Rattie

Nice work Andrew. I've just ordered the kit and LED. I made myself a similar unit to decode the PWM to the fog light telltale on the R3/4/500 Savage button dash and synthesize a brighter one when the fog light is on. But since you've gone to the trouble for us on the fuel gauge I'm happy to defer this time Martyn

Hi James Just a quick note to say I copied your homework and did the same mod to our SV which as also on a Powerflex centre and was slopping and clunking. I used the NMB bearing and turned aluminium for the cups, then turned down the Powerflex centre to 17.5mm My puny Axminster SIEG had to be nannied with that centre tube! My quick road test proved satisfactory. None of the unpleasant twitching or knocking and no movement of the cups. I used the same interference dimension, so hopefully Bedford GT next month won't unsettle it.

Quaife ATB now in and test driven. I had to overhaul the rear calipers, having spotted a seal weeping on one side while reinstalling the DD ears. Works great, nice and smooth. Looking forward to a trackday in the new year.

I had to drop the diff with the frame since it was an interference fit in the frame. No way would it have dropped out or gone back in without applying a significant spreading force on the sides of the frame. Since Geoff had no problem I'm guessing there's some batch variation. I did find it useful to open the slot in the handbrake adjuster tab, then also warp that a little to pop the cable out. I then had to warp it back straight once the cable was back in. The ATB works great by the way. I did it myself, but apparently Birds BMW will happily do the swap if needed.

Worth checking that the "carbon seats with padding" (620 style) will be the SV variant, as the S3 one will flap around in the cockpit. As far as I know there aren't any SV width variants of the race seats. IIRC, the 620 seat is a variant of the Tillett B6, where the SV gets less of the rolled edge trimmed off. This a) leaves less room in the cockpit for the seat to deflect and b) makes the seat stiffer, which also limits the deflection. £800 makes this a bargain option, since the seats are £2500 a pair from the parts shop, vs around £1300 for the GRP race seats, which are a less than ideal fit for the SV.

Yeah, I understand that is the received knowledge. It strikes me that it's more of a FWD danger, where you can lift a driven wheel under power. In RWD, the only way I can think of doing it is by taking a sausage kerb shortly after the apex, while putting the power down. Very much a racer specific scenario, fair enough. The other thing is, how would this be any different to on open diff? I'm assuming the damage is due to an airborne wheel spinning up to a crazy speed, then suddenly decelerating to ground speed as it lands. Am I missing a difference in this scenario between ATB and open? The reason I ask is I'm considering flipping the table and going back to ATB, since after 3000 miles (approx half on track) our BMW Titan is down to about 2lbft of preload, i.e. toast and I don't want to have to revisit the diff more than once. I didn't notice any trackday benefits of the plate LSD over the ATB we had in the original Sierra units, and I'm not a racer and don't intend to race this particular car ever. So please fill in my gaps if I'm missing something, I'm still not fully decided on my course of action, but I'm definitely erring n the side of a fit and forget option that I've had previous good experiences with.

Doctor, interesting you mention "the pain of Quaife ATB...". What was the pain point for you with that diff? I only ask, because I started out with a Sierra based ATB and apart from the CW&P mesh noise, I actually liked the behaviour of the ATB. Obviously it becomes an open diff if one wheel is free of the ground, but is there some other showstopper that you found?

Interesting, sprocket. Sounds like we could do with replacing the half shaft joints with some better examples. Our lash is terrible. The diff on the other hand is fine. It has the Titan clutch diff though, so different beast I guess

I had to do this too. The PDF and John's posts were very useful. It's not hard, but it does take a while. Check the routing of your silicone bead a few times before mating and don't be either too stingy or apply it like a brickie ;) Good luck

Out of interest, if you jack the rear, hold one of the UJ cups stationary against the diff body, what play do you get in the wheel? The reason I ask is that 23 degrees you are seeing at the propshaft flange would only be 6.3 degrees of play in the halfshaft UJs if the diff had no play at all. 23 / 3.64 (replace with your final drive ratio if different) Certainly ours have something like that and they dwarf any play in the rest of the system. Not saying yours do, but worth evaluating. I for one dislike the tripod joints because of this play and would prefer at least the inners to use Rzeppa CV joints, like actual BMW halfshafts

I say this every time this backlash thing crops up, but certainly on our R300D, with both the original Sierra and the current BMW diffs, we have had backlash significantly worse in the tripod-type universal joints than in the diff. You can check this by putting the car into gear, engine off, then watch from below, e.g. with a mirror on a stick as someone rolls the car back and forth. The play I'm talking about can be seen as the wheel side tripod cup (with the toothed speedo ring), rotating before the diff side cup moves. I find there's more rotation between these two than there is "inside" the diff (and indeed through the gearbox. Obviously YMMV

Tom, I suspect you've got a particularly thin casting. Definitely should talk to Caterham about it. Your videos show the issue very well. If I were you I'd avoid switching to the alloy boat anchor. It causes heat soak issues, particularly on trackdays. Not only does it pull air from behind the hot block, it also then adds soaked heat from the block for good measure. That and it weights a ton! If CC think it's normal, ask them if they are happy indemnifying you against the cost of an engine rebuild if it does fail and get eaten.

For reference, I do now have the response data. Yet again, Dave Kimberley at Demon Tweeks came through with the goods. If anyone needs it in the future, drop me a BM

Today, yes. I thought I'd also ask you guys as well, in case someone had already gone through the same process. M

Hi all, While replacing the cracked sump on our Duratec I took the opportunity to fit the ST764 oil temp sender and threaded blue plug that I've had for a while. I'd like to hook it up to my DL1 logger, but I never found a set of coefficients for its thermal response. Of course now it's fitted I'm going to have a bit of a problem characterising it myself. Does anyone have data for this range of senders? Ta Martyn