Diff noise?

[my_mad_z]

Hi all,

 

Hope you are all well.

 

I've been going through a process of elimination with my 240Z and I'm down to the diff (R200 VLSD from a HR31) - I've attached a sound recording I took when I was turning the rear wheels back and forth by hand; 14 sec into the recording is the sound I think I'm hearing while driving but it's more pronounced when driving. I couldn't get the sound to happen every time when turning the wheel by hand. I've eliminated a few things, hoping to get some advice on what to do/try.

 

In the process of elimination, I came across a few issues that sounded very similar to what I'm hearing when under acceleration. Mind you it doesn't happen every time I accelerate, it's somewhat random. I'll try to keep it short:

 

At first I thought it was my rear discs that were moving slightly (slack between the holes and the wheels studs) due to my wheel adaptors coming a bit loose over time - confirmed it wasn't this by fixing the disc to the hub using a counter sunk bolt. The noise didn't happen for sometime after that but after a few hard dumps in 2nd and 3rd gear, it started again.... turns out the studs in the adapters I made for the Z31 CV upgrade sheared/snapped. I fixed this by putting new studs and reinforced it by welding the adaptors to the hubs... all seemed fine for a while until I turned the boost up.... the noise came back 

 

I pulled the tail shaft out; it's only a year old and the uni's are in good order. I didn't have the original tail shaft bolts and noticed that the bolts I'm using don't fill the hole completely and this could be allowing the tail shaft to twist slightly under acceleration. I didn't get a chance to get new bolts today, hopefully tomorrow. My moustache bar has new superpro bushes as it kept destroying the rubber bushes; diff mount is in good order and the front of the diff is strapped down with chain (snapped the original strap and then snapped the first chain). I haven't checked the pinion yet, will do that tonight if I get a chance. Next step was to disconnect the CV drive shafts to make sure it's not the CV's (don't think it is) and last remove the diff and open it up for inspection.

 

If my diff is on it's way out, any suggestions on the best option for replacement? I've searched the forum and online and I don't know which way to go 

 

Marc.

42663_5d235e0086df26e7e9fc8a2d40feb03173176f0d.zip

[dat2kman]

Clutch dumps in 2/3rd, snapping bolts, loosening screws, turning up boost, incorrect bolts ( no shanks) on tailshaft, unkown history cv's.

What can go wrong!

Viscous centre, pinion gear teeth, crownwheel bolts, checked these items.

Fit correct shanked bolts to tailshaft

Sometimes, the front diff mount "looks" fine, but needs to be pulled out and stretched/deformed to check if rubber is perished/cracked.

The SuperPro type rear bushes tend to transmit more noise.

[my_mad_z]

Thanks for the response dat2kman.

 

Just to clarify a few things, I wasn't doing clutch dumps, WOT in 2nd and 3rd is what I meant by hard dumps - I'll choose my words more carefully next time.

 

I am going to replace the bolts for the tails shaft, just haven't had a chance to get them yet; I did find some old shanked bolts from my 260Z but they weren't a good fit either.

 

I have removed the diff mount and checked it, it's still in good condition, no cracks.

 

I realise the SuperPro bushes transmit more noise but since I've put them in the rear end definitely feels much better.

 

The CV hub adaptors went over a year without an issue; my fault for not doing a routine check on the bolts - I used Loctite on them but only mid strength; it's not like they were hanging on by a thread. I used high tensile bolts and when I made the adaptors, don't know why they snapped, could have been that I over tightened them after I found they were 'slightly' loose.

 

I don't think my CV's are an issue, before I put them in I had them checked and I cleaned/regreased them; I haven't checked them since I installed them so that's why I mentioned removing them to check them.

 

I'll check the diff as soon as I get a chance to pull it out.

[my_mad_z]

After pulling the diff out and inspecting everything, all looks good - backlash was well within tolerance so it wasn't the diff. Took the drive shafts out and had them checked again, looks like they were the culprit - they were good when I put them; the guys at the drive shaft place said they couldn't be overhauled.

 

What they ended up doing was putting oversized bearings in and swapping the left/right cages to try and buy me a bit more time. Did the job, haven't heard the noise since putting it all back together. Tried to offer the guy money for doing what he did, wouldn't accept anything! There are some decent people left in this world!!! A & F Drive Shaft Repair in Hawthorn if anyone is interested.

 

Next step is to see what options there are for Z31 CV replacements... checking the forum now :-)

 

 

[Riceburner]

I have some Z31 shafts you can have, they're of no use to me. Maybe you can mix n match to rebuild yours?

 

http://www.viczcar.com/forum/index.php/topic,14348.0.html

[my_mad_z]

Hi Gareth,

 

Really appreciate the offer mate but they're different to the one's I have; I've got the 4-bolt pattern from the turbo model I believe.

 

[Riceburner]

No worries, hope it lasts until a better solution. Too much torque!