Transmission “banging” noise and jerk

[FoxRidgeOutdoors]

I took my truck in for the recalls and warranty needs, I brought up to the dealership the transmission concern. Per Ford technical department, what we are all experiencing is "normal" for these transmissions. See the attached doc from Ford.

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[alrashid2]

I'm going to do a Flood Ford 10 Year/ 100,000 Mile Powertrain warranty just to have some peace of mind with the tranny. I probably won't put on more than 9k miles a year, but even still that should get me to 90k miles...

 

[Lion77]

Once you shift into any drive gear, the hydraulic torque converter is engaged, meaning your coupling drive energy from the engine to the transmission via the fluid turbines. That's why in automatics, you can creep forward at idle, but then start to go uphill and the car will eventually slow down to a stop and seemingly sit there not moving.

Your essentially slipping the transmission (in a non-harmful way) since it's coupled by fluid, unlike a manual that is either locked in or not. The jolt or bump you feel when shifting gears is because instead of being in neutral, where the torque converter turbine is just free spinning the input shaft to transmission, your now suddenly putting torque on the input shaft and all the drive train slack gets taken up.

My RR "jolts" and clunks every time I shift from N or P to D or to R. Even my little Mazda 3 has a tiny "jolt" or "clunk, but it's much more subtle since it's a FWD transmission with a lower powered 2.5L 4-cylinder engine that doesn't have a lot of low-end torque and the gearing isn't particularly stout (low) since it's geared for sport and fuel economy.

The PCM tuning also plays a role, some mfg's work to reduce engine torque output when shifting to give a "smoother feel" so you get less of "jolt or clunk" from shifting, while others like Ford, seem to not think it's worth the effort since it has no effect on mechanical reliability.

My Raptor can give a pretty decent jolt and strangely enough, I actually like it because to me it says, "I'm built for hard use, not wimpy luxury, lets ride!".

Here's a really good illustration of how Hydraulic Torque converters work. Most US automatics use this overall design because it is the MOST RELIABLE transmission architecture (vs. Dual Clutch or CVT):

Torque Converter – How Does It Work? (3D Animation)

Once the vehicle is moving, the torque lock clutches will lock in, thus hard coupling the engine to the gearbox / drivetrain (that's what they mean by converter lock-up), so it's 1:1 instead of 2:1 or some in-between ratio where the converter allows endless slip via fluid shear.

But at low speeds, light throttle or just idle, the torque locks are not engaged but the transmission is hydraulically coupled to the engine output shaft via the turbines, so there is torque being transferred. That sudden clunk is when the gearing is engaged and your now feeling the torque from the engine through the converter, when then takes up all the gearing / drive shaft slack, often resulting in a bit of a clunk.

My manual mustang would also sometimes have drivetrain clunk when I pushed the clutch in from reverse or 1st gear to shift, because suddenly you engage or disengage the engine form the transmission while the drivetrain is under some tension / bind from moving the vehicle.

What your describing sounds PERFECTLY NORMAL unless it's a very severe lurch, such that you might actually tap the bumper of car in front of you, that case would not be normal.

BTW, I drove a Ram 2500 I rented from HomeDepot before I had my ranger to pick up a piano for my wife and it did the same thing, also a F-250. Pretty normal, obviously those trucks use much heavier duty transmissions.

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