Drivetrain comparability problems

[Corfly02]

Hey guys,

I have searched the forum without any luck finding info on this particular topic so your assistance is appreciated. I recently installed all of my drivetrain and suspension upgrades and I had a hell of a time getting my driveshaft to fit with the Ford racing 3.55 loaded diff bought from cjpp. The driveshaft adapter on the new diff is for a gt driveshaft so I had to send back the DSS Ecoboost driveshaft that I bought. Then after in installed the new diff I found out that the GT driveshaft was too short. Apparently the Ecoboost has a slightly longer wheelbase. So I had the car towed to a shop where they pulled the adapter off of the old diff and installed it on the new diff. Factory driveshaft fits. But now I'm hearing a rattling noise on the passenger side. So I'm wondering if the DSS Ecoboost half shafts are not the correct fitment. I'm not using the car atm and haven't looked under the car beyond checking the cradle to subframe bolts. But I also lowered the car with h&r sport springs, steeda fixed dampers, BMR vertical links, BMR toe links, BMR bk005 cradle lockout kit, steeda alignment bushings, poly diff bushings.... I think that's it. I'll update if I remember anything else.

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[DANA44]

I don't believe there are different wheel bases. There are different drive shafts based on the transmission configuration. The 3.55 you picked up is set up for a manual configuration AFAIK. Do you have an automatic?

 

[Corfly02]

I do have a manual. I called the driveshaft shop directly and the Ecoboost and gt driveshafts are different lengths so maybe it's the pinion shaft in the differential? That's the only thing I can think of.

 

[Cobra Jet]

The difference between EB and GT may be the bell housing to which the 6R80 or MT82 transmission mounts; that could explain the delta in driveshaft length.

Also to note, it's been brought up in suspension or trans forum that the driveshaft variations are also due to:
1) with rubber guibo
2) w/o rubber guibo
3) GT vs EB transmission flange
4) GT vs EB rear pinion flange

Again, I believe the flanges are going to be different if the driveshaft has or does not have a guibo.

There's absolutely no variation in wheelbase between S550 models.
There's absolutely no variation in the mounting points of the IRS or the rear diff location between models.

 

[Corfly02]

I do have the mt82 transmission and I'm pretty sure that Ford put the same tranny in all trim levels. I'm certain the difference is the pinion flange on the Ford racing diff. To make it work I would've had to order a custom driveshaft from the DSS. When the shop installed the old flange the factory driveshaft fits. Also I realized that all of the half-shaft options are compatible with all options so that can be put to rest.

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