SL55/63/65/R230 AMG: Will the SL55 be equipped with 7 speed transmission?
09-21-2004, 11:57 PM
#2
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I'd be surprised if the SL55 will be because it's likely to be dropped in the next couple of years as Mercedes moves away from supercharging. Any visual make-over a la SLK would most probably be accompanied by a new model line up.
It's not clear to me what the benefit of 7 speeds is anyway, maybe an increase in fuel economy but giving the electronics 7 speeds to choose from instead of 5 just makes for more room for confusion and inappropriate choices as it tries to second-guess your driving style. With a broad torque curve, where's the beef?
Consider also reliability. The SL55 uses a gearbox called a 722.6 which was first introduced in 95/96 - the 5 speed electronic box with the W/S switch. My SL600 had one of the early ones and, as readers of the R129 forum may know, it failed big-time earlier in the year at a Mercedes replacement cost of $9000. The 722.6 box was heavily revised in 98/99 to strengthen it and without those modifications, the SL55 would shred it to bits. My use of the early box (SL600, V12, me driving) obviously was too much for the unmodified version and the carnage wrought by the V12 when bits collided which should not have done had to be seen to believed. In the finish, I had it rebuilt with current level parts, especially the main input shaft roller bearing, replacing a bronze bushing which had disintegrated leaving the positioning of the shaft somewhat, how should I say, approximate?
So, when people talk about a gearbox being torque limited, I'm more than ready to believe them and the current 7 speed is just that - it cannot handle the V8 Kompressor of V12 bi-turbo's torque.
It's not clear to me what the benefit of 7 speeds is anyway, maybe an increase in fuel economy but giving the electronics 7 speeds to choose from instead of 5 just makes for more room for confusion and inappropriate choices as it tries to second-guess your driving style. With a broad torque curve, where's the beef?
Consider also reliability. The SL55 uses a gearbox called a 722.6 which was first introduced in 95/96 - the 5 speed electronic box with the W/S switch. My SL600 had one of the early ones and, as readers of the R129 forum may know, it failed big-time earlier in the year at a Mercedes replacement cost of $9000. The 722.6 box was heavily revised in 98/99 to strengthen it and without those modifications, the SL55 would shred it to bits. My use of the early box (SL600, V12, me driving) obviously was too much for the unmodified version and the carnage wrought by the V12 when bits collided which should not have done had to be seen to believed. In the finish, I had it rebuilt with current level parts, especially the main input shaft roller bearing, replacing a bronze bushing which had disintegrated leaving the positioning of the shaft somewhat, how should I say, approximate?
So, when people talk about a gearbox being torque limited, I'm more than ready to believe them and the current 7 speed is just that - it cannot handle the V8 Kompressor of V12 bi-turbo's torque.
09-22-2004, 04:23 AM
#3
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Mercedes-Benz A170 CDI
BlueSL, so sorry to hear about your transmission failure. I hope it was under extended warranty? I had first gear melt out on my A170 CDI, they replaced the first gear and control logic, it now shifts smoother, and there is none of that jerky engine braking effect.
Anyways, 7 speeds are much more beneficial to any type of engine. Just as 8 speeds, even more so. Whether an engine puts out 1000NM or 500NM of torque, quicker final ratio gearing and 7 speeds to choose from, will greatly aid acceleration. Just look at the M5, if it had 6 speeds, it wouldn't have beaten the E55 with its superior torque. But because Mercedes was/is limited to using a 5 speed box, they have to rely on the torque of the engine to gain acceleration, this results in longer gearing. Longer gearing means the engine makes do with 700NM to propel the car forward, because it takes longer to get to the engines power band (6100rpm for the 55K).
7G Tronic will debut along with the release of the 6.3 N/A V8 with some 500bhp and 600NM. With a very short 2nd gear, it should make acceleration equal to or better than the 55K, due to less torque aiding traction. However 600NM is still a lot of torque. But as for the original answer to the question, the SL63 will debut late next year, with a 7 speed AMG Speedshift box.
Anyways, 7 speeds are much more beneficial to any type of engine. Just as 8 speeds, even more so. Whether an engine puts out 1000NM or 500NM of torque, quicker final ratio gearing and 7 speeds to choose from, will greatly aid acceleration. Just look at the M5, if it had 6 speeds, it wouldn't have beaten the E55 with its superior torque. But because Mercedes was/is limited to using a 5 speed box, they have to rely on the torque of the engine to gain acceleration, this results in longer gearing. Longer gearing means the engine makes do with 700NM to propel the car forward, because it takes longer to get to the engines power band (6100rpm for the 55K).
7G Tronic will debut along with the release of the 6.3 N/A V8 with some 500bhp and 600NM. With a very short 2nd gear, it should make acceleration equal to or better than the 55K, due to less torque aiding traction. However 600NM is still a lot of torque. But as for the original answer to the question, the SL63 will debut late next year, with a 7 speed AMG Speedshift box.
09-22-2004, 10:51 PM
#4
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7g
What's the future look like for the V12 and the 7G?? In particular the AMG version's timetable along wqith long overdue 4 valve heads and direct injection.
TIA
MAP
TIA
MAP
09-25-2004, 06:52 PM
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Mercedes-Benz A170 CDI
Mike, I have no concrete information regarding the future of AMG engines. However, numerous magazine sources have commented that the 65 engine will stay for the top AMG models, just as the 5.5 V12 for the future 600 cars. I have also read rumours of 700bhp for future 65 cars, but don't believe everything you read. 4 valve heads, could make massive change to the output of the 65 engine. But pushing 700bhp will be ludicrous-ly enjoyable 
I think the 7 G Tronic could possibly be upgraded heavily to match the torque output of the 65 engine. But with so much torque, and such short 1st and 2nd gears, getting 0-60mph will be near impossible without blazing your tires. But once on the move a 65 -engined car, putting out close to 700bhp equipped with 7 gears will make for near SLR performance. But that may be just wishful thinking at this stage.
I think the 7 G Tronic could possibly be upgraded heavily to match the torque output of the 65 engine. But with so much torque, and such short 1st and 2nd gears, getting 0-60mph will be near impossible without blazing your tires. But once on the move a 65 -engined car, putting out close to 700bhp equipped with 7 gears will make for near SLR performance. But that may be just wishful thinking at this stage.
