Differential on it's way out??

[FastWoman]

Hi all,

So... I got my fuel pump all connected back up, new lines, etc., and thought I would change the differential oil while the car was jacked up. The oil was sort of brown and slightly smelly -- not a burnt smell, but another smell that is somewhat hard to describe. The magnetic drain plug was slightly "hairy" with filings stuck to it. There was the tiniest bit of debris in the bottom of the pan I collected the oil in. Some of it glittered (i.e. filings). The longest filing I found was about 3/16" long and about 1/16" wide, but most of what I saw was about 1/32" in size. When I was finished refilling the oil and cleaning up, my hands were a bit glittery too.

My differential has been softly whining at highway speeds on deceleration and coasting (i.e. with engine speed matched to coasting speed, no power applied either way). It often clunks when I change gears. Finally, there is a bit of leakage of oil from the side seals. The sides and bottom of the differential are quite well covered with oil deposits.

Having recently bought the car, I don't know how long all this has taken to develop. The differential oil has been changed before, judging from the rounding of some of the facets on the fill plug. I've notice no change in behavior, noises, etc. since I've owned the car (about 2 months now).

So is accumulation of filings sometimes normal, or does it sound like I need a rebuild? If the latter, whom do I find to do the work, and what should I expect it to cost? My local resources are a Nissan dealership and a local Z specialist, as well as a multitude of good machine shops in Norfolk.

I'd appreciate any disinterested third party advice before taking my differential to someone who wants my money.

Thanks!

Peace,

Sarah

Edited August 24, 2009 by FastWoman

[ezzzzzzz]

Welcome to diff hell. Seriously, sounds like your diff is trashed or on it's way out. The burnt smell isn't a good sign nor is the metal debri. It may be possible to rebuild it depending on what all of those metal shavings came from and/or chewed up. Cost varies depending on what has to be done. It's no point in guessing at it here. The good news is I may have a R200 (3.54 ratio) ready to bolt in. It hasn't been rebuilt but shows no sign of damage. I'm having another quaife-equipped R200 (3.90 ratio) built for my 240Z at Tidewater Z Auto Service (in Poquoson). They can help you with your problem too. Lastly, Have you heard of TZCCVA? It's the local Z car club. I'm the VP. We meet the second Monday of every month at 7:00 over at Frankies Place for Ribs in the Kempsville area of Va Beach. We like to have you drop in to visit us!

Edited August 24, 2009 by ezzzzzzz

[jmortensen]

Clunking is almost never a sign of differential damage in a Z. It has to do with mounts, U-joints-, mustache bar bushings, etc, but almost never the diff itself. Search "differential clunk" and you'll find tons of info on that problem, which is very common in these cars. Whining to some extent is normal too, and more pronounced with poly mustache bar bushings and stiffer diff mounts, etc.

I'd say that what you describe sounds relatively normal, especially if the gear oil hasn't been changed in a long time. Used gear oil often smells burnt IME, and even new stuff never smells good. Gear oil just stinks. If you do decide to try and fix your diff, I'd suggest that you forget about actually fixing that one and just buy another good used one and swap it in. Rebuilding one of these is expensive and ring and pinions and other parts like spider gears are practically impossible to come by separately, but a good used diff should run you $100 or $150.

[FastWoman]

Thanks, guys! I guess if good differentials are that plentiful, I'll just drive with this one until it presents a problem. This might be like the ripped drive shaft boot on my little Saturn. Every mechanic who's looked under my car has insisted I should spend the $300 to replace the boot, so that the drive shaft doesn't wear out. The price to replace the boot AND shaft is perhaps $30 more than that. I decided about 50,000 miles ago just to drive it until the shaft went out and then to replace both the shaft and boot together. The thing still hasn't failed. ;-)

I might drop in on a TZCCVA meeting sometime. Unfortunately VA Beach is a bit of a drive for me, as I'm on the other side of the bridge tunnel. The last time I drove to VA Beach, I felt like I was driving in the Daytona 500 -- some crazy moves by some of those drivers! Do y'all ever do anything on my side, where it's all calm and peaceful?

