Hi Ted
Pre ATB, the box had a standard Renault diff. These we know suffer when you wheel-spin a lot. What tends to happen is when wheelspinning, the planet gears within the diff spin extremely fast. They are of plain bearing design and the pins on which each are mounted then get very hot. Once hot, they risk siezing and the pins then break. Once broken, then you either lose drive (not too bad), or the pin (or part of) exits the large hole in the side of the diff and then either locks the rear wheels, or it then gets between the crown and pinion (ouch!!) - I know of 4 other competitors who sufferred this type of failure before changing to Quaife ATB.
Roy and I fitted I believe the first ATB to a UK competetive car (I think) but had not sufferred failure of the Renault type. (Gentle aren't we? /ubbthreads/images/graemlins/grin.gif)
Anyway, the differences have been described before but I will repeat our own observations again.
PRE ATB - the car was more difficult to launch well, especially if wet and the more power Roy provided, the worse it got.
POST ATB - the car can be launched with confidence, we often launched in second gear with the 347 motor and acceleration at Longleat Hill climb was logged at 0-60 3.7s and 0 to 100 at 7.6s. It was also noticed that the car would readily leave two, 12" wide black lines from a standing start if pressed hard. (checkout the 2004 Brighton Speed trials clip on our
Website Video Section )
PRE ATB - when driving round circuits it is always difficult to press hard, when cornering, a small amount of body roll + a little too much throttle would lead to the inside wheel spinning. This loss of traction also resulted in both a loss of lateral grip and a reduction of forward drive, which would tend to make the rear end suddenly step out and break-away with possibly fairly dramatic oversteer. Whilst it can be caught if you are quick, it never gave what i would describe a 'positve feel' and having additional power available just made matters worse.
POST ATB - Circuit driving is much fun, the car feels more stable, you can push hard through corners, knowing that if you start to lose traction, it is on both tyres and progressive. i.e. no sudden loss of lateral grip - which in turn leads to an ability to 'drift' the car around some of the faster corners. This was being done to reasonable effect at Lydden circuit when only Roys car was fitted with the ATB. As we double drive, and I ran out of class, the other drivers got a chance to view/video and whilst I was not aware it was happening to any great extent, you could clearly see the car drift first its rear then the front (slightly) through the fast right hande at the bottom of hairy hill (?). It also meant that if the car was understeering slightly, which it tended to do at the tight hairpin at the top of the hill, a bootful of right foot would loosen the rear in a more controlled manner allowing the front to tighten up on the corner. It is a lot more fun now, especially with more powerful engines.
Of the bunch of us in the UK that Sprint and Hillclimb - I think they ALL now have ATBs. I also recently fitted one to Club member Bjorn Arnils GTD40 (Also UN1) and he too is amazed at the difference. Again he has a fairly powerull car (400+BHP) and its road manners, especially when pulling off from junctions, or in the wet, are far less frantic than when the std diff was fitted.
So there you have it - 'A Totally Biased' opinion /ubbthreads/images/graemlins/grin.gif
Once last thing, the unit has been on Roys car now for at least 3 maybe four seasons (or is it five?) and it has been totally reliable. The one time we thought there was a problem, in fact there wasnt....
ps - we have a filter on the g-box and will be checking it after each event.
regards
