Z31 axle boot split

[rossman]

The passenger side Z31 axle inner boot on my '72 240 split and slung grease all over the bottom of the car.  I need some help figuring out what caused it to split so I can prevent it from happening again.  

 

For reference, my 240z is turbo'd with a Z31 LSD differential, Z31 axles with shortened shafts, 280z mustache bar, Ron Tyler front differential mount, and stock rear suspension with urethane bushings all around.

 

I assume the boot hit passenger side LCA under hard acceleration causing it to rip.  The boot is within .25" of the LCA; looking at it with the car jacked up and suspension at full droop.  I assumed this was worst case.  It's been awhile since I drove the car but I remember it making a metallic popping sound, kinda like an old fashioned oil can end popping in/out when I would accelerate quickly from a standstill. It would go boink, bonk every time.  A while back I checked and everything seems tight under the car.  

 

Thinking about it now I've sorta convinced myself that the sound was the mustache bar flexing under load and contacting the axle boot. I am considering buying a TTT mustache bar, thinking that will reduce differential flex and fix the problem.  While I'm at it, I'll shave off some LCA material near the LCA boot to give more clearance.  What do you guys think, am I on the right track?

 

Thanks,

Ross

Edited August 27, 2017 by rossman

[74_5.0L_Z]

I just split the inner passenger side boot on my car as well.  I have a very similar setup (Z31 CLSD R200 with CV axles).  My inner passenger boot split at Daytona while I was doing about 155 mph, so I had grease everywhere.  Luckily I inspect the car in between sessions and found it before the CV joint burned up. 

 

On mine, there is no evidence of the CV boot contacting the LCA even though I have about the same clearances that you do (my LCA are painted and clean so I would be able to see rub marks if there was contact).  I attribute my boot splitting due to age and the centrifugal forces caused by going 155+ mph for an extended time.

 

So, because I attribute the major cause of failure to be age related I decided to replace all four boots and clean and re-grease the CV joints.  I ended up using the EMPI boots (P/N 86-1170-D for the outer boot  and P/N 86-2127-D for the inner).  They fit well and seem to be well made.  I did reuse the factory retaining rings where possible, and used Redline CV-2 grease instead of the EMPI grease that comes with the boot kits.

 

I haven't run them at speed yet.  I'll test them this coming weekend on the Sebring long course where there are two straights where I will see about 150 mph.

[rossman]

Yah, mine hasn't been broke long either.  There doesn't appear to be any dirt in the joint.  My boots were new so I'm pretty sure they would hold up to the few ~100 mph runs I've done.  Unfortunately I didn't get a picture before I took it out, but the split looked like it was right where the tip of the LCA was closest to the boot.