4R70W 2-3 Shift Delayed

[C420sailor]

'99 5.0L AWD, 4R70W, 120k miles. Trans looks original. Fluid is a little dirty, orange-ish, not burnt, proper level. No flashing OD light, no codes. Just bought it 500 miles ago.

Trans goes in and out of gears smoothly. Honestly, when the trans is cold, it shifts beautifully. As it warms up, the 1-2 and 3-4 shifts remain great, but 2-3 starts to get a little wonky.

If I baby the gas pedal and keep it below ~2200rpm, it'll shift to 3rd fine. If I step on it and rev above about 3000rpm, it'll shift to 3rd fine. With the RPM between ~2200 and ~3000, she'll stay in second for a whiiiiiiile. Doesn't drop out to neutral, just behaves like it would in '2'. If i bring the RPM down, she'll shift. If I bring the RPM up, she'll shift. Cold? Fine. But warm, with RPM between 2200 and 3000 in second? She's like "nah, I'll just stay here. It's nice here."

What do y'all suspect? Sticking 2-3 accumulator? Old fluid? I'm thinking about doing the J-Mod while I'm in there. If I'm going to change the fluid and filter, I may as well drop the valve body and take a look, I guess---I'd hate to do the fluid twice...Mercon V ain't cheap. Thanks, all.

 

[JK080]

The computer determines when the transmission shifts so the first question would be is the computer commanding the shift and the transmission is just not shifting or is the computer keeping it in 2nd and the transmission shifts when it commanded. If it's the latter then you dont have a transmission problem you have a control problem.

Hopefully you have a scanner that can display transmission data that would show the gear commanded or the on/off pattern of the two shift solenoids. Getting this info without a scanner can be a challenge but its essential in determining what is really happening.

 

[C420sailor]

I do not. My OBD scanner will pull transmission fault codes, but no data like that.

Can you recommend a good scanner for auto transmission live data like that?

 

[JK080]

We use high end scanners here and that's all I am use to using, these scanners would be too expensive for just personal use. So I don't know of any scanner that would be price appropriate for you. Maybe ask this question in the forum section that matches your vehicle, I would think that those people have all kinds of scanners and they may have first hand knowledge of it's capability's.

Or find your local transmission shop and let them check it, most will do that for free, we do.

 

[C420sailor]

Update:

Let the trucklet sit for a few weeks while I was out of town. Came back to a dead battery (expected this...it was old) so I replaced it with a new one and started it up. Same 2-3 shifting issue, but on my first 8 mile drive, she wouldn’t shift into 4th/OD. Flashing OD light. Code P0741, TCC solenoid. Cue the four letter words.

I started the trucklet up about an hour later, light was still flashing. Started driving...she shifted into 4th with no problem, good TC lockup. Light went away on its own. Shifting fine since.

Not sure if the battery swap threw it for a loop, or if the solenoid is sticking. I’ve got new accumulators and servos, fluid, VB gaskets, solenoids, and check balls ready to go in. Hopefully this helps.

 

[C420sailor]

Hoping for some quick advice. I need to have the trans back together by tonight.

Pulled an disassembled the valve body. Was going to J-mod it, but it has the truck VB—and I had read that sometimes the mod isn’t great on truck VBs. Left the stock plate, replaced the check balls and gaskets.

Anyway, someone must have already been in here because there wasn’t a 2-3 accumulator spring between the piston and cover. Hmm.

The mod specifies removing the 2-3 spring. Since it wasn’t there to begin with, I guess I’ll just leave it out? Also, there isn’t a spring above the accumulator, right?

Haven’t pulled the 1-2 accumulator yet. Should I remove that spring as well, if the 2-3 is out?

Any advice would be greatly appreciated.

 

[C420sailor]

Disregard. Got it all sorted out.

Ended up doing the following:

-Dropped valve body. Cleaned, replaced check balls. Didn’t drill separator plate per J-Mod. Reassembled with new gaskets.
-Replaced shift solenoid pack and TC lockup solenoid. Didn’t do EPC solenoid bc I was behind schedule and lazy.
-Replaced 1-2 and 2-3 accumulators. 2-3 already didn’t have a spring, and I removed the 1-2 spring in accordance with the J-Mod.
-Drilled a hole in the pan and welded a castle nut to the inside. Threaded in an old engine drain bolt. No leaks. New gasket and filter.
-Fresh fluid, obviously.

Truck drives and shifts GREAT. No codes, no delayed shifts, good TC lockup, no shudder. Perfection. Hopefully it stays this way!