Administrators RTz Posted November 20, 2006 Administrators Share Posted November 20, 2006 Don't Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 20, 2006 Share Posted November 20, 2006 Ron is exactly right. Look at the front mount/crossmember setup on the S130. Makes the S30 mustache bar look wimpy. http://forums.hybridz.org/showthread.php?t=116117 Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 20, 2006 Share Posted November 20, 2006 Yeah, don't get frustrated and give up. Learn, and be happy about it. EDIT--Just want to say that I mean that sincerely, when I read it it looks like it could be taken as kind of an assholish statement, but that's not how I meant it. Quote Link to comment Share on other sites More sharing options...
Clifton Posted November 20, 2006 Share Posted November 20, 2006 Yeah, don't get frustrated and give up. Learn, and be happy about it. EDIT--Just want to say that I mean that sincerely, when I read it it looks like it could be taken as kind of an assholish statement, but that's not how I meant it. The frustration comes from the lack of others understanding something so simple. Yes s130's are solid mounted in the front only. 'm not sure abpout 130's but Z31's are bolted to a subframe. It doesn't change the fact that the mounting point is narrow, why, because it doesn't see torque applied to it in the direction of the driveshaft rotation, if it did it would need more than one bolt cenetered for the rear mount. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 20, 2006 Share Posted November 20, 2006 Well I'm running out of ways to explain. Anyone else care to take another crack at it? Quote Link to comment Share on other sites More sharing options...
Pyro Posted November 20, 2006 Share Posted November 20, 2006 Nion, I used the mount as a template to drill the holes. It would be better to drill those with a drill press to keep the holes straight but it can be done with a hand drill using some care and help from a friend to eye ball the drill bit straight while drilling. The holes end up being right at the edge of the crossmember. Also, the hump on the cross member can be hammered down a bit so the rubber mounts don't ride up on the curve (like Team Zleep mounts). The hump doesn't need to be hammered in that much, just a little around the mount. It also took a few more washers, more than shown in the photo, placed under the lower mounts to raise the diff back to stock height. I used a 0.406" (13/32 drill bit). Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted November 20, 2006 Administrators Share Posted November 20, 2006 Clifton, If I read you right, you are suggesting that the diff. could be mounted in bearings front and rear (rotisserie style) and that an application of torque would not cause it to rotate? Quote Link to comment Share on other sites More sharing options...
olie05 Posted November 20, 2006 Share Posted November 20, 2006 The frustration comes from the lack of others understanding something so simple. Yes s130's are solid mounted in the front only. 'm not sure abpout 130's but Z31's are bolted to a subframe. It doesn't change the fact that the mounting point is narrow, why, because it doesn't see torque applied to it in the direction of the driveshaft rotation, if it did it would need more than one bolt cenetered for the rear mount. Ok i will take a crack at this. The narrow mount point that the S130 diff has on the front is SOLID mounted (i.e. metal to metal with bolts) to the rear subframe. This keeps the diff from rotating along the front to back axis of the car. Since that is now limited, the only thing needed to keep the diff from rotating along the axis of the rear axle is a bumper... in this case a single bolt. If you want to apply the bearing analogy that ron is gettting at, then you could have a bearing on the rear mount of an S130 diff, because it sees no torque. For the S30 you could mount a bearing on the front because that mount sees no torque. You could NOT mount a bearing on the front and back, unless you mis-aligned the axes of the bearings. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 20, 2006 Share Posted November 20, 2006 Actually the S130 front mount controls both types of torque. the wide spacing of the crossmember mounts controls the twisting torque, and the solid mount controls the lift. In the case of the S130 the rear bolt is just a hanger as Clifton described. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted November 20, 2006 Share Posted November 20, 2006 Here's another mental experiment: consider the force exerted by the torque from the drive shaft (driven of course by the engine) when you start to let the clutch out in 1st gear with the parking brake set. In order for everything to stay in one piece, there has to be an equal and opposite force to counter act it (otherwise things would move to the point they broke). Besides the diff, what else in the rear end could possibly exert the opposite force? There is nothing.Clifton, you didn't address this point I made in an earlier post. If you're theory is correct that there is no side/side torque on the diff, what is providing the opposing force in this example? I'm sure you agree that with the parking brake on securely, if you let the clutch all the way out the engine is going to stall. Something had to provide a force opposite to the direction of rotation of the drive shaft to stop the engine from turning. What was it if it wasn't the diff? Quote Link to comment Share on other sites More sharing options...
