Forgive me if this is all laid out somewhere, but I've searched, and read, and seems there's a lot of info, but it's scattered throughout several different threads. I'm just going to lay out what I think I've learned from reading, and would like someone in the know to say yes or no, please.

Okay, first of all my curiosity started by the fact that I have a slight gear whine. It seems worse when cold, and changing out the nasty "good for life" oil with first Mobil 1 75W-90 then Royal Purple 75W-140 didn't help. I'm still not 100% convinced it's the diff, but probably is. I only hear it above 50mph, and seems worst in 6th gear between 65-70mph. It's only audible when under light/cruising throttle. More gas it goes away, let up and it goes away. Sometimes, it doesn't seem to be there at all, and sometimes I think I hear it slightly when letting off the throttle from a heavy acceleration (within the above speeds) with the windows down I never hear it.

So, moving on. This is what I've learned...

1. All Crossfires have the same carrier. SRT's have a different ratio 3.07 vs 3.27 (I think I got that right)
2. My 2004 owner's manual calls for 75W-140, apparently 2005-2008 calls for 75W-85.
3. 2004's have bolt on axles
4. 2005-2008's have slip in axles
5. Not found any verification yet, but I assume the wheel/hub end of either axle is the same.
6. 2004's had gear grinding issues from being setup incorrectly and some/many have been replaced. Can't find anything to say that this was a problem in later years
7. Found several mentions of a pin shearing off. This seems to be mostly related to SRT's and the extra power

So, if I'm correct in the above, and I do have gear problems...

I'm assuming I can either find a diff from another 2004 for a direct bolt-in, and hope for the best, or I can find a diff and axles from a 2005-2008 N/A for a direct bolt in and I should be good to go.

I've yet to see new gear sets sold anywhere, however I'm guessing maybe the stealerships still have some. Setting up gears is one thing I leave to the pros, but know a guy who does it well.

Wavetrac and Phantom Grip are also options, but very pricey for a N/A daily driver. I think I only paid $400 for a new Eaton Posi setup for my Chevy a few years back. However, it would still be nice to have.

Thanks for reading, if you made it this far...

 

Am I on the right page here?

 

If the oil was not silver, forget about it and drive. If you hammer the rear it will break, noise is often the nature of the beast. Me I dont care and run up the radio, a rear is going to be north of 400$ if it is used and more than you can pay for from a dealer. Woody

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Well, eventually I'll have to replace it. It may not be a problem, but just knowing the noise is there is driving me crazy. Diff oil had some metal in it, but didn't seem excessive for 90k+ miles...

I'll probably just keep my eyes out for a low mileage 04 rear end...

 

Hi

I had the similar problem with my car. Noise above 45mph, the problem was with the rear right wheelbearing.

/Adam

 

Really? How did you determine it was a bearing? Never had a bearing that didn't make noise all the time. Was yours only under light throttle as well?

 

When I was installing the rods from MikeR I felt that the rotor was not rigid there was a little movement. Then when I took of the hub I saw that there was some movement on the actual bearing. When I changed that bearing everything is totaly rigid without any movement.

/Adam

 

Thanks. I will be installing new Lemforder flex discs this weekend (assuming UPS brings them as expected tomorrow). I had been wondering if maybe they could somehow be invovled, but I'll have the back wheels up. I'll pull them, and check everything out with the bearings. That would be great if it was just a wheel bearing!

Otherwise, I found a few Diffs on ebay, Crossfires and SLK's. I assume first gen SLK320 diffs are the same. They appear to be the same size, and have bolt on axles. Just not sure on gear ratios.

So, when you did change the bearing, was the old bearing obviously/visually bad?

 

Correct me if I'm wrong but I think that the N/A has 3.07 in gear ratio. Yes, the old bearing was bad, when I got the new bearing in place it was then I realize how bad the other one was.

/Adam

 

If it is a stick, it could also be the throwout bearing, if these cars have a throwout bearing?

 

n/a has a 3.27 ratio srt -6 has the 3.07

 

It's a two piece driveshaft, make sure you mark it before seperating the two pieces or you will have a balance issue to deal with. FYI my 2004 has slip in axles not bolt in.

 

Well, I have considered the trans, and while I know noises can be deceiving, I'm fairly certain the noise is coming from the rear. BTW, I've been under the car several times, but last night I just had to check. Yes, I have slip in axles. That should open the door door for more lower miles options that hopefully don't have issues, should I need to go that route. So, I wonder what the cut off was for bolt in. Mine was built in 10/03.

Also, I replaced the discs once. Those were bad, so put originals back in. You don't need to remove or dissassemble the driveshaft. It's actually quite a bit easier than changing u-joints.

 

Well, checked bearings while up on stands. The driver's side had just a slight bit of movement, so I pulled the brake pads and tried again. More movement. So, I'll be looking for bearings, and hoping that's the noise...

Silverarrow, is there a write up on bearings or is it in the FSM posted here on the site? Thanks...

 

I bought SKF bearing on ebay for 64usd. Then umnounted the hub and gave it to my mechanic to change the bearing. I was not able to change the bearing myself. Didnt have the right tools for it.

/Adam

 

Well, I found Timkens on amazon for $61/ea shipped. I'll see what I can find on what's needed.

Thanks...