No pressure rise

[tayto]

Thanks for the list, helps with all the guess work . I have a 99 2500 with the 4l80 and it is SMOOTH, but i haven’t considered the swap.

I just figured i couldn’t feel or hear as much of the shift cause it’s a diesel. The 60 shifted great, just didn’t like the continuous in/ out in/ out lock up but after blocking the PWM i was happy with it. And no matter what i did, i could always feel a firmer shift to 3rd ,but it wasn’t a issue just more noticeable than other gears. Maybe the band release? Idk

Are they pretty much the same Internals as far as rebuilding? They the same length or did you have modify the drive shaft? Did you have to get a new/different pcm or can you program your existing one? Or is it as easy as wiring the harness up

And i dunno if i asked, but about my pressure issue, since it’s getting line pressure, wouldn’t that mean the pump is working? I don’t have experience/knowledge in torque converters so i dunno if that could effect anything with my pressure issue or not.

shift feel is hard on the 4L60E because 1-2 is band coming on, 2-3 is band coming off and clutch pack engaging and 4th is band on again. a band will never feel like a clutch pack and vise versa. this is why shift timing is important on the 2-3 shift as there is a lot going on. as well as why it's important to fix 3rd gear leaks as the circuit can easily be starved of oil. this is why we up the pressure, increase shift hole sizes for quicker shifts and fix internal leaks (input shaft to input drum, block both 3-2 valves inboard,etc), it is mandatory on a 4L60E.

we want to see FULL pressure gives us a good indication that the pump is healthy. as you increase throttle, the engine makes more power (simplified), if you don't get pressure rise then the clutches can't hold because they require more and more clamping force as the rpm increases. once a clutch pack slips, its the beginning of the end. this is why you can nuke a brand new transmission easily: low fluid.

Real easy to make the 4L80E shift firmer: block the 3rd and 4th accumulators with a block off plate. I like the Sonnax LB1 valve here, run the stock 4L80E spring you do not need higher pressure until you get over 700fwhp! you are just making the pump work harder than it needs to and robbing HP. Increase shift holes, don't go crazy on 2nd feed 0.075", 3rd can go .100" range and leave 4th stock, around 0.050". there are a few other (free) things you can do and you don't need to spend $100+ on a Transgo kit...

 

[Bluechevy18]

UPDATE: finally got it straightened out, the clip that holds the AFL valve was not installed correctly.. instead of going over the end plug it slid beside it eventually allowing it to slide past and let the valve be stuck open.. it only ended up hurting the 2/4 band other clutches were still in spec ..
NOW my new problem is 1-2 shift is way too hard at low throttle % but over 50% it does great- chirps tires- which i DONT want it to. But i think it’s from turning the EPC up 1/4 turn when i was trying to fix it and i forgot to turn it back down cause it’s shifting at 155+ psi at 10-15% throttle which i think is too high and WOT i seen it go over 250psi,
I have the transgo sk4l60 kit NOT the hd2 so i wouldn’t think it would be the kit making it so high .. it had the sonnax LB boost valve so i no it would be a hair higher than stock..

What’s the usual range of psi for 10-20% throttle for 1-2??

 

[tayto]

UPDATE: finally got it straightened out, the clip that holds the AFL valve was not installed correctly.. instead of going over the end plug it slid beside it eventually allowing it to slide past and let the valve be stuck open.. it only ended up hurting the 2/4 band other clutches were still in spec ..
NOW my new problem is 1-2 shift is way too hard at low throttle % but over 50% it does great- chirps tires- which i DONT want it to. But i think it’s from turning the EPC up 1/4 turn when i was trying to fix it and i forgot to turn it back down cause it’s shifting at 155+ psi at 10-15% throttle which i think is too high and WOT i seen it go over 250psi,
I have the transgo sk4l60 kit NOT the hd2 so i wouldn’t think it would be the kit making it so high .. it had the sonnax LB boost valve so i no it would be a hair higher than stock..

