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Thread: Are the rear diffs on these cars a little whinny

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    Default Are the rear diffs on these cars a little whinny

    After spending a couple of years refeshing a 76 2+2 I've finally got it on the road. One thing I've noticed is that the rear differential seems to whine considerably. However, there doesn't seem to be any clunking or other issues with it. I originally had Amsoil synthetic GL5 gear lube, 75w-140 but switched to conventional valvoline gl5 85W-140 thinking it may be a little quieter, but it isn't. Are the rear differentials on these cars normally a little whinny or might my tooth pattern be off or something. The car has 83,000 original miles on it and everything else seems to be going OK so far.

    Thanks
    Gary

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    Registered User Jarvo2's Avatar
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    I've got the clunk but no whine in the R180 in my '72 240z. I don't know which is worse to have!
    Dave
    Windy City Z Club (Chicago)
    1972 240z, restoration in progress
    http://jarvas240z.blogspot.com

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    I think you are correct, the clunck might be worse. There is a very reputable business near me that specializes in rear diffs, and I've had them do work for me before, but I'm sure they won't be cheap this time either and if a little whinning is usual, I'll probably put up with it for awhile. Also, there are no leaks and the magnet on the drain plug looked clean (no metal).

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    My understanding, and own experience (three different diffs in my car over the years) is that they are generally whiny or howly. The cut of the gears and the lash specs apparently just lead to noise. Probably why Nissan tried to isolate them with lots of rubber.

    Worn bushings can lead to more noise. One bushing that's hard to diagnose is the main front diff mount bushing. It will collapse over time and let the metal pieces get closer together, allowing more noise transmission. The mustache bar bushings can do the same allowing metal to metal contact during driving.

    I've also found that a simple layer of insulation under the back deck carpet can cut some noise down. I used mylar bubble type, but anything is probably better than just the thin layer of carpet.
    1976 280Z, with some minor modifications

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    Registered User Mike W's Avatar
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    I can't say that mine was whiny before, but any noise that I did have coming from that area seemed to have been cleared up after changing my fluid to Royal Purple. People have reported very good results with this brand and I have had the same experience.

    May be a relatively inexpensive way to see if this might make a difference.

    Mike.

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    Quote Originally Posted by Jarvo2 View Post
    I've got the clunk but no whine in the R180 in my '72 240z. I don't know which is worse to have!
    Haha, yeh no whine on my 72 here either. Just a clunk. Seems they either whine or clunk. It is the second R180 diff in mine and they both clunk.

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    Noise is relative, not just based on the differential design, but also on the body of the car. I purchased a new '68 510 2 door stick shift and traded it in for a new '70 510 wagon automatic. The rear ends of these two vehicles are about as close to identical as you can get.

    Even though the coupe only had a rubber mat in the trunk, the differential was noticeably quieter in the coupe compared to the wagon with a finished interior. I've always attributed this to the seal between the trunk and back seat. On that basis, I would expect our Z's to have some noise intruding into the passenger compartment. That said, the factory service manual provides a trouble shooting guide for differential noise.

    You can pull the back cover and measure the backlash between the ring and pinion. At only 83,000 miles, I wouldn't expect to see any excessive in the gear teeth or bearings.
    1971 240Z HLS30A 17574 L24-021025

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    Another two cents (maybe the same actually), but I've had the super-howly I-can't-live-with-this diff noise, and the so-quiet-I-can't-believe-it-was-ever-noisy that I have now. It was super-noisy when I was tightening up the system to get rid of the clunk. The tighter I made things the howlier it got. But now I have a fairly specialized set of mounts on the car, along with the insulation under the carpet. An RT-style diff mount with the GM transmission mount, and urethane mustache bar bushings, but with a small spacer to allow an air gap during cruising. The pathways for noise through the mounts is minimized and the big resonator of the hatch area floor has been muffled.

    The gears are the same, so the noise is there in the diff, but it doesn't enter the cabin. Also, I found that there was a certain no-load speed, freeway speed, where the howl was really bad. I assume it's the pinion and ring gear bouncing off each other and ringing.

    Just offering more stuff to think about. I hated that howl.
    1976 280Z, with some minor modifications

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    Registered User siteunseen's Avatar
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    Red Line 75/90 got the whine out of my '72. Whatever came out was orange like Sunkist.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    My untouched 73 diff has had a whine that starts about 53 mph and quits at about 58 mph since I bought it in 1977. I was told years ago not to worry about it because that speed range was where the PO drove it at when new. No idea if this is true or not. The fluid has always been off the shelf gear oil. It is not annoying but a reminder I'm at / near 55 mph.

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    I changed to the "thicker" conventional Valvoline gear lube thinking thicker might quiet it down, but it seemed quieter with the synthetic Amsoil. Since its easy to change the fluid, this weekend I'll probably try some synthetic Royal Purple or Red Line to see if thst makes a difference. Although these synthetics aren't cheap, at this point, its a lot cheaper and easier than pulling the diff and cover to check the gear contact pattern, etc. Or I could do like my dad and the other old timers used to do to their Models As and add some saw dust to quiet it down! (not really an option). Gary

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    I bought a 72 with only 80,000 mi 2 years ago and was shocked at how quiet the rear end was.

    It seems to correlate with wear.
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    The rear end in my71 that, I drove quite spiritedly for over 20 years, didn't howl or clunk. All the clunks and vibrations were eliminated with u-joints, drive line & half-shafts, many times. Maybe I just got lucky & got a good one. I certainly wasn't easy on it & it was probably the most neglected item on the car. Mark
    Now I'm curious if the 260 is going to howl or clunk when it goes on the road. Damn, I've got enough to think about as is.
    Last edited by Mark Maras; 08-14-2014 at 02:54 PM. Reason: after thought

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    I just changed my rear diff from a 3.90 to a 4.11 LSD. The 3.90 was a little loose and clunked some, but it was a spare so I didn't care. I had the 4.11 rebuilt and put it in a few days ago. The new one has no clunk at all, and there is a whir that accompanies it...until about 55mph and then it howls like an opera singer. It stops at around 65. I know it's all super tight as it's new, but I'm wondering if it'll ever go away. Anyone else broken in a new diff before?

    I also seem to remember that the tranny had a whine in it at about the same speed in 5th gear, and I'm thinking maybe the tighter diff is making the tranny whine worse and that's what I'm hearing? I'm still breaking in the diff, and it gets pretty danged hot after just a few miles so I'm not going very far. My thinking is to take it for some more shorter rides and not use 5th to see if that changes anything.

    It also has the solid mount to the tranverse link...maybe some cushion in there would help, too?
    Current Z: 1971 Datsun 240Z, 3.1 Stroker (F54 block, P90 head, 490-290 cam, triple Webers); 95% complete
    First Z: 1972 240Z, destroyed in a shipping accident. Ack!

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    no clunk lots of whine in mine.

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