4L60e/700-R4 Accumulator Pistons Tech Tip 

David Smith thanks for the compliment, David. I have seen several of your videos, very good information in them!

David Smith Dave, do you know about Th400 ? My first time adding a transgo shift kit and my plastic accumulator 2-3 is broken and I am replacing it with an aluminum piston. My question is- should I leave the spring out to get a better 2-3 shift or will that hurt the tranny? The spring in it is very stiff it seems. Should I look for a softer spring, leave it out or just keep the stiff one in? Thanks for any help. ?????

I’m doing the pin less to mine tomorrow any típs?

Did u have to use a spacer inside w the sonnax 1-2 pinless ?

What was the transmission doing? Was it shifting hard from 1-2? My 07 Silverado is shifting hard from 1-2... could this be the reason for that?

biginkman Did you figure out your issue? My 07 Sierra is having a delayed shift from 1st to 2nd, and it thumps hard once it shifts... Just started doing this 2 n8ghts ago... Was thinking on ordering new accumulator piston, but wasnt sure if this would help... Thanks

My trans has been shifting usually above 3k rpm from 1-2... The shift itself is nice and smooth, not harsh or slipping, but it just seems like it stays in 1st longer. Didn't always do this, used to shift in the low 2k rpm range and it didn't take as long for it to decide when to shift. Solenoids recently got replaced because they went out, which slightly fixed the 1-2 shift timing, but it still persists. Kinda of a weird problem, wondering if it's the accumulator piston or tps? No codes are being thrown.

ForzaClutch I have no codes either... My 1st is holding longer than it should, but i dont want to throw parts at it, unless it will help!

sad shame on the rebuilder .they should be honest w people

Same thing I do. I always save the worn out ones so I can double up. Shifts a lot better and beats hammering a ball bearing in the case!

While unlikely to see a high enough speed for a wot 3-4 shift someone with low gearing could see a high throttle 3-4 shift. I wonder how this affects the 3-4 shift. Could it possibly become violent and break something?

@@DillonTurner395 Great question, but not likely. The pressure has to hold two clutches while bringing the intermediate band back on. There are some quirks about the design of the intermediate band and the servo, but 1) the band is prone to burning and 2) the servo isn't being used as an accumulator, strictly speaking, but because it's using different pistons for 2 and 4, it tends to act like one anyway. There's also a fairly restrictive separator plate (people do sometimes drill them out too much; the area of a circle increases very quickly when you increase radius and some guys forget A=πr2). GM just built a lot of extra "comfort" into this transmission to begin with and the risk usually goes the other way, especially when you are running a lot of power and torque through a transmission that was intended for a Caprice sedan with a 150 horsepower 305 and a pretty conservative driver.

I believe you have a six speed auto not the same

Ever get this figured out, In same boat

Probably broken band or burn up

Replace the checkball capsule and did you use a new molded 3-4 clutch pack piston? I know some of the older 700r4/4l60e had one with O-rings instead also replace the 3-4 accumulator piston with a pinless piston from sonnex they seal better I dont use a spring in the 3-4 just put the piston in the bore but its up to you. You can replace the accumulator piston and capsule without pulling the transmission.

splash I have the same exact issue with my transmission, did u ever fix it? If so, what was the problem? I will appreciate ur feed back please, am going crazy with my transmission....

@@mariomendez9399 that sounds like a sloppy lock up from your torque converter there is a product called fixal its a michined valve with o-rings that goes inside the TCC regulator valve next to the TCC solenoid. The stock TCC regulator valve has a spring that allows the valve to oscillate wearing out the bore and it starts to leak what the replacement valve does is Seal up the bore and stops the leakage and doesn't oscillate. GM used a pulse-width modulated TCC I guess to smooth out the shifts but you really don't need it. Since you're going to have to pool the valve body off I'd replace all the accumulator Pistons with pinless ones from sonnex.

Hell yeah I replaced my forward, 1-2 and 3-4 accumulator Pistons in my 99 4L60E. They have two seals so they dont leak for shit I also toss the 3-4 spring you dont need it just the piston inside the bore to keep it sealed.

@Los G you can thats what a lot of builders do but just putting the piston in the bore without the spring accomplishes the same thing, you will need to plug up the 1/2 accumulator housing though when you buy the piston it come with ball bearing you hammer in or you can tap it and put a set screw with sealant. I also replaced the forward accumulator piston with a pinless thats the little one on the valve body itself.

@Los G yes with just the piston in the bore without the spring the cavity will just fill with fluid pushing the piston all the way down against the seperator plate basically just eliminating the cushion, doing it this way allows you to go back to original setup not that you would want to.

What ended up being the problem