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Originally Posted by Zulfiqar
If you notice the tripod flange, it has sunken holes to receive the protrusions on the flex disc, Thats what I called sunken bosses of the flange.
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agreed. That has the sleeves taking some rotational force instead of the bolts alone. Maybe most of it.
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I dont know the exact cut off date of the "soft" flex disc for the W126 - but it was somewhere in the mid80s. Before that all cars had the same front and rear disc.
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You sure have a way of confuzzling me. Whenever I see a change for the discs of various models(&yr) it is ALWAYS in this sort of form: this part fits "Both front and rear on models with chassis serial number through A1xxxxx, front only on models from A1xxxxx." So certain: 1) Originally the same disc is appropriate for both ends and if one were to orient them with a particular side to the shaft, the one mounted in the front would face back to the shaft and the rear one would face forward to the shaft. They would be rotating in the opposite direction compared to the face markings on the disc . And all forces/torque/whatever would be reversed on either compared to the other. This would imply that if orientation mattered they would both be oriented to the front of the vehicle or to the rear. Or it doesn't matter. It could be that the orientation matters as to the flanges on the shaft being different to those on the diff and tranz. I haven't inspected them yet. That would also imply that the disc faces are different to accommodate. So I dragged out my nice new boxes again ... nope. Flip them over and you are looking at the same thing again. At some point ( in the model serial number progression) the rear was changed while the front remained the same. I have no way of knowing if the flanges/bolt spacing dimensions changed or what. Would they add a 'softer one' in the rear only? If indeed that part number is softer and not a flange dimensional change. If it was about softer the usual significant force is from the tranz under acceleration and perhaps the front one takes the brunt of it and they could get away with a cushier ( presumably weaker) rear disc because it is subjected only to the forces moderated by the front disc. . Only time that take more of the heat is racing style downshifting. Low percentage of the time for most w126's I'd guess. but even then, until the trans is reacting to the force there is not much on the rear disc, and perhaps the front one takes the heat is that situation as well? Can we find out if flange geometry changed? I guess the part number search comparison is more than I need to do today
An Aside: If the dimensions are unchanged you could use the later rear part no in the front, but would have to flip it to still face forward rather than back at the shaft. But would it hold up? 150k mi instead of 200?
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The nudge I mention is when you are slowing down to a stop - you will feel a gentle nudge as the transmission shifts to 2nd or 1st gear (dependant on your car) - The soft disc was to eliminate that "lash" feeling from the driveline. Its very subtle but its there.
If you own a later electronic transmission car, you will definitely feel that downshift to 1st as you slow down to a stop. Thats the nudge I was mentioning.
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This particular vehicle has a 722310 02 xxxxxx trans. When in drive I never notice any downshift on decell unless I called for it or I have it in an gear other than D, or in sport mode. I do notice shifting when resuming speed. If I had come to a full stop it would have changed out of top gear at least for sure, but without me noticing. I'll have to look for that. And it starts in 2 unless I force 1st or stomp it. So typically there is not that much shifting going on unnecessarily. Did that model trans need downshift nudge taming by softer disc?? But while we are on this, if they improved the drive-ability with disc softening with no changes to flange geometry/dimensions, why not just spec that retroactively for all ? We see plenty of occurrences of NLA superseded by .... part number such and such all over the parts supply world.
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Originally Posted by Zulfiqar
I follow whats written on the part literally - "this side to driveline" is enough for me to orient that side towards the driveshaft. (usually seen on soft disc as it has a specific shock absorbing purpose and wont work backwards)
On ones that dont mention any text like this - I will have to look up if they have an orientation - like some BMWs have.
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So these don't say anything and i suppose that confirms non directional. If one needed to worry about direction we should expect to see it stamped on the disc. Normal downshift (coasting, breaking) force not due to driver demands is about zilch compared to acceleration forces. seems odd they would work to dampen that alone. I know ya'll want more but this makes me thirsty for a martini
12-15-2022, 04:39 PM
Linear Mode
