charlie_pank Posted August 24, 2012 Share Posted August 24, 2012 There have been a lot of threads on here about noisy diffs recently. It's always a tricky one ad there are several confounding factors: The car's design means the diff noise is far more noticeable than in a tin-top Some 7s have tunnel covers, upholstered seats etc some do not and this will affect the noise heard Some of us drive with windscreens, some with aeros Some of us drive with hearing protection, some don't The diff noise sounds different from driver and passenger seats Some have exhaust exits on the right some on the left (exhaust/induction noise may mask diff noise) Some of us have engines that give max torque at 3500, some at 12,000 rpm Some of us have rubber in the drivetrain some don't, some have rubber in the engine/gearbox mountings, some don't Many of us run wildly different gear ratios and diff ratios, even different ggearboxes, some with short propshafts, some with long 2-piece affairs with intermediate uj Some have lightened flywheels And so on... all of these things and more will affect diff noise My point is there are many many reasons why it's very difficult for one owner to comment conclusively on another's diff noise. More often than not the cause of the noise you hear from the diff is elsewhere, even if it actually does make the diff louder. So, to put the complaints about noise in perspective, how many people have suffered a diff FAILURE, how did it fail and did it make a specific or louder noise before doing so? Link to comment Share on other sites More sharing options...
Bellissimmo Posted August 24, 2012 Share Posted August 24, 2012 Charlie, I completely agree with your comments but I had one of the now notorious 'noisy diffs' in my 08 Sigma and they were a good distance along the quiet<---->noisy spectrum. Mine started out at what I would call an acceptable buzz/whine - the sort of noise that you sometimes hear from an elderly saloon when it is driven fairly fast in reverse IYSWIM. By the time I got it changed, it was so loud that I couldn't hear myself think and it was impossible to hold even a shouted conversation in the car at anything over 30mph. Furthermore, I couldn't hear the engine noise over the diff - regardless of how 'briskly' I was pushing it. When it had been changed, it was like they'd given me a different car - it just felt so much faster because the noise of what sounded like imminent self-destruction had disappeared and been replaced by something like one should expect from sitting in an aluminum box two feet away from the diff. The amount of time I spent in the car went up and traveling with passengers became a pleasure. Over time, the whine has started to get louder but it is nothing compared to the original fault, which sounded much much worse than any kit car I've ever been in. Link to comment Share on other sites More sharing options...
charlie_pank Posted August 24, 2012 Author Share Posted August 24, 2012 Did you ever find out what it was that had caused it to get so loud? For the record, I've never been able to hold a shouted conversation in my 7 before or after the engine swap at over 30mph! Edited by - charlie_pank on 24 Aug 2012 15:49:48 Link to comment Share on other sites More sharing options...
Bellissimmo Posted August 24, 2012 Share Posted August 24, 2012 Charlie, I'm not an engineer and diffs have always been a bit of a black art as far as I am concerned but what I was told was that the internals were built using pattern parts and were not the original Ford items. The diff went back to get the pre-tension (or something? ) adjusted and came back at about half volume. A couple of hundred miles later and it was back in full volume banshee mode. Then they changed the diff and it's been acceptable ever since, although I don't get out in it as much as I'd like so the jury is still out as far as any deterioration due to age is concerned. I've been kicking myself for not keeping the pressure on and trying for a BMW diff but it's beginning to seem like they have their own problems. Incidentally, I also get 'diff clunk' regularly during gear changes and sometimes going from drive to overrun. This has led me to a new (for me) gear-change approach. I was taught to drive with the 'clutch down; change gear; clutch up' approach but I've found that if I start to change as the clutch is on the way down and let the clutch back up as soon as I've changed gear, I get a smoother transition and no 'clunk'. *rolleyes*Waits for dozens of verdicts from POBC varying from "you should have been taught to drive like that" to "your engine and gearbox will fall apart if you drive like that" Link to comment Share on other sites More sharing options...
charlie_pank Posted August 24, 2012 Author Share Posted August 24, 2012 It's even smoother if you leave the clutch out completely :) Link to comment Share on other sites More sharing options...
charlie_pank Posted August 25, 2012 Author Share Posted August 25, 2012 So NO ONE has had one actually FAIL, they just get noisy? In which case the next question is: why do they get noisy in 7s but not in other cars? Link to comment Share on other sites More sharing options...
EFA Posted August 25, 2012 Share Posted August 25, 2012 The diff is something I never managed to break. And I tried quite hard. Link to comment Share on other sites More sharing options...
