Just got a "Cobra" diff installed and have driven it 40 miles. While coasting, the *** end sounds like a deck of playing cards in a bicycle wheel, and the ride doesn't seem quite as smooth as when giving it gas. Is this normal? I used Royal Purple 75-140, which is already suppose to have an adequate amount of friction modifier. I even drove it in circles both ways several times. It's loud enough it's embarrassing. Any ideas?

...maybe because they didn't soak the friction plates in FM due to the RP?

 

Did ya try backing up in circles? I'm thinking the shop put in the L/S wrong, it shouldn't sound like that, especially going straight, they should have no reason AT ALL to be making friction. Are you sure it's the clutches?

 

Oh yeah, the "chatter" is in sync with the tire revs.

I didn't try reverse. It sure sounds like it to me, but this is my first L/S. I've gotten it to go away temporarily until I give it gas again, then it usually comes right back. There were concrete wall separators in the median the whole way home, (reflecting the sound) and I was running 60-80. It's most noticeable when going about 25 MPH.

BTW, I used Royal Purple, so it should be good to go on FM.

 

Take er back to the shop and have them look over their work, and replace the Royal Purple that is in there.

 

Well, figured it out. It was doing it something fierce this morning on the way to work and the truck was shaking like crazy. I turned around and took the ol lady back home so she could drive herself to work safely. I decided to go ahead and drive to work, then when the shop opened I would take it in, and have the rest of the day off. Well, it quite doing it about half way to work, so I drove it around the city for a while to see if I could get it to act up again, and it was fine. I called to make them aware of the situation and they said to watch it, and to call if it comes back. Well, not 5 minutes later, I launched a wheel!!! Thank god it missed everyone and took out a stop sign. The shop screwed up and are taking care of everything. Ruined the aftermarket wheel, rotor, and the rotor "dust cover" deal.

I am already well aware that you CAN NOT get ANYTHING done right, no matter the cost or the laborer, so I very carefully chose the shop. They deal primarily in exotics like Vipers, Cobras, C6 / Z06, even Lotus...so I thought it was all good. Just another lesson learned I guess. It could have been BAD.