-C is the correct part number for both the GT 500 and the Mustang GT housing since Dec. 2006, which applies to us as SGT owners. Should you need to replace the housing, you would not have a choice in selection, or, so I have been told by a factory rep.

 

If anyone can shine some more light on this, please post? Specific part numbers would be helpful to me, I would like to update my library after confirmation. This 411 could be very helpful down the road.

 

Hope this helps, happy motoring, gents.

[RCSignals]

I'll try and say that an exact number is a little tough but plenty have seen 5-600 RWHP with out failure.A lot depends on how it is treated also,Obviously.The GT500 and Bullitt have a slightly different rear axle assembly.The carrier bearings have more surface contact area than the Mustang/Shelby GT.The 8.8 can benefit from a rear cover support system,But the ones to fit an S197 are a little different thanks to the panhard or locator bar.Slicks and a stick shift will be worse than slicks and an automatic,You get the idea.

 

OK old post and new member. Please don't jump on me for resurrecting an old post. Hopefully this info is of some interest/use.

 

on the axle assembly used in the '08 Bullitt. Here is a quote from a post on the Bullitt forums from one of the Bullitt development team members

 

 

The following is the complete list of all upgrades for the Bullitt 3.73 axle:

 

1. Higher strength differential case material

2. 9x13 differential gear tooth combination (GT is 10 x 14)

3. Differential gears receive premium shot peening

4. Anerobic adhesive added between the differential case and ring gear

5. Higher capacity head bearing (with shim)

 

All other components in the Bullitt axle are common with the base GT 8.8" axle

 

Also, the axle code is V-257. The code is found on two stickers on the axle. One is on the right axle tube, near the vent cap. The other is on the differential cover.

 

He doesn't mention it but I'ver also heard the axle tubes are slightly bigger than stock GT.

 

In the August issue of Hot Rod magazine it is mentioned the FR500s uses a Bullitt rear axle.

 

(Hi Mac)

[LuLu]

Hello, Duncan, how have you been?

 

Thanks for the 411. I haven't been able to track anything down, no one seems to know more. I appreciate this clarification.

 

Is it safe to presume these small changes also apply to the GT 500?

[07SHELBY GT]

Same everything,Except the gears.3:73 Bullitt,3:31 GT500.I didn't know you guys knew each other.Should have put the Marauder thing together.You Marauder guys are sharp.

[LuLu]

Same everything,Except the gears.3:73 Bullitt,3:31 GT500.

Thank you, this 411 has been added to my library.

I didn't know you guys knew each other.Should have put the Marauder thing together.You Marauder guys are sharp.

Well, I don't know how sharp I am. Compared to others in the Marauder community, I'm on the slow side. However, my "Marauder Daze" taught me a lot in the school called hard knocks...Thanks again.