What’s the usual range of psi for 10-20% throttle for 1-2??

turn epc back down. what did you drill the 2nd feed too?how is the 2nd accumulator stacked up

 

[Bluechevy18]

Pretty sure it was set at .093 . Accumulator is sonnax pinless, 2 springs -piston facing plate. I drilled all the holes that transgo kit recommended to .093.

 

[tayto]

.093 is HUGE for 1-2. it is easy to make that shift overly firm unlike the 3-4 shift. I would peen it with a checkball and shrink it down to the .070" range (not 0.082"). the sonnax pinless piston by design with stock springs will also make the shift firmer because it is taller it makes the stroke shorter. DO NOT use the transgo "over under" springs with the sonnax piston, they will coilbind and break. what springs did you run here?

Also do not shim this location with washers. like I said above it is easy to make this shift overly firm/ violent.

 

[Bluechevy18]

Mybad - the accumulator has 3 springs not 2- Looking back at the instructions it didn’t say drill the 1-2 to .93 so I assume i left it stock but i finally got some time today to pull the pan and turn down the epc and I’ll check the feed holes

drove it yesterday about 8 miles and when cold it shifted perfect- soon as it warmed up it was shifting HARD . Felt like a sledge hammer hitting full force and clunk noise when i commanded up/down shift .. gauge was showing 160-180psi shifting under 3k rpm.. drove her back in 1st so it wouldn’t cause any damage if it hasn’t already

I’m hoping it’s just the force motor, if so then it’s INSANE what a tiny turn off a screw can do to that thing

Before i fixed it ,shifts were pretty butter smooth but it was also staying at 70ish psi

 

[tayto]

ya I would turn the epc down. you can also try cutting the "legs" off the sonnax 1-2 piston. this doesn't require dropping the valve body and is easy to do while youre turning down epc.

what shift kit are you using? SK, HD2 or PRO?

EDIT: you also might want to put the stock 1-2 springs back in. i think EPC isn't helping but i think the main issue is the Sonnax piston. I have never used it as I think it is a waste of money and the hardened gm pin and piston (or transgo's) works fine.

 

[Bluechevy18]

The SK kit.. the 1-2 accumulator valve called for the softest white spring with my bushing code and vette servo (24oz i believe ) next up is 56oz.. how does that effect the shift with soft/stiif spring’s? And the 1-2 accum. Is 3 spring not 2

 

[tayto]

ya amended my post above. but you are mixing parts into Transgo's shift kit. either go back to the OE style pin and piston or be prepared to drop the pan a few times.

Like i said, I would grind the legs off and put the stock springs back in. Also turn the EPC back to where it was, this adjustment rarely needs to be touched especially on a stock setup.

here's a good read: https://ls1tech.com/forums/automati...l60e-1-2-accumulator-piston.html#post20411878

here is the spring setup that is recommend in the link above:
"As a general rule....I advise against anything larger than a 093/Vette Servo on a stock band unless you stay very conservative with the 2nd feed orifice (No larger than .082" with .076" preferred)
*Run a Inner Cushion Spring, GM# 8681195.....Or the 2 Inner Cushion Springs out of a TransGo SK-4L60E WITH the original GM# 8642539 Outer Cushion Spring.
*Run the lightest TransGo Accumulator Spring (24oz)
*Do Not shorten the range of the 2nd Accumulator......No Spacers, No Sonnax Pinless Piston etc
*Adjust Band Clearance to .040".....This will limit the Servo having a running start at the Band."

In conclusion if you are staying with the Sonnax piston: grind the legs, discard the Transgo springs and run stock springs. If you post pics of your original springs I can probably tell you what you have.

 

[Bluechevy18]

Got the force motor turned back down and the 2nd feed hole is — i assume stock— not as big a as 3/32nd but bigger than 1/16th - couldn’t find any 64th’s bits around to check

When cold the 1/2 shifts like stock.. not used to vette servo so maybe its setting it up a little harsher?? After trans gets good and hot it has a small but noticeable snatch when 1/2 shifts.

I’ll pop the pinless accumulator out and grind it off to see the difference . Ill lay those springs out to get a pic and see where I’m at
Thanks bud