Cement 910 Report post Posted Monday at 06:37 AM Keen to hear if anybody has experienced this issue or similar previously. I've got the PowerFlex purple polyurethane bushings https://www.powerflex.co.uk/product-details/Rear+Diff+Rear+Bush/11051.html and ended up with a snapped bolt which left the back end of the diff swinging within the subframe making a horrid knocking noise ... check out the fun video of this linked below Essentially it looks like the solid centre of the bushing managed to press into the large 'washer' (the one next to the diff cover), deforming it to the point it was tightly pinching the bolt ... over time the bolt has fatigued and snapped right at that point. I would have torqued this to the correct spec when assembling, and there was no lube on the threads. Really happy it finally let go about 1.5km from home !! Rear side of the deformed washer, was clearly supported where the pressure from the chunky centre piece was. Severely deformed and you can see the threads from the bolt formed into the washer also ! Bowed washer from the 'outside' of the sandwich where the nut goes, not optimal but not a deal breaker. Showing the relative hole sizes, no longer can I get a M14 bolt through the deformed hole ... would have not found this whole mess if I could, as would not have removed it after many attempts just thinking i was not quite aligned. The video of what your diff looks like with no rear bolt Quote Share this post Link to post Share on other sites
Eagle 1734 Report post Posted Monday at 08:16 AM Nope but the design looks subpar which is probably compounded by the lack of elongated holes. Quote Share this post Link to post Share on other sites
BMTHUG 1100 Report post Posted Monday at 06:38 PM Not a very common thing Dave. check your driveline components such as centre hanger bearing etc and make sure everything is as it should be. Something would be putting the angle of the diff off putting strain on the bolt for it to snap like that. Or it could be a simple case of the bolt just not being strong enough? Quote Share this post Link to post Share on other sites
Cement 910 Report post Posted Monday at 09:08 PM Yea I'm leaning towards a poor design, where the centre of the bush is too small and the clamping from the bolt (plus torque / driving) is squashing the sh*t out of a small area on the washer causing it to deform. Don't think the bolt is at fault really as it was essentially being guillotined in half by the washer ... sure doesn't help having it threaded where the washer was though !! Have written to PowerFlex to see what they think but will likely look to replace with a different design i think. Quote Share this post Link to post Share on other sites
Vass 991 Report post Posted Monday at 10:02 PM Wow, that's a trip! You're probably right about the cause of the failure but would be interesting to hear what Powerflex come back with. Do you really need poly back there though? Could just go with Meyle HD with solid rubber - sure, it won't last forever but, evidently, neither does this. How have you found NHV with poly diff bushes btw? Quote Share this post Link to post Share on other sites
Cement 910 Report post Posted yesterday at 07:32 AM Got to be honest here, I don't have much basis for comparison as this is the only BMW / E46 I've had and didn't drive it much when stock. I think it's pretty quiet when cruising apart from the things that are supposed to make noise, definitely no noise you can pick up and say 'that sounds like the diff' etc. Have poly bushes essentially throughout (all PowerFlex). Got it all back together tonight after making some temporary washers from some stainless sheet and life threatening times with the 85mm hole saw in the cordless drill 😂 It's super quiet again, turns out the mild clunking I have been hearing (before the loud clunking) for some time was the early stages of the bolt letting go or having excess play. Quote Share this post Link to post Share on other sites
