Shifting issues and flushing

[Mike534x]

Brother that's *WILD*, those spectacles you surveyed all sound full of malaise. I congratulate you on not accepting tetanus frames, and effectively dismissing that crapola pre-emptively.

I know it was going to be hard finding one, but damn I didn't realize exactly how difficult it was going to be finding one in decent shape. Like, yeah the platform is old, and nothing is "perfect" but these people are absolutely nuts thinking they can list their junk in "good" shape/condition and expect top dollar for it. We're holding off on searching, letting time takes its course and see what pops up down the line. Its been an exhausting almost 1 month long venture.

Not a whole lot done with the Envoy since last update. Bought new Bosch wiper blades, got 3 years out of the other set which is great! Pricey, but worth it when they don't need to be swapped out every 6 months. The hard 1-2 shift is coming back. It cleared up for awhile, but I suspect now that the PCM/TCM have re-learned themselves it's settled back into that condition. Its more intermittent, like it'll be somewhat firm some days, and then once you're at 30-40% throttle its very firm. I'm terrible at describing it, but if you had the level 1 shift from the PCM tune it roughly hovers between a 1.5-2 on the firmness level.

I'm still certain the 1-2 accumulator housing and piston are in good shape, only thing I can think of that "could" be a potential culprit is the Sonnax Purple Accumulator Spring I installed prior to the Transgo kit. When I purchased everything for the install, Sonnax had the spring listed as being like the OE Green one. However, when squeezing them (the old green one) in hand the Sonnax felt much more firmer. So I my guess is the Sonnax is too firm on its own, and requires the inner smaller spring to provide the cushion (?) during the shift. So I ordered the AC Delco Green Outer, and Yellow Inner to install. If that still doesn't resolve it, I guess the issue lies somewhere in the valve body since this didn't happen until after the kit, or something is wrong with a component from the kit and this is the result. I'd drop the valve body myself, but I don't feel too confident messing with it this time around without additional hands/someone more familiar with the install/removal/inner workings of it.

Which leads into my next question, I know May03LT made a video a while back on how to do a "flush" on the transmission. I think it was a Tahoe, where he dumped 4 quarts with the truck running with the front cooler line disconnected and proceeded to do it in 4 quart and fill increments until the fluid came out clean. Is this still the preferred method? My fluid is still clean, and was clean prior to the install and when I go the truck. I'll need to recheck the service records, but it looks like the tranny had a normal pan/drop schedule. So if I'm dropping the pan, I might as well consider just getting the system replenished entirely with Dex VI maxlife fluid.

 

[Mooseman]

Moved this post to its own thread as it was an actual technical question and would benefit others.

 

[Mike534x]

Thanks @Mooseman got a bit carried away with the typing last night!

 

[6716]

I mean, presumably you could do a flush that way. Most of that method is how I have emptied the fluid and changed the filter. I ran the engine until the fluid quit kicking out, then dropped the pan and changed the filter, then bolted up the pan and refilled. It is a good way to use the built-in pump.

 

[Mooseman]

I usually just use the cooler line to drain it (like @6716 above) however, if it hasn't been serviced in a while, the fluid is dark or a new acquisition with unknown service, I do the flush using the line. Otherwise, it's just a pan drop and change.

 

[Mike534x]

I'm trying to remember everything off the top of my head. When I bought it in 2017, the carfax report was like 7 or 8 pages long. Every entry was reported by a Chevy Dealer in Indianapolis, and it was nothing but 3-4k oil changes, on top of whatever services the owner was paying extra for each time it was brought in. So I'm 99% sure it was very well maintained going off its history, and I'm almost certain I remember seeing and being surprised by a full tranny service being done exactly at 100k. There's an invoice in the owners manual from 2007 for a replacement windshield at Chevy with a odometer reading of 98 or 99k. So its full on high way miles this thing has.

When I bought it from the dealer, the fluid looked and smelled new. The tranny pan had some loose bolts after I couldn't figure out why it had a slight "slip" going around corners and noticed the garage floor being slightly wet. Tightened her up, and topped it off and she's been good since. Then a year later the first to second shift solenoid was acting up, and that's when I changed out the OEM pan for the Dorman one with the drain plug. The pan back then (late 2018) had mostly clean fluid, it was a little dirty but it still had an overall red color. Fast forward to changing out the accumulator in Summer of 2020 (a month before the trans go kit), and the fluid was still pretty darn clean with no dirty, or metal bits on the magnet.

