BMW diff removal

[ScottR400D]

#48 yes, I think that's why 7W said 'a quick e mail to confirm'. I'd looked earlier and figured that that one is probably for a BMW diff anyway, if it fits at all. CC don't make it easy do they?

The RH driveshaft isn't the correct one either, there's another with the sensor ring on, which is presumably what I'd need.

A lot to be checked but it's getting me interested.

 

[ScottR400D]

#50 I think I'll have to find a friendly owner of a Sierra diffed car to see if it's any better than what I've got. I don't fancy spending £3/4K to no real advantage.

 

 

[John Vine]

If you're anywhere near West Dorset next week, you could get an idea from a little tour in my R400D with Ford diff.  I don't find it unduly noisy (the diff, that is), but then I wear industrial-grade ear protection!

JV

[7 wonders of the world]

a lot of the noisey Sierra final drives were supplied from a source that has since been found to have used the incorrect clearances.

If built correctly they  are quiet.

[ScottR400D]

Thanks for the offer John, a little far at the moment, I’m in Norfolk! 

7W. I have heard that before but thought that would apply to the BMW one too.

Presumably SPC know how to set them up? 

[7 wonders of the world]

Steve will build you a cracking final drive - he does like a chat though   

 

[Billy.Whizz]

I'm becoming a bit confused about how crap the LSD's are in the Caterhams, I'm about to order a new 420R and I must say all this talk of the shortcomings is starting to put me off going ahead. I can't understand how CC cannot get this right considering the high cost of these cars. Does anyone know what would be the best replacement diff and cost when the original one gives up being fit for purpose. Thanks,Bill.

[aerobod - near CYYC]

31,000km on my R400D Titan carbon plate LSD diff with no issues or excessive noise. Recent 3rd oil change (Redline 75w140) showed little wear material in the oil. The car has also done a couple of thousand of those km on slicks with enough lateral forces and wheelspin to tear out the deDion metalastic bush, so not used too gently.
 

[ScottR400D]

Hi James. 

The exception that proves the rule? My diff ran on MTL, from its first change at 1000miles and changed every 2 years. I never saw any debris in there though I was aware that the wheel rotation test was becoming inconsistent. 

Road use and 1 or 2 TDs each year on ZZRs and close to collapse after 8000 miles  

What power has your engine? Mine is 220/173ft lbs. 

I guess the only thing we know is that there is a lot of inconsistency about the whole question. 

 

[ScottR400D]

#57

It would appear that another diff, with LSD, drive and Propshafts would be about £3k plus the work to fit, which is easily enough DIY if you’ve already built the car. 

Less the proceeds from the parts replaced which might, or might not, be more consistent in a lower powered car. (I have no evidence to suggest that's the case and no idea what the market might be) 

I’m going to thoroughly investigate and consider it for when the car’s off the road over winter. 

[aerobod - near CYYC]

Hi Scott, did you actually use MTL in the diff? Redline MTL (the oil synonymous with MTL) is only 75W80 and GL4 instead of GL5 without friction modifier for the LSD. Highly suitable for the manual transmission, but not the diff (although I use MTL 85 which is 75W85 in my transmission at the moment).

My engine is the standard R400D plenum 210bhp with a custom ECU and map that makes it smoother and better revving than standard with a slightly higher 7,900RPM redline, but not measured on a rolling road for before and after power. Although I only normally get 3 TDs and about 5 auto-Xs  per year, each wheelspinning start to warm the slicks at an auto-x is fairly brutal on the diff, with my son and I driving each session includes about 12 starts like that. This year I have 7 TDs booked over the next 3 months, so I shall see how the diff holds up.

[ScottR400D]

James, no, that was a mistake! MTL in the 6 speed, RED LINE Synthetic Gear Oil 75W-90 GL5, in the diff. 

That was recommended to me by Opie, but I note that you are using 75W140?

Currently I have, since the rebuild, got RRT’s oil in it, I wonder if the 75w140 might quieten the chatter?

 

 

[ChrisC]

Billy, there is a lot of Caterham haters on this site, its always their fault that Ford stopped making the Sierra (27 years ago), not that the Ford diff was quiet.   When the BMW diff was released loads of owners converted due to noise.   

The fact is the diff in a BMW or Ford is much better insulated, in comparison to a 420R, and Caterham don't engineer their cars to trundle to the shop and back in silence.  Basically they don't consider the word "refinement" as part of the experience.  I have driven Caterhams for 11 years, with no diff problems.   I did have a suspected diff problem with my Sigma 150, which turn out to be a driveshaft spring. 

