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I'm suggesting a rules change to make the minimum weight 2800 instead of 2650. The car is as light as anyone else's, but the fat *** behind the wheel ain't getting any lighter.
The article didn’t specify who, I made the assumption based on the context...three-time national champ who started in 2010 or something like that. So if that’s not him, I stand corrected and that’s what I get for assuming...
Before allowing a change that potentially could affect relative performance of the cars, I think we should consider steps that can be taken to extend the life of the existing equipment. Having raced in SPB since 2011, We have seen a lot of broken gearboxes. We were losing about 10% of the transmissions per event and getting tired of spending an evening at the track under a car, so a couple of years ago we started to pull them apart. There seem to be three main failure modes, listed roughly in order of frequency:
1. The aluminum shift shaft pins shear, sometimes after having previously partially backed out. Symptoms are difficulty in selecting gears, whether in motion or at a standstill. Solution is to replace the pins with steel pins (which were stock on very early '97 boxes), or at least to make sure the aluminum pins are properly torqued and to carry spares. I think more than a few gearboxes have been replaced or tossed that merely had broken shift shaft pins that could easily have been replaced at the track with the transmission in the car.
2. Third and, especially, fourth gear synchros wear, leading to 3/4 slider wear. Early symptoms are occasional difficulty selecting fourth or third gears. Middle symptoms are 'crunching' while shifting. Late symptoms are frequently being blocked out of gear. Solution is to replace the 3/4 synchros and, unless caught very early, the 3/4 slider. If left too long the dog teeth on the floating gears get rounded and the floating gear needs to be replaced. This alone used to cost close to a junkyard box, but might be worth replacing now (parts are available from Porsche).
3. Third or fourth gears shatter on 2/3 upshifts or when an unloaded rear tire suddenly gets fully loaded (such as when jumping a berm at full throttle or transitioning from Astro turf or grass to tarmac on throttle). Common wisdom is the hollow input shafts flex (note that this will also be a problem with any of the 5-speed Audi boxes; not sure about the 2.7 liter boxes). Solution is ??? Might make sense to scavenge unbroken parts, especially gears and sliders.
In addition to the above gearbox failures, it is worth noting that if the shifter cables stretch, the connectors at the shifter (or at the transmission if after market cables are used) need to be adjusted. Symptoms are gearbox popping out of gear or 'grinding' of 2 and 4 or 1, 3, 5 (but not odd and even). The 'grinding' is actually the slider hitting the dog teeth because it can't fully engage, not the gears themselves.
Also, the plastic piece at the front of stock shifters can break, leading to sloppy shifting/missed shifts. Solution is to inspect and replace shifter or use after market bushings.
We started rebuilding our transmissions a couple of years ago and recently pulled apart a couple of un-raced junkyard transmissions. Both had worn 3/4 synchros and, surprisingly, worn 3/4 sliders (especially 4th gear. Other unraced boxes have been pristine. I'm thinking it may make sense to replace 3/4 synchros and, where necessary, slider on 'new' junkyard boxes. This involves pulling the input shaft and pressing off and back on the fixed fifth gear and the 3/4 hub (20 ton harbor freight press and Kukko bearing puller). some other special tools help with bearing removal and installation. The output shaft doesn't need to be taken apart. Parts cost $200-$300. We haven't done enough of these to know whether they will last any longer than junkyard boxes, but they seem to shift better. One idea is to proactively do this service annually or every other year, under the theory that our time away from the track is cheap and at the track is priceless.
Here's the view Sunday in front of the Provost tent at Watkins Glen (TWO discarded SPB trannys)..
In 2018, there were NINE SPB gear box failures at COTA. (There were actually 10, because mine went belly-up on the first lap the following weekend).
COTA is particularly tough on the SPB boxes because of the FIVE 2nd-gear turns.
Before allowing a change that potentially could affect relative performance of the cars, I think we should consider steps that can be taken to extend the life of the existing equipment. Having raced in SPB since 2011, We have seen a lot of broken gearboxes. We were losing about 10% of the transmissions per event and getting tired of spending an evening at the track under a car, so a couple of years ago we started to pull them apart. There seem to be three main failure modes, listed roughly in order of frequency:
1. The aluminum shift shaft pins shear, sometimes after having previously partially backed out. Symptoms are difficulty in selecting gears, whether in motion or at a standstill. Solution is to replace the pins with steel pins (which were stock on very early '97 boxes), or at least to make sure the aluminum pins are properly torqued and to carry spares. I think more than a few gearboxes have been replaced or tossed that merely had broken shift shaft pins that could easily have been replaced at the track with the transmission in the car.
