Driving my '71 240z in the hills today.  Leaving the scenic outlook, decided to chirp the tires a little.  Something went BANG loudly in the rear end.  Coasted to a stop, did a visual inspection, nothing found. 

Continued driving, but the loud BANG started happening again and more frequently, only when I was on the gas, not when coasting.  Parked it again, no visuals again.  Called the tow truck, now back home.

Put rear up on jack stands.  In neutral, rotated the tires forward at same time, while friend grabbed the drive shaft.  Some times the shaft would turn in sync with the wheels, other times it seemed to skip or jump.

Asking the experts in the group for suggestions on further trouble shooting.  Don't know if it's the shaft itself, the U-joints, the differential, etc.  Stock diff, looks like it's never been opened.

'71 240z, Rebello 3.0 engine, Z Car Garage suspension, brakes, CV joints, new clutch, 5 speed tranny recently serviced.  

open diff? sounds like the roll pin that holds the spider gears failed. 

This is just a shot in the dark, but I had a clunking noise when shifting.  Found that the two 

fasteners securing the mustache bar to the rear diff housing had loosened up.  The clunking

went away when re-torqued those nuts.

Im with Jonbill, open the diff up for a look

4 hours ago, kenward1000 said:

Something went BANG loudly in the rear end.  Coasted to a stop, did a visual inspection, nothing found. 

Continued driving, but the loud BANG started happening again and more frequently, only when I was on the gas

 

4 hours ago, kenward1000 said:

Put rear up on jack stands.  In neutral, rotated the tires forward at same time, while friend grabbed the drive shaft.  Some times the shaft would turn in sync with the wheels, other times it seemed to skip or jump.

 

4 hours ago, kenward1000 said:

Rebello 3.0 engine

 

There should be no skipping or jumping ever.  You broke something.  Probably not worth fixing, even if it's possible.  Find a new diff.  Consider an R200 conversion, Nissan started using them to take the torque of the L28 engines.

p.s. please post pictures of the destroyed gears or shafts after you open it up.

Stock r180 with a Rebello power and one weak point and bang . I’m with everyone here about checking diff . Try the Subi diff swap - it makes for a tougher r180

Here's my old r200 open diff. You can see the end of the shaft that carries the spider gears and its a bit chewed from the roll pin breaking and the shaft rattling around. 

Car is going into ZCG on Thursday for a post-mortem.  Images to follow.

Yep, turned out to be broken teeth in the R180 open diff.  Replaced it with a rebuilt R180 LSD.  

 

What gear ratio did you end up with? OSG diff? Where are the pics?! 😇

On 8/11/2022 at 3:06 PM, heyitsrama said:

What gear ratio did you end up with? OSG diff? Where are the pics?! 😇

Z Car Garage in San Jose, CA fixed me up with a 4.10