Also I see so many owners driving their cars without ear protection, this is such a stupid thing to do, your hearing can't be repaired.   Once you have decent hearing protection you find worrying about the diff noise is a thing of the past. 

[John Vine]

Once you have decent hearing protection you find worrying about the diff noise is a thing of the past. 

+1

JV

[ScottR400D]

That’s true for you Chris. There are plenty of stories of premature failure and noise in the BMW LSD in particular, my example’s not a one off. 

As for the noise my car is currently making, it’s a lot louder than it ever was which to me indicates an issue other than lack of refinement. 

I wear hearing aids in both ears, I don’t hear at all well without. In the 7 I don’t, of course, and I do wear ear plugs. The diff chatter is still heard clearly above all other noise. 

Are you suggesting that’s all OK?

[ChrisC]

Ok, but you have had your diff rebuilt by one of the countries specialists, and it's been given (now) a clean bill of health.  Based on that being true I would have to say it's something I would have to live with.  You can call it a characteristic of the car, based on the DeDion setup/design where the diff is secured to the chassis, in combination with an LSD that's not been design to be refined. 

If I had just had my diff rebuilt by the Phil, I would be happy to trust him, and be happy to live with the design of the car.    That said I have owned road cars with straight cut gearboxes, and stupidly lumpy cams, which made street driving noisy and challenging, but I have loved these cars far more than any refined tin top rubbish offered by main stream manufactures these days.

Obviously it's your car and your opions that matter, you can look for a quieter diff / diff design, but how quiet are you going to get it?   Have you seen or driven an equivalent spec car that's making you think its unacceptable?   If you have I would be checking every element of the cars spec to confirm, from the oil used to the diff internals used, age of the drive shafts, age of the mounting bushes, carrier design, backplate design, etc etc...   The quest for a quiet LSD is very long based on the post history of blatchat.

 

[ScottR400D]

I agree with all that, though I will try and get my recording on Dropbox so you can hear it. I’m still not convinced this is just normal noise. 

I’ve owned race cars in the past with straight cut Hewland and Sadev boxes so I know how noisy transmissions can be

I will arrange to listen to others, I haven’t done that yet, I’m comparing it with how it was. 

I appreciate the comments though and hope you’ll all have a listen and comment when I get the file up. 

.

[ChrisC]

In the past oil has been proven to play a big part in the noise, from my own experience of a BMW diff 360R (with a Titan LSD) the initial kit oil was used to fill the diff, but at 1000 miles I changed the oil to the Motul 75w140 (the blue stuff) and the diff became more noisy.   

I know you know the oil you have now, but did you know what it was originally filled with? 

[ScottR400D]

https://www.dropbox.com/sh/7xjo8hlsehrqpvb/AACr0K11dXqs4WIz80vHrLTda?dl=0

if I’ve done this right here is a link to the sound file I made. I’m accelerating up through the gears then I lift off. 

If it works I’d appreciate your comments. 

It seems to work if you copy and paste it. The noise is most noticeable between 25/35s and after 40 when I'm on the overrun.

[ScottR400D]

#68 Chris. It had the original Comma for 1000 miles then was changed to RED LINE Synthetic Gear Oil 75W-90 GL5 until the LSD failed. It has now had the RRT 75/90 put in.

[ScottR400D]

Another link, moving more slowly. 

https://www.dropbox.com/s/348zbzd3dahifou/34%20Market%20Place.m4a?dl=0

[John Vine]

Linky

Well, I could certainly hear that!

It's difficult to know whether that's normal or not, though, as I always use serious ear defenders when on the road.  However, on the occasions when I do drive the car without ear protection (boarding Eurotunnel trains, for example), it sounds pretty much like your soundtrack.

Have you asked Phil to listen in?

JV

 

 

[Shortshift]

Hmmm.  Interesting sounds (on overrun) around 1:13-1:17 and again around 1.40 and then again at the end of the recording (final link you sent through).  Clicking, as you said.  Took me a while to dial-in to them, given the other (totally normal) groans, whines and clunks!

James

[Shortshift]

And I also listened to the first recording you sent through.  Quite a heavy "grrrrr-ing' sound - whenever you're on overrun.  Certainly doesn't sound 'normal' to me.  I can understand your concern (and frustration).

James

[ScottR400D]

Thanks for listening. It is on overrun and is a very fast chatter, just like a CW and P would make. As I've said, I use to get a much less noisy similar sound on gentle lift off, it would stop under full lift off/engine braking. It's now louder and only on full lift off.