I have yet to talk to Todd at Tidewater Z. I will eventually. I'm just working my way through as much as I can on my own. It's part of the bonding process, and it's a lot easier on my wallet. I figure I'll reach a point where I need a more seasoned opinion or where I'm stumped about something, and then I'll drive the few miles to see him.

Thanks again!

Peace,

Sarah

[WingZr0]

Heh Sarah you might try DRIVETRAIN.COM They sell rebuild kits for transmissions and may for Differentials too. Don't have the printout list of parts on hand but they're located in Vegas. And prices reasonable if you need a source for the parts.

[Diseazd]

Todd's the man in the Tidewater area......get a good used diff and he'll drop it in for you. Did you have a car at this years Hampton show? I thought you had a white Z.

[ezzzzzzz]

Jon, I agree with you about the clunking noise. My attention was drawn to the metal debri Sarah spoke off. That is never a good sign in my opinion. I drove my 240Z with the R180 singing an increasing whine for a couple of years until that and the 'clunking' became a real nuisance. The mounts and halfshafts were tight so I knew it wasn't the culprit. An inspection proved the NiSMO LSD was completely worn out after 38 years of service (I've only owned the car for about 6 years).

Sarah, we do get together for events other than the monthly meeting. There was a great pigpicking this past Sunday. Check out our website at http://www.tzccva.org for information about upcoming events. We hope to meet you soon.

[Travel'n Man]

I would change the gear oil and see if that helps. Make sure you do not overfill. You may want to put a little kerosene in the diff and flush it out real good and put some gear oil back in..........if it is still screaming get in touch with Roger........I'm sure he can help you with a R180 or a R200. If you change rear ends be sure to count your teeth or know your gear ratio, you may have to change your speedo gear.

http://www.zbarn.com/

[jmortensen]

Jon, I agree with you about the clunking noise. My attention was drawn to the metal debri Sarah spoke off. That is never a good sign in my opinion. I drove my 240Z with the R180 singing an increasing whine for a couple of years until that and the 'clunking' became a real nuisance. The mounts and halfshafts were tight so I knew it wasn't the culprit. An inspection proved the NiSMO LSD was completely worn out after 38 years of service (I've only owned the car for about 6 years).

They put the magnet on the plug for a reason, to pull the larger chunks of metal out of the oil. It's normal for them to be a bit fuzzy when you pull them out, and I think it's normal to have a little bit of metal in the oil. A lot of metal in the oil or big chunks of metal are a different story. But by her description it didn't sound too extreme to me. It's tough to diagnose over the internet, but based on the description I'd change the oil and look for some other culprit for the noise.

As far as your experience goes, LSD's have clutches that wear, and the R180 LSDs from back in the day were mostly 2 pinion units. Both of the people that I know that had 2 pinion LSD's broke them. The later ones were 4 pinion units and much stronger (at least judging by the anecdotal evidence). The spider gears in an open diff really don't wear at an appreciable rate if the lube is kept full and in good shape. The thing that does wear out spider gears is burn outs and drag racing starts (again from the anecdotal evidence).

[doradox]

I'm with Jon on this one. A little whine doesn't mean much. Change the fluid, fix the leaks, look for loose mounts, bushings, u-joints, and stub axle nuts for your clunk.

Steve

[FastWoman]

Thanks! This view (that the filings aren't unusual) is apparently also shared by the car's former Nissan mechanic across the state. I had occasion to call him with a question about the service history and asked about the differential too. Anyway, the differential has a fresh change of Mobil 1 now. I'll have the car out on the road again today

Now if I could only crack open the drain and filler plugs on the transmission! Oooof!

Regarding the U joints, there's a GSP (Chinese) CV half shaft available for this car from Advance. I'm not thrilled about Chinese manufacture, but it carries a lifetime warranty and costs only $70 per side. Hopefully that would be a cure for the common clunk. Any thoughts?

[Travel'n Man]

Anyway, the differential has a fresh change of Mobil 1 now. I'll have the car out on the road again today

What weight was that Mobil One?