Agreed. I had a local shop RIPPMODS do the initial 4.08 install and after 2 attempts they couldn't get it right. I redid it myself and even with SPL solid bushings the gears are close to silent. The exhaust covers up any sound it may make.

 

Mine just got significantly louder. It happens above 40, only when the car is cruising. By that I mean on accel or decel it goes away but at steady speed it whines. I changed the diff oil, no change.

 

Took the car to a differential specialist. He thinks the pinion retention nut is loose. Yet another mess up by my mechanic from heck.

6-900.00 to do and 2 days after all the parts get here possibly a week from Thursday.

He strongly suggested I not drive the car so I'll get to see what an open 3.5 feels like tomorrow when it goes in.

This is my fault because I thought whew, the car is done and all is well THE NIGHT BEFORE THIS STARTED

GAAAAAAAAAAAAAAA

 

I'm sorry to hear that. Really sucks when a small detail screws up all your plans.
At least you can do some nasty 1 wheel burnouts now. Just make sure nobody can see the driver side of the car when you do them or they'll all laugh at you

 

Setting up a diff is definetly not a task for your standard ASE mechanic for sure.

Took me a good bit of work for me to do it myself but very rewarding when I got it in and working silently.

 

The thing I don't get is it was fine for over 10k miles.

http://www.azdifferential.com/

They have a huge facility dedicated to differentials. I am 100% certain they will get it right.

 

Diff swapped out. It's weird how different the car feels Having only the rear solid bearing reduces vibration, torque feels down, obviously being pushed by only one wheel feels totally different. The whine is gone.

Ring and pinion look ok, hope they are.

 

282.02 (with a discount) in differential rebuild parts.

 

I just installed a quafe LSD tonight. The test drive was awesome until i got up to about 60mph+. I heard a slight whine during acceleration and only after 60mph. It gets a bit louder the faster i go. I suppose the gears are meshing a bit too tight. Everything checked out during the install. is there any problems that can happen when if i'm getting that gear mesh whine? I'm also wondering it the noise will go away after a decent break in. so far i've only drove about 10miles.

 

You only changed the quaife or also the ring and pinion? My 4.08 & quaife never whined, until it had more than 10k on it, then the ring and pinion failed due to improper install and it started making noise.

That just cost me more than 1200.00.

 

If you are reusing the 3.5 final drive and its whining then your out of adjustment somewhere. Given that you didn't change anything on the pinion side and only swapped carrier essentially I would suspect you didn't check the carrier (diff side) bearings preload?

Reusing old bearings or replaced with new?

 

I used new bearings from nissan. I reused the 3.5 final gear. only thing i can think of is that the backlash is out. Kinda kicking myself in the butt for not really checking that part. Through reading some other DIY guides some people simply reused their old shims and everything was fine. I did paint the gears and made sure i was getting a good contact. oh and i use redline 75-90.

 

The diff shop that did mine said Redline is bad. They told me to use 75-140 syn only form Amsoil and dyno from only Mobil or Valvoline.

They said to change the oil in 1500 miles.

*EDIT* they gave me a bottle of Morotcraft friction modifier.

 

i hear so much debate about redline, and amsoil fluids. some people swear by it. others really don't believe in it. either way... you think redline is causing whine with my differential??? hmmm...

 

jinkoba: I assumed when you said everything checked out you had checked the mesh pattern & backlash. Definitely check backlash before anything else.

e30cabrio: Being a quaife helical gear diff that friction modifier really isn't going to do much at all, its for clutch style diffs. For 95% of applications (quaife diff with some track time) I highly doubt anything "better" than Mobil 1 synthetic gear lube is going to make any difference. I'm curious what their reasoning is for giving it to you.

I'm running Redline MT-85 in my transmission and Redline 75W90 in the diff, I broke in the diff with Mobil 1 simply because it was a cheap synthetic. I'm Redline b/c its what i've used since i was 16 and truly is just brand favoritism.

 

I think backlash is the problem. I'll drive it for a little while and break in the diff... When I'm ready to change fluid for the diff ill pull it back out and check backlash/change shims. The whining isn't that loud right now. Really sounds like a trans with straight cut gears, haha. Anyone know of a decent place to get shims??? Kinda hard though, since I don't know exactly what size I need..

 

guess i'll be posting again in a couple of months and let you guys know if there is any changes with the whine noise after i re-shim it. thanks, peoples who shared interest in this.