71 240Z rear diff questions, clunking

[xray]

...I can grab the driveshaft and turn it about a half inch. It does not translate up or sideways. This has me thinking that the ring and pinion has some slop in it, how much is normal I do not know, but this seems excessive, but the bearing on the pinion seems fine.

Item two, I can grab the fat part of the left and right driveshafts/halfshafts and I can physically move them up and down with my hand a little. I am thinking that the bearings on both sides are probably worn badly, or something greater is amiss inside the R180. Keep in mind the Ujoints felt solid and did not move, I could see the whole drive shaft coming out of the diff move up and down just a little. .

I am thinking I may need to start looking for either a new R180 or a new set of bearings. What worries me the most is the ability to turn the driveshaft so easily. Keep in mind I am on ramps, not on jack stands. So the wheels did not move.

In the vast world of clunk investigations, how does this rate? Any opinions, before I start ordering the parts I think I need.

I had some free time today so I hiked my car up for comparison. The diff itself has not been rebuilt. There is very little, like 1-2mm, of backlash when I try to rotate the driveshaft with the car up on ramps. The halfshafts have no backlash in them at all. All the mounts, bushings and hardware are new. (I have no driveline clunk, but traced a slight thud in the rear of my car to the shifting spare tire.)

Since the kids were still in nap mode, and my wife was otherwise occupied, I grabbed my USB camera and strapped it to the passenger side rear transverse link, aimed at the diff, and threaded it up through the spare tire drain hole. Went out for a little drive, and here's what it showed. I wound it up to 5500, did some hard shifting, and punched it some while in gear trying to induce a thunk. I have extra video of some forward/reverse nature, but it shows the same as what's below (sorry for the low res)

<embed id="VideoPlayback" style="width:400px;height:326px" allowFullScreen="true" src="http://video.google.com/googleplayer.swf?docid=-3727888468389030522&hl=en&fs=true" type="application/x-shockwave-flash"> </embed>

Not sure, but hope this helps some

[speedracer906]

Wow! you have too much time on your hands!!

No really that was super smart. At first I was thinking that the amount of movement the diff was getting didn't look like it could cause a clunk like you or I may be triing to describe. But then at 2:14 or so you dropped the clutch and the diff jolted enough to maybe hit something. Then you were working the throttle and I saw the same kind of movement and felt that if mine moves as much as yours or worse than you could associate the noise with the diff movement. The diff could be hitting the mount frame it's self.

If you could find a urithane replacement I would replace it with that. I'm going to. That kind of movement could not be reinforced with triangulation with out carring the stress to some othe point and that could mean cascading distruction. Beaf the mount Ya'll. Just my opinion, hope it helps.

Do some more video on the under bits, that's super cool stuff.

[sblake01]

You're overthinking it. Just replace it with a stock mount. They last...just not 35 years.

[xray]

Uh...you might misunderstand. My rear end does not clunk. It has a new mount, new strap, new nuts and bolts all torqued correctly. The diff moves against the torque generated by the motor (and the resistance from the wheels), so the strap keeps the nose of the diff from slamming against the trans tunnel. The U-joints keep the torque forces from binding the driveshaft against the pinion of the diff (or the output shaft of the transmission). That motion is normal.

One could buy a solid mount (Arizona Z Car, for example) to eliminate the motion altogether, but the ride quality might not be desirable.

[speedracer906]

"When you put the car in 1st or reverse and let out the clutch, no matter how gently or slowly, you hear something mechanical make a very muted thud. Its just one thud, but it makes it each time you go from 1st to reverse. I also hear a thud from the back end each time I get on and off the gas in 1st or 2nd gear, like the diff is torquing up."

Ok well mine is a clunkish thud. I still like the idea of limiting the overall movement of the diff. It could help replaceable parts last longer. I race and find that bearings bushings and ujoints etc. tend to go at an eccelerated rate do to movement like that.

I over build. I drive with spirit. Buy some parts for you differential and make more videos.

[Poindexter]

xray, you rock! Excellent idea. I'm going to do the same thing in several directions in hopes of documenting any unwelcomed motions under the car.

I'd love to be able to just hit it as hard as I wanted on every shift. It just doesn't respond that well to such treatment, at least until the clutch is fully engaged- too touchy- but then she just loves to be run up hard. :laugh:

I sometimes forget just how violent the forces involved in the powertrain can be.

[sblake01]

But, really, all you have to do is make sure that everything is good condition as far as mounts, u joints, etc. Nissan did a pretty good job of engineering these cars. If all of the compenents are in good working order, there's no 'clunk'. Speedracer, if you want to put solid mounts, etc. on it, do it. It's your car. I could go into all of the reasons, like the ancillary damage that will eventually cause, but, based on your previous responses, I doubt if you would listen. When you say 'you race' that most likely means that you abuse the hell out of a street car which isn't the same thing.

[speedracer906]

Well ok. I'm missing the point but I was just trying to help with a strand of thought that I had.

I'm 40 years old and not a yahoo. I drive sportily every chance I get in my street car. I rebuild my cars with theory's that make sense from my race builds. The biggest build I was apart of was an ex world rally car campaigned by Francois Delacour in 95. A good friend of mine bought the Ford Escort Cosworth from Great Britain and we had to completely re assemble the car from scratch. What a great opportunity. I co drive with Mike Whiteman, my friend in Hill Climbs that we run now out here in Colorado. We both have years of experience in Rally. Mike has had more in that he actually started Rally in the west when other friends of his in California would hold invitation only events in the middle of the night. That grew into 8 or so rally’s from California to the Rocky Mountains. California Rally Series or CRS was the Organization under SCCA at the time that I won my first Championship in 2wd in my Mazda RX-7. It was my second car the first car being an 84 Dodge Colt. (Interesting car) I then took a championship in 2001 in what we organized to be the Western State Championship Series. The next year due to not having enough funds to run all the events, my first place standing dropped to a tie for third. My cars won events because they lasted the tortuous riggers of rally.

I’m way off the point and will avoid posting as to not complicate the process with my misunderstandings. Sorry.

[sblake01]

All of that is fine but I was just trying to keep within the context of what Stephen originally posted.

[Zedyone_kenobi]

From the sound of this, it sounds like I may just want to try to get a new strap and new diff mount. I may back the car against a curb and video what the diff does. If it moves, it may explain the bulk of my issues. As a rule you should always start with the simplest things first. Then work your way forward.

THanks so much for your Video Steve. When I get on and off the gas like you did is when I hear my clunk. My arrestor strap when the car sits actually quite lose. I will look into the rear diff mount. If yours moves that much, then there is a good chance if mine is original, that could be the source of my problem. The more I think about it, the more I dont think its my half shafts. But we will check these out tonight.

Again, thanks for going above and beyond the call of duty.

[moonpup]

When it comes to clunking in the rear, another cause that hasn't been discussed yet are the struts. You may have a strut that is either loose or shot/toast/kaput! Usually this becomes more evident on bumpy roads vs. under acceleration.

This doesn't sound like the case for the original poster, but I thought I'd throw this out there for any other members trying to determine the source of their "rear clunks".

[7277]

simplest thing is just to replace all the rubber parts/mount/bushings/strap, etc with new OEM stuff...with urethane on crossmembers and mustache bar. like sblake01 mentioned, the cars were built well by Nissan.

xray: awesome video!...it almost looks UTube-ish...i was kind of waiting for something to EXPLODE! LOL