Our noisy diffs

[The Pikey]

Not too sure about that Jeff.. All hatchback Sierra's has inch thick felt boot carpet and the saloon versions only had a thin carpet they did this for one reason, because the diffs were noisy which obviously sounded a whole lot worse in the hatchback ... I'm not saying the diffs caterham supply are set-up correctly because I know some are not but there's also something going on with a caterham that makes the noise sound a whole lot worse especially with the metric chassis. I found an as-new Sierra carpet when I build a 150 superlight about 3 years ago and cut it to suit the boot, this did make a difference but it was still not perfect. In fact the only perfect one I have heard is the one in my old imperial chassis and this was set-up by Phil at Road and Race.

 

Jason

 

 

[diggerman]

I don't beieve that ford produced noisy diffs. I don't think that the Caterham chassis, metric or not makes the diff sound worse than it is. I think that the QUAIFE diffs are not set up correctly and suffer mal-meshing and unecessary backlash.

 

My noisy diff after being rebuilt properly by Quaife is now all but silent, but still with some backlash, and thats in a metric chassis 150 SV sigma.

 

Lets not be fooled, Caterham DO have a diff problem and we are paying top dollor for sub standard goods. A Caterham with a good diff is a delight, with a noisy grinding diff, its an embarrasment!

 

Peter c

[Pete-B]

There's obviously hundreds of us out here who have bought new Caterhams and are letting this diff problem spoil our motoring. I personally have spent another £200 plus to get Phil at Road and Race to rebuild mine and whilst it's much much better it still clonks and whines a bit These cars, even if we build them ourselves are not cheap. We all know were going, to some extent, back to drive by wire but the basic mechanics should surely be solid and do the job they're intended to without all the clonking and whining. So instead of all this speculation of what CC's is, or is not doing about it, would it be too much to ask them, in view of all the queries to this problem, to post some sort of response on here.

 

Peter

[patneale]

Without doubt the Diff is the most unsatisfactory part of a Caterham. If is it really true that Caterham is going to fit a different make then so much the better. The old Ford unit is a very old 1980's design possibly older and modern computer designs have improved the gear angles and fit so they are much quieter in newly designed diffs. There is really no satisfactory answer to this problem as oils and rebuilds are only minor improvements to a steam age design. The only good thing is that they are generally reliable. I have now "done" 56,000 miles in two Caterhams and am now so familar with the dreadful clonks and other noises that lead you to often look in the rear view mirror to see if you am leaving bits and oil behind that I now hardly notice it ! The other night I thought that it was getting quieter, but fear I might be going deaf !!. An oil change seemed to help, but probably only in the mind. At least the oil is yellow coloured now instead of grey ( ground up bits of metal ? or it might have been Molyslip?)

[jeffi]

Having only driven my new build for two days now, I'm somewhat paranoid about the clonks and every time I return home I look underneath to check nothing is working loose!

 

Would some one kindly clarify the different idiosyncratic transmission noises I should expect to hear? In traffic when constantly pulling away or accelerating in 1st or 2nd then lifting off the gas to slow down, I usually get a clonk, but on the open road where I can accelerate quite hard all is well. Is the clonking the backlash? Does the prop make a slapping or clonking noise or is this purely the noise from within diff mechanism?

 

I get a droning noise on the open road when cruising along but it's not off-putting and I can still hold a conversation with the passenger. The higher pitched whining is currently very minimal. All noises are nicely drowned out by the engine and exhaust when flooring it, so I guess once it's run in the answer is high revs and foot to the floor!

