when i did my JDM swap including drive-train, i noticed that the rear end made noise, i am not sure if this is normal. normally there is not much noise when i am accelerating till i reach and keep about 50-60mph. also if i down shift or slow down with out pushing in the clutch it will make a different noise. with the clutch in at any speed it is pretty quiet. I do have brand new tires on there and the noise didn't change. it is a S4 rear end and i think it is an LSD.

 

Sounds like it could be a potential bearing problem. the carrier or the pinion could be moving a little.

 

Hard or improperly installed mounts on the back suspension will transfer quite a bit of noise to the body. Could that be whats going on?

 

this may be a dumb question but i have actually seen the appropriate answer to the question from it before:

did you check the oil or put oil into the transmission and differential after installation?

 

I have a high mileage S4 N/A and a low mile S4 TII. Both differentials make a slight whine when cruising steady at about 40 to 45 mph. I consider that noise to be normal.

The noise on deceleration sounds like a problem.

 

Are you sure it's the diff?

 

^I was thinking the same thing. This is only related in that it was noise coming from my car and I assumed it was a symptom of one thing and turned out to be totally different symptom.

My car was making whining noise from the transmission. I forget the particulars of it but it only made it while moving and possibly when idling in neutral. Based on online advice about similar noise being throwout bearing I took it to a shop and had them replace the clutch. Turns out the noise was actually either a motor mount or transmission mount. It was throwing the drivetrain out of alignment and putting strain on the u-joint.

 

there is fluid in there. and i have stiff mounts on there now. engine, trans and diff.

 

I too am having the same issue right now. The rear on my S5 TII whines after I reach about 15mph on up to like 60mph where the noise levels off. It whines at slow down also, kind of like a jet engine whine.

I just swapped out the diff. fluid this weekend (redline 75W90.....RED-57904) and it made no differance. Still the same ****. The LSD still works fine (both wheels spin) so my guy thinks its the bearings.

My TII is pushing 575hp at the wheels (dynoed) so I think its time to reinforce the rear. When we pulled the plug on the rear there were metal flacks..........time to send some loot. My guy told me the flack were signs of normal wear. In the end bearings or not something is wrong and the rear needs to come down.
Good luck with your whinning..........

 

by stiff if you mean solid, it is perfectly normal...

575 is about the most you can expect the stock differential to hold up to. very minor metal flaking is normal, if it is gritty enough to actually feel in your fingers then your differential is in need of help.

honestly though you're in a different ballpark, running that much horsepower you should be looking at alternative 8.8/9" differential options.

 

they are MMRs that are BLACK UHMW Polyethylene. soo.........

 

with the way most of those aftermarket poly-x/delrin mounts actually mount to the chassis, they may as well be solid.

 

My diff. deffinetly needs to come out, but I plan on leaving it in, provided that it holds up for the next few months.
I would love to add an independent 8.8 rear to my car but from what I understand no one makes a mount for the TII. I know the mount is avail. for the 3rd gen. and I know I dont want a solid rear. Would you happen to have a lead on whom makes a mount for an independent 8.8 for the TII?

 

http://www.norotors.com/index.php?topic=5084.0 This 8.8 IRS kit is getting close to being for sale. I have personally met the person who is designing it and not only is he a mechcanical engineer by trade, but he is also a stand up guy.

 

that's the closest i've seen for a kit for the FC.

 

Hey bergrx7..........you have just mad my day!!!!!
I like the man already
The price is a little steep........Im not comprehending what the price actually includes. Ill be following the progress of that piece though. Thanks a million for the lead
This will help out alot of us FC guys.

 

I hit that link and actually started smelling Gear oil!..(smellovision?)

 

Anyone have the number to Ronin Speedworks or to the dude whos building that 8.8 rear diff mount?