IRS swap question.

['03GTinFLA]

*Search function is disabled at this time so don't kill me with the "use the search button"
I have an 03 GT and I had a very reputable shop swap in an IRS from an 03 Cobra. They did not swap driveshafts. I now have a vibration around 40 mph. We hope this will be fixed by using the maximum motorsports pinion angle adjuster kit. I was going to order an aluminum driveshaft also, from stangsuspension, and they called me and asked if I was sure the GT driveshaft would fit. :dw: They said the Cobra DS is a 2 piece with some rubbber dampner somewhere that helps deflect vibrations. *This is not a direct quote, just trying to give you guys as much info as I can remember about the conversation* So they are waiting to hear back from me on whether or not I want to order the GT DS. He also said something about using a Viper DS? Has anyone done this swap and had this issue? What DS should I go with?
Last question. I noticed there is an audible thud/clunk when engaging/disengaging the clutch coming from the rearend. I was told this is an IRS thing and no big deal. I'm cool with that if that's true but is there any way to get rid of the clunk.
P.S. I will use the search button like a mofo once the website is fully functional. :rockon:

 

[sunburned]

When I did the IRS swap, I used my stock driveshaft. The only reason to change the driveshaft is if you change the transmission because different trans are different lengths. The IRS diff has a bigger pinion flange than the solid axle, so instead of changing that, I just swapped the yolk on the rear of my stock driveshaft with the one on the '03 cobra driveshaft. Not sure what part # it is because I did a direct swap with a cobra driveshaft. The u-joint you need is an adapter joint that goes from a 1330 style to a 1350 style (found it, precision 459 u-joint). I'm not sure what the vibes would be from because I don't know exactly what parts the shop put on your car. As far as the 2-piece Cobra driveshaft that he is talking about, that's dead wrong. The Cobra driveshaft is just like the GT shaft except it is aluminum and a bit shorter. If you don't have a driveshaft yolk from a Cobra driveshaft, you can probably get it from Ford, I just don't know where to look for that part number.

I had exactly the same clunk coming from the rear diff. It is caused by the bushings at the front of the diff wearing out and allowing the diff housing to move up and down when you put load on or off the drivetrain. Go buy maximum motorsports p/n MMIRSB-45 diff bushings to fix the problem. The front two are the most important and are fairly easy to install. The rear bushing is a bitch to get to, and I never actually did it on mine. Didn't matter though, the front bushings made all the clunk go away.

 

['03GTinFLA]

Thank you. That clears a lot up. I'm ordering those MM parts and looking into the adapter.