: Knock when trying to shift into higher gear while rpm's are high



rumble86
06-30-11, 02:18 AM
I just recently bought a an 04 cts v with almost 60,000 miles on it. This is my first cadillac, and I'm not very familiar with its odds and ends. Whenever I push it hard and rev it up into the higher rpm range and shift, I get a strong knock as I shift into the gear. The problem doesn't happen when I don't rev it up, and it shifts smoothly. Any ideas on what it could be?

rand49er
06-30-11, 07:54 AM
Need more info. Is this "knock" coming from the motor itself? Do you feel or sense a vibration? From the motor? Do you get a vibration from the motor when you turn it off?

Skidmarcx
06-30-11, 08:40 AM
sound clip will help

Twitch
06-30-11, 09:23 AM
Randy's talking about your motor mounts. Common on the V.
You gun it and the torque tries to rotate the engine lifting it off the mount. Then you push in the clutch pedal/back off the throttle and the engine drops back down making a thud. If this is what's happening then you need new motor mounts.

Tony

GDPossehl
06-30-11, 09:31 AM
It's probably ALSO the rear differential bushing. It's soft and that torque will compress the front diff bushing (same effect as axle wrap) and when you clutch in to shift to 2nd the disconnected torque will quickly decompress that bushing and slam the axle back down which is the knock or banging noise you hear when shifting.

Creative steel makes 2 products to reduce this effect:
A polyurethane bushing and a "diff block" which goes above that bushing to further reduce movement.

I have the poly bushing and it reduced that bang and other clunkiness at low speeds by %50. Much better.