'03 M45 Rear Diff clunk/slip... What is it?

[M45Caliber]

OK -- while I wait 15 more days for the Elite Warranty grace period to end, something new has just cropped up over the past few days.

When shifting from reverse to drive (car is stopped and not rolling when I do this...) I occasionally get a loud CLUNK sound and it almost feels as if the wheels spun for 1/4 turn on some oil or water - which it hasn't, because I stopped and went back and looked at the road.

Once again, this puppy now has 38K on it, and I had the rear diff fluid changed out by the Infiniti dealer about 3K miles ago.

If this thing had a LSD, I'd say it was the clutch pack going out or grabbing... but my uderstanding is that's not the case on these cars.

Any ideas or suggestions. It's very un-nerving when it happens. Once I am in drive I hear nothing out of the ordinary, even under full-throttle acceleration.

Thanks in advance, M45Caliber

[qship96]

Too low miles to be universal joint or diff bushings? Check level of diff fluid.

[SteveTheTech]

I reread this a few times thinking about it. I would take a look at the center bearing on the driveshaft.

If you power brake it a little in either forward or reverse can you hear it?

Can you get the noise to reproduce when you want it to or is there a geographical or climatic variable that effects the noise you are hearing?

Did you notice this after something or just something that started randomly?

[M45Caliber]

Steve -- I notice it mainly when I am backing up while turning (like out of my driveway onto the street). Now that I think about it, I am always hearing it when backing up and turing the steering wheel counter-clockwise (example -- car facing north and backing up (south) and turning the wheel so that the front of the car is pointing east - if that makes sense). I stop and drop it from "R" into "D", and touch the gas -- I hear that "Clunk" or "grunch" type of sound and it feels like the wheels slip for a mili-second, then off I go and never hear it again until I do the back up/turn scenario. But NOT all the time -- maybe once outta 4 times do I hear/feel it.

I will play around with it some tomorrow and see if I can replicate consistantly. I hate to do too much as the Elite Warr doesn't kick in for 12 more days! Yikes.

[qship96]

Are you sure it is not just the ABS doing its self test procedure?

[M45Caliber]

Oh yeah -- that's an electrical/pump sound... this is something new and not normal.

[SteveTheTech]

Could it be a loose rear shock?

[M45Caliber]

I'll check -- but I just had a 4-wheel alignment (like 4 weeks ago) and everything checked out OK - but I guess anything is possible.

[Q45tech]

6 years [even with 38k] is long enough for hundreds of non warranty items made of rubber to have worn and changed.

Check all driveline bushings from transmission thru diff to hubs.

[maxnix]

Not that familiar with the RE05, but I wonder ...... have you checked your ATF level? I think you have to buy the dipstick tube separately.

http://www.infinitpartsusa.com

The color of the fluid compared to new on a white paper towel would give you some idea of degradation.

All the other suggestions are good also.

[M45Caliber]

OK -- I have a good foriend who is an ASE Certified master mechanic and he owns his own independent repair shop in Mesa, AZ. I've used him for years on our "Kid Cars" -- i.e. cars out of warranty and being driven by our kids. He's honest and he's a great mechanic (heck man, he works on Land Rovers and Jaguars when the Scottsdale dealership can't figure out whats wrong... so he's almost a magician - LOL).

Anyhow I drove over to his shop and we put it up on the Hunter alignment rack so we could poke around. Diff fluid started coming out before we had the refill (upper plug on the side of the diff) plug out all the way - a nice clear/pale amber color (just a few dribbles so the plug went back in). So we closed that up. Checked all the struts/shocks, checked the driveshaft and various Ujoints - solid. Double-checked all the suspension bolts as he performed the 4-wheel alignment a month earlier ( newest Hunter rack = like watching a laser light show - cool stuff). Checked the wheels and everything seemed bolted down OK. So, Everything underneath solid. Keep in mind that this car was a garaged California car - in MILD semi-arid climate it's whole life, so ALL of the rubber components look new. Amazing - at 38K miles and you could eat off the undercarrage - NO grime or dirt what so ever. Everthing clean and easy to look at, grasp, and "shake" or try and move around.

