Discussion in 'E46 M3 (2001-2006)' started by rem1858, Jun 26, 2016.
How difficult is it to change the diff bushes? I'm assuming just the diff would need to be dropped and not the subframe too?
I've got yellow subframe ones and black diff ones going off these photo's.
It would be nice to stop the clunk from the diff so OEM would be best with the revised bolts by the sounds of it.
I haven't got any groans or whines just a thud when I engage / disengage the clutch.
Benn this is the problem, you cant fit BMW bolts with those black series bushes. You have to stick with the powerflex ones and they are a POS.
It is that and the fact the black series are a 90 shore material. Just transmits NVH.
I think the bushes could be ok if you could improve the bolts and you had a freshly built diff. But an older diff and then crap bolts = extra noise.
Not sure you can buy the rear diff bushes on their own. I think you have to buy the whole rear diff casing which has them preinstalled.
Interesting. If it's just the bolts do you think a longer version of the revised BMW ones would fit. Must be somewhere to get them / have them made.
If those bushes have an internal metal sleeve it might be easier to get a new sleeve, same external dimensions, just internally threaded so then there would be a perfect fit between it and the bolt
Was thinking bolts might be easier as I won't have to remove the diff to change?
If someone gets me the dimensions of the required bolt (and ideally a drawing) I may be able to source one with/without sleeve/shoulder etc.
I have all of the bits in my garage. I have a full diff in pieces with the powerflex bushes installed and the powerflex bolts. Ill get a pic and some more info later.
That would be awesome.
I was going to say if someone can confirm whether they would work I would be happy to buy the updated BMW one and send them to a manufacturer to make some longer ones (they'll sell on here easy enough afterwards)
I'd need to know the length needed for powerflex first though.
These are OEMs (old vs new design) and think they look something like this? I have powerflex and didn't look at the bolt before fitting (but remember Dave @ Infinity Racing saying he uses the bolt that comes with the bush)
I've just had powerflex black series subframe, front and rear diff bushes and inner upper arm bushes installed. nvh has increased very slightly I'd say (can barely hear anything over the supersprint lwr exhaust.
No diff clunking or increased whine that I can hear that everyone has mentioned, Gear change feels very purposeful but slips straight in (SMG). If anything before the bush install it felt slightly ponderous changing gear, the bushes seem to have had a very positive effect.
^ You are in the minority to be fair. Good news you have a healthy diff! Mine wasnt making any noises at all until I changed my diff bushes and then they started, so its definitely that.
Anyway for those who wanted pics of the powerflex bolts here you are.
Unfortunately I do not have a pitch gauge (i do need one!) but im sure some clever clogs will be along with the pitch soon enough.
Just to be clear these are the two rear bolts, not the front one. The standard OEM front can be used.
I'm trying to work out how the powerflex bolt is any different. Is the uprated BMW wider on the part where there isn't any thread?
Its longer for a start, about 20mm longer.
If you look at the minor differences from Pharmed's photo above in the "revised" bolt (which can stop clunks) and then compare the revised bolt to the powerflex bolt its literally night and day...
different bolt material
etc... Its nothing like the same bolt, and given that the clunk can be rapaired with a simple bolt swap I would use this information to conclude the diff unit is quite sensitive to bolt/ bush types.
Then you go and put in a completely random bolt i.e the powerflex ones....No wonder its worse.
Neither of the OEM bolts are tapered. OEM is probably a 10.9 grade at a complete guess, not sure what the Powerflex supplied bolt is but I can find out. Either way I'm still baffled at why people still think these revised OEM bolts are some kind of magic bolt and if they are not fitted then you will get problems. My old style OEM bolt was fine, as was the Powerflex supplied bolt I fitted as well.
The unthreaded shank on the revised OEM bolt isn't significantly bigger in diameter than the old style bolt. Thats a fact. What could differ is the grade and the finish. The grade change could result in a differing clamping force which is all the bolt is trying to achieve anyway. As long as the clamping force is sufficient the actual bolt type, style, colour, shape etc.. is irrelevant.
Revised bolts are stretch bolts. But if they are a better fit you don't need the clamping force if their is no wiggle room.
Over time the peaks of the thread on the old bolt may have become flattened, or more likely as case hardened, bit into the sleeve allowing more wiggle room and hence a clunk, due to having less contact area.
Tell me this is wrong?
I was considering swapping back to OEM with revised bolts soon as I'll be having the car in for some other bushes refreshing.
Afraid so. You need part no 33112282482. Plus a gasket/seal I would presume.