Rob Walker Posted August 25, 2012 Share Posted August 25, 2012 IMO the sierra diff get noisy because it is out of the airflow and gets very hot. The ali case expansion rate is greater than that of the steel internals and thus the diff backlash which MAY have been set correctly when cold and static becomes excessive, then the noise/transission shunt increases. Of course it doesn`t help that the unit is about 2ft from your lug hole and mounted to the chassis with very thin metallastic bushes. In theory the BMW steel cased diff should not suffer so much from this problem , I have no experience of these so cannot comment. One well known transission builder told me that he sets the diff backlash greater than Ford spec because the diff will be used on track and in competition and will tighten up due to expansion? I cannot agree with this theory and have tightened up my own diff which has reduced noise and shunt. Rob Edited by - Rob Walker on 25 Aug 2012 10:13:35 Link to comment Share on other sites More sharing options...
Titanium7 Posted August 25, 2012 Share Posted August 25, 2012 Beg to differ in regards to having one fail. New car really noisy Ford diff, 90 miles on the clock the diff seized on our first long distance trip down to Cheltenham on the M5. Confirmed by the RAC. Link to comment Share on other sites More sharing options...
charlie_pank Posted August 25, 2012 Author Share Posted August 25, 2012 Any info about what turned out to be wrong with it? Link to comment Share on other sites More sharing options...
Titanium7 Posted August 25, 2012 Share Posted August 25, 2012 CC did not inform me, had another (more noisy one) under warranty. Now have the BMW and my hearing back Link to comment Share on other sites More sharing options...
charlie_pank Posted August 26, 2012 Author Share Posted August 26, 2012 Did you fill it with oil or did they? Link to comment Share on other sites More sharing options...
Titanium7 Posted August 26, 2012 Share Posted August 26, 2012 Self build car. Yes, verified by it all running out on the garage floor when removing the diff for the swap! (you have to do the swap yourself when under the CC warranty). The end result was I had a BMW diff supplied and fitted FOC thanks to Ansar who was very understanding. Link to comment Share on other sites More sharing options...
evotell Posted August 26, 2012 Share Posted August 26, 2012 The new BMW diff is noisy when fitted with an LSD, however there is a mod for it that deals with the problem. Will let you know when the additional parts are fitted in the next few weeks. Link to comment Share on other sites More sharing options...
charlie_pank Posted August 26, 2012 Author Share Posted August 26, 2012 I just have this nagging doubt at the back of my mind that if the Ford diffs are alright in Fords, they should be alright in 7s. Perhaps it's to do with getting the alignment right with the washers? If they're not aligned maybe the pinion bearing wears prematurely leading to excess play in the pinion/crown-wheel interface. What about the propshaft? In our cars the propshaft is splined where it enters the gearbox - although this is actually unnecessary as the diff is fixed to the same chassis as the gearbox. What about in the original Ford installations? Does the gearbox end of the propshaft terminate in a spline or a flange? Someone has suggested that the Escorts had a 2 piece propshaft with a central UJ bolted to an intermediate bearing. I wonder what difference our different configurations have and why... Link to comment Share on other sites More sharing options...
DougBaker Posted August 27, 2012 Share Posted August 27, 2012 I thought that the problem with the recent "Ford" diffs was that they were no longer filled with ford made internals. Tolerances not being quite so good meant some were a lot louder, next year will be the twentieth anniversary of the last new Sierra. Link to comment Share on other sites More sharing options...
mic Posted August 27, 2012 Share Posted August 27, 2012 The main problem is as already stated the cw and pinion are no longer genuine parts. When Ford made them the tolerances and finishing procedures were much better, but they were made in far larger quantities and Ford could reject the ones that were not right. I also think that the rebuilders of these diffs do not spend the time needed to build them as Ford intended. It is quite a lengthy job setting the depth of mesh and can not be done just fitting the shims that have been fitted previously. A few diffs do fail, lack of oil and faulty or old bolts seem to be the main cause. Link to comment Share on other sites More sharing options...
DJ. Posted August 27, 2012 Share Posted August 27, 2012 There's nothing wrong with Ford diffs. In some ways the design is superior to the new BMW diff, and they are definitely lighter. I wasn't happy with the backlash from my remanufactured diff and although it certainly wasn't the noisiest, it wasn't brilliant for a new car. Now I have a 1983 Ford diff in my 2011 seven! £65 off ebay, rebuilt by Road and Race, and it's great :) Incidently, there were a lot less metal particles in the old diff when I opened it up than there were in my new one after 500 miles- the oil was silver I know which one is going to give better long term service. Duncan Link to comment Share on other sites More sharing options...
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