Originally Posted by meccjoo,Jan 22 2008, 03:38 PM

ive actually found that if you slowly push the shifter into gear then the thump will either be minimized or you wont even feel it. i guess depending on how fast you engage the gear the more youll feel the thumk

Originally Posted by hoof,Jun 2 2003, 06:24 PM

I often get a thunk when I have the car in neutral while stopped with the clutch out, then depress the clutch and engage the gear.

The reason for this thunk has to do with how the gearbox is set up. The clutch has two parts to it, one is attached to the engine crankshaft, another goes into the gearbox. This second shaft can spin freely (when in neutral) or is "engaged" via gears to the rear wheels. However, when the clutch is engaged, this second shaft *must* spin at engine rpm or slip.

Thus, when you have the clutch out in neutral, this shaft/clutch half is spinning at idle rpm, because the engine is spinning it. When you push the clutch in, the clutch disengages, and the shaft is essentially free-wheeling. When you engage the gear, if the shaft is still spinning, the synchromeshes in the gearbox have to accelerate the shaft to wheel speed, which is zero when stopped. *That* is the thunk I was talking about in the first part of the post.

The "solution"? Wait a few seconds after pushing the clutch in before engaging the gear.

The way to check if this is the thunk is to drive your car. At a red light (or anytime after stopping), put the car in neutral and let the clutch out. Then push the clutch in, followed (within a second or two) by putting it in 1st. You should hear a "thunk". If this is the same sound thunk you're hearing, then there is no problem. If this is not, there may be something else going on (which might require a mechanic to look at).

Someone mentioned that this shaft piece weighs 18lbs. I'm not sure if that's the right number, but it is a fairly hefty piece of metal, if I recall it right.