Buzzing during shifts when cold after tune?

[Bartonmd]

OK, so a question...

'07 5.3L 4x4 SWB TB with 97k on the clock.

I got a PCMforless tune a few months ago, got shift trim #2, and since then, any time it's below freezing, the first time I take off, during the 1-2, and the 2-3 shift, there's a buzzing sound like "weeeeeooo". It's lower pitch than a dry-pump whine. Usually only the first shift, but sometimes can be the second or third as well, if it's really cold. It also makes the noise through gears and shifting if I get in the gas when it's still cold on a sub-freezing morning. When it's above freezing, the first 1-2 of the day is a little harsh on light throttle, but when it's making the noise, the shift tends to be about like stock, or maybe just a touch faster.

I assume this is the over-pressure valve that doesn't like it wanting to shift harder than stock, when the fluid is cold, and is nothing to worry about, right? I suspect it only does it once because the computer sees the high pressure and backs off the shifts after that?

Thanks,
Mike

 

[Bartonmd]

I talked to Alvin, and he said it sounded, from what I was telling him, like the alternator overrun pulley. I'll try reving it in neutral to see if it does it there.

To be honest, I'm not convinced. The fact that it shifts slower when it makes the noise, and is completely silent when it shifts faster makes me go Also, the fact that if I'm hard in the throttle, it'll make the sound continuously in gear and during shifts, when it's cold. At that point, the clutch isn't overrunning, but maybe it's messed up and makes noise when pushed hard both ways?

Anyway, I'll check that one out, this evening.

Mike

 

[Bartonmd]

Well, that one's shot down. This vehicle doesn't have an overrun pulley on the alternator, and it doesn't make the noise in neutral.

Mike

 

[moneypit]

Hi Mike, our 02' TB ext has been making a whoosh sound at 1-2 or 2-3 shift point on cold morning too? which I only notice within first 2 miles with 2-3 stops. kinda like a spray being exhausted from a can?? shift points seem high too, up to 4k..!

 

[Bartonmd]

My shift points are fine, though.

I may put the stock tune back in and see if it still does it. The PCM4Less tune, I noticed, is almost brutal on the 1-2, and a little on the 2-3 in the summer, for the first couple shifts (but no noise) on a cold start.

Mike

 

[Bartonmd]

Had my Dad ride with me, and he said it sounded a lot like clutch chatter from slightly glazed clutches. He said it would probably last forever like that, because once they glaze, they don't wear, but who knows?

Anyway, I changed the fluid like another guy did when he had the same noise, and it went away completely.

Mike