Which Diff/LSD cover?

[Mugzilla]

Are you going to pop in the Z1 urethane bushings while the pumpkin is out?

 

[5thZ]

Are you going to pop in the Z1 urethane bushings while the pumpkin is out?

I wasn't planning on it. Someone else said it wasn't necessary right now

 

[Mugzilla]

If your bushings aren't leaking, they are fine.

It was probably me that posted, "I put in a pumpkin from the Nissan parts catalog from a performance 6MT. I left the stock bushings, as I didn't want to change too many things, and not 'feel' if something feels off with the new one."

For the Independence Day sale at Z1, I'll pick up the rear diff support and install it at the same time I put in the new bushings.

 

[5thZ]

Yep, it was you! Someone else also made a similar comment.

No leaking bushings...at 250 miles so that's good. But I noticed some surface rust? TF is that about? Cmon Nissan

 

[Mugzilla]

I think the big bushing is metal on metal, so rust is possible. If Z1 could get the bushing sleeve out of the cross member of a 20 year old 350Z that weathered NJ winters with the pusher, my garaged 2024 should poop them out just fine.

I'll have a chunk of dry ice on me though. I'll pop out the rubber center, then set the dry ice on the inside of the sleeve.

I'm just tired of dropping the exhaust! Will plan whatever else needs done so I can focus on other things.

 

[heritageownerKurosawaz400]

Yep I did they were included in the kit from Nismo directly. The only thing not included was the oil ? but that's okay. I was thinking of calling the Nissan and Infiniti dealerships around here. I know a service manager or shop manager (I forget) of my local Infiniti dealership. Met him at road Atlanta and he was one of my instructors. He's offered to help build my car and says it's not the first race car they built/maintain, so fingers crossed. With two hours of labor it's still cheaper than the comparable Nissan USA part or aftermarket parts, but after that it gets expensive. No idea how much labor is involved. Most of the instructions are in Japanese ?

You should Use the Nismo competition Oil, it is significantly better at temps than the alternatives that can go in, and it chatters less than the others from my own research. When the differential gets up to temp it's very predictable and easy to use. I'll just attribute all of that to the Competition Oil.

 

[heritageownerKurosawaz400]

I wasn't planning on it. Someone else said it wasn't necessary right now

I believe we had a discussion about that not too long ago, Z1 i wouldn't recommend bushings from as your first option, look into SPL and GKtech though Z1 is also good, I would bias the SPL and GKtech more. Solid steel bushings would probably be my choice from Z1 though, I would say if you are changing bushings might as well go all or nothing rather than urethane but again I won't be driving so you do the decision you'll be happy with.

 

[5thZ]

You should Use the Nismo competition Oil, it is significantly better at temps than the alternatives that can go in, and it chatters less than the others from my own research. When the differential gets up to temp it's very predictable and easy to use. I'll just attribute all of that to the Competition Oil.

Solid info, thanks! I already have the redline so I'll run that for a few thousand and swap either before or after track days to nismo comp oil <3

 

[Mugzilla]

snip

Solid steel bushings would probably be my choice from Z1 though, I would say if you are changing bushings might as well go all or nothing rather than urethane but again I won't be driving so you do the decision you'll be happy with.

From a leverage standpoint, remember, the Z diff is held by 2 points in the front vertically, but only one axial one in the rear. The Z1 cover is (i believe) a grade 5 stud. When you get on it, the diff hinges from the 2 front points against the SIDE of the rear axial stud because of the "equal and opposite reaction" form the twist.

Yeah, Z1 would at this point make the case for their rear diff support/jacking point brace.

Now, just from @heritageownerKurosawaz400 's garage pedigree he has listed, he's at another level of performance understanding and usage than me.

 

[5thZ]

From a leverage standpoint, remember, the Z diff is held by 2 points in the front vertically, but only one axial one in the rear. The Z1 cover is (i believe) a grade 5 stud. When you get on it, the diff hinges from the 2 front points against the SIDE of the rear axial stud because of the "equal and opposite reaction" form the twist.

Yeah, Z1 would at this point make the case for their rear diff support/jacking point brace.

Now, just from @heritageownerKurosawaz400 's garage pedigree he has listed, he's at another level of performance understanding and usage than me.

I've been up since 4am without coffee and I'm not about to pretend to understand that.

Do I need the Z1 diff brace because the diff is now handling more torque and the way the z1 diff cover is designed? pinging both @Mugzilla and @heritageownerKurosawaz400

Maybe not for street, but what about track? I am not looking to pull out the last 2% performance or anything, I just don't want anything to break at the limit

Thanks you guys for keeping forums great <3

 

[heritageownerKurosawaz400]

I've been up since 4am without coffee and I'm not about to pretend to understand that.