ARZ_ Posted November 20, 2006 Share Posted November 20, 2006 Heres my take: On an S30 to suggest that any solid front diff mount failed, because it was asked to limit axial twisting (about the axis of the pinion) is silly. Yes the Moustache bar does limit the twisting of the diff and it does so very well because the levers are very long. To suggest that the moustache bar is not designed to flex for and aft OR try to rotate about the axis of the output shafts is silly. A solid diff mount is perfectly suited to eliminating pinion jacking bcause they are singly mounted in the center and that (single) fastener will fail before any other component in the whole system. If you have a solid diff mount and you are going to change it for any other reason than "it makes too much noise for you" you are wasting your time. The point of diff torsion is such a minimal concern is illustrated perfectly by a current day rock crawler. No where else is the use of unlimited torque applied to feather soft springs in an environment so visibly apparent. Take a Jeep with soft leaf springs drive it in low range (extermely slowly) straight into an obsticle that stops forward progress. Shift into 2wd The first and most obvious change is the rear pinion angle, the nose of the pinion jacks skyward radically, only when pushed to its (the springs) limits does this torque start to exert on the roll of the vehicle. If controlling the roll of the vehicle were the most improtant order of business, then the sway bar would have been employed at the dragstrip and in rockcrawling long before the axle anti wrap device. Yes the 280ZX and the 300ZX and every rear independent nissan suspension does control the roll of the diff by solidly mounting it to the rear subframe. But limiting its anti wrap by fastening it as far from its rotational axis THE OUTPUT SHAFTS (ie; the axle) is the most important order of business. I think we all agree, that on all the later model nissan independant rear suspensions the rear diff mount is just for holding up the rear diff and damping shock associated with dropping the clutch and other drive train related shock. The torque load placed on the rubber mount in tension is just the weakest link and a solid diff mount is the easiest and cheapest way to eliminate this anti wrap. I do love seeing everybodys creative and sometimes crazy solutions. I think we can all agree the stock diff mount design SUCKS!!!! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 21, 2006 Share Posted November 21, 2006 On an S30 to suggest that any solid front diff mount failed, because it was asked to limit axial twisting (about the axis of the pinion) is silly. I think this is a misunderstanding. It's not the billet mount that fails, it's the stamped steel crossmember. It has happened enough times for it to be more than just a coincidence. If you have a better explanation I'd love to hear it. As far as I'm concerned until I see a better explanation I'm going to go with the torsional force on the crossmember tore it up. The trick seems to be putting the solid diff mount on with stock rubber bushings on the mustache bar. That's when it seems to happen I think... Quote Link to comment Share on other sites More sharing options...
briann510 Posted November 21, 2006 Share Posted November 21, 2006 Well I'll let ya know how long ours lasts with our billet mount. Im not worried about it and im not changing it and when it tears the crossmember up ill just replace it with another one. The car isnt driven much and it will probably last longer than me. Quote Link to comment Share on other sites More sharing options...
Twoeightnine Posted November 21, 2006 Share Posted November 21, 2006 Well in my opinion Zmanco wins the award for the most simplistic shot at describing the existance of torsional forces on the differential. Lets not forget the famous "for every action there is an equal and opposite reaction". I love that one. So Im getting a NO on bolting to the crossmember? Dang, thats too bad. A much quicker fix. I started to ponder reinforcement of the crossmember but decided in the end that the time and materials spent would negate the initial benefit. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted November 21, 2006 Share Posted November 21, 2006 So what was the drawback on Team Zleep's idea above? The only one I picked up was that there might be some noise transmitted, not as bad as a solid mount, but not as quiet as the stock one. Did I miss something else? Assuming I didn't, this seems like the simplest for those of us without metal fabrication equipment and skills. Quote Link to comment Share on other sites More sharing options...
ARZ_ Posted November 21, 2006 Share Posted November 21, 2006 The only drawback on the above I can see is if the dude ran an old style 280 bushings and let the diff twist like JM states it might work the diff mount crossmember evemtually but depending on the HP/TQ and amount of use you might never see that type of failure. Thats just my opinion. jmortensen: I think this is a misunderstanding. It's not the billet mount that fails, it's the stamped steel crossmember. It has happened enough times for it to be more than just a coincidence. If you have a better explanation I'd love to hear it. As far as I'm concerned until I see a better explanation I'm going to go with the torsional force on the crossmember tore it up. The trick seems to be putting the solid diff mount on with stock rubber bushings on the mustache bar. That's when it seems to happen I think... I can believe that, but only with the caveat that the mustache bar had the stock smushy 280Z style bushings. I agree that given that much play and hard mounted to the diff cross member would generate enough movement axially to eventually fatigue the crossmember. I believe if the old style 240Z mustache bar bushings (the solid ones above and below)would radically decrease the likelihood of a crossmember failure. Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 21, 2006 Share Posted November 21, 2006 The Mustache bar bends into an -S- shape when the drivetrain loads up... it allows the differential to wiggle around enough to fatigue the front crossmember... The fatigued mount I have was on an L-28 track car with an R200 3.54 rear... several seasons of track use... The mount is much worse once I removed it entirely... all of the bolt holes have dozens of radial stress cracks all around them... there were several cracks that went all the way through the upper stamping... leaving only the bottom stiffener plate holding it all together... the big cracks originate from the bushing clamps(chassis bolt holes)... NOT the single center mount hole... Quote Link to comment Share on other sites More sharing options...
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