Clunking during shifting

[Howard]

2005 Cadillac CTS 2.8L 6MT

I find myself at a red light every now and then in neutral. Then when it's time to go, I shift into first and experience a fairly loud clunk when the shifter pops in. What's going on? Obviously while I'm shifting I'm not revving it (not like that should matter).

 

[exdeath]

Dual mass rubber flywheel? Diff mount bushings?

 

[Howard]

My mechanic checked over the engine and diff bushings and said they were all fine, including the giubo joints on the driveshaft. No idea what kind of flywheel I am using.

I don't think anything south of the transmission output is the culprit, since the clutch is not engaged and the car is not moving when this is happening.

 

[HybridSquirrel]

shifter bushings?

 

[exdeath]

Loud clunk implies that it's something being caused by engine power, since your hand isn't enough to bang the shifter that hard and you have control over how smoothly you operate the shifter.

If you can reproduce the problem while looking under the car, and the engine and drive train are not flopping around, it has to be internal. And if you feel and hear it in the front of the car for sure, it's not differential.

I suspect flywheel/clutch. Dual mass flywheel is a two piece unit connected by lots of rubber, so it can bind and wind up the rubber and clunk when power is engaged. GM considers this to be normal.

Also if it's anything like the T-56 in the V, the shifter isn't direct mount on the tail shaft, there is a extension bracket with cables and linkages; another place to look for something mechanically binding, slipping, and popping as the shifter is operated.

 

[bbs lm-r]

Maybe an unlikely possibility, but could it be a worn (or wearing) synchro blocker ring? If the threads on it are wearing it could take a (slightly?) longer time for it to grab its mating gear, match speeds and let you shift.

Spitballin here really :/

 

[overst33r]

3 of my cars have done something similar to this. I attributed it as normal operation. *wizardry*

 

[Howard]

I found out that the CTS-V of my generation has a 42 lb dual-mass flywheel. Wonder if it's the same as on my engine...

 

[KentState]

I thought that cluncking was pretty common in the first gen CTS. Could even be something like your rear diff bushings.

 

[Howard]

I thought that cluncking was pretty common in the first gen CTS. Could even be something like your rear diff bushings.

Not possible. Transmission is not in gear when it happens.

 

[KentState]

Ah, misread the post. Thought you meant in first gear and going, not the initial shift. I know the TR-6060 in mine is much more audible than past ones I've had. Does this happen when the car is off also?

 

[Howard]

Ah, misread the post. Thought you meant in first gear and going, not the initial shift. I know the TR-6060 in mine is much more audible than past ones I've had. Does this happen when the car is off also?

Never tried, good point.

 

[Howard]

Never tried, good point.

No, only when the engine is on.

 

[pauldun170]

Sorry about the issue but I do commend you on your purchasing decision.

 

[KIAman]

Does it only happen in 1st? Did you ever try to do the same but shift to 2nd from a stop?

 

[Howard]

Does it only happen in 1st? Did you ever try to do the same but shift to 2nd from a stop?

I only do that in the snow or ice, which means it's been too long for me to remember.

I'll try it soon.

 

[Howard]

Loud clunk implies that it's something being caused by engine power, since your hand isn't enough to bang the shifter that hard and you have control over how smoothly you operate the shifter.

If you can reproduce the problem while looking under the car, and the engine and drive train are not flopping around, it has to be internal. And if you feel and hear it in the front of the car for sure, it's not differential.

I suspect flywheel/clutch. Dual mass flywheel is a two piece unit connected by lots of rubber, so it can bind and wind up the rubber and clunk when power is engaged. GM considers this to be normal.

Also if it's anything like the T-56 in the V, the shifter isn't direct mount on the tail shaft, there is a extension bracket with cables and linkages; another place to look for something mechanically binding, slipping, and popping as the shifter is operated.

Really I can only think of the flywheel being the issue now. Would a new flywheel exhibit these symptoms or is mine broken somehow?

