Ska Posted December 6, 2007 Report Share Posted December 6, 2007 Can anyone tell me how much their engine jolts or moves when you take up drive or reverse gear? Following on from this thread ( Bad vibrations part 1 ); I’ve replaced the drive shafts, CV joint and pulled off the out put flange from the final drive– a ZF transmission specialist has ruled out the diff. bearimgs as there is no whining noise and he reckoned that sort of Vibration would rip the final drive casing apart. So I’m making no headway on this vibration/shudder issue. Until perhaps last night I went out to the car and drove it round the block (warm up) then parked up with acres of space around me and opened the bonnet. Then I carried out the engine mount test by placing the car into drive whilst left foot firmly planted on brake pedal and giving it some throttle (similar to torque converter test). The thing is I didn’t even need to apply any throttle; the amount of rotation from the engine/Gearbox was phenomenal as it just took up Drive; I’d say at least 3-5 inches rise and similar downwards displacement when selecting reverse. When I applied the throttle it was unbelievable more movement! My theory is that a couple or more of the engine/Gearbox mounts are shot and causing extreme levels of geometry misalignment I.e. excessive drive shaft angles when accelerating at certain speeds. I’ll try and post a video of the movement and you guys can hopefully compare with your own cars. Link to comment Share on other sites More sharing options...
LostKiwi Posted December 6, 2007 Report Share Posted December 6, 2007 That sounds like a whole heap of movement I must say! I'd be looking very closely at the engine mounts - I'd almost guarantee one of them to be shot... Link to comment Share on other sites More sharing options...
Ska Posted December 6, 2007 Author Report Share Posted December 6, 2007 There are four of these mounts arranged in a square base and the movement seems equal in both directions. Just looked up the mounts in the manual and there seems to be a torque reaction mount at the front of the engine as well (the movement is in this plane i.e. back and forth as opposed to side to side), which is adjustable (according to stealers), though I doubt simply adjusting this will compensate for the other dodgy mounts. I say STEALER and yet again mean it each mount is around £80 each and theres four! Question is, is it a simple case of relieving the load from the mounts and swapping them over or does the engine need to separated from the box and lifted out? hope the feck not Link to comment Share on other sites More sharing options...
IT_S8 Posted December 6, 2007 Report Share Posted December 6, 2007 [ QUOTE ] There are four of these mounts arranged in a square base and the movement seems equal in both directions. Just looked up the mounts in the manual and there seems to be a torque reaction mount at the front of the engine as well (the movement is in this plane i.e. back and forth as opposed to side to side), which is adjustable (according to stealers), though I doubt simply adjusting this will compensate for the other dodgy mounts. I say STEALER and yet again mean it each mount is around £80 each and theres four! Question is, is it a simple case of relieving the load from the mounts and swapping them over or does the engine need to separated from the box and lifted out? hope the feck not [/ QUOTE ] Nice find, er sort of... Seems logical to me that an engine with that much play is definitely not a good thing... You now have almost exactly the same mission ahead of you as A8VIP... He needs to sort out his broken subframe, and you too would need the subframe out of the way to change these mounts. In theory, if the engine can be braced from above, and you can find someone brave enough to work underneath it (!) then I guess it could be done without actually removing the engine, but i'd get someone elses opinion too as I've never tried it. We find it far easier to take the engine and gearbox out complete when we do it... Detaching the two in situ is as far as I can see almost impossible. Especially with no rear prop shaft though, taking them both out on the subframe would be 'relitively' easy... I've attached a couple of photos of subframes in and out of the car to give maybe a better visual to all... These are from a 4.2, and no doubt yours is slightly different, eveything else is Subframe standalone.... And in its rightful place... I dont envy you I have to say...., but best of luck, I hope you get it all sorted.. Link to comment Share on other sites More sharing options...
LostKiwi Posted December 6, 2007 Report Share Posted December 6, 2007 It should be just a matter of relieveing the weight of the engine and replacing each mount. It highly unlikely to require all 4 - I'd guess that its the ones on the side that lifts that are duff (although if these are hydraulic mounts - I've never looked - then its possible more than one have gone but if they have there will be oil all over them). If they are hydraulic that would go some way to explaining the cost too... Link to comment Share on other sites More sharing options...
