Earlier this month I purchased a 1972 240Z that hasn't been on the road in a while.  I only drove it a little in the first week or so that I bought it as it wasn't registered yet, and the brakes were pretty bad.  I definitely noticed a good amount of driveline noise, even at very low speed.  Also, when turning the rear wheels by hand, you could hear and feel some notchy gear sounds coming from the diff.

I'm now in the middle of a full suspension and brake rebuild with all the suspension components and the differential out of the car.  The magnetic drain plug had some metal shavings, and it seems that the noise is coming from the spider gears

Youtube video link

I'm guessing that these are signs that this diff is on it's last legs?

The stub axles aren't cheap, but I'm leaning towards swapping a Subaru R180 at this point and getting an LSD in the process instead of rebuilding this one.  I had planned on doing this at the same time as a 5 speed swap so that I could match the ratios well, but I'd hate to put a bad diff back in the car when it's already out.

You could probably just get another Nissan R180 from somebody who did an R200 swap, if you wanted to get back to basics quickly.

Diff removals and installs are pretty easy so the issue of putting a worn diff back in doesn't really matter much, does it?  Really?  You just want the Subaru LSD diff.  Right?  Rebuilding an old R180 doesn't seem effective at this point in time.  Some day they'll be hard to find there's probably a decent one out there somewhere that is better than a rebuilt one will be.  They're pretty durable.

The STI diff will cost you some dollars but will be worth it. 

 

11 hours ago, Zed Head said:

You could probably just get another Nissan R180 from somebody who did an R200 swap, if you wanted to get back to basics quickly.

Diff removals and installs are pretty easy so the issue of putting a worn diff back in doesn't really matter much, does it?  Really?  You just want the Subaru LSD diff.  Right?  Rebuilding an old R180 doesn't seem effective at this point in time.  Some day they'll be hard to find there's probably a decent one out there somewhere that is better than a rebuilt one will be.  They're pretty durable.

My concern with just picking up another Datsun diff is that it's going to be in the same or worse condition than mine.  You say they're durable, but is this kind of wear normal for a 130k mile car?  Maybe my car has 230k miles :-)

An STI R180 can be had for around $600 on EBay it seems.  The stub axles are $400, so it's going to come in around $1000.  I have no idea how much it would cost to have the Datsun diff rebuild, but I'd be surprised if it's less than $500

Edited April 1, 20178 yr by kstewart

The guys that really know diffs say that wear of the spider gear shafts and their holes is commonly from one-wheel burnouts.  It causes the diff to spin abnormally fast, and thus the spider gears, and wears the shaft bearing surfaces.  In some cases you can see the wear around the shaft as the hole takes on an oblong shape.  It can get really bad.  This allows the shaft to **** (male chicken) and the spider gears to get misaligned.  It sounds like what's happened to yours.  If that's the case it can't be rebuilt anyway.

If the fluid is changed and they're driven normally they really do seem to last almost forever.  I'd examine what you have more closely to see if you can find what's worn, then examine any used ones to see if they're better.

On the other hand, the STI diff is pretty nice.

Edited April 1, 20178 yr by Zed Head

I got a 4.11 "k" r180 which bolted right up to my '72 240z and it's a lot more fun to drive now!!


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Those deposits on the magnetic drain plug are not unusual for a car with those miles. If you are strapped for cash, replace it for now, get yourself another diff, rebuilt it and put it in when you have the time. On jack stands the diff can be swapped in under 3 hrs. Do it enough and it takes 1.5hrs.

The Subaru diffs are nice and you might want to consider replacing the bearings (side at a min) and seals before installing it. You'll need the R180 front coupler (goes to the driveshaft) so you'll be more than half-way to taking the unit apart and I'd replace the pinion bearing too along with the front seal.

The K R180s in either 4:11 or 4:38 make your Z very responsive but you'll be hitting the redline sooner. I have both with a Quaife and Giken installed. Performance with the Giken is better but I'm not sure it's $500. better (read quicker).

It's the noise that concerned me the most.  

I went ahead and bit the bullet and picked up a 2015 STI diff with 17k miles on it here locally.  I paid $600, and have ordered the stub axles for another $375.  At the moment I've got more money than time with things getting even busier at work later this year, so I made the call.

I finished painting the suspension parts yesterday and my big orders from MSA and Courtesy with bushings and everything should arrive soon.  I may be able to get everything back together by the end of the weekend if everything shows up on time.  

What ratio is that 2015?

It's 3.545 which wouldn't be the best with the 80-83 close ratio transmission.

I'm thinking I'll swap a FS5W71C in later this year.  With a 205/55R15 tire at 23.9" diameter it would be roughly the same final ratio as the stock trans/diff/tire combo.