Seafoam TransTune

[knockknock]

Hey all, just wondering what you opinion is regarding Seafoam TransTune. Mostly, I just want to know if this is something to avoid dumping into the transmission.

I have a '99 Chev Lumi with 4T60-E, 108K on original, replaced fluid and filter at about 70,000 (yeah I got it used, don't know if it was changed before or not). Anyhow the car did this before and changing the fluid and filter didn't help...

When warm, harsh upshifts, intermittent between 1-2, almost guaranteed from 2-3. Fine when cold. I can only go by speed (no tach), shift 1-2 < 20MPH smooth, shift 2-3 <35MPH smooth, shift 3-4 always smooth no matter what.

Was doing some reading around, appears people with this condition, a lot of Centurys mostly, I've read about it in the 4T65-E, people blame it on PCS. No cheap job, for sure. So I figure my symptoms are pretty similar, harsh upshifts, downshifts are just fine. No apparent slippage. Just a very harsh upshift from 2-3, sometimes from 1-2 but not that often.

Don't feel like replacing the PCS unless it's absolutely necessary. It's something I can baby if I let off the accel lightly before it shifts. What are y'alls opinion on this and that TransTune (probably won't do anything for this condition, thought I'd ask before I waste the whole $6 and potentially fuck up something down the road).

Thanks

[sharkey]

additives dont fix transmissions, at most they patch them. additives cant replace friction material on worn clutches, repair solonoids, replace the metal worn of planets, ect. that being said, dont waste your time. some people will tell you to use gm seal conditioner, i dont beleive in the stuff but some swear by it.

as for it being the pcs (pressure controll solonoid, also known as an epc or electronic pressure controll solonoid), if you have a 4t60e it wont be that, as 4t60e's dont have them. line pressure on a 4t60e is controlled by the vacume modulator, they only have 2 shift solonoids and a lockup solonoid.

[knockknock]

Thanks, sharkey. Guess I would have learned that [vacuum modulator] if I re-read the 4T60-E section; I just went off whatever Google gave me and those "reliability ratings" given by MSN Autos.

Without scanning (if even possible) and before considering other deep-rooted problems, what's more likely to fail causing such a drop in line pressure, the shift solenoids or the vacuum modulator; and how big of a job is replacing either?

Thank you.

[pwmin]

both are pretty easy to get to. you'll have to drop the subframe to get to the side pan, which holds the valve body, where the solenoids are. if you change those, i would also get a transgo jr. shift kit as a cure kit. the vac mod is easier to get to: just take the pan off. i had to change the tcc apply valve in mine. what year is yours? some 96 60e's had the larger, newer style tcc apply valve like the 97 trannies got.

[knockknock]

It's a '99, thanks for the info.

[pwmin]

okay, then you dont have to worry about that. i ended up with the wrong valve and had to do some research to find out i needed the newer style with the larger diameter. i also had reason to believe the valve body in my car wasnt the original.