I was going to comment before your last post that you may want to check your diff temps after a track session. Did you change out the stock VLSD?

 

It's a stock vlsd with nismo finned cover

 

Well at least that makes sense why it failed. although its a bit shocking to me. I know our differentials get hot on the track, but to get hot enough to melt the bushing even with a finned diff cover?

 

I don't think it's melting. The constant heat stress is making the metal sleeve come loose from the polyurethane.

 

Odd, I still have my original boots on the RT side, left side I had to swap the axle when the threads got destroyed changing a wheel bearing. I know my temps get hot, really freaking hot with the OS unit back there

 

I was under the car today installing a differential oil vent catch can and I just happened to look at my rear differential bushing. Mine is shot as well. Less than 2000 miles on the bushing. the only difference on mine is that my bushing cracked all the way through at the 6 o clock position.



Guess i'll be emailing whiteline.

 

Damn man. Same type of failure. Thanks for sharing.

 

I suppose its time to go solid in the rear. I suppose I should have done that from the beginning. Are you staying with whiteline or going solid?

 

While this type of polyurethane (PU) is harder and has better wear resistance then rubber (in general), it sacrifices operating heat range. Meaning the OEM rubber part can withstand much higher temp ranges. Additionally, PU doesn't like hot water (Steam). It doesn't look like Whiteline uses a mechanical bond, but a chemical one and that bonding area tends to fail first if not done correctly.

I replaced my bushings with both Whiteline (diff & subframe) and energy suspension for suspension bushings. Honestly, they didn't impress me as high quality items. The Whiteline instructions weren't even correct for the install.

As the bushing fail I will replace then with custom made Teflon. I only decided to replace everything this winter since I had everything apart and didn't have time to make the parts myself.

 

Spl solid. Should have it all fixed this month.

 

Those SBC RPF1s look amazing

 

Great progress!!

 

car is looking great. best of luck with the upcoming races!

 

Wow, this is an amazing thread. Really glad I read this, opened my eyes a lot and gave me some ideas for when I can make the Z a not-so-daily driver :P

Keep up the progress!!

 

Update. Got the car all prepped and ready for Pocono this weekend. Looking like good weather for now.
Installed the SPL solid diff bushings. The freezer installation technique worked perfectly and I did not have to drop the subframe.
I would like to point out when I removed the diff the whiteline bushing literally fell out. This is not a Motorsport grade bushing please be careful when using it.

Also sent off both axels off to the drive shaft shop to hopefully resolve my issues. They sold me on axle boot venting and Motorsport grade grease. The idea is the axle boot expands like a balloon under track heat and stress conditions then pops. It will be tested this weekend.

Axle venting from the drive shaft shop by mhulbrock, on Flickr

 

That is odd, I have yet to pop a boot. The drivers side still has the OEM boots with 157k on them.

 

I'm at 170K on original boots as well.

 

Got back from pocono last night. We had mixed dry and torrential downpours on Sat! Sunday was mostly dry. The rain was truly intense, what a great learning experience. Pocono infield in a track in the middle of a huge field. Nothing to hit here, tried to push the car to the limits and really explore these tires and suspension setup.
The new axles held up perfectly. Talked with a few racers, apparently axle boot venting is a very common practice. They use WD40 tubes ect for the same result. Good to know for future projects. No problems at all with the car, drove 100% all weekend.

South East Course. Best time was 1.13.3. I am going to process some videos to share later this week. Lots of rain drifting and spin out.

Untitled by mhulbrock, on Flickr

Pocono rtr 2015 by mhulbrock, on Flickr

Pocono rtr 2015 by mhulbrock, on Flickr

 

very cool and good to hear that the venting hack did the trick. Did you also install the SPL solid rear differential bushing? Could that have also been the culprit?

 

Yes, I did also run the solid bushings. Very well could have been the fix like you sugest. As long as it keeps working im happy!