Dropped the car and fired it up and checked the motor mounts - nadda. That monster motor doesn't move when torqued in gear. Checked the trans fluid level (that was fun -- never knew there was a 10mm bolt holding the transmission fluid dip stick down - must be some serious pressure in there!) Anyhow, the fluid was clear and full - between the two holes on the stick where the word "HOT" is stamped between them - actually touching the top hole but NOT into the hashed marks on the stick above the holes. I did the sniff test and all I smelled was transmission fluid -- nothing even remotely burnt.

QUESTION: What color is the Nissan ATF? This looked almost clear on the dipstick and no color to speak of when wiped on a towel.

So, now I am at a complete loss. I will continue to drive this until I can replicate the issue for the mechanics OR it just goes away. Any other thoughts appreciated -- thanks again guys.

[maxnix]

Differential and ATF should be changed at 30K intervals. If the fluid degrades any, the damage has already begun. Same with PS fluid. Even coolant and batteries should be suspect after 3 years in high heat areas.

Sure your tension rod bushings were not leaking and all rubber links and steering rack bushings were tight and not brittle or cracked?

Check ATF cold again for certainty. The 10 mm bolt is to keep the civilians out. You can lose it.

[SteveTheTech]

1never knew there was a 10mm bolt holding the transmission fluid dip stick down - must be some serious pressure in there!

2QUESTION: What color is the Nissan ATF? This looked almost clear on the dipstick and no color to speak of when wiped on a towel.

3So, now I am at a complete loss. I will continue to drive this until I can replicate the issue for the mechanics OR it just goes away. Any other thoughts appreciated -- thanks again guys.

1The bolt is there because all 03-04 started using Nissan J-Matic that does mix with Dextron or any other transmission fluid. The only fluid that can be safely used is the new Nissan Matic S that is used on the RE7.

2The color of new J-Matic is a light red, it feels very light. It ages to a light brown (~60K under normal conditions) with little to no smell. A visual examination will not give you as much information as a paper towel test. I have a white Post It note stack that I use, the denser paper dissipates the fluid < paper towel keeps any particle matter in a concentrated area. Many times I do a before and after if the owner is interested in seeing it.

3If it is happening infrequently at this point you may have to wait till it's a little more prevalent. Or you could spend hours chasing things, or take it to the dealer once your warranty kicks in to get it looked at.

[M45Caliber]

Thanks S T T -- my trans fluid has been changed twice in 38K miles, which probably explains why it appears so "clear". I'll just keep driving her until something more frequent shows up.

[M45Caliber]

MaxNix -- as an FYI, this is probably the most anally cared for M45 on the Planet. Coolant flushed @ 30K, PS and Brake fluid flushed/changed at 30K, Trans has been flushed Twice over the past 38K miles (16K and 35K). Rear Diff fluid drain/fill at 30K. Oil/filters every 2,500 to 3,000 miles. All services performed ONLY at Infiniti dealers. It ain't for lack of maintenance that I am experiencing any issues -- that's for sure.

So if the motor needs to be replaced (consumption test starting in 2 weeks) and it turns out it's my transmission slipping, Infiniti would have to shell out what, maybe $15K? And the wholesale value of my car is maybe $10K? I wonder if I could just ask them to give me a $20K credit towards a new car? Hells Bells, they certainly could use a new car sale right now! Might be worth asking the regional rep about that -- guess we'll see what the outcome is first.

[maxnix]

Thanks S T T -- my trans fluid has been changed twice in 38K miles, which probably explains why it appears so "clear".

Does "changed" mean drain and refill, thus retaining 60% of the contaminated fluid, or mechanically exchanged like with a BG or Sun machine? Big difference.

Might want to seriously consider am ATF cooler like the B&M70268 or 70264 like we run on the heavier duty RE04.

Unless you really want a newer M (M50 might be interesting!), I would keep what you have.