Funny 4L60E sound question

[tksoldierx]

So when I first started driving my 95 K1500 when I was 15, one of the most fun things to do on-road was go to a particular stop sign in town that went straight onto the highway, so I could accelerate from stopped to highway speeds (and above ) without impeding traffic by stopping in the middle of the highway or speeding in the middle of town.

So, when absolutely flooring it at this spot with no restraint, the 95 would go up in RPMs in first gear, then like almost stall out for a few seconds (with the gas still floored) and then THUNK! very loudly into second and launch forward, with more acceleration than usual. It doesn’t do that any more, but it was crazy fun stuff for a 15 year old, probably part of what led to the demise of that 4L60E.

I was just wondering, is that a normal thing for these transmissions to be doing, or was that an early warning sign of that transmission having issues? And is there a technical term for the near-stalling-then-THUNK?

 

[NickTransmissions]

Were there any mods done to that transmission before its demise (shift kit, vette servo, etc)?

What you're describing happens when shift calibration isnt set up for intended use patterns and typical rpm regime. In short, the shift speed was too slow relative to acceleration...

 

[tksoldierx]

Were there any mods done to that transmission before its demise (shift kit, vette servo, etc)?

What you're describing happens when shift calibration isnt set up for intended use patterns and typical rpm regime. In short, the shift speed was too slow relative to acceleration...

It may have had a shift kit installed. I recall my dad saying once, while it was still just the farm truck, that the transmission was “heavy duty”. The transmission was definitely a 4L60E when I pulled it out, which matches the RPO codes said it should be. And a stock 4L60E is not what I would call heavy duty lol. So it could have been modified. My dad doesn’t remember any more what all he’s done to which vehicle, but that sounds like a likely culprit. Thank you for your input, and your username definitely makes you sound qualified by the way

 

[NickTransmissions]

It may have had a shift kit installed. I recall my dad saying once, while it was still just the farm truck, that the transmission was “heavy duty”. The transmission was definitely a 4L60E when I pulled it out, which matches the RPO codes said it should be. And a stock 4L60E is not what I would call heavy duty lol. So it could have been modified. My dad doesn’t remember any more what all he’s done to which vehicle, but that sounds like a likely culprit. Thank you for your input, and your username definitely makes you sound qualified by the way

You're welcome...Yep, my user name makes me sound qualified, haha.

All kidding aside, my guess is either the band clearance was excessive and whomever installed shift kit did not adjust servo travel to take up the slop and/or the 1-2 shift was not properly calibrated. And you're correct - a stock 4L60E is not very heavy duty at all.

 

[Schurkey]

when absolutely flooring it at this spot with no restraint, the 95 would go up in RPMs in first gear, then like almost stall out for a few seconds (with the gas still floored) and then THUNK! very loudly into second and launch forward, with more acceleration than usual...

...I was just wondering, is that a normal thing for these transmissions to be doing, or was that an early warning sign of that transmission having issues? And is there a technical term for the near-stalling-then-THUNK?

Was this a "transmission" problem at all?

My first thought was low fuel pressure at high-load, high-rpm. A fuel-delivery issue, not a transmission issue.

So, to me, the technical term for this is "starving for fuel".

I have no idea how you'd test for this unless you can get it to have the same symptoms again. Maybe you remember changing the fuel filter or the fuel pump (or both) and then the problem went away. Or there was some other repair done--TPS, maybe--and then the problem went away.

If the only thing that changed was the transmission...I guess I'm wrong.

 

[NickTransmissions]

Was this a "transmission" problem at all?

My first thought was low fuel pressure at high-load, high-rpm. A fuel-delivery issue, not a transmission issue.

So, to me, the technical term for this is "starving for fuel".

I have no idea how you'd test for this unless you can get it to have the same symptoms again. Maybe you remember changing the fuel filter or the fuel pump (or both) and then the problem went away. Or there was some other repair done--TPS, maybe--and then the problem went away.

If the only thing that changed was the transmission...I guess I'm wrong.

I interpreted his mentioning of "stalling out" as having to do with the converter achieving fluid coupling which is almost certainly not what he was trying to say as i read it again in retrospect, lol.

So yes it may have been a fuel starvation problem which would have had consequences for the 1-2 shift characteristics. But he mentions it not happening anymore so who knows...

 

[tksoldierx]

I interpreted his mentioning of "stalling out" as having to do with the converter achieving fluid coupling which is almost certainly not what he was trying to say as i read it again in retrospect, lol.

So yes it may have been a fuel starvation problem which would have had consequences for the 1-2 shift characteristics. But he mentions it not happening anymore so who knows...

I hardly knew how a transmission worked or what the numbers on the tachometer meant when I was 15, so I guess what I wrote was an interpretation of my memories with my present knowledge filling some in. I don’t know what happened with the RPMs because I didn’t pay attention to that stuff back then, but this is what I remember observing without filling in:

Flooring the gas pedal, exhaust sound gets louder and higher pitched until it sounds a bit louder than it normally does when it shifts, then it gets very quiet for about a second and a half and I lurch forward in my seat a bit as acceleration slows, then the THUNK and it starts accelerating again, I get pushed back into the seat and it gets very loud again

 

[NickTransmissions]

I hardly knew how a transmission worked or what the numbers on the tachometer meant when I was 15, so I guess what I wrote was an interpretation of my memories with my present knowledge filling some in. I don’t know what happened with the RPMs because I didn’t pay attention to that stuff back then, but this is what I remember observing without filling in:

Flooring the gas pedal, exhaust sound gets louder and higher pitched until it sounds a bit louder than it normally does when it shifts, then it gets very quiet for about a second and a half and I lurch forward in my seat a bit as acceleration slows, then the THUNK and it starts accelerating again, I get pushed back into the seat and it gets very loud again

Sorry man, that wasnt a dig at you but at me...i always have transmissions on the brain so potential a fuel stavation issue never even crossed my mind...

 

[tksoldierx]

Sorry man, that wasnt a dig at you but at me...i always have transmissions on the brain so potential a fuel stavation issue never even crossed my mind...

Oh yeah no offense taken, I was just expressing that I also had a bias toward it being a transmission thing and trying to clear up any RPM confusion I may have caused