Ska Posted December 6, 2007 Author Report Share Posted December 6, 2007 The manual says that if one gearbox mount needs to be replaced then the gearbox needn't be supported. So by the same virtue if you support the engine from underneath (and so long as you can get at the bolts for the brackets) couldn't you just replace them one by one without lifting the engine out or removing the subframe? The direction of lift to fore and aft so its a little difficult to ID a particular bad mount non of the mounts looked as if they had leaked though I think there is a tear on the right transmission mount. @ IT_S8 you've got the subframe marked with four engine mounts surely the ones at the back are for the gearbox? Link to comment Share on other sites More sharing options...
IT_S8 Posted December 7, 2007 Report Share Posted December 7, 2007 - Yes, rear ones are gearbox... Sorry to mislead. Gearbox and Engine are very firmly bolted together, hence we take them out as one lump. The removal of one mount at a time sounds plausible if you can get a little lift from above. There is no oil in the mounts - I cant begin to justify how they are 80 quid a piece. I'll have to start saving them from now on I'm quite interested in the outcome of this - For your engine to be moving 'inches' the whole mount must have pretty much perished and fallen out... I'd be surprised if it wern't more obvious on closer inspection which one is the culprit.. If it can move with a bit of revving, some delicate crowbar action might be very revealing.. Link to comment Share on other sites More sharing options...
Ska Posted December 7, 2007 Author Report Share Posted December 7, 2007 I will take the car to the garage tomorrow for a closer inspection. But from one of my earlier videos I found this: I cant believe I missed this ; this looks like a defo. split! IT_S8 are those gearbox mounts on your subframe cracked as well? Actually just saw a pic of a gearbox mount on Audiworld seems like there some sort of metal plate at the top I think. Link to comment Share on other sites More sharing options...
LostKiwi Posted December 7, 2007 Report Share Posted December 7, 2007 Easiest way to support the engine/gearbox is to use a jack with a large piece of wood under the sump (at least an inch thick and going from side to side of the sump in its entirety). Loosen the mount(s) lift the jack to take the strain and pull the mounts out, insert the new ones and lower the engine on to them. Make sure when lifting that you have all the weight of the sump on all the block of wood and the wood is central on the jack too. That engine and gearbox is a heavy sucker so the wood is needed to spread the pressure pad of the jack over a larger area to prevent damage to the sump itself. The only way to verify the mount is good is to stress it (using the jack method) and look for relative movement and signs of perishing or detachment of rubber from the metal fittings. Link to comment Share on other sites More sharing options...
Ska Posted December 7, 2007 Author Report Share Posted December 7, 2007 [ QUOTE ] The only way to verify the mount is good is to stress it (using the jack method) and look for relative movement and signs of perishing or detachment of rubber from the metal fittings. [/ QUOTE ] I was think of sticking the car on a ramp and just putting in gear and observing the movement of each mount? though the ramp in question will not support the wheels; we could place long jacks under the suspension to simulate the drive geometry of the suspension. Link to comment Share on other sites More sharing options...
LostKiwi Posted December 7, 2007 Report Share Posted December 7, 2007 You could do it that way too but it requires a second person who can follow instructions... I gave the other way as a means to do this on your own if necessary (and its also part of the mount changing process as well)... What ever you do make sure you do it safely so you don't end up with a V8 shaped lump on your head! Link to comment Share on other sites More sharing options...
