Alright Allison techies, flare for 1-2 and 2-3. Everything else golden

[fastline]

I'll get right to it. LMM 3500HD, 300k current miles. Bought with 225k, did filter but not fluid as it seemed perfect, likely not original. For years truck would sometimes flare (long time to shift, feels like slip, slight increase in rpm) at 1-2 and 2-3 only. This would only occur at medium throttle. WFO is fine, light throttle, fine. Towing is fine, no codes, no other concerns.

I have a PPE on lowest tune, used only for the "extras" those programmers have. It has ability to invoke the trans relearn. I did that and drove. Light throttle fine, but the first time I had to feed it about 1/4-1/3 throttle from a stop about 5miles after the relearn start, it flared in a BIG way at 1-2, 2-3. After that, all other shifts were perfect, and all subsequent 1-2,2-3 shifts were good. I'd like it more firm but feels mostly like all the others.

my concern, and probably valid, the relearn would reset to factory defaults that "should" be close, and they weren't. Probably indicating shifty solenoids, internal leaks, or at least something. The fluid is perfect level, good color, zero odor of clutches. Smelled by 3 of us. Dipstick did transfer a little black/gray deposit on paper towel. Not enough to alarm me.

Curious what the next steps are and if doing the fluid change "might" help it recover? Can I send fluid for analysis? Seems like it could help understand what might be happening. Or maybe I'm being a bitch and need to just drive it? It's not parked, but I'm paying attention and something is a bit off with those 2 shifts.

Oh, I might mention as this could be of issue with trans learning. I commonly use T/H when decelerating unloaded to get some down shifties and get a little engine braking. It ain't much but.....

 

[2004LB7]

Completely return to stock and see of the issue continues. Might need to drive it a bit to have the TCM relearn any power level changes

 

[fastline]

Completely return to stock and see of the issue continues. Might need to drive it a bit to have the TCM relearn any power level changes

Um, no chance I will reflash again unless critical. Lots of issues doing the flash and got ultra worried about bricking the ECM. That PPE handheld is born right out of the 90s. The truck certainly had some of this drama before flashing. Very certain it isn't related.

BUT, maybe possible the slightly higher power made it worse, and I don't really know if I did the TCM relearn. I was desperately trying to fix a plugged exhaust issue. That one was odd. Not even sure if common knowledge or not but I just went off experience as I was getting MAF codes and limp. My engine and turbo thanked me for that intervention and appendage removal.

 

[fastline]

You know, I should have been more clear. Programmed truck about 2Y ago. Not sure if I did a TCM relearn at that time. But the other day I plugged in the programmer purely to invoke the TCM relearn.

 

[gmduramax]

Time for a trans rebuild

 

[fastline]

Time for a trans rebuild

Or just leave it hooked to a gooseneck since it does that just fine?

 

[2004LB7]

Log the clutch slippage

 

[Ron Nielson]

The fluid is perfect level, good color, zero odor of clutches. Smelled by 3 of us. Dipstick did transfer a little black/gray deposit on paper towel

I wonder about this. If my dipstick showed this, I would investigate further. Maybe there is a reasonable explanation for this. Seems that one contradicts the other. J wonder if sticky valves/solenoids may be causing the problem.

 

[shakenfake]

Does it just fine but posting a thread online hmmmm

 

[shakenfake]

Idk what the hell I psoted I am drunk

I think what i meant to say is thatvit sounds lik it has annissue lol

 

[fastline]

I wonder about this. If my dipstick showed this, I would investigate further. Maybe there is a reasonable explanation for this. Seems that one contradicts the other. J wonder if sticky valves/solenoids may be causing the problem.

In my other professional experience, many steels can naturally become mildly magnetic, which can attract a few particles, as in the dipstick. I generally like to get even small samples in the sun to look for a glitter party.

I very much agree with thoughts on solenoids. I wish I knew these transmissions better, but having to go with a gut feel that I think most of the 'minor' concern is the 2-3, but if I can find a common link, like they share the same apply servo, that might be something.

All in all, I am generally trying to be proactive and if I am doing a fluid change, I am dropping the pan, changing the filter, and probably looking for cause to this shift issue. I will say that probably 95% of people would not even detect what I am feeling. I know it's slipping more than it should. One thing is for sure, the pump can still charge enough pressure to hold all gears without issue, which means clutches are good enough. I kind of wonder if this is more of a release issue where apply is fine, but release is dragging ass, causing the slip because fluid won't dump fast enough.

I sort wonder if the release side valving is a bit fouled. Possible fresh fluid alone could rinse it but I'd like to know more.

I drove it tonight and there was no "flare" as one might call it, where rpms actually increase. When in the throttle a bit, I just can't feel the shift on 2-3. I want to feel that slight bump. I'm the only driver on that truck, and lost count how many times I've felt that slight slip and purposely chopped throttle a bit out of instinct. I've seen others where something is up with the valving and totally kills the clutches. Taking a belly repair to a full tear down.

I'm a little more surprised that the TCM is tolerating it with no codes. Minor enough, even it doesn't care....lol If it lasts forever, you won't buy another.