2. Third and, especially, fourth gear synchros wear, leading to 3/4 slider wear. Early symptoms are occasional difficulty selecting fourth or third gears. Middle symptoms are 'crunching' while shifting. Late symptoms are frequently being blocked out of gear. Solution is to replace the 3/4 synchros and, unless caught very early, the 3/4 slider. If left too long the dog teeth on the floating gears get rounded and the floating gear needs to be replaced. This alone used to cost close to a junkyard box, but might be worth replacing now (parts are available from Porsche).
3. Third or fourth gears shatter on 2/3 upshifts or when an unloaded rear tire suddenly gets fully loaded (such as when jumping a berm at full throttle or transitioning from Astro turf or grass to tarmac on throttle). Common wisdom is the hollow input shafts flex (note that this will also be a problem with any of the 5-speed Audi boxes; not sure about the 2.7 liter boxes). Solution is ??? Might make sense to scavenge unbroken parts, especially gears and sliders.
In addition to the above gearbox failures, it is worth noting that if the shifter cables stretch, the connectors at the shifter (or at the transmission if after market cables are used) need to be adjusted. Symptoms are gearbox popping out of gear or 'grinding' of 2 and 4 or 1, 3, 5 (but not odd and even). The 'grinding' is actually the slider hitting the dog teeth because it can't fully engage, not the gears themselves.
Also, the plastic piece at the front of stock shifters can break, leading to sloppy shifting/missed shifts. Solution is to inspect and replace shifter or use after market bushings.
We started rebuilding our transmissions a couple of years ago and recently pulled apart a couple of un-raced junkyard transmissions. Both had worn 3/4 synchros and, surprisingly, worn 3/4 sliders (especially 4th gear. Other unraced boxes have been pristine. I'm thinking it may make sense to replace 3/4 synchros and, where necessary, slider on 'new' junkyard boxes. This involves pulling the input shaft and pressing off and back on the fixed fifth gear and the 3/4 hub (20 ton harbor freight press and Kukko bearing puller). some other special tools help with bearing removal and installation. The output shaft doesn't need to be taken apart. Parts cost $200-$300. We haven't done enough of these to know whether they will last any longer than junkyard boxes, but they seem to shift better. One idea is to proactively do this service annually or every other year, under the theory that our time away from the track is cheap and at the track is priceless.
is there a list of what items in the box can or can not be changed out? you mention the steel pins replacing the alloy, anything else that one can change thats within regulation. ??
Servicing / rebuilding sounds compelling if it allows the net costs to stay more or less where they are for another 5-10 years. Get a spare box and send the broken one off for rebuild. (Keeps things the way they are)
If this is considered, the drop-in Audi boxes deserve serious thought as the costs are very low and the spares pool is very large. (Disposable approach)
Alternatively if the 2.7 trans or any other similar-cost drop-in trans will offer a big life improvement, it’s worth considering a move for reliability as the one time replacement (especially following a failure) would reduce total running costs after a few seasons. (Reliable approach)
If a new SPB box works well with an LSD, that could be a long term rules evolution. For better or worse!
I've driven against these G86/01 transmissions and, from my perspective, they offer no real advantage. We typically only use 5th gear at Daytona or COTA. And 4th gear has one extra tooth. Hardly a significant advantage.
I'm not a mechanic but I've owned both a 2.5 car and a 2.7 car and I think there's a bit more math involved than just the gear ratios. I could be wrong. The thing is that the 2.7 could be an advantage at a place like Daytona or WG but could also be a big disadvantage at Mid-Ohio or similar twisty track. At NJMP I run out of 4th on the front straight. The 2.7 box would save me a shift there. Maybe coming up out of the esses at WG I would be able to hold 4th longer and pass a guy who has to shift to 5th. At Summit I run out of 4th.
The bottom line is that we would no longer all be racing the same cars and that kinda screws the whole series philosophy out the window.
I don't have a good answer other than Walt et al approve replacement parts that are stronger or everyone has to install a 2.7 box.
In some ways this is a good problem to have. It means a whole bunch of us are racing SPB!!!
06-05-2019, 11:32 PM