 

 

[Stephen Long]

I can hear everything eccept my exhaust

 

[patneale]

Jeffi,

The noises are alarming for the newcomer to Caterhams. If you have torqued up everything correctly, especially the special bolts on the prop shaft you have nothing to worry about. Remember both the Diff and the gearboxes use very old Ford designs, when Fords were really Dagenham Dustbins.( Are they better today ? Thankfully never had a Ford) Gear angles and tolerences are by todays standards more suitable for machines made by Brunel than a modern car and there is of course no sound proofing and everything is mounted very rigidly... the bushes are very hard. The clonks are worrying to start with, but are usually only the backlash in the diff, If the clonk appears to be around the handbrake/gearlever, then check that you have mounted the back of the gearbox centrally in the mounting bracket. If not central then reverse torque could cause the gearbox tail to hit the inside of the tunnel. On the 6 speed box Top should be "silent" as it is direct drive I.E straight through gearbox not through the gears, as is 4th on the 5 speed box. My 6th speed has a fair amount of chuntering noises on the overrun which I have always reckoned was slack tolerences in the tailshaft bearing, but it is no worse now at 42,000 miles as it was new in 2003........ There is no sign whatever of any oil leaks on diff, gearbox or engine K series 1.8 at this mileage so in spite of the alarming noises all must be OK and certainly the box is a joy to use when warm. When the diff was fitted to Sierras it had massive rubber mountings and the back of the casing had an ear ( which on earlier Caterhams Kits, you had to saw off) which mounted in a huge block of rubber to try to quieten things down.

[jeffi]

I've popped the gal on axle stands and checked all the bolts for torque and they are all fine. No play in anything, or sign of rubbing. I'm sure the noise is from the diff and my initial worry was the shims, but I'm inclined to think it's all backlash related and within 'spec' - I'll get CC or an agent to give it a check at some point but it isn't getting any worse and it's not alarming. I'll hopefully be able to compare it to another in the Devon blats.

[Jason Plato]

I recently tried tightening up my diff by rotating the castelated bearing holders things up. the drivers side turns towards the rear of the car and the pax side turns towards the front of the car. I adjusted them 4 castellations each side and felt the backlash reduce by upwards of 80 percent .

 

I was amazed at the difference on the road - the noise and whine has reduced tremendously and is now realy sweet. I can actually hear the induction noise now

 

it's a huge improvement

 

 

 

dj

 

 

here is my Duratec R .... C7 TOP

Taffia AO

 

Edited by - Dave J on 5 Aug 2010 09:58:17

[billyboanerges]

Dave, how did you know what you were doing tightening the caste----ed nuts? Don't they just affect play in the bearings and not the mesh of the gears? I'm no expert - just the opposite, but surely most of the noise comes from the meshing or otherwise of the pinion?

 

Tony

[The Pikey]

Tony

 

turning one castelated nut in and the other out will move the crownwheel closer or further away from the pinion.

 

Jason

 

 

[billyboanerges]

Thanks - Don't get my newly built R/S 125 back from CC Mids 'til next week after IVA (passed) tax and plates etc. Lots to learn!

 

Tony

[Nev]

Dave J (or anyone else), can you tell me what size and type of socket you used to remove the locking plate on the castellated bearing carriers. This was something I've been looking at doing for sometime now, but never got around to it.

I have a bundle of backlash that has been there since new ( 1st diff sent back under warranty for the same issue, but did not bother again when replacement was only slightly better).

How easyily do the carriers move and did you need to remove the half shafts or leave them in ?

Thanks

Nev

[The Pikey]

Nev

 

you need to take the half shafts out and as well as a T50 (think) torx to remove the locking plate you will need one of these to turn the castilated nuts.

 

Jason

 

 

[Jason Plato]

its a torx head on the castelated retainer. I can recall the size but I can check when i get home

 

I simply removed the rear section of boot floor, whipped off the retainers and then tapped the castelations round with a soft drift and a light hammer. Everything stays in situ with the car on axle stands.

 

I felt the reduction in backlash as i moved the castleations by having the car jacked up and simply moving the rear wheels with the palm of my hand back and forth.

 

i am tempted to go back in there and do one more castleation turn, but I'll do 300 mile run this weekend and a trackday and I will see what the backlash is like when the diff is really hot rather than just 90c on the road.

