bmwcarmagazine.com Forum Index » 3-Series » From The Project: The Right Tools For The Job Goto page Previous  1, 2, 3, 4, 5, 6, 7  Next    View previous topic :: View next topic  Posted: Wed Apr 04, 2007 8:32 pm M3 Compact Administrator   Joined 18 Apr 2004 Posts 41106 Location Reality. byteflyte wrote: I think most engineers would want to do a full overhaul, at least a full strip to inspect everything, it is their reputation after all. Agreed BF, but what's there to replace? No parts are available other than the bearings, surely they won't disturb the pinion or strip the LSD cluster unnecessarily. What would you do in Neil's position, BF? Personally, I'd replace the obviously damaged bearing only for £25ish and give it a run (with cheap oil until I was sure it was sorted). _________________ Posted: Wed Apr 04, 2007 9:03 pm Neil Established   Joined 22 Jan 2002 Posts 17309 Location Woking, Surrey A bit of a development. Without another diff out to reference it's hard to tell, but neither bearing looks obviously damaged. Both show a small amount of movement - but I'm not sure what's normal. None at all, presumably? Anyway, more importantly the wheel that passes through the sensor has one 'blade' that's slightly bent. That explains how a tiny amount of movement has caused a blade to rumble against the broken speed sensor, but the lack of horrible damage to the bearing makes me wonder how this has happened? If the grumbling noise changed on/off load, then something inside the differential casing must be moving as the load changes. The cheapest option right now is to change the speed sensor, bend the blade back and refit to the car. Worth changing the bearings, or gamble the extra labour for a quicker result? _________________ blog | twitter Posted: Wed Apr 04, 2007 9:24 pm M3 Compact Administrator   Joined 18 Apr 2004 Posts 41106 Location Reality. Quote: The cheapest option right now is to change the speed sensor, bend the blade back and refit to the car. Worth changing the bearings, or gamble the extra labour for a quicker result? Imo that depends whether you're going to attempt the bearing swap yourself and how much you value your time. I'd be bending that trigger wheel straight, borrowing the sensor from the open diff and giving it a whizz. (With £10's worth of B373 until I was sure it was ok.) Check that no bolts have come undone on the crownwheel/LSD end-plate Neil (not unheard of), something bent that trigger wheel. How floppy is the sensor? Could it be that that's moving on over-run, as opposed to the trigger wheel? _________________ Posted: Wed Apr 04, 2007 9:28 pm Neil Established   Joined 22 Jan 2002 Posts 17309 Location Woking, Surrey M3 Compact wrote: How floppy is the sensor? Could it be that that's moving on over-run, as opposed to the trigger wheel? Very floppy - but *why* would the sensor move over on overrun? _________________ blog | twitter Posted: Wed Apr 04, 2007 9:37 pm M3 Compact Administrator   Joined 18 Apr 2004 Posts 41106 Location Reality. Neil wrote: M3 Compact wrote: How floppy is the sensor? Could it be that that's moving on over-run, as opposed to the trigger wheel? Very floppy - but *why* would the sensor move over on overrun? Dunno, possibly unlikely (or possibly should have said 'as well as'), there's movement inside the diff and it wouldn't take much to catch slightly, especially if the sensor's flopping around a bit. Worth a try imo. I'm willing to gamble a whole Geordie pound that it's fixed with a straightened trigger wheel and new sensor. _________________ Posted: Wed Apr 04, 2007 9:39 pm SmogLee Fanatic   Joined 16 May 2005 Posts 7003 Location The Tees Valley. Proud to be a Smoggy ! M3 Compact wrote: I'm willing to gamble a whole Geordie pound Flippin eck, he's cocky ! He must have seen this elsewhere to be splashing money about like that. Posted: Wed Apr 04, 2007 9:40 pm Neil Established   Joined 22 Jan 2002 Posts 17309 Location Woking, Surrey M3 Compact wrote: I'm willing to gamble a whole Geordie pound that it's fixed with a straightened trigger wheel and new sensor. I'd have to bet more than that - £10 worth of oil and an extra two diff swaps of labour. Long weekend ahead and all that.... _________________ blog | twitter Posted: Wed Apr 04, 2007 9:44 pm M3 Compact Administrator   Joined 18 Apr 2004 Posts 41106 Location Reality. leeg330ci wrote: M3 Compact wrote: I'm willing to gamble a whole Geordie pound Flippin eck, he's cocky ! He must have seen this elsewhere to be splashing money about like that. E30 M3 diffs are strong, people use them in close to 400 BHP race cars. Oil capacity/overheating is their only weakness, endurance racers usually use coolers. Mine's given no trouble at all, sticky tyres strain the diff massively. I recall one fierce grip/launch with Neil sat in my car that he commented about, imagine how much strain that puts on the diff internals Neil. _________________ Posted: Wed Apr 04, 2007 9:48 pm M3 Compact Administrator   Joined 18 Apr 2004 Posts 41106 Location Reality. Neil wrote: M3 Compact wrote: I'm willing to gamble a whole Geordie pound that