Andrei

iTrader: (7)

^In 1st and 2nd I'm guessing over 400 rwtq, IF... it doesn't run in open loop. But what can we do, you know. If Willard would of been POTUS in 09 I might have been able to afford a more better car, I bet, like the E90 and E92 ///M Power M3.

Andrei

iTrader: (7)

A quick update on this. There are only 2 possible ways to fix this with the R51 cover. One is to use a pipe as a bushings and push the pipe through the subframe all the way to the surface of the 2nd stud hole on the diff, and cut the pipe at the same level as the back of the subframe, or leave it longer by a 1/4" to use a large 1/4" plate as a large washer which is not necessary but it will be stronger. Put a M14x2.0 stud through the pipe and torque it into the diff stud hole, and then slightly torque it down with 2 nuts from the front of the subframe to torque the pipe against the diff cover/stud hole surface, weld the pipe on the back side of the subframe, remove the stud and then weld the pipe on the front of the subframe + weld the plate if one is to be used. Then cut the stud to size and use a nut and a large regular washer.
2nd way is to use a pipe as a bushing but cut it at the same length as the subframe thickness and weld it in the subframe after lining it up with the stud hole, and use 7mm thick jam nuts against the diff stud hole surface and against the surface of the back of the subframe, and bolt the stud in. A 1/4" plate can be used with this method too but I do not know if there is enough room between the back of the subframe and diff stud hole to allow the use of 2 jam nuts. Any other way would crush the hollow subframe which is what the Sound Performance and Injected Performance braces do.

The 6061 pipe has a wall thickness of 0.147" and a 0.840" diameter with an ID of 0.546" and the diameter of the class 10.9 stud is 0.5". The diameter of the stud hole surface on the diff is 1.5"

Andrei

iTrader: (7)

So here is our salvation. R51 vs. Z33 V35 V36. The studs for the R51 are next size up from M14x2.0. The z33 v35 v36 stud does not fit. M16x2.0 is the correct stud. The fins are not extended for ground clearance. Apparently they knew the single stud and the small size was a problem on the V35/Z33, but they green lit production anyway.

Andrei

iTrader: (7)

Well the inside diameter of the stud hole of the R51 is still a 14 mm but the M14x2.0 stud is loose fitting but close. Maybe it's a M14 with a 1.5 mm thread pitch? Does a 2.0 thread pitch weaken the stud over a 1.5, because the stock stud on the V35 broke inside the stud hole where the pitch is 2.0, not outside where the diameter is smaller and the pitch is 1.5.

Also the outside diameter of the pipe is 0.840 and not what I had before which was too small, and inside diameter of 0.546 and the M14 stud is 13 mm or 0.511 inches

ReStylin

iTrader: (1)

Wow sounds like a smart upgrade reguardless.

Andrei

iTrader: (7)

I measured the M14x2.0 stud from the V35/Z33 at work today using a dial caliper, and it's 0.544" and the inside diameter of the pipe is 0.546". I ordered a stud from the V35/Z33 thinking it would fit in the R51. The tolerances are too close for comfort even though the pipe and stud would reinforce each other with those tolerances. I'll have to look for a pipe with a bigger inside/outside diameter.

PercisionDriver

iTrader: (1)

A finer pitch stud/bolt will be stronger; given everything else is the same. Going from 2.0 to 1.5, I'm not sure how much of a difference we'd see.

Why are you worried about the 0.002" clearance? That would be great, unless you don't yet have the physical parts and the tolerances do cross over.

Andrei

iTrader: (7)

I'm going off Solidworks drawings. You cant press the stud in the pipe, the stud has to come out easily and pressing it might damage the thread. Buy it, http://www.mcmaster.com/#4559t111/=og9edg

Neimad

Your poor car, you took the thermostat out and killed your engine, you don't replace motor mounts and break a diff stud, and somehow it's all Nissans fault?

phunk2

Got the part number for that diff cover? Maybe I will add that to my 370z this winter.. I plan on changing some rear control arm stuff around and might pull the crossmember anyway. Would make for an easy job to weld it up to accept that diff cover.

Andrei

iTrader: (7)

The motor had a blown head gasket since the wreck of the donor car, since the reason bank 2 ran lean since day 1 with a tstat installed. And not running a tstat does not blow a head gasket. The motor mounts could of had something to do with the stud breaking, but it's more a problem with the rubber subframe bushings and wheel hop which cause the stud to break and there are many more people who broke the stud as well, some repeatedly, and they didn't all have bad motor mounts.

Then again the subframe cracks as well and that has nothing to do with anything other than a bad design and the shitty choice of using aluminum, since the reason they use lighter and stronger steel now.
2wd r51 pathfinder.

PercisionDriver

iTrader: (1)

Solid motor mounts def could have contributed to the failure of the diff stud. The shock and load that was once absorbed by squishy motor mounts isn't just going to disappear. It's going to jump on the next willing weak link; in this case, the diff stud.

