It looks like transman is the board transmission expert and a GM master, so I'm hoping he'll stop by though obviously I'm thrilled to get wisdom from all corners.

2000 Chevy Venture van, 3.4L; 4T65E transmission
130K on the van but only about 75K on the transmission as it was replaced at 55K under GM factory warranty. I don't know why (probably the same problem I have). I bought it at about 104K from the original owner. The new trans had a flush with 38K on it and I just did the pan and filter at about the 75K mark. (I posted a question about fluid in the trans servicing thread). The pan had what I think is typical black sludge in the bottom (but not a huge amount) and no metal.

Anyway, I have that thing going on with the transmission - that thing that seems to be really common with the 4t65e - which is that it will occasionally enter a bump shift mode with loud pump whine and a P1811 code being set. I can stop, shut the van off, start it back up and it then shifts normally. It is not all that predictable or reliable - e.g. its not a heat thing like it is for some others. It might be a stop and go thing, however. (I say its not heat though b/c I've had it start acting up when the van is not yet up to temperature). It is not common, but lately it has gotten to be more frequent.

The shop that read the codes wants to rebuild it. No surprise there. I do basically get the meaning of the P1811 - "max adapt long shift." Under normal circumstances it sets when too much slipping is detected and the PCM commands full line pressure to eliminate slip. Too much slipping comes from worn clutches - i.e. you need a rebuild. (I'm also not surprised that a shop wouldn't want to do more minor repairs on a higher mileage transmission).

The thing is that this trans only has 75K on it, it hasn't been abused, and most of the time it works well. Its whole life was spent in small suburban-style town/rural highway/interstate highway driving. The first owner was typical working soccer mom. We pretty much use it the same way. I refuse to believe that the clutches are gone. (I should have taken a picture of the pan).

I'm sure I'd be the most annoying kind of customer because I have now combed the web for info
about this issue. There is plenty of it, and I am not just going to rebuild the thing since there may be other less drastic solutions. (EPC solenoids, shift kits, aux. coolers...)

For now I'm just looking for a couple of things. One, are there common issues/remedies that produce this condition where a rebuild is not necessary? Second, how do I talk to a trans shop? I.e. they can scan it and read all sorts of things that are going on like the actual shift times and line pressures and commands to solenoids, etc. What scanning info would help me figure out the root cause of this intermittent 1811? (In my first conversation with the shop I mostly got out "humina humina humina"

If anyone has even read this far then I thank you - and I'd be grateful for any kind of input.

Edit: I should have mentioned that once the trans is fully warmed up, IMHO, the 1-2 (a little) and 2-3 (especially) shifts get "sloppy." I've had transmissions slip and shudder before and its not as drastic as that. I'd say that it sometimes likes to slide and flutter into gear. The shifts don't feel firm - I don't take that as a good sign.

I have to assume that this problem is so complex with so many variables that there is just no way to do "mechanic by internet." But I'm not coming back in with any more questions - more of a report in case anyone is interested. I posted in the midst of some "fact finding" and went ahead and acted. Pacecar has one of these vans and may find my experience worthwhile.

I don't even like this van very much so there is no way that I would go for a transmission rebuild. I was willing to try other things. The problem is very common with the 4T65E even at very low miles. There is a TSB that identifies a problem with the electronic pressure control solenoid (even though this has its own code - not the P1811, so I've wondered about that). The EPCS has to go in through the side case which means lowering the subframe which means it is not a minor repair - people seem to pay anything from $300 - 600 for it. But it very often doesn't really work. There are plenty of folks out there who have had several of these installed (seems like yearly maintenance for some). There are plenty of others who have had a rebuild only to have the same problem return before long. (Maybe bad rebuilders - I don't know, but right now I don't have anyone that I trust even if I wanted a rebuild).

There is also info out there that the #2 & #3 clutches basically just start out at next to nothing - so they reach dead quickly.

There is also info out there that the accumulator design in this transmission many not be so great - a design that erred on the side of softer shifts rather than longer lasting clutches.

Wrapped up in the mess somewhere is a relation of this problem to heat - maybe shorting out the EPC solenoid, maybe something else.

Anyway, there are quite a few reports online about people installing shift kits into the 1-2 & 2-3 shift accumulators. These basically stiffen up the accumulator and speed up the shifts. If you speed up the shifts, this should prevent the P1811. These accumulators are easily accessible through the pan so they are easy to install anytime the pan is dropped. Almost all of the installs come with a report of having no more shifting problems after that - who knows, maybe those who are unsuccessful just don't report.

Anyway, I picked up a Transgo shift kit - SK4T65E. This kit actually combined other upgrades (or whatever anyone would want to call them) and seems mostly intended to be installed during a rebuild. But it does include the parts for the 1-2 / 2-3 accumulator. (There are other kits specifically targeted only at those accumulators). The shift kit parts are basically a set of heavier duty springs and spacers for the accumulator pistons.

I put it in and refilled with Dex VI and 10oz. Lubeguard red (as I have frequently seen transmission people recommend it). The shifts are way better - not harder at all, just faster and actually smoother. I have now done over 2000 miles of all kinds of driving, much of it in very hot weather, and have not had a single hard shifting episode. Every once in a while the 2-3 shift will do something a little funky if the trans is hot - but apparently not funky enough to trip the code. I did buy an auxiliary cooler that I haven't installed yet and didn't use all of the Transgo springs - the original setup includes one large diameter spring under the piston. The kit has a much stiffer one plus two smaller nested springs inside. I kept the OEM larger spring & put in the smaller, nested ones from the kit. The next time I drop the pan I'll likely put in all Transgo springs.

Anyway, maybe I've just bought a little time. I don't know - but a) that's all I was hoping for anyway, and b) the van shifts beautifully now. I've seen some people call this a band-aid. I've actually come to believe that it is a sorely needed upgrade to solve a GM design problem.

Hope this helps someone out.

P.S. I should have mentioned that the shift kit cost me all of $50.