 

dj

 

 

here is my Duratec R .... C7 TOP

Taffia AO

[Rattie]

Scorpio Diff Overhaul pdf might be of use...

 

Martyn

^_R300GRR

[Nev]

Thanks guys, guess I'll try tapping them around first ( equal amounts on each), if that won't work then I'll look to remove half shafts.

Have to get the T50 socket first.

Thanks again.

Nev

[Jason Plato]

T50 socket in Halfords

 

no need to remove driveshafts.

 

 

here is my Duratec R .... C7 TOP

Taffia AO

[Angus]

Dave

 

If reducing diff noise really is as simply as adjusting the castellated nuts then that has to be worth a try.

Can you clarify your post ref the castellated nuts:

the drivers side turns towards the rear of the car and the pax side turns towards the front of the car.

?

I think what you are saying is to turn both anti-clockwise ? Does that loosen them off or is it a reverse thread ?

 

So is the net effect of what you have done to allow more sideways float on the diff internals ? Rather than move the carrier unit from one side to the other ?

 

Or am I just being thick ?

 

Angus

 

 

[Jason Plato]

see the PDF on an earlier post. The adjustment in this manner moves the crownwheel in relation to the pinion.

 

out last night - its loverly, no snatching at 1500rpm at 25mph through traffic. No clunking on light gear changes. The whine is now only noticable in 4th gear (owing to the gearbox design). There is still some whine but its more than 80% reduced in my honest opinion.

 

Cant wait to do the 300mile blat this weekend

 

 

here is my Duratec R .... C7 TOP

Taffia AO

[Pete-B]

Am I being totally thick here, looking at the PDF file it shows turning both cast-d nuts towards the rear of the car

 

Peter

[patneale]

Dave J,

 

A a veteran Caterham owner in terms of miles......56,000 miles in 2 cars. the diff noise has always been an issue and the most unsatisfactory thing about the car. I had a replacement unit shortly after new and the replacement was little better. I reasoned with Caterham that turning the nuts would bring the pinion into tighter mesh with the crown wheel and cut down the backlash. They suggested that it was best to leave it well alone as too tight would cause excessive wear. I think you need to watch your diff very carefully and check the oil to see if it is going "grey" which will indicate that metal is being ground up by too tight clearances...... The basic design was a 1980's one when tolerances were very slack. Remember that most of the British car industry had very out of date machinery some as old as war time which could not produce very accurate parts. One of the Caterham engineers went as far as saying that you could not always guarantee that the depth of the teeth was the same all the way around the crown wheel ! Hopefully they are better made on more accurate machines now ,but the caveat remains, too quiet could mean too tight and excessive wear ! Which is why I have left mine well alone and changed the oil several times and added additives. If nothing else my present one has done 42,000 miles without failure!

[Jason Plato]

Patneal

Me too in my 90000 miles of sevening I too have been through quiet diffs and noisy diffs. My first diff in 1997 was a beauty then had the lsd changed and it was a whinney one , then I had the CWP ratio changed and it was a whinney one and a clunker - you absolutly right and I will monitor the wear.

 

However I do know that the well known company that installed and setup my diff did so by hand with no gauages and a simple question of - is this for raod or race and trackday use?. And for race and trackday use the diffs are set with more backlash simply felt by hand. This is in contradiction to the fact that the diff casing is ally and expands at a greater rate than the CWP etc and hence why the diffs are realy quiet for the first 5 miles of driving and then get progressivly more noisy and clunky.

 

If all else fails I've got another 3 diffs under my bench as spares I'm quite comfortable with the adjustments I have made and the orginal ford diffs I have under the bench do have a very similar level of backlash to what is now present in my car.

 

For me these little cars are all about playing and tweeking - they are not rocket science and its only a diff plus mistakes are usually easily rectified

 

 

here is my Duratec R .... C7 TOP

Taffia AO