I blew up my kid's 240.....sorta

[jvandyke]

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.

 

 

[AydinZ71]

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. 

 

 

[jvandyke]

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.

 

[AydinZ71]

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.

 

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  

[NewZed]

Put some jackstands under the rear control arms, start it up, and run it through the gears.  Don't do it with the wheels hanging the u-joints will probably bind from the angle.

[jvandyke]

no idea on HP or torque numbers, ZZ4 crate 350, 700r4 auto, it is a little monster and we love it.  Very much a "rat rod" and we both (my son and I) kinda like it that way. Okay I'm thinking the R200 if they can be had.  autopsy comes first of course but pretty sure the 180 is baked.

[AydinZ71]

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. 

[jvandyke]

Raised rear, put in neutral, turned wheels, seemed okay, turned driveshaft and seemed fine until BAM hit a wall.  Crappy video attached.  the knock you hear is the whole works coming to an abrupt halt. Time to pull the diff me thinks.

Youtube version

 

 

Edited May 5, 2021 by jvandyke

[JMortensen]

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.

[jvandyke]

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 May 5, 2021 by jvandyke

[JMortensen]

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.

[jvandyke]

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. 🤯

[jvandyke]

finally had time to autopsy;

 

[AydinZ71]

Looks to me like the retaining pin for the spider gears sheared off? I think I stated earlier, the spider gears are the week point if it fails under torque. Good luck friend! 

[jvandyke]

there's a R200 available in Cincinnati,

https://www.facebook.com/marketplace/item/453259465957942/?referralSurface=messenger_lightspeed_banner&referralCode=messenger_banner

which I'll be driving past this weekend, I could snag that and then source the other bits (mustache bar here?

https://www.ebay.com/itm/223539776365?fits=Model%3A240Z&hash=item340c024b6d:g:EpAAAOSw76hZjaqt or better source?

Then I still need a few more bits.  I could just pop another R180 in there too I guess.......

[NewZed]

The Facebook R200 seems like a decent deal.  Axles, half-shafts included for $200.  Probably close to what you'd pay in wrecking yard prices today.

 

I mentioned gear ratios in your other thread but with a V8 you could probably use a taller gear anyway.  The torque doesn't need the low 3.9 and you'll get better cruising RPM with a 3.54.  You only need an R200 diff mount and the curved cross-piece for the suspension drop-downs(to clear the bigger diff cover) to complete the package, I think, but should probably get something like the Technoversion RT mount to handle the power, if you don't have one already.

 

https://www.technoversions.com/DiffMount.html

 

Here's your other thread.

 

 

Edited June 21, 2021 by NewZed

[jvandyke]

okay, gotta get my terms straight; the "rear transverse link mount" on our '72 is already curved, is this sufficient? (top pic)

and the differential case mounting bar (aka "mustache bar", you called it "diff mount" above?) (middle pic) needs to be replaced?  As per the ebay link above?  Is that the best way to go for one of those? and I think I agree, the technoversions diff mount (front) is a good idea.

Last pic for overall reference

 

Edited June 21, 2021 by jvandyke

[AydinZ71]

28 minutes ago, NewZed said:

The Facebook R200 seems like a decent deal.  Axles, half-shafts included for $200.  Probably close to what you'd pay in wrecking yard prices today.

 

I mentioned gear ratios in your other thread but with a V8 you could probably use a taller gear anyway.  The torque doesn't need the low 3.9 and you'll get better cruising RPM with a 3.54.  You only need an R200 diff mount and the curved cross-piece for the suspension drop-downs(to clear the bigger diff cover) to complete the package, I think, but should probably get something like the Technoversion RT mount to handle the power, if you don't have one already.

 

https://www.technoversions.com/DiffMount.html

 

Here's your other thread.

 

 

+1 on the taller gear ratio and “RT mount”

 

The oem mount will tear apart within a year with the amount of torque you have, so go with the top-mount and ditch the OEM bottom-mount. 
 

You are going to struggle with traction with that much torque. A taller geared diff will help by reducing the mechanical leverage of torque to the rear wheels, and give you lower rpm’s at highway speeds. 3.545’s are more prevalent than 3.9’s anyways, so you should be able to snag one for cheaper. 
 

just as a sample for cost, I sold my 3.545 r200 w/ shafts for $350 4 months ago, and my 280z r200 mustache bar for $80. 

 

you can go with an R180 if you like, but if you search the forums you will find that they will inevitably break with V8 torque. The more traction you have (LSD, wide STICKY tires), the sooner it will break. 
 

 

[AydinZ71]

@jvandyke 

 

1) you already have the curved tranverse link mount. Check. No need to change that.

 

2) yes, the mustache bar is the bar that mounts to the rear cover of your diff. R200 has wider mounting stud spacing. The right bar comes from a 280z. 
 

3) in your last picture, your front transverse link mount/crossmember has been removed. You need to eventually put it back but remove the actual diff mount attached to it (the rubber/steel brick with the stud molded into it). You will be using the top-mount from the RT kit.

 

4) double-check the forums if you need a 280z driveshaft as well. I thought the r180 vs r200 driveshafts where slightly different lengths and/or yoke mounting bolt pattern but I could be totally wrong. 

 

 

[jvandyke]

okay the busted R180 was a 3.54 as well, I think as per this picture of ring gear numbers:

this car was assembled in 1995 and it lasted that long, with lots of drag racing slips (from PO) to prove it was beaten on, so that's one that went for a while anyway, it doesn't look like it was swapped before, at least to my eye