I was mostly curious after watching how May03 did his, if there would be any downsides to doing it on mine at 213k with (as far as I know) a good service history, and knowing the fluid has been in normal/good condition for something that hasn't been abused. Since the fluid isn't being pressurized, or forced through the system, it doesn't seem like anything bad would happen by doing it by his method of dumping 4 quarts at a time while replenishing another 4 until it was nothing but clean red coming out the hose. I have no doubt in my mind that the old Dex lll (I'm assuming) still lingers internally deep downside inside it, and the benefits of running a HM Synthetic Dex VI could potentially add? It was just a thought I had for a while now. Since I'm going through the work of removing the Sonnax Spring from the accumulator housing, and putting the OEM ones back in. Or would it just be better to do a drain and fill every 5k and slowly introduce new fluid into the system rather then all at once, I assume by doing it this method it would eventually get maybe 70-80% of the old stuff out.

There was some time I spent reading through various old threads, and not too many of them had a follow up, or update to how things turned out after doing either method. So my goal is, aside from providing useful help in regards to how the types of springs used in the accumulator housing affect the shift, but any useful recent experience on doing the flush on a pretty high mileage unit could be of any use to someone.

 

[Mooseman]

Just for my own peace of mind, after swapping the springs, I'd do the flush. Can't hurt and only has the benefits of having 100% new fluid. However, the only caveat is that if your tranny is borderline to dying, this may hasten it as this would take the clutch material that's floating in the fluid out and make it less "grippy", allowing the clutches to slip more. If that happens, it was already on its way out and will force you to deal with it sooner rather than a little later, but would have happened eventually.

 

[Mike534x]

Fair point, I guess there really is no way of preventing the inevitable. I suppose seeing a stock original 4L60E survive past 200k is a feat on its own, I suppose if this was done at 130-150k it'd be a little safer I'd assume?

 

[Mooseman]

My 02's tranny survived to 320k KM (200k miles) and it was a hard mechanical failure, not the clutches (my guess is the sunshell). It was poorly maintained prior to me. Would it have survived longer if it was maintained? Probably not since it was a hard part that failed. You never know when it will go. You could have two identical trucks and one will fail while the other will not. There's no rhyme or reason sometimes to these failures. Sure, a flush earlier will help extend its life but it's the same as anything else if you maintain it.

I'd just flush and hope for the best.

 

[Ilikemy3s]

I have been thinking of flushing/replacing all of the fluid as well. (And his video was with and Envoy) I have 248k+ miles on the original trans. And it shifts fine. Every time I had a service to the trans done, it was with DecVI fluid. But then again it never really seemed fully bright red so I just though it just mixed with the old fluid. I am really contemplating doing the full fluid flush as I would love to get hte old gal to 300K miles.

 

[Mike534x]

I'd just flush and hope for the best.

I may do the ole pan/drop and fill method. After spending the last week debating about it, and with how my luck has been I don't want to tempt fate just yet. So with the abundance of Tranny Fluid Walmart provided, I think I'm going to do 3k drain and fill over the next few months. I think by doing it this way, I could work in the newer fluid with slowly replacing the older stuff and gradually get it cycled through most of the tranny. I'm not sure how effective it is though. Aside from that, the tranny still shits fine, aside from that 1-2 second hard shift that comes and goes. Its much more pronounced when the A/C is running, which also had me questioning if my half working fan clutch is adding enough power draw to cause it, otherwise its usually smooth/slightly firm without the A/C running.

I have been thinking of flushing/replacing all of the fluid as well. (And his video was with and Envoy) I have 248k+ miles on the original trans. And it shifts fine. Every time I had a service to the trans done, it was with DecVI fluid. But then again it never really seemed fully bright red so I just though it just mixed with the old fluid. I am really contemplating doing the full fluid flush as I would love to get hte old gal to 300K miles.

Damn! That's impressive. I'd love to see mine hit 250k before going for a rebuild, but I'm pretty sure mine is slowly making its way into the grave.

Shooting for dropping the pan this upcoming weekend, after a slight medical problem flared up I've been unable to walk or do much these last few days. So fluids are ready, the 1-2 Accumulator Springs arrived Tuesday, along with the WIX Deep Pan filter. To air on the side of caution, I was going to re-attempt using a Sonnax Pinless Accumulator but opted for a Transgo-OEM style piston. Its a bit thicker going off the RockAuto images compared to the AC Delco one. So between this, and the new springs I'm "hoping" I can get this sorted out.

One thing that crossed my mind, was GM introducing Adaptive Shifting in the early years that I believe carried over to this platform. I've seen mention of a Tech-ll being needed, but I've also seen conflicting information of just pulling the PCM/TCM fuses for an hour. Another guide I found mentioned switching the ignition to "ON" and pressing the gas pedal down for 10-15 seconds, after which you turn the ignition to off and turn off the ignition. Then you wait 1-2 minutes, start her up and drive it around normally without gunning the engine while letting it re-learn your driving habits. So I'm wondering if the sporadic 1-2 hard shift is a result of a messed up calibration of the TCMs old memory and how its all working with the Transgo parts.

 

[Mooseman]

That would be the shift adapts. That requires a Tech 2 or other high end scanner. HPTuners can also do it. Never heard of resetting it other ways, even disconnecting the battery.