 

[RocksteadyDotNet]

Maybe clutch isn't all the way in.

Check your clutch fluid level.

 

[Gs dewd]

I am going to go a different route as I don't think it is the flywheel by what you said in your op. I am going to go with either a worn synchro or possibly a shift fork being wore. How many miles are on the car? Also why I say this is that you stated it makes the clunking while you are putting the shifter in first gear. You didn't say it was doing it in all gears or when you let the clutch out. Only going into first at a stop. If it was the flywheel it wouldn't matter what gear it was in. Whether it be first or reverse or so forth. To me it has to be tied to something with first gear hence the synchro or shift fork theory. Unless there is something I misread or you forgot to include in your op.

 

[Howard]

I am going to go a different route as I don't think it is the flywheel by what you said in your op. I am going to go with either a worn synchro or possibly a shift fork being wore. How many miles are on the car? Also why I say this is that you stated it makes the clunking while you are putting the shifter in first gear. You didn't say it was doing it in all gears or when you let the clutch out. Only going into first at a stop. If it was the flywheel it wouldn't matter what gear it was in. Whether it be first or reverse or so forth. To me it has to be tied to something with first gear hence the synchro or shift fork theory. Unless there is something I misread or you forgot to include in your op.

Good call. It definitely feels the strongest going into first from neutral.

 

[Gs dewd]

Now I take it that you don't hear/feel it going into any other gear especially reverse right? If it was a clutch issue like the clutch not disengaging all the way you would have a harder time going into reverse with more noise then first.

 

[exdeath]

Really I can only think of the flywheel being the issue now. Would a new flywheel exhibit these symptoms or is mine broken somehow?

Even if it's not broken, clunking during shifting is normal. It's a side effect of the rubber binding up as the dual masses accelerate at different rates. The only cure to that specific problem is switch out with standard flywheel/clutch assembly (Z06 alum flywheel and clutch is a popular mod). This affects any gear, particularly 1st to 2nd under hard acceleration.

You have a clunk just putting it into gear right? That sounds like a clutch adjustment problem possibly if it's really loud/hard and only occurs when the engine is running.

Does it do it when the engine is off or only while running?

Those cars user a remote shift linkage that provides plenty of opportunity for something to be loose. You might be able to remove the console and rubber boot and observe this assembly while shifting, and it will even make the noise louder and easier to locate.

If it still happens with the engine off and ONLY first gear, I'd start to suspect something internal like the first gear fork, slider, synchro, etc.


Edit: sorry my info is specific to the Vs, not sure how much is applicable to the V6.

 

[Howard]

Even if it's not broken, clunking during shifting is normal. It's a side effect of the rubber binding up as the dual masses accelerate at different rates. The only cure to that specific problem is switch out with standard flywheel/clutch assembly (Z06 alum flywheel and clutch is a popular mod).

You have a clunk just putting it into gear right? That sounds like a clutch adjustment problem possibly if it's really loud/hard and only occurs when the engine is running.

Does it do it when the engine is off or only while running?

Those cars user a remote shift linkage that provides plenty of opportunity for something to be loose.

If it happens with the engine off and ONLY first gear, I'd start to suspect something internal like the first gear fork, slider, synchro, etc.

Only when engine is on. The other gears MIGHT show a little of it but not enough to be significant.

 

[exdeath]

Only when engine is on. The other gears MIGHT show a little of it but not enough to be significant.

Can you hear the input shaft spin down completely when you press in the clutch?

If it only does it when the engine is running, and even the slightest hint of the same issue in other gears, that's a dead give away it has to be clutch related.

Can you feel this clunk more in the shifter handle or in the floor? Mounts are also a possibility if the clutch is grabbing/slipping with the clutch pedal to the floor.

 

[Gs dewd]

Now feeling it in all gears which I was under the impression it wasn't is a sign of a clutch not disengaging fully.