The newer steel subframes are stronger, but I don't believe they're lighter. I recall reading a 15lb increase going to steel. Incase anyone gets into a pissing contest with a 370Z owner; or just talk about how god awful ugly they are.

jerryd87

iTrader: (4)

no, they dont contribute what so ever the stock motor mounts dont seperate the "shock and load" of the engine from the rear end that would be the of the drive shaft. the engine block creates a twisting force that twisting force causes the transmission to twist. if the engine dosnt twist(which solid mounts stop) then it dosnt twist the tranny and trys to twist the mounts which distributes the force into the chassis. even if the tranny COULD twist the driveshaft isnt mounted to the case of the transmission, its mounted to the output shaft which the case can twist around its absolutely impossible for the case to exert any force at all on the driveshaft. the only possible way solid motor mounts could damage the rear end is if 1) your k member was weak and broke allowing the engine to twist, 2)you welded the U joints on the drive shaft so it cant flex, 3) you welded the driveshaft hub to the transmission case......... but then you couldnt start the engine.

what ACTUALLY breaks the stud is the fact of every force creates a equal and opposite reaction, the driveshaft spinning causes the rear end to want to spin in the opposite way. normally this force is perfectly fine and is generated solely as a function of engine power output, however when you increase power you increase this force. then when you launch the car you have the drive shaft trying to turn which is connected to the tires and the axles as well as the pumpkin itself trying to turn in the opposite way, when the mechanical strength of the weakest point is exceeded that point breaks which in this case is the stud and was known long ago if you want to launch the car at any decent power needs to have a brace, or if you launch at stock power repeatedly needs a brace since each launch weakens it.

also axle hop in absolutely no way imparts any force on that stud, the axles flex at both the hub and the pumpkin completely disconnecting it from up and down and forward to back motions the only thing that would affect is inward/outward(x axis) which would require breaking a whole lot of other bolts first. what axle hope does break however is axles. i know we covered this before, i believe in this very thread.

PercisionDriver

iTrader: (1)

I'm trying really hard to see where you're coming from. I find a lot of these opposing thoughts that occur from time to time stem from merely having different perspectives of the same thing; but there are a few dead ends I'm running into. I guess the cool thing to do would be a break down.

I'm having difficulties deciphering this... sentence. I believe you're saying solid motor mounts don't contribute to the failure of the diff stud what-so-ever. This would be the root of our disagreement. I didn't say anything about anything "separating" anything else. As you do later mention in other words, the motor does produce shock and load on the motor mounts, and the mounts do definitely absorb SOME shock and load. I don't think it could be said that they "separate" anything.

The engine block does create a twisting force; and due to how the transmission is affixed to the engine, it shall twist too, with the engine. We're on the same page there; but then you say the the force is distributed into the chassis due to the solid mounts... as if that's the end of that: it just disappears into the chassis. That is not quite so, and I'll expand on that at a better opportunity below.

The tranny would twist: with the motor, if on OEM rubber mounts; since they're affixed to each other. Technically the tranny isn't twisting the drive shaft (not that I ever said it did), I agree. Ultimately, the twisting force is coming from the engine, as you had stated. All the twisting force that would be thrown into the trans is instead, sent to the now solid motor mount due to how they are affixed.

I'm not sure why any of this was said. #1 is incorrect because if the crossmember failed and allowed the engine to twist, then there would be a drop in peak torque force being sent through the drivetrain; and then after that there would be catastrophic drive failure resulting in a large lawn ornament with an intact diff stud. Also forgot one:

4) I'll start it off with an example. Say the car is at a dead stop and you perform a hard launch. The motor generates its twist force and sends it all the way down the drivetrain to big meaty pissed off rubbers. On OEM bushings, that motor is going twist. By how much? Not going to get into that, but it twists, and because of that, it's going to take some of that torque by compressing the mounts; and when the load drops enough, the mounts will rebound and twist the engine back to nominal location. When engine does rotate back to nominal it does send torque back into the drivetrain, just at a lower engine load. Say we measure and record the rate of,and peak, torque being exerted on the wheels at launch. Now, we do the exact same thing, and perform an identical launch (somehow) this time, with solid engine mounts. The engine won't twist (or just very very little) but the torque wont just completely disappear into the chassis. There's a lot of kinetic energy leaving this motor. That energy is going to exit through the easiest path, the drivetrain. With that huge spike in torque is coming out of the engine with solid mounts; how do you think the peak torque at the wheels will compare to that of the launch with the OEM bushings? If the peak torque acting on the wheels during this clutch dump is identical with solid mounts as it is with OEM, then yeah, I'm mistaken; but thats not the case. If I were to rotate the engine the opposite way as the engine twisted the output shaft, would that effect peak torque and rate of torque to the wheels?... I think it does.

I can agree with everything here. I just also believe that solid mounts can be a contributing factor to this.

Well I mean, it imparts something. I mean, you still have a massive diff bouncing around putting its weight into the stud in shear force when the back of the car is bouncing around. It's not much, but contributes to fatigue failure.

