Hello guys, has anyone an explanation for the following behaviour of my F355: When accelerating hard from standstill in first gear, the rev somewhat drops for a few seconds or so as it reaches around 6.500-7.000. I'm not lifting my foot, though. After that short drop, it revs up normally and reaches 8.500 smoothly for me to shift into 2nd gear. Any ideas? sorry for my poor english.
Isn't that the opposite of clutch slip? I thought when your clutch slips you stop gaining speed and your RPM's go up
Clutch has not grabbed all the way until the TQ fall off over 5500 RPMs. When TQ drops off, clutch <finally> locks up. Get ready for a new clutch.
Does this only happen in first gear? Is full throttle acceleration to red line in second gear normal? Is it throwing any codes? Long ago I had a Jag that did something like that. It turned out to be the fuel pump. It couldn't keep up with gas demand under full throttle as the revs got way up. Backing off a bit for a few seconds so it could catch up returned operation to normal. It was an electric pump that was just tired. Replacement fixed the problem. Just spit balling here so not sure if this fits your situation. If you have no codes to help diagnose the problem, you might try monitoring fuel pressure to see if it maintains normal pressure under full throttle demnds.
That is exactly what happened to my F355, then I continued driving for a while and the propeller shaft snapped. The car is under repairs, but I agree with the behavior being the opposite of clutch slip. I need to fix the shaft to find why it acctualy happened "Reverse" clutch slip could be a result of drop in torque, like intermitent failure of ignition, slowdown triggering or worse, something jamming in the gearbox. I would stop driving the car and try to find out if something wrong with the engine. Have a look in my thread, I posted a video. I believe it is the same issue you described. http://www.ferrarichat.com/forum/348-355-sponsored-bradan/518898-major-failure-f355-broken-prop-shaft.html#post144621782 Cheers, Fred
A possibility except that, in my experience with insufficient fuel supply, the revs would not drop in such a situation but just "freeze". I would agree with this theory (and the Lord said "When accelerating hard"). Possibly gear oil leak pass the triple seals ("wet clutch") or just worn clutch disc.
Thanks for your answers and suggestions. Yes, it only occurs in first gear. In all the other gears I can go till redline with no issues. No codes. And no, its not as bad as in your post with that broken shaft. I think it is most likely a clutch problem. Makes sense. Although I think if the cluch would slimply slip, the revs would go up, not down. I'll have the clutch checked and keep you updated. Thanks!
If you are at low rpm in 6th gear and try to accelerate does the clutch slip then? Or does it pull cleanly all the way? Usually clutches slip when you put a big load on them.
If you have a serious slip, the revs will rapidly go up but the speed of the car will not really follow. In the case of a small slip (like what you presumably have) the revs will not shoot up but will be somewhat higher than what they should be until a point when the clutch finally fully bites causing the revs to drop back somewhat. It's like when you are moving-off from standstill holding the revs at say 3000 rpm. As you release the clutch pedal, the revs will drop somewhat as the clutch engages.
The problem Lord described is with foot out of the clutch. Rev drop in that case is "reverse" clutch slipping as result of torque reduction, engine miss firing or something in the gearbox/differential package. It might be associated with a worn clutch, but the source of the problem is different and it need to be tackle before breaking the propeller shaft that turns the flywheel. See the video yourselves, it happened to me. I don't want this to happen with another F355 owner. This shaft is hard to get and eye-watering expensive. https://youtu.be/TybEAL2IZKI
