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So, my kid's Z is sitting here, he's not.  I'm human.  I took off Friday night, just gunna see if my diff oil top off stopped that weird whining noise, you know, a good dad.  I got a little gas, a nice cruise in the sunset. Then outta nowhere some punk kid in a new Challenger blows by me, oh Lord no.  I blew by him.  We meet at the next light, windows go down and we chat, nice guy.  Light turns, I take off like a Bat Outta Hell (because, that's why this thing exists after all) Very fun.......but....... I hear a "bang" and then a rhythmic clunk, I start limping home, the noise is NOT GOOD.  I pull over, sure I'll see something slapping around down there....nothing, keep limping........gets worse. I'm under idle speed now....5mph, the noise is very unpleasant.  Sounds like someone with a hammer smacking the chassis every revolutionI pull over again, sure I'm gunna see carnage, nothing.  Limp home.

I think I blew the diff.?

Starting homework.  I think it's the original R180? (see video).  Plan is to pull it and open it and see what's what.  Dad might be springing for a new diff.....I'm okay with that.  Car is just too good for me, best therapy known to man. Money well spent.  Thoughts welcomed.

 

 

zonlift.jpg

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looks like an R180, but it’s hard to tell from this angle. They don’t handle much torque, so if it is the diff I would replace it with an R200. Plenty of posts on here about that. 
 

First, confirm it’s not the engine, flywheel or clutch. If you hear the noise when you rev the engine in neutral, it’s not the drivetrain. If the noise is 100% dependent on the cars speed and on/off throttle just makes it worse, it’s downstream of your engine. 
 

next, feel for play. It could be your trans, driveshaft, diff, or axle shafts. If it’s the driveshaft or axle shafts, you will notice obvious looseness (play) in those U-joints when you try to turn them by hand.

 

diff: turn the axle shafts and driveshaft by hand with the car in neutral and on off the ground. If the diff makes a clunking noise when you turn any of those shafts, the diff is toast. The most likely failure in the Nissan diff in my experience are the spider gears. They are really loud when damaged, especially on engine braking. The spider gears won’t usually add much play when you turn the driveshaft, but you will hear/feel it if the car is in gear and you turn one of the wheels off the ground. If the play is felt on the driveshaft side of the diff, then it’s likely your ring/pinion gear. 
 

it could also be your front diff mount. Lots of torque often pulls up on this mount and eventually comes loose. Happened to me, and there is a product out now that solves this by converting to a top-mount. 

 

it is unlikely to be your trans since that will make an obvious whining or grinding, and not a loud thud like you described. Also, it would be right next to you since the trans is literally 6” from your calf. 
 

I have blown everything except for a trans in my 240z career. 

 

 

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okay, will do.  So far all I did was lift the right rear and turn the wheel, certainly a bit of slop but not excessive but it was in gear and the left rear was still on the ground so will raise both and put in neutral and see what it feels like, the drive shaft and u joints look okay, gotta love the cable on the front mount, engineering on this build and subsequent "fixes" are, shall we say, questionable, but we own it now so it's on us to put it right.  I'll probably be looking to source a full replacement I guess.  R200 or the Subaru swap, found some info on that.

 

cablemount.jpg

diffright.jpg

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2 hours ago, jvandyke said:

okay, will do.  So far all I did was lift the right rear and turn the wheel, certainly a bit of slop but not excessive but it was in gear and the left rear was still on the ground so will raise both and put in neutral and see what it feels like, the drive shaft and u joints look okay, gotta love the cable on the front mount, engineering on this build and subsequent "fixes" are, shall we say, questionable, but we own it now so it's on us to put it right.  I'll probably be looking to source a full replacement I guess.  R200 or the Subaru swap, found some info on that.

 

cablemount.jpg

diffright.jpg


how much torque is your V8 pulling? Just remember, torque is what breaks things on a drivetrain. I would avoid the Subaru unit. It is also an R180. The LSD in there will make launching fun but even more traction means even more things breaking LOL. I’d go with the R200 open if you don’t mind peeling out in low gears. The cheapest LSD options that are worthwhile on an R200 start at around $1k, and still require some assembly. Meanwhile, I sold my open R200 recently (with  axle shafts) for $350 recently. 
 

also, search “technoversions 240z” in a browser and pick up a top-mount for the diff. About 130 bucks but you can get Rid of that lower front diff mount altogether. You can keep the cables as a souvenir :) 

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I have never tried what @NewZed suggested by lifting the car and running through the gears, but he has a lot of experience. I was always too chicken to try that, but with 2 people you will find the problem in no time. 
 

The R180 was going to break with a SBC. I looked up a ZZ4 crate motor and it looks like you have around 405ft-lbs of torque! Even at 300, the r180 would be suspect. 
 

there is one other option... if y’all want to go big. @Invincibleextremes sells a kit for dropping in a mustang super 8.8 diff. His total kit is less than $1500 and you can use an off-the-shelf mustang GT diff. Just an idea. 

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Upload to youtube or something. Right now says I need to buy a codec to watch. 

Many moons ago, when I first put my car together and before I knew anything about diffs, I paid to have all new bearings installed in my R200. Huge waste of money I didn't have at the time. Anyway, the shop left the pinion nut finger tight. I drove it around the block and it was making a weird noise, so I went and grabbed my roommate (also a Z guy) and attempted to take him for a ride. The pinion gear walked up the ring gear and into the carrier and locked the whole drivetrain solid. Luckily, this happened 2 houses away from ours, so we jacked up the back end and dragged it back home. Since it happened at maybe 5 mph, no damage was done, but I have a cool looking wear mark on the LSD. Kinda looks like a scar. 

Might be a place to start for you.

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Posted (edited)

video in above post replaced with youtube version, hard to hold the phone on target and grab and turn the driveshaft at the same time, but you get the idea, turns okay until "thud" it turns no more, busted gear I would guess.

I was still driving it this way (I imagine the 350 can power past the break whereas my hand strength in turning the driveshaft, although legendary, cannot), very very slowly about 1 mile. I expect I'll see a busted gear in there?  it will turn past it (violently) until the next revolution then repeat the process, it was a sad crawl home.......

Edited by jvandyke
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31 minutes ago, JMortensen said:

Video is private. From the description sounds like a broken ring or pinion gear. Ring gear the crunches come slower because it turns 1 time for every 3.54 or 3.70 or whatever turns of pinion gear.

wow, youtuber fail, fixed now I think, I agree, it's busted. 🤯

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