goducks10 wrote:
TrevorL wrote:
no brake problems with my 2011 F-150.... i do have the transmission thud when i stop and take off... dealer says its not an issue but it drives me nuts..not loud but you can feel it...i need to buy a tuner to tweak the trans settings..
Oh the infamous 'bump'. Had that on my 2010 F150. Drove me nuts. Took it in to the dealer and they flashed the tyranny. Said drive it for a week or so. NO change. Took it in a second time. This time one of the tech guys rode with me. He said don't worry about it you have a warranty. In other words they don't have a fix and to just drive it till it breaks then they'll know what to fix.
There are 2 (relatively) new aspects to automatic transmission designs.
1.)
FULL fuel cutoff during coastdown periods in order to improve FE. Fuel flow is cut off completely and the tranny is sequentially downshifted to keep the engine turning over above stall speed. Once roadspeed is low enough that this cannot be sustained 2 things happen simultaneously, fuel flow is restored and the tranny is upshifted.
"Bumped from behind, or "slingshot" effect" results, you feel as if the brakes were just slightly released....They were...engine compression braking was suddenly, without any action on your part, lowered.
NOW...the tranny is downshifted into first ONLY after coming to a FULL STOP...BUMP!
2. WEAK torque converter... Since the lock-up clutch is always engaged whenever the A/F oxygen sensor is in control, cruise mode, EXCEPT for clutch functionality at low speeds or stopped, the new torque converters are less "robust".
So you now need/have "hill-hold" in order to stay motionless when stopped on an incline. Some designs only engage this mode if the driver applies "extra" brake pressure once stopped, others use the ABS sensors to detect "roll".
In any case "hill-hold" will automatically apply the brakes and then DBW will be used to delay the onset of engine torque when the driver says "go", in order to have the few milliseconds to release those brakes.
Acceleration "JERK"...
