4l60e Buzz Or Vibration Whens Shifting

chris_kucia · September 17, 2010

Have a 2000 Sierra Z71 4x4 extended cab with the 4l60e.

I did a mild rebuild of the trans last summer due to a broken sun shell. Replaced seals, bushings, etc. and a fractured 1-2 accumulator piston (replaced the plastic with an aluminum one). Also replaced the shift solenoids and TCC solenoid since I had it apart.

Been working great up until a few months ago.

When the trans is cold, I hear an odd sort of vibration during the 1-2 and 2-3 shifts. The 1-2 goes away pretty quickly, and the 2-3 noise takes longer, but will eventually stop occuring once warmed up. It's taking longer and longer for the noise to go away however, although that may be partially due to the weather cooling.

The sound is like a slow buzz or a fast vibration, almost like its about 50 cycles. Sort of the noise that is made by an alarm bell if you take the bell off.

The 1-2 noise doesn't seem to have any effect on shift quality, but the 2-3 seems to delay the shift for a second or two - as the shift starts, the noise starts and when the noise stops the shfit is completed. If I accelerate gently, the 1-2 goes away. On harder acceleration, the 2-3 takes even longer and the shift is more of a stumble. I try to take it easy on the acceleration until the noise goes away in the mornings.

If I shift manually, I don't get the 1-2, but I can get the 2-3 to occur, although it is much shorter in duration.

To me, it sounds like one or both of the shift solenoids is malfunctioning, but my (perhaps mistaken) understanding is that the solenoids should either be off or on and shouldn't be vibrating. I also considered that one of the sprags is making noise. Or maybe one of the valves bouncing. Would the PCS be a culprit?

I'm sort of baffled as to what it might be. I've been letting it warm up longer in the morning, but as the weather is turning, I expect this will be a larger problem when it takes longer to warm up in the winter, and I also don't want to do damage by letting it go.

It's about time for a fluid/filter change anyhow. I'm considering replacing the solenoids just to rule them out since that's an easy job.

Any other ideas?

No check engine light and fluid level looks good. Did some web searches and haven't been able to find anyone with similar symptoms.

Thanks in advance for any advice...

chris_kucia · September 17, 2010

I did a little research on the web today.

Far as I can tell, the shift solenoids are not cycled - they're either on or off.

The TCC and PC solenoids do cycle.

I can't see a reason the TCC would be activating during a shift, but it would seem the PCS would be cycling, or vibrating to regulate pressure to control the shift firmness.

That's looking like a likely culprit to me, but I'd like to hear some other opinions before I drop $100 on a presure control solenoid.

chris_kucia · September 24, 2010

Well, the PC solenoid is about $100 through most sources.

Mackco had a full solenoid and harness replacement set for $149 on sale so I got that and replaced all the solenoids and the harness.

Ticking sound is gone. I still think it was the PCS that was the culprit, but no real way to know for sure without a lot of extra work. I hate to just throw parts at a problem, but its' such a time-consuming PITA to get to the pan on a 4x4 that this was the quickest solution.

FWIW...

Doug_Scott · September 24, 2010

Well, the PC solenoid is about $100 through most sources.

Mackco had a full solenoid and harness replacement set for $149 on sale so I got that and replaced all the solenoids and the harness.

Ticking sound is gone. I still think it was the PCS that was the culprit, but no real way to know for sure without a lot of extra work. I hate to just throw parts at a problem, but its' such a time-consuming PITA to get to the pan on a 4x4 that this was the quickest solution.

FWIW...

I know what you mean by hating to throw parts at something, but, I tend to also look at the total cost as well. For the extra $50 you spent, do you think you saved yourself $50 in your time? And don't kid yourself, your time is not no charge. For me I would have done the same as you, it was not that much extra to potentially save you lots more.

chris_kucia · September 24, 2010

I know what you mean by hating to throw parts at something, but, I tend to also look at the total cost as well. For the extra $50 you spent, do you think you saved yourself $50 in your time? And don't kid yourself, your time is not no charge. For me I would have done the same as you, it was not that much extra to potentially save you lots more.

Yeah, Doug. That was part of my reasoning. If I guessed right, I'd have saved $50, but if wrong, I'd have to take it all apart again (time) and buy the next suspicious part (more money). With the deal on the parts, I narrowed it down to one teardown to replace all the electric components. Didn't make sense to go through the teardown multiple times to rule out the individual component, much as I wanted to. I knew that if replacing them all didn't do the trick (barring getting a bad part) then the problem had to be mechanical or outside the trans, and that would have been a whole different issue to troubleshoot, likely with far greater time to teardown.

But, I've learned so much from this forum that I was hoping (when I started) to identify the exact component, so I could save the next person some time and money. I guess I narrowed it down to one of seven components, with a pretty informed suspicion that it was probably the PCS, and possibly the TCCS.

Hopefully someone can use this in the future.

BTW, the company I've used (and I've used many times in the past) for parts is http://www.makcotransmissionparts.com/

Great prices, fast service, and they have just about anything you could possibly need in transmission components. Been using them for about 7 or 8 years now for several vehicles and am always satisfied with them.