Solved - Torque Converter Clutch Flutter

[Opeth]

I have the 3.42 and a deep pan as well. When I bought the kit, the tech note said the pan would have a step down. The shallow pan would be flat. I'm also 4x4...

James - what were the reasons behind leaving out the 2-4 servo springs? I'm just curious....

[Trail X]

I read somewhere on a forum discussion (a S-10 forum if I recall) that someone said not to touch the 2-4 with the shift kit.

Since it was not the reason I was going in there anyways, I figured I can always pop it out at another time, and heeded the warning of the random forum commenter guy. I would have honestly been happy just changing out the single isolator/converter valve, but figured I'd try to include as many other 'fixes' from the kit as I could. Who knows, maybe I'll go back in there and change the servo out sometime.

I have heard that swapping it straight for a corvette servo is a good modification too... maybe something to consider.

[fishsticks]

My issue turned out to be a loose U-joint strap (and a mangled cap as a result) on the rear diff yoke.


Still, this seems like a worthwhile mod to move forward with. Even with my tune, this trans has always felt mushy to me.

[Trail X]

If you really want to firm it up, there is an HD2 kit that includes more changes and allows for more customization. Mike (Dirty Anton) installed that one and would be able to provide some more insight into that kit.

[dvanbramer88]

My shifts have been firm for a while now, especially 1-2 with the truck cold. The other night, and twice yesterday the truck stalled because of the transmission. I have no codes. I took it to the local, very reputable transmission shop. The owner drove my truck around with the computer hooked up for about 40 minutes. (I was with him) Shifts were taking the normal .15 seconds' except 3-4. 3-4 was taking 6 seconds. I can feel a little shutter/bump as it drops into overdrive. My slop in the torque converter was -4rpms. Almost 100% lockup. The guy said the older 4L60e's didn't have slop built in, but the new ones did. So he says from the info from the computer that my clutch packs and TC are fine, especially because they aren't slipping. He says the balls on the check valve's wore out the plate (Like yours, and very common with our trans) causing the slop/hang up while shifting. He also expects to find a broken spring or valve that started causing the truck to stall when cold. He is selling me the Transgo shift kit for $80 and $200 labor (includes fluid and filter) He said that he may decide to change 2 $30 parts (pumps or something) while he's in there, which may also be causing the periodical stall. No extra labor. I brought up a tans temp gauge and he even offered to weld a bung in the pan for free. Does his diagnostics sound about right to you? I know you're not an expert.

[DirtyBacon04]

your symptoms are sounding like mine. Minus the cold stalls, but the long shifts from 3-4...

[DirtyBacon04]

did he happen to mention what year of 4L60e's became "older" vs "newer"?

[Trail X]

My shifts have been firm for a while now, especially 1-2 with the truck cold. The other night, and twice yesterday the truck stalled because of the transmission. I have no codes. I took it to the local, very reputable transmission shop. The owner drove my truck around with the computer hooked up for about 40 minutes. (I was with him) Shifts were taking the normal .15 seconds' except 3-4. 3-4 was taking 6 seconds. I can feel a little shutter/bump as it drops into overdrive. My slop in the torque converter was -4rpms. Almost 100% lockup. The guy said the older 4L60e's didn't have slop built in, but the new ones did. So he says from the info from the computer that my clutch packs and TC are fine, especially because they aren't slipping. He says the balls on the check valve's wore out the plate (Like yours, and very common with our trans) causing the slop/hang up while shifting. He also expects to find a broken spring or valve that started causing the truck to stall when cold. He is selling me the Transgo shift kit for $80 and $200 labor (includes fluid and filter) He said that he may decide to change 2 $30 parts (pumps or something) while he's in there, which may also be causing the periodical stall. No extra labor. I brought up a tans temp gauge and he even offered to weld a bung in the pan for free. Does his diagnostics sound about right to you? I know you're not an expert.

How do you know the stall is being caused by the transmission?

By slop in the torque converter, I'm guessing he's talking about input vs output rpm sensor readings while locked up in 4th gear? Mine shows 1 rpm now when fully locked up in 4th, so I'm guessing that's what he was looking at.

I'm also guessing he was talking about changing out a relay valve or servo when he said he may change 2 parts.

I'm not familiar with stalls being caused by an auto transmission, but my only guess is that the TCC is trying to apply when not in 4th gear. I'm not sure what could cause that, not being too familiar with the trans fluid routes, but I'm guessing his logic is that a check valve is letting fluid bypass at the wrong time and engaging the TCC - which is essentially like letting out the clutch in a manual trans.