it's fixed with a straightened trigger wheel and new sensor. I'd have to bet more than that - £10 worth of oil and an extra two diff swaps of labour. Long weekend ahead and all that.... Have you given it a good visual check? No signs of uneven wear on the crownwheel? (Polished appearance on a section of the teeth.) Does it turn smoothly? It doesn't whine! BF, Roofer? _________________ Posted: Wed Apr 04, 2007 10:15 pm byteflyte Advanced Driver   Joined 31 Dec 2005 Posts 2057 Location England There should be no play, in fact a slight pre-load in the diff bearings. Overhauling diffs and 'boxs was a favorite pastime of mine years ago, sadly I only get to replace them these days. I am of the opinion that if a jobs worth doing... The cost of parts is not too bad, 4 bearings, a collapsible spacer, a few nuts and washers and a seal or three. Then you can forget it and drive the car with confidence. As for the LSD cluster, that is usually a bit longer lasting, might be worth the gamble and seeing how it gets on. Posted: Wed Apr 04, 2007 10:23 pm Roofer Forum Moderator   Joined 31 Jan 2004 Posts 19711 Location Dunno. As B/F......while its on the bench, get some engineering blue on the teeth as well... Posted: Wed Apr 04, 2007 11:20 pm Neil Established   Joined 22 Jan 2002 Posts 17309 Location Woking, Surrey Vin number is 1892723 _________________ blog | twitter Posted: Thu Apr 05, 2007 12:23 am M3 Compact Administrator   Joined 18 Apr 2004 Posts 41106 Location Reality. Great thread. I'm gonna have a whole pound each off BF & Roofer. Deffo agree with Roofer about some blue to check the mesh and with BF about doing jobs once. But... ...If you put yourself in Neil's position guys. Not sure I'd be in a rush to pay £350 to mend a diff that doesn't whine. What's caused it is a concern tho. The wheel clout is a possibility, but there's a fair amount of play in the shafts and I'd expect the arm to be bent if it's been whacked hard enough to load the shaft up. (I've bent two arms and a strong wheel without damaging a shaft or the diff.) You don't fancy a go at DIY replacing the side bearings, Neil? _________________ Posted: Thu Apr 05, 2007 9:56 am Neil Established   Joined 22 Jan 2002 Posts 17309 Location Woking, Surrey byteflyte wrote: in fact a slight pre-load in the diff bearings Can you tell me more about this? I've heard it mentioned before, and it strikes me as quite a complication for a DIY job. This is one of the reasons I'm quite hesitant Simon. Tom - what's 'blue'? Simon - we don't know that the arm/shaft hasn't been replaced at the time of the incident. Anyone around on Saturday to assist with a diff swap should I choose to proceed _________________ blog | twitter Posted: Thu Apr 05, 2007 10:23 am Ian332isport 3 Series Moderator   Joined 26 Feb 2003 Posts 2350 Location West Sussex Neil wrote: Vin number is 1892723 That confirms you need the earlier sensor (62 16 1 369 905). For future reference, your build date is Feb 87. Ian. _________________ Posted: Thu Apr 05, 2007 10:42 am Neil Established   Joined 22 Jan 2002 Posts 17309 Location Woking, Surrey Ta. _________________ blog | twitter Posted: Thu Apr 05, 2007 11:15 am Neil Established   Joined 22 Jan 2002 Posts 17309 Location Woking, Surrey I've updated the project diary, but I'll post the relevant photos here: In the photo below, the blade marked with a red arrow is bent left relative to the rest of the blades. This might not look obvious as the camera appears to be square to the blade's end, but note the left edge of all the other blades can be seen. In this photo below I've rotated the wheel so that the suspect blade is at the bottom - this shows the difference in angle more clearly. _________________ blog | twitter Posted: Thu Apr 05, 2007 12:38 pm M3 Compact Administrator   Joined 18 Apr 2004 Posts 41106 Location Reality. Blue is 'Engineer's Blue' to check the CWP mesh Neil. Don't worry about preload, you don't have to load anything up before assembly. There's a good chance that the mesh will be correct after reassembly if the new bearings match properly. Comprehensive instructions are on the TIS disc. _________________ Posted: Thu Apr 05, 2007 12:56 pm Woody Established   Joined 09 Apr 2002 Posts 10871 Location United Kingdom Sorry to take this of on a tangent but how easy would it be to increase the lock whilst it's in bits and is it worth doing baring in mind Neil's driving style (sideways!). Posted: Thu Apr 05, 2007 1:07 pm M3 Compact Administrator   Joined 18 Apr 2004 Posts 41106 Location Reality. Woody wrote: Sorry to take this of on a tangent but how easy would it be to increase the lock whilst it's in bits and is it worth doing baring in mind Neil's driving style (sideways!). It means stripping/altering the LSD cluster, Woody.... M3 Compact wrote: I find the % of lock explanations a little misleading; once these units have locked they can transmit 100% of the torque equally across a locked axle. My understanding is that the % is more representative of the amount of torque that is allowed to slip before the unit locks. (A 25% LSD allowing 75% to