Ska Posted December 8, 2007 Author Report Share Posted December 8, 2007 Update: took the car to the garage this morning and put it on the ramp and simply put the gear shift through D, N & R found the following having removed the noise baffle from underneath: Engine/Gearbox pitches about the engine mounts when in D or R. so in essence the rear gearbox mounts are knackered and the Engine mounts seem OK as there is no true vertical movement at the engine mounts and the fact that there is little or no vibration at idle engine speed. There is however, excessive movement (which in day light is more like 2-3 inches ), on the o/s Gearbox mount where the vibrations seem to come from and an audible noise is also evident when you get to 30mph. This pitching causes the engine torque reaction mount at the front to hit the bracket as well. On closer inspection of the Gearbox mounts, whilst prising the rubber cover off we found that both were leaking their Hydroscopic fluid (water/Alcohol mix) O/S more than the N/S one. Neither of the mounts are catastrophically broken from what we could see whilst they were in place but is enought to put the UJ on the drive shaft under duress (thats my thought anyway - What do you guys think?); will only know the true extent when they are removed. So will put in an order for new Gearbox mounts (OE AUDI ones) on Monday from VAGparts who came in at around £63 incl. VAT as opposed to the stealers £87each. Incidentally, I did think about adjusting the torque reaction support bracket but decided against it as this should only be adjusted once the new mounts are on there. So next week means new Gearbox mounts, new final drive flange seal (started leaking because of the number of times we’ve had that open), ATF & final drive fluid change and checking the exhaust as the engine/Gearbox movement is placing a lot stress and strain on it. (will take pics and post back as I found it difficult to find any A8 related posts on this issue) Link to comment Share on other sites More sharing options...
Ska Posted January 7, 2008 Author Report Share Posted January 7, 2008 OK new mounts went on and the vibrations got better but not enough to constitute the mounts being the cause. In fact the mounts were proly knackered due to the vibration; the front torque reaction rubber was cracked. So I put my attention back on the diff/driveshaft assembly. I've come a full 360 back to one of my earlier ways of thinking about my diff, which was discounted by a tranmission specialist. I had noticed play in the driveshaft which is infact play in out put Flange shaft. We tested this by putting the car on a ramp and raising the suspension to about the same geometry as per road conditions and then placing the gearbox in drive. We held the O/S front wheel and noticed the flange/inner cv joint still moving in an odd fassion. To confirm this I bought a small spy camera from maplins and tied it to the shock and observed what happened whilst out on a test drive; sure enough there is a lot of play on this joint at the said 30mph + speeds. there is also a lot of back lash when shifting from drive to reverse. What I believe to be the issue is the diff. carrier bearings and possibly the pinion shaft bearings as a result. You can see the state of the bearing from the outside I think its had it, what do you guys reckon? Notice the cage at about the 1 to 2 o clock position, there is a smaller gap around the circumfrance at that point along with the fact that there is wear from where the output flange shaft is rubbing against it and loads of oil to boot. Also the play I mentioned was there even when we held the wheel whilst the Gearbox was in D. This means the crown wheel on the diff is still rotating even though the wheel being held is not; the other front wheel starts to spin at the same speed of the crown wheel how diffs work , the point is the diff is still rotating on the carrier bearing which seems shot and thus causing the play. The only way to be absolutely sure is to open it up; I'll be damned if I'm going to mess with any preload adjustments so its going to a specialist on wednesday, let me know what you guys think and pray for me Link to comment Share on other sites More sharing options...
Ska Posted February 27, 2008 Author Report Share Posted February 27, 2008 OK, found the cause to this and I thought I’d update for future reference – Note to my self; I should trust my instincts more often . After spending loadsa monies and several parts being replaced under advice from stealers and independents; ranging from plugs, coil packs, ignition leads, fuel filters, lambda sensors, drive shafts, flange shafts, CV joints, wheels, and engine mounts. It turns out it was the differential after all. I got fed up and just forced my car onto the specialist and tolled him to take a look see; by this time this guy is getting annoyed at me so says he’ll charge me for the full job whether he finds a fault with the diff or not , as he is adamant that the symptoms aren’t indicative of a failing diff or bearings . Anyway he phones me up yesterday to gloat about that fact that there’s nothing wrong with the diff bearings and asks me to come down to garage. When I get there I see them closing up my car and he shows me my diff; I was totally blown away by what I saw . Yes the outer bearing had moved axial along the diff end but that wasn’t the cause the bearings rolled fine and the wear pattern was normal. What caused the vibrations and the bearing to slide and the torque reaction mount to split was the broken housing of the diff which was being held by the locating pin for the internal bevel gears! Both of us were astounded at the fact that it hadn’t ripped out of the final drive casing on one of its many test drives during the past months of diagnostics, where sometimes the car was run to 60mph! Two things for sure the symptoms were very peculiar and difficult to pin point and not at all symptomatic of differential failure. The second I am glad to get back behind the wheel of my 8 again, Thanks gang for all your help along the way Link to comment Share on other sites More sharing options...
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