Well heres how i see it, although my engineer may well have corrections! The flywheel comes balanced from the factory. it is done first then fitted to the voith system behind. the voith systems do then seem to have the odd balancing weight attached to the rear of them, although always very small. So they are balanced as well. Now whether with the flywheel or without I don't know, although one of the wsm says not to remove the flywheel due to the balance issues which might suggest with. Although this contradicts directly the figures for grinding which of course necessitates removal. Anyway, this makes a sense of the maximum imbalance figure of 250 g/mm for voith system In practice I always mark parts to keep them in same place as when removed. But have also found a need to rebalance any flywheel after grinding so bring it back, they are always out. The voith system retains its balance, and has the grease added to it as well of course, which must throw that out a bit anyway, no matter how hard you try to evenly spread it. The clutches are of course balanced separately. hope that helps kick this hijack strand off!
Upon grinding the FW any good shop would balance it. Then PP and Clutch plate are balanced as a unit. Voight is factory balanced and grease does the rest with centrifugal force. Interestingly, I forget the exact numbers for the 348 but the WSM has the grease less than the later TSB. The cans of Kluber come in 500 gram tubs. Is it any wonder how 250grms became the amount needed for the 348 and it's successor.
If only that were true here, so many don't balance. Interesting point FB re the grease, I can only get it in 25 kilo tubs, so would be very interested to know if you can source in 5oogm sizes. It was the older 348 that had 180 stated as the correct amount and less, 150, in the 355. Never seen the need to do differently myself. Just had a 355 flywheel made will post a pic later on.
I don't think it is a very precise measure evidenced by multiple changes . The goal is probably to not have the plastic parts slop around and trigger/confuse the crank sensors. The 348 had that problem show up as a hot start issue that the 355 had less. Those triple seals were never a good design. I have suspicions of why the 355 had less issues there than the 348 but could never bothered to prove them. Either way the fix is easy.
my new 355 flywheel! Made from a specialised chrome moly billet by a local race specialist company. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
I suspect the 355 hasn't had the hot start issues yet because the grease isnt quite as old. Give it time and it will get there! can do nothing but agree with the triple seal design, you can see the thinking oh one doesn't work ok add another, ok that doesn't work either, lets try a third. ok fed up now that'll do.
Billybob I was thinking that if my 355 flywheel ever went that I would weld and balance the flywheel like you did. How do you think it would work for a street car?
I don't know. You have to have a good reason for doing it. There is something different about the 355 and it's triple seals and the 348 and its triple seals where the 348 leaking a lot more and wet the clutch pack causing the grease to thin and plastic voight parts to rattle resulting in no hot starts due to funky feedback to the crank sensors. For one thing the 355 box is supported and the 348 uses a saggy rubber mount. Were there other changes? We have a solution for 348's today. Back then we all scratched our heads. I decided to do away with the cr@p completely but I was racing my car. The theory goes you want the dual mass to dampen bad harmonics. Are the harmonics annoying, non existent, or destructive? I have no clue. But 355 guys do break the input shafts while racing. So...are they weak? Would bad harmonics cause failure at street speeds? I got questions but no answers but those are some of the things you got to deal with. My 348 racecar was 2750 lightened clutch by 8-10lbs and stock motor only 300hp. It lived at redline so maybe the harmonics are not bad there. I have no clue. Those are the only datapoints I can offer. Personally I think the shaft will survive, you might have annoying harmonics at some speeds, and you will launch out of turns better. I had no issue getting off the line with lighter flywheel and clutch pack. I think the biggest cost would be if an input shaft broke.
Cant agree the 355 triples leak any less than the 348s in the ones I've seen incl mine now on 2nd box all still weep. and cant see the difference gearbox mounts would make. the pumpkin, where this all is, is nearly identical in both. Too true Ive only heard of the occasional 355 drive shaft break when racing. I always thought just the extra stress from more power being more aggressively put down with less damping was the cause, not these harmonic things you mention. is there a really annoying noise? I would certainly suggest drive shafts are cryogenically frozen to try and prevent this.
