My 350 (probably) powered 260z!

[nolant178]

I've been slowly replacing the U Joints in my car to remove this rhythmic clunking noise. I started with the half-shafts thinking they were the most likely culprit. I finished those last night and took it for a test drive fully expecting to hear the noise still... and I did.

 

At the recommendation of @NewZed I took it to an open parking lot and did some testing. First I held the brakes and gave it some gas (not enough to burn rubber), and found that I could hear the noise even when the car isn't moving.

 

Next I drove in tight circles in both directions at the same speed - the noise was consistent in both directions. 

 

I think this means its something to do w/ my Drive Shaft - so I'm gonna try replacing those U Joints next to see! The lack of difference in tempo/volume when going in different directions tells me its probably not the diff, which is encouraging! If anyone reads this and has any other ideas as to what it could be let me know!

 

To diagnose this noise I've: 

• Checked under the car for any loose bits/exhaust hangers etc
• Replaced worn mustache bar bushings
• Replaced half-shaft U joints

Hoping its the drive shaft U joints that resolve it at this point, otherwise I'm worried I've exhausted my current troubleshooting ideas.

 

Thanks for reading!

[NewZed]

5 hours ago, nolant178 said:

First I held the brakes and gave it some gas (not enough to burn rubber), and found that I could hear the noise even when the car isn't moving.

 

I looked through the thread and can't tell exactly, if the car has an automatic transmission.  But, if by "not moving" you mean zero MPH, then the problem is probably in your torque converter or transmission.

 

The wheels, differential and various drive and propeller shafts are all solidly locked together.  The only part that can move with the engine crankshaft is the torque converter and transmission input shaft, if the car is not moving.

 

When I watched your video "torque converter" popped in to my head as a cause.  It might be as simple as loose torque converter flex plate bolts.  I would check them soon, the beating will be damaging.

[nolant178]

1 hour ago, NewZed said:

 

I looked through the thread and can't tell exactly, if the car has an automatic transmission.  But, if by "not moving" you mean zero MPH, then the problem is probably in your torque converter or transmission.

 

The wheels, differential and various drive and propeller shafts are all solidly locked together.  The only part that can move with the engine crankshaft is the torque converter and transmission input shaft, if the car is not moving.

 

When I watched your video "torque converter" popped in to my head as a cause.  It might be as simple as loose torque converter flex plate bolts.  I would check them soon, the beating will be damaging.

This makes an unfortunate amount of sense. I did notice that after having the rear of the car lifted for a week and a half I found a puddle of ATF under the car. 

 

Looks like I'll be checking this out! Thanks again, you're extremely helpful!

[nolant178]

The sound is distinctly coming from the rear, not the Torque Converter or trans. The video I posted is close, but the location is wrong. I think what's going on is I've broken a tooth (at least) on my ring or pinion gear in my diff. I'm gonna crack it open over the weekend and see what I can find out.

 

If that's the case, I'm going to look at doing the R180 lsd swap from an STI. I'll post pictures of the diff when I crack it open to show you what I find!

[NewZed]

The driveshaft could easily transmit motion to the diff, making the pinion gear bounce off of the ring gear.  The noise might be from the diff but the problem is probably in the trans or converter.  There's no way the car would move like it does if you had a tooth missing.  And at zero MPH the pinion gear would have to be slipping over the ring gear.  That would make a terrible grinding noise.

 

Put your camera under the car while you do the zero speed load test.  You'll probably see the propeller shaft bouncing back and forth a degree or two.

 

On the other hand, taking things apart is always a good learning experience.  You'll want to know your diff condition anyway.  The R180 really is small for a 350.

[nolant178]

6 minutes ago, NewZed said:

The driveshaft could easily transmit motion to the diff, making the pinion gear bounce off of the ring gear.  The noise might be from the diff but the problem is probably in the trans or converter.  There's no way the car would move like it does if you had a tooth missing.  And at zero MPH the pinion gear would have to be slipping over the ring gear.  That would make a terrible grinding noise.

 

Put your camera under the car while you do the zero speed load test.  You'll probably see the propeller shaft bouncing back and forth a degree or two.