Neimad

The mounts also control vibration. It's a complex arrangement and without testing all the variables it's really hard to determine primary cause. But, it is best to just replace things as they wear so you don't end up guessing when something else breaks.

I need to replace my rear shock bushing, one side is worse and the tire wear pattern is noticeably different. I'm sure this is stressing other things at an faster rate then normal.

There are many, many high hp track cars out there using factory single bolt diff with reliable results.

And having no thermostat changes the time to reach full warm oil temperature, which affects metal friction wear. And the coolant flow rate is too high for proper heat exchanging, which can lead to many nasty things.

jerryd87

iTrader: (4)

your missing a large part of what is going on in a vehicle chassis, all the twisting from the engine and transmission CANNOT be transferred to the differential housing, the only thing that connects them is the drive shaft, which spins inside both the transmission housing and the differential housing aka pumpkin. the twisting force of the engine and transmission are both caused by the block and case, and it twists in the OPPOSITE direction the driveshaft is spinning, the only thing the engine mounts affect is the case twisting forces not the drivehshaft therefor its impossible to break a differential(even a live axle) from swapping motor mounts.

want a example? grab a larger spool of wire, stick a fender washer or bearing(if you have one) into the center section and slide a smooth rod into the washer or bearing then spin the opposite end with your hand. thats exactly how the forces are being imparted by the driveshaft and its spinning in the opposite direction that the engine is rocking, heck you can even see it, the crankshaft pulley spins toward the driver side of the car but the engine rocks to the passanger side, equal and opposite reaction cant beat physics.

next no forces dont vanish when transferred to the chassis the chassis flex's as well some more then others impossible to eliminate all of it(and in some cases it helps improve times even) its impossible for energy to vanish or be destroyed your simply converting it, you simply dont notice it because it is spread over a much larger area then motor mounts.

the issue your having is visualizing the basic principles of physics in that the engine is producing two seperate kinetic forces each equal, one is dissipated through the motor and transmission mounts, the other is dissipated through the drivetrain to the tires and is in no way affected by the motor mounts. also your not putting enough power out on anything except the mid to high end boosted setups to flex the oem mounts, thats why people dont notice increased noise going to solid, because stock is stiff enough to act like solid already.

you will also notice that the stud broken isnt broken by side to side movements like the engine does, it happens from the fact that the pumpkin trys to twist the flange up and the cover down when the driveshaft imparts force on it, its the basics on how ladder bars and a four link work and is 100% a function of power output not motor mounts.

Neimad

The engine can lift off the mounts, changing the driveline angle, and thus it is possible to shear the diff bolt, if that is the weak link at that point at that point in time. The engine lifts as well as twists, and can bind the driveshaft in this circumstance.

http://www.thelostartof.net/gsellstr...uff/booka3.pdf

jerryd87

iTrader: (4)

lol dude good job adding useless info thats completely untrue since first of all the stock mounts allow more movement then solid so your first comment helps contradict your second as well as the whole "solid motor mounts can shear the diff bolt" and two the ONLY vehicle that engine lifting would change the driveline angle on is a corvette with its torque tube. seriously have you even seen a driveshaft? i know you havnt worked on a car because if you did you would know that just to take up the slack in the driveshaft(since they flex at a u joint at either end really dont take my word for it hop under your car and look) you have to lift the engine over 3 feet, and would have to cut the driveshaft tunnel out of the car for it to clear without hitting and that isnt lifting on the rear end AT ALL yet. your also making comments and quoting a ase manual on driveshaft bind which is SOLELY in regards to live axle vehicles where the pinion angle is flexible due to bushing and the fact the rear end travels with the suspension vs solidly mounted on our vehicles as well as the live axles have a negative pinion angle at rest(pointed to the ground)

this is another perfect example of a google mechanic trying to pretend like they know more then a guy who actually rebuilds vehicles.........

and oh yah on the g35(which the op has) its impossible to lift the engine enough to take up the slack in the driveshaft because it has a carrier bearing which flexs and when it hits max deflection it pulls up on the chassis it is bolted to not the second half of the driveshaft.

jerryd87

iTrader: (4)

they only control vibration transmitted to the cabin they dont actually reduce it at all. also no there arnt many high hp track cars out there using the single bolt...................... they all use diff braces, think i might be one of very few high power builds that dosnt and thats only because im building a custom 4 link for the factory irs so there is no sense. its only complex to people who dont actually know whats going on.

Neimad

The whole thing moves, pushes back on the diff, it's all flexible with so much rubber, strange things happen. Nice job of assuming too. I passed that ASE, and the rest. I wouldnt be posting if I hadnt had a few drinks so I'll admit I could be wrong. I don't really care who's right, as a mechanic I research before I fix something. I don't assume my memory is working, there's alot to remember. i did not say solid, read again, was talking about op's statement of broken mounts, and then deciding to overengineer something without analyzing the situation better.