Knock on wood I think I have my shifting issues resolved. This is a relatively low mile trans(30k) that set unmaintained for I don’t how long. Years I’m assuming. It would shift through all of the gears and it wasn’t slipping, but the 1-2 shift was usually late and hard and the TC would shudder on occasion at slow speeds under light throttle. It would shift better with more throttle than less and it would drop into hard into D or R from P. Especially before it warmed up. About a year ago I replaced 12 qts of fluid by sucking it out of the fill hole and pouring and sucking again after a few miles driven and that helped a little. The car was down for a bit due to rear end woes so I didn’t drive it much for awhile. After getting the rear fixed I started driving it again and the transmission was still so so. Since it had all the gears and it wasn’t slipping I didn’t think there was anything mechanically wrong with it. I was betting that the root cause of the issue was “gunk” in orifices left behind from 24 year old broken down ATF. I rolled the dice and poured 16oz of Seafoam Transtune in, which is primary Naphtha, to try and clean the “gunk.” If I was needing a rebuild anyway, (which I doubted kinda) what’s there to lose? It worked almost immediately. After letting it idle for 15 or so minutes I put it into reverse and went into gear nice and easy. The shudder was all but gone and the shifts were sooner softer with each passing mile and shift. Seafoam says you can leave it in indefinitely (I didn’t intend to) but after about seventy miles it was what I’d call “85% good/normal” acting, but it wasn’t getting any better. I rolled the dice again on what I thought might be partially clogged causing what I was assuming to be a low pressure issue so I ordered a new EPC solenoid & manifold switch. I replaced them today along with the filter and I’m glad to say that so far it shifts like a “normal” transmission now. It got late on me so I only drove it long enough to get it thorough all the gears and up to 55’ish mph, but it hasn’t ran that well in the short little time that I’ve owned it. The magnet was pretty dirty. But the fluid didn’t look shiny to me really. The fluid wasn’t that old though it was still red. I got most of the original fluid out the first time I did the multiple suck and fills. The nozzle on the EPC didn’t look too dirty to me really but the screens or whatever they are on the manifold switch were black. I bet maybe that was causing the issues I don’t know. One thing for sure though is that the 16oz of Naphtha cleaned something that made a vast improvement. We’re talking night and day. It didn’t “fix” it 100% though. I’m thinking and hoping the new solenoid & switch brought it all the way home. I drained and replaced five quarts this time. I’m going to drive it a time or two and then I’m going to suck out what I can through the dipstick and then add some more fresh fluid. It’s usually pretty close to four quarts. I’m using Valvoline Maxlife fwiw. I should’ve bought a pan with a drain but I didn’t. So far no leaks though knock on wood. I’ll report back if any more issues should occur. If your transmission hasn’t been abused but it’s been sitting and it’s acting funny maybe try some Seafoam Transtune prior to a filter change. Naphtha the active ingredient, is mild and safe for plastics so it can’t be too “caustic.” It’s even sold in plastic containers where it’s used for other things. At any rate I think and hope I have mine shifting like a “new” car.

 

That's great news, hopefully when you get some more miles on it you will find that any lingering issues are totally gone.

 

I drove it about twenty miles today (10 each way) in a mix of hwy and city stoplights (mostly lights) and it ran great. I think it even idles a little n smoother but that might be in my head. This evening I sucked out a little over 3.5 qts of pseudo dark red fluid and I added 4 qts. I’m gonna call the fluid clean enough I do believe.
Y’all know the Seafoam Transtune that I used prior to changing the solenoid, switch, & filter? I was thinking about how Seafoam advertises that you can leave it in the fluid indefinitely, and I had a thought as to why that might be. I was betting that the reason you can leave it in is because it probably just burns off, so I looked at the SDS (formerly known as the MSDS) and the flash point is only 12.8*C or 55*F. So yeah, it looks like it burns off pretty quick if 55*F is all it can handle. So if one is to use this product I bet it’s best to pour it into a “cold” transmission so it has a minute to slosh around on the parts before it turns to vapor. It does work though for the things it works for/on.

I figured that it was being burned off but I wasn’t guessing at such a low temperature.
Seafoam Transtune SDS

 

Not to be disrespectful but that's not what flash point means.

