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Yea I give up. The OP did what I suggested and he said it worked the way he wanted it to. I have no idea why apparently, but someone had a problem and now it's fixed.
Maybe the guy saying I was wrong didn't understand something. Maybe I explained it wrong.
This I know:
Way back whenever, I made the first dumb mistake with a transmission. During a filter change I took the 1-2 accumulator housing off and replaced the springs with a few 3/8 nuts. This replicates a very very stiff incompressible spring.
The 1-2 shift was brutal. It's the only thing I did. The piston could move up towards the plate just as before. So why was the shift so brutal if accumulation comes from the piston moving up?
I obviously put the stock springs back in and from that point on learned that a stiff spring makes for a hard shift.
If you put the nuts behind the piston (between the piston and the housing) and not in front of the piston (between the piston and separator plate) then the nuts weren't acting as stiff springs...they were acting as the lightest spring possible. no spring at all. hence when the spring force is on the same side as the apply fluid...lighter is firmer shift
Yea I give up. The OP did what I suggested and he said it worked the way he wanted it to. I have no idea why apparently, but someone had a problem and now it's fixed.
This is why we love having you here. You almost always get people back on the road and happy with their setup
color me cornfused.....with the springs ( inner and outer ) on one side of the piston there is no resistance on the other side to affect anything other than say maybe...any fluid on that side....which i think would hardly be any resistance at all unless the fluid is up against small holes in the VB plate
i have that GM book but following all those fluid paths is soooo cornfusing !!!
The Backside of the pistons have "accumulator" oil behind them. See the photo below, it's drive oil that gets metered into the circuit via a combination of spring force and torque signal fluid on the left of the valve that moves it to the right until fluid has filled the (green) accumulator circuit.
So, there is pressurized oil on the separator plate side of the 1-2 accum, and that pressurized oil also has it's exhaust path controlled by the accumulator valve. Pressure must rise, shuttle the valve left and uncover the exhaust port, which will control the exhaust rate of the fluid. The further it moves left, the larger the exhaust path gets, the faster the fluid can exhaust and thus the faster the accumulator piston can travel.
If you pay attention to the many variations and changes in shift kits over the years from transgo and other suppliers, you will see that the spring behind the accumulator valve can change the behavior of the shift pretty drastically. Off the top of my head I think the white spring is something like 24 or 28 oz. This is the lightest spring in the bunch and it's what is recommended (might be the only spring sent even) with the hd2 kit. For the SK4l60 however they send 5 different spring options ranging up to something like 88 oz. There is a chart to pick the right spring based on 2nd gear servo and accumulator sleeve stamp # but the fine print says that if want a FIRMER shift feel, you can select the next higher rated accumulator valve spring. So if you have the white spring in the mid 20's then go to a different color spring in the mid 50's, you will have a firmer shift.
This ultimately adds more pressure to the left of the accumulator valve which means more pressure needs to build up on the right