noisy differential, how loud should it be?

[hogie]

I know loud is very subjective, but I will try to make some sense of it. I have never ridden in another 240z so I don't have a good baseline to compare it against. For most of the summer I have been driving with my windows down so I never noticed the differential whining before.

I am currently running a stock 3.54 R180 with an 83 280zx 5 speed. The front diff mount is fairly new and solid. The rubber stopper is in good shape as well.

With the windows up and going 55 I can hear a slight whine from the rear end over the wind and exhaust noise. With the clutch in and engine idling it is quite obvious. It doesn't matter if I am maintaining pace or slowing down the noise is steady. While decelerating, the noise goes away at around 10mph. Under acceleration, I really can't hear it over the exhaust.

I know that Z's are old and noisy anyways, but am curious if they should be that loud? We usually have a good supply of 240sx for rear end swaps if need be. I already replaced the fluid with Redline 75w90 and that didn't quiet it down much at all. It seems like most of the posts I searched in mention a howl or clunking. I wouldn't describe my noise as a howl of imminent failure.

Edited September 11, 2011 by hogie

[beermanpete]

I have wondered about this as well. Our 240Z had a bit of gear whine with the original (high miles) 3.364 R180. We replaced it with a 3.54 R180 LSD from a Subaru and it got louder.

[hogie]

I think mine has around 131k miles, that sucks that yours got louder after the swap!

[Reverend]

What procedures you can do to make old loud differential to stop whining? I've changed oils, it helped a little but im about to remove it and open it up. Just don't know what to do with it..

[beermanpete]

From what I have read/heard, the 240Z earned a reputaion for gear whine during the first few model years. Some noise must therefore be normal I suppose. I don't know if it was massaged out over time or not.

Our car had a lot of gear noise when we got it. Some went away with a transmission rebuild. We also have a solid mount on the nose of the diff. which can't possibly help.

If the differntial looks good upon inspection you might try adding some sound insulation in the rear area of the car.

[Casey_z]

Your butt is basicly sitting on the suspension so every sound is heard and felt.

[Bonzi Lon]

Yep, mine has the same whine from about 51 to 58 mph, always has. Got it in 77 with 88k, now 128k.

I was told 'back in the day' it was from being broke in at that constant speed, hmmm. Years later on the forums it appears to be normal.

The up side would be its like a speed-minder, you hear the whine, you know your speed, 55. Sorry Sammy Hagar,

Bonzi Lon

[gira]

A certain amount of whining is normal, but the cars didn't come from the factory with the level I think you are describing, therefore it's in the rubber isolators and the perfect set up of the differential. The set up is a little tricky. The ring and pinion gears are matched at the factory based on their wipe pattern. They do wear and you may be able to slightly adjust the backlash between the two gears. A possible difference in the noise when under power or not is in one instance the pinion gear is driving and in the other the ring gear is driving the unit. I have used many junkyard units with minimal noise. I use them for racing and they are pretty durable units. The sound is more than likely creating heat too but I have used these before with very loud noises in some situations.

Greg Ira

[hogie]

Glad to know I am not the only one. I checked the rear end the other day after a half hour drive and it wasn't any warmer than I would expect it to be at least compared to non-noisy nissan and toyota truck rear ends. I don't beleive my tranny is adding to the noise at all as it is very quiet compared to my 4 speed with bad bearings

I haven't had a chance to pull the cover, I only looked through the fill hole and it looked ok, but then that is a very limited view. Most of the bushings in the car have been replaced with urethane so maybe the mustache bar is passing a bit more sound through as well.

Thanks for the input...I will take it off of my fix it now list.