Do I need the Z1 diff brace because the diff is now handling more torque and the way the z1 diff cover is designed? pinging both @Mugzilla and @heritageownerKurosawaz400

Maybe not for street, but what about track? I am not looking to pull out the last 2% performance or anything, I just don't want anything to break at the limit

Thanks you guys for keeping forums great <3

The diff brace simply in my eyes with experiences of my FD, was that the rear end isn’t a glass akin to my FD. The Brace simply gives more rigidity and doesn’t force your bushings to flex as much, if we were to compare it to say a strut bar in the engine for performance wise it would be probably a third of that, Nissan’s differentials have always been very stout. But if you seek a tiny performance gain then go ahead, bushings, Nismo LSD, they are good as is. It’s simply a reliability mod at a certain point due to multiple factors, I would only ever worry about your diff falling from the subframe if you are a drag vehicle and are at the strip- launch it; then bog down and lurch everywhere.

 

[5thZ]

The diff brace simply in my eyes with experiences of my FD, was that the rear end isn’t a glass akin to my FD. The Brace simply gives more rigidity and doesn’t force your bushings to flex as much, if we were to compare it to say a strut bar in the engine for performance wise it would be probably a third of that, Nissan’s differentials have always been very stout. But if you seek a tiny performance gain then go ahead, bushings, Nismo LSD, they are good as is. It’s simply a reliability mod at a certain point due to multiple factors, I would only ever worry about your diff falling from the subframe if you are a drag vehicle and are at the strip- launch it; then bog down and lurch everywhere.

Awesome explanation and thought process as always! Really appreciate the helpful and helping nature everyone on Nissan Z Club has, thanks both of you for keeping it great!

 

[Mugzilla]

Here's the point I was trying to make;

The Z1 diff cover is not handling more torque. Same mounting point. Same positioning of the rear stud. Same torque transferred. Yeah, it probably has more meat around it to grip that stud better. But the torque goes from the cast iron of the diff, to the 10ish bolts on the cover, to the cover, to that one stud that is inserted in to a bushing.

My concern is on that stud being the sole point that handles the twist torque.

The pic is looking down on my old open diff.

The green points are bolted from below upward. That makes them a hinge point.

The RED spot is the stud that goes through the rubber liquid-filled bushings. The axles twist, causing the diff to rotate upward and downward. That means the force is on the top and bottom of the stud.

So the stud is pushing against the bushing. Does that mean those liquid filled bushings are softening/evenly distributing the torque over that stud? Do urethane bushings allow for some softening of the torque load on that stud's side? What if ALL the rear bushings are SOLID? Does that mean that there is absolutely no hinging from the green OR RED, and there's no side load on that stud?

Questions for a mechanical engineer, and not a guy that stayed at a Holiday Inn Express a few months ago.

NOW, does that mean that the stud is a ductile metal to allow some flex inside of the rubber bushing? Sure, grade 8 is harder, but not as ductile.

 

[heritageownerKurosawaz400]

Here's the point I was trying to make;

The Z1 diff cover is not handling more torque. Same mounting point. Same positioning of the rear stud. Same torque transferred. Yeah, it probably has more meat around it to grip that stud better. But the torque goes from the cast iron of the diff, to the 10ish bolts on the cover, to the cover, to that one stud that is inserted in to a bushing.

My concern is on that stud being the sole point that handles the twist torque.

The pic is looking down on my old open diff.

The green points are bolted from below upward. That makes them a hinge point.

The RED spot is the stud that goes through the rubber liquid-filled bushings. The axles twist, causing the diff to rotate upward and downward. That means the force is on the top and bottom of the stud.

So the stud is pushing against the bushing. Does that mean those liquid filled bushings are softening/evenly distributing the torque over that stud? Do urethane bushings allow for some softening of the torque load on that stud's side? What if ALL the rear bushings are SOLID? Does that mean that there is absolutely no hinging from the green OR RED, and there's no side load on that stud?

Questions for a mechanical engineer, and not a guy that stayed at a Holiday Inn Express a few months ago.

NOW, does that mean that the stud is a ductile metal to allow some flex inside of the rubber bushing? Sure, grade 8 is harder, but not as ductile.

The Z1 diff cover is not handling more torque. Same mounting point. Same positioning of the rear stud. Same torque transferred. Yeah, it probably has more meat around it to grip that stud better. But the torque goes from the cast iron of the diff, to the 10ish bolts on the cover, to the cover, to that one stud that is inserted in to a bushing.

My concern is on that stud being the sole point that handles the twist torque.
Many things to go over here, firstly the torque is distributed amongst the entirety of the rear end, the 10mm bolts arent taking the grunt, that’s your differential on the inside, the cover, the axles, and the driveshaft. The cover and housing of the differential is meant to evenly distribute it the stud you are referring to is simply; “A” an axis to keep the suspension geometry and differential in check, and “B” is more so about keeping the differential in check in relation the the differential cover location and keeping it on rather than taking the torque load if that makes sense. For the rest, a quick run down is rubber < urethane < solid steel. The harder the bushing the less flex, which means that before that flex it can handle more of a load, so while increasing the bushings rigidity will make the stress a lot less, it’ll just in a way put more stress on the bushing itself and subframe- but remember the torque is already managed by the differential itself so it’s really a matter of chassis rigidity and stiffening the car, the bolts don’t see the true grunt of everything.

a quick run down sorry it’s not too to in depth.