“Flash point” is the minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with the air near the surface of the liquid. The lower the flash point, the easier it is to ignite a liquid solvent.

https://en.wikipedia.org/wiki/Flash_point

That being said, it has its own boiling point of 82.2C or 179.96F as a raw Liquid by itself. I am sure it takes more than that to burn it off especially once it's added to ATF.

 

Yeah I think the 12.8*C is a typo on their part. However, naphtha the main ingredient, turns to vapor (flash point) around 60*C, or 140*F. That being said, doesn’t ATF get hotter than 140* F? So if it vaporizes at 140* one would have to assume that it’s no longer in there once it turns to vapor. Or are you saying that it doesn’t vaporize at 140*F since it’s mixed with ATF that has a much higher flash point? I think it’s like 190* Celsius. I don’t think the seafoam lasts very long in there to be honest.

 

I drove it today without letting it warm up as long before taking off as I usually do and the 1-2 shifts were harder than the rest until the fluid got up to temperature (I’m assuming). After it was warm the first to 2nd shifts weren’t felt. There were no other issues other than the first to second gear change even prior to getting up to operating temp. When it was shifting hard I wouldn’t call it “harsh” really. It was smooth and quiet but you could feel it when it would shift from first to second. It would sort of lurch forward if you would. Maybe sort of like a “shift kit feel.” None of the other gear changes were felt and it didn’t shudder. This was with light to moderate throttle.
The theory at this point is that the slightly thicker “cold” fluid is causing the pressure to be too high but I don’t know what might be causing the issue. Bad 1-2 accumulator? A clogged something somewhere? What else besides everything else? Ha. How bad of an issue is this to have? If not addressed is it doomed? I don’t suppose it’s normal for the first to second shift to be harder than the rest until it’s up to operating temperature is it? Wishful thinking I know probably. I thought I had this thing licked.

 

This is a screen shot of a YouTube video. Is the accumulator on the left bad & the one on the right is good? The youtuber says so.. When I took mine out to replace the EPC the accumulator piston was “out” like the one on the left. Is that my problem? It also rattled. Would a bad accumulator even care if the fluid is hot or cold?

Is the one on the left messed up based on where the piston is?

 

I think the original Delco part number for the 1-2 accumulator is 24226359 but it seems like they’re aren’t any readily available. Amazon says I might get it in June. Does anyone have an alternate part number suggestion?

 

I dont see any wrong as such with either accum, the one of the right appears to have eitehr a missing or broken spring
OUTTER SPRING
inner spring-
And I would if you have the plastic one replace the piston -
You should be able to have all of this in a couple days from amazon.

 

All the links I posted for you at least with my prime account show delivery in 1 to 3 days .

 

Honestly while I would of course not want a slammed shift at part throttle with the 60e I would actually be far more concerned if i didnt feel much orf or feel the shift. Ideally part throttle even with a stock 4l60e should IMO be a slight bump

 

So it doesn’t matter if the piston is all the way flush with the edge of the housing? The picture of the new ones has the piston recessed a little and I think mine was pretty flush with the housing.
Would a bad accumulator only shift hard when the fluid is cold? If no, where would you look if you have a hard 1-2 shift only when cold?

 

Accumulator is fine , likley places to look are PCS or AFL valve leaking

 

I replaced the EPC solenoid last weekend. Is that what you’re calling the PCS?

 

yes EPC = electric presure control PCS= presure control soleinod ok well then you could have afl valve issues with VB or or leaking presure valve in pump , Also have you checked that the trans temp sensor is reporting reasonably accurate?
Any tuning been done?

 

It’s stock. I’m still living in the Dark Ages with no way to retrieve or record data unless it throws a CEL and it has not.

 

I think thats going to be your achelies heal here as without that you are flailing in the dark blind throwing parts at it .

 

I ordered an OBDII Bluetooth deal and I’m shopping trans pressure testers. Is this $50 rig the one to go with or is there a cheaper one that will suffice? I’ll probably only use it once or twice.

 

I would not trust any "cheaper" pressure tester. That looks like a good deal for what it is, but I wouldn't be too confident about the accuracy of that gauge if you accidentally drop it.
Also, I forgot what your application is, but I think a 6-foot hose might be too short to leave connected and still drive the vehicle.

 

‘00 Z28. How long a hose do you think I’ll need?
Thanks