slip before locking, which isn't the same as having the ability to redirect 25% of the torque.) Quote: Simon aka M3Compact as I am sure he has increased the locking effect in his diff by fitting extra discs Fitting the extra clutch packs makes the unit more durable and much more pleasant to use, but doesn't necessarily increase the readiness to lock. (Although it can be used to the same effect as extra 'wavey' washers etc, by increasing the LSD cluster pre-load.) Ford Atlas axles use the same ZF LSD unit with four clutches as opposed to the BMW's two clutches. A four clutch 'repair kit' for an Atlas axle (£120) can be fitted in to the BMW LSD cluster by machining the housing and leaving out a flat washer from the cluster, if the machining is calculated so that the pre-load is unaffected, the locking % characteristics are also unaffected, but the 'action' is much improved and the unit will last longer. There are two ways to increase the 'poise'/locking action (readiness to lock) of the LSD unit. One way as already mentioned is to increase the LSD cluster pre-load, either via stronger spring/wavey plates, or by extra clutches/shims. (Basically changing the height of the cluster so that the unit has extra pre-load). This is the most commonly used method but isn't my preferred choice. (Although I do use slightly increased pre-load to supplement my preferred method in my diff, for gravel use.) My preferred method for increasing the locking is to alter the pressure ring ramp angles. The pressure rings have opposing triangular recesses machined on the inside edge, when one wheel spins, the shafts that run in these recesses try to climb the ramp, which in turn forces the pressure ring outwards to 'nip' the clutches within the cluster. Altering the angle of the ramp faces makes it easier for the shaft to climb; consequently the clutches are nipped more readily without any increased pre-load inside the cluster. Another advantage of using the altered ramp method is that the unit can be machined in such a way that it can operate differently in opposing directions. Many track/race drivers prefer a 'softer' unit on the overrun/trailing throttle, to avoid savage lift-off/trailing throttle oversteer on corner entry. Anyone who's familiar with the transmission locking the inside rear wheel with a clumsy downchange, can imagine how disconcerting it could be for the unwary driver, if this caused both rear wheels to lock. (Similar effect to pulling the handbrake on.) The ramps are infinitely 'fine tuneable' to allow different locking in each direction. A popular choice is to machine the ramps to 30 degrees as opposed to 45 degrees. It is essential that the shaft sits at the same height in relation to the pressure ring when in the 'neutral' position. Because of this, it isn't possible to alter the existing ramps, but new ramps can be machined adjacent to the existing ramps. Standard pressure ring ramp...... Modified pressure ring ramp...... Together...... Calculating/predicting the locking % isn't an exact science imo, I've been told that an 80Lb pre-load with standard ramps will give 40% locking in each direction, I've no way of measuring this. For my diff, I use 30 degree ramps in both directions with an 80 Lb pre-load, this makes a very 'tight' LSD unit and imo this is perfect for gravel use, but in an ideal world the same ramp set-up with standard pre-load might be more appropriate for tarmac use. It's down to individual preference really, but my guess for a nice sporty road car set-up would be to use 30 degree ramps for power on, with the standard 45 degree ramp for overrun and a fractionally increased pre-load. (Four clutch conversion optional.) Increasing the pre-load with standard ramps is an easier but still effective method. Apologies if it sounds complicated with my long-winded post, once you get it apart it'll all become clear, it isn't too difficult. M3 Compact wrote: t1000 wrote: I am still a little lost as to how the differential locks in acceleration/de acceleration, is it the 2 little nicks on the inside edge of the pressure rings that cause the diff to lock under de acceleration ? The two 'little nicks' control it in both directions, it's difficult to explain without seeing inside the cluster, but basically the shaft climbs one way with acceleration and the other way with deceleration. This pic shows an exploded view of a (non-BMW) cluster, when in operation it's all bolted up inside the housing as per the green arrows. (End plate bolted to housing.) _________________ From The Project: The Right Tools For The Job   bmwcarmagazine.com Forum Index » 3-Series You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum All times are GMT + 1 Hour   Page 4 of 7   Goto page Previous  1, 2, 3, 4, 5, 6, 7  Next All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First  Select a forumBMW Car Magazine Forum & MeetsTechnical AreaGeneral Motoring Discussion3-Series5 & 6 Series7 & 8 SeriesAll Other BMW ModelsBMW Cars / Parts For Sale / Wanted [UK]Non-Motoring Discussion

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