1999 Suburban 4l60E 2-3 flare with a twist

[android]

So, long and short of it is, it had been flaring 2-3 shift for about a week on medium throttle only. I had put some seafoam trans tune in it in case it was something dirty in the valve body. That helped a lot, it pretty much completely went away. About a week later I pulled out and gave it the wood and had 1-2 only. I got to the top of the hill and it did 3-4 shift as one VERY lazy slip of a shift and went to lock up. For the next two big hills it went from lock up to 2nd at 50 and skipped 3-4 completely. Truck has 206k on it and I am like the 3rd owner (one of those good deals from a buddy...right) I went ahead and did a pan service, fluid and filter, seeing as I pretty much figured it cant get any worse, push come to shove I'll rebuild it. I put a whole bottle of Lucas stop slip in and then new atf. Well then it really had its tongue hanging out 1st was good, had most of 2nd then slip, 3rd slipped, 4th slipped, no lock up. As I drove it it got somewhat better, 1-2 shift was good, 2nd slipped half way, 3 and 4 were unusable and it sometimes had lock up. Here is the twist in the whole deal I could how ever shift it manually and like magic, NO slipping just lazy shifts. I drove it like that for about and hour, forgot and put it in drive and BAM everything is fine. No more slipping no lazy shifts, floor it and the shifts are there and quick and crisp. Only thing is it has a very occasional 2-3 flare still. I know this is super long but does anyone have any input on this whole deal, and should I still get it rebuild or just ride it till it goes out for good? I did take some pictures if anyone wants to see, ill post them.

 

[rhino]

It sure sounds like you don't have long at all. I would be planning a rebuild on that one pretty soon. Although, I have seen some strange things like a 2/3 shift valve hang ever so often causing a no 2/3 shift. It is rare however. Another common problem is the servo release ball sticking. It won't exhaust band pressure and holds 2nd. You can however hit 4th going downhill at 65mph for a quick test lol.

 

[android]

Yeah, I went and talked with a good local re builder, they want 2200 and give a 3 year unlimited mileage warranty. I asked him how long I had, his response was "it could go today, tomorrow, next week, or next year, just ride it till it quits and come see us" . It is acting fine for now, so I'm just being easy on it even goes down the highway at 70 just fine....there magic boxes that run on fluid in my opinion haha.

 

[Spack9]

You may have gotten lucky. Last time I seafoamed a transmission it went 20 miles later. Sometimes a marginal trans if left better uncleaned if the fluid looks decent. My 96 K1500 as had a clunky shift between 2-3 under light load for months. Went away while towing 4500lbs then came back soon as the trailer was disconnected. il let the magic box do its thing lol.

 

[Supercharged111]

Sounds fun. Don't venture too far from home.