 

On the other hand, taking things apart is always a good learning experience.  You'll want to know your diff condition anyway.  The R180 really is small for a 350.

I wanted to make sure I understand: You're suspecting that an issue in my TC or my AT is transmitting excess motion to my diff, where the noise is manifesting?

 

I'm asking questions because I'm getting a lot of info from a very  helpful community and I want to make sure I'm understanding everything, not because I'm doubting anyone (in fact I'm extremely grateful to have people so willing to help diagnose!)

 

1. So it was my understanding that the u joints exist so that the diff and trans can move independently of one another without causing issues - could this be a drive shaft u joint gone bad after-all? 
2. And also, if there was an issue with the TC, wouldn't there be something noticeable while in neutral? Currently I can put the car in N and rev it to my heart's desire.
3. My final question is in regards to the diff being small. I've read that its small for the 350, i've also read that auto trans are easier on diffs, also the r180 LSD seems to hold up fine in the STI, which seems to have comparable torque to many SBC 350's.

[NewZed]

Yes.  The R180's and R200's are notoriously loose and clunky diffs.  Lots of slop in the gears, and splines.  

 

In neutral there's no load.

 

Good luck.  You'll find it.

[nolant178]

My plan keeps shifting, as they do.

 

Tonight I'm gonna open up my diff and see what's going on in there. If its bad, I'm gonna start sourcing parts to do an r200. I realized that STI's can run the r180 because only 60-70% of the power is going to the rear at any given time...

 

I'll be sourcing parts now!

[nolant178]

Alrighty, making progress!

 

I cracked the diff open, and found some broken teeth! I may be the most excited person to ever find a busted diff on their car... but I think my issue is finally found. I'm currently trying to find everything to do the r200 swap, Ideally I'd go straight for an LSD, but may get an open diff to start out and swap to LSD later on for budget reasons.

 

You can see bits of broken teeth sitting in the bottom of the housing! And look at how dirty that fluid is. New diff time!

 

 

[NewZed]

Looks like your pinion haft was about to blow a hole in something.  It's trying to get out.  It happened to me long ago, on a GM diff.  Blew a hole in the diff cover.

 

Look at how the propeller shaft turns those gears and how they work.  Ponder how the gears could turn and slip on the broken teeth when the car is not moving.

 

[nolant178]

12 minutes ago, NewZed said:

Looks like your pinion haft was about to blow a hole in something.  It's trying to get out.  It happened to me long ago, on a GM diff.  Blew a hole in the diff cover.

 

Look at how the propeller shaft turns those gears and how they work.  Ponder how the gears could turn and slip on the broken teeth when the car is not moving.

 

 

I hadn't even noticed that... wow! Good eye! And I see what you're saying. I won't be able to test any further until the new diff is in, but this'll be a good time to inspect the trans and flex plate as well.

[nolant178]

As of about 15 minutes ago, I've ordered all of the parts I need including an r200 to install into my car! They should all arrive sometime during next week.

 

This weekend I'm going to drop my diff out of my car and take it apart to see how much damage I've done. I'll be attempting to sell anything that is usable.

 

After I take my diff out, I'm also going to replace the u-joints on my drive shaft, and inspect my Trans and Torque Converter for potential issues, since I'll have relatively easy access to them! I'll try to take pictures as I go.

[nolant178]

I've successfully installed the r200 in my Z! This is the most involved project i've done to date, and it went pretty well! I had a few hang-ups here and there, but overall the installation went very smoothly.

 

Much to my delight, and expectation - the knocking noise is gone! I was finally able to put some time behind the wheel to see what other issues I'm dealing with.

 

I also attempted to fix the speedo reading. I swapped to a 24 tooth speedo driven gear. My readings are closer now, but still need to be adjusted, I may just get a GPS speedo and be done with it.

 

My first weekend of cruising in the car has been great! So many people love the car, they are asking questions about it, taking pictures and videos. I knew it wasn't a super common car in the Chicago area, but damn people really love it! I'm excited to finally be on the road (for now haha...)