By way FBB did you just take out insides and weld up your voith system or design something to replace all of that? Was just thinking about a design for the 355 with a replacement to bolt a lightened flywheel to. but unsure where we then put the starter ring, either on the flywheel or on top the clutch pressure plate like the 348.
Finally have the parts and ready to start putting this all back together. Couple of questions: 1) When installing the new pressure plate, how do I know which way to orient the balancing mark? I can not find any corresponding marks on the flywheel. 2) I have seen several different values for the torque specs for the pressure plate mounting bolts. Does anyone know what the actual correct value is?
sorry i didnt reply last time, the wsm figure is 1.3 daNm which is 13 Nm for the clutch mounting bolts. If there is no clear mark on the flywheel your a bit stuck, usually you just put it in opposite that mark. However these are so well balanced now it wont make any difference where you put it to be frank.
your welcome, the clutch will tighten down onto the flywheel as a very tight fit. You know when it is home when the allen key stops hard. I tighten the middle ones first a turn at a time. then add the outside ones afterwards. I do use new sets of hardened steel bolts and new spring washers. send me your address if you would like a set. I'll put in the post. I use these harder bolts because they last longer. The spring washers don't dig into them like the softer oem ones but add some loctite and your sorted.
Another clutch in the 355 being done, unfortunately I am a long way from solid resources and parts being in Guam. So my Flywheel needs to be surfaced, just like all of them, and hopefully with some luck it will end up "ok". Worst case is a new flywheel from MD Clutches, but hopefully the machine shop will be able to do a competent job of it. Anyway, on to the question, is there any trick to doing the triple seals to get the best chance of them sealing??? Is there anything that would either lower the chance of them working vice increase the chance? To say that this has been the messiest job I have ever done is an understatement. Kluber grease everywhere, gear oil everywhere, disintegrated clutch everywhere. On the positive side the Kluber grease never leaked out, the flywheel and pressure plate did not show signs of being overheated, and the only thing "really wrong" was the triple seals leaking onto the clutch plate which in turn ate the plate in fairly short order. The Kluber grease was a bluish grey with reasonable consistency, but the car would rattle a lot when it warmed up, was this due to the viscosity of the Kluber grease changing, or something amiss with the Voith damper assembly... Someone in the past mentioned a plastic thrust washer, but I didn't see evidence of any such beast... I am trying to find this rattle in the back and I am hoping that rebuilding the Voith system is the answer. Thoughts?
Good luck with the flywheel, do make sure it gets done right up to the edges on the side pegs, that its ground under water and doesn't create any heat and is balanced afterwards. They always get thrown out a bit. With the triple seals I use a piece of a drinks can, the very thin aluminium, and use that to slide the water heated seals up and over into place. I try to keep them warm with a hot air gun and use same ally to wrap around the outside this time and squeeze them a bit to make small enough so when I tap end shaft with rubber hammer they fit into chamfer on the housing. obviously don't squeeze too much! was the kluber still sticky or runny? was it all in place still around the springs? sometimes it can all go to the outside gaps leaving the springs to rattle. in the 355 there has been talk about adding a little more than the 150gm to stop this problem. up to 180. the plastic washer is in the 348 not 355 so dont worry about that.
So they had to remove nearly 1mm to get it flat, is there anything that needs to be shimmed or adjusted? I was thinking that the rear spacer might need to be a different thickness but was unsure, so that the throwout bearing was in the same orientation. As for the plastic washer, I realized that the snap ring places the bearing in the correct location to maintain the correct spacing after I looked it over more carefully.
as long as this is first skim 1mm is on edge of your limit and clutch bearing should handle it OK. although I have known some throw a wobble when in a new position!
Worst case is I buy one of your flywheels, I can live with that. I believe it was the first skim, but I have no way of knowing for sure. I can certainly shim the unit to where it needs to be from looking at all the parts, but would prefer to monkey with the fewest parts. The Kluber grease was not at all runny and even balled up when hit with water to rinse off the springs and plates. It seems impervious to brake cleaner and degreaser, necessitating a whole bunch of rags/paper towels. All parts are cleaned up now, degreased, appropriate parts have been abrasive blasted and looking like new (voith cover externals). It's a good weekend project. M PS - Thanks for all the support.