[dvanbramer88]

My shifts have been firm for a while now, especially 1-2 with the truck cold. The other night, and twice yesterday the truck stalled because of the transmission. I have no codes. I took it to the local, very reputable transmission shop. The owner drove my truck around with the computer hooked up for about 40 minutes. (I was with him) Shifts were taking the normal .15 seconds' except 3-4. 3-4 was taking 6 seconds. I can feel a little shutter/bump as it drops into overdrive. My slop in the torque converter was -4rpms. Almost 100% lockup. The guy said the older 4L60e's didn't have slop built in, but the new ones did. So he says from the info from the computer that my clutch packs and TC are fine, especially because they aren't slipping. He says the balls on the check valve's wore out the plate (Like yours, and very common with our trans) causing the slop/hang up while shifting. He also expects to find a broken spring or valve that started causing the truck to stall when cold. He is selling me the Transgo shift kit for $80 and $200 labor (includes fluid and filter) He said that he may decide to change 2 $30 parts (pumps or something) while he's in there, which may also be causing the periodical stall. No extra labor. I brought up a tans temp gauge and he even offered to weld a bung in the pan for free. Does his diagnostics sound about right to you? I know you're not an expert.

How do you know the stall is being caused by the transmission?

By slop in the torque converter, I'm guessing he's talking about input vs output rpm sensor readings while locked up in 4th gear? Mine shows 1 rpm now when fully locked up in 4th, so I'm guessing that's what he was looking at.

I'm also guessing he was talking about changing out a relay valve or servo when he said he may change 2 parts.

I'm not familiar with stalls being caused by an auto transmission, but my only guess is that the TCC is trying to apply when not in 4th gear. I'm not sure what could cause that, not being too familiar with the trans fluid routes, but I'm guessing his logic is that a check valve is letting fluid bypass at the wrong time and engaging the TCC - which is essentially like letting out the clutch in a manual trans.

Servos thats it! Yes, the difference between input/output rpm's. I'm right around 3-5. I'll elaborate on the stalls. They're usually when you stop and go to put it in reverse, shifting in reverse stalls it. It also stalled a few times while idling at a red light (i was cruising at about 50 before the red light and the down shifts were rough while slowing down) I'm guessing, yea the TCC is staying locked up or is hanging up going it and out causing the long shift. Also in regards to bacon, I don't feel the long shift, and I've read your symptoms. What mine does is while dropping into overdrive i feel a couple really soft shudders or bumps. Maybe early stages of flutter.

[Trail X]

Going from what your mechanic said in your earlier post - I don't think that your transmission isn't capable of TCC flutter. He said something about how the older 4L60Es don't have slop built in - seems to imply that the PWM mode of the transmission wasn't added until later? Just a guess as I do not know the history of these transmissions. Mike may know.

Either way, your description of the shudder doesn't really make much sense as early stages of flutter. Sounds purely like a shift issue to me... I would also guess that it is unrelated to the stalling.

I must ask - have you posted or searched on a site that specializes in K1500s? They may yield more pertinent information.

[bartonmd]

All '96+ TCC clutches are capable of PWM apply, and have a beefier "carbon" clutch than previous generations.

'96-'97 were a "soft apply" where it locked up 100%, but was applied more slowly using PWM.
'98+ are all the full-PWM, all the time, like ours.

Mike

[Trail X]

Ahh, well if it's soft apply, that COULD be valve flutter.

[bartonmd]

Ahh, well if it's soft apply, that COULD be valve flutter.

I agree.

[dvanbramer88]

He's almost certain that the shift kit will address my issues. And he did get it to stall for him. And no, i haven't posted on anther forum yet.

[15TCarter]

First off, You guys are amazing. After 3 years I finally am back. That's how long it took me to come up with the time, money, and will power to do my engine rebuild. That's a long story for another thread. After the rebuild was completed, I am still in the break in period and I get this symptom. My first thought is to drive my TB into a field and light it ablaze. I was told by some friends this was not a good idea. So I found this tread and I checked the xmsn fluid and it was low, I filled it up and the problem went away for the most part. I still get a hiccup from time to time. So now I plan on doing the shift kit. My question is, Is there a way to find out what kind of filter I have before I tear into the xmsn. Thank you guys again for being an amazing group of people to help solve TB problems. Today I plan to make my truck all pretty again and service her front diff. I fear with the winter coming in Kansas that I may want to have my 4WD ready for anything.

[Trail X]

As I understand it, all GMT360s shipped with the deep pan.

[15TCarter]

Awesome, thank you so much. Time to buy parts.

[v7guy]

I'm with James, I haven't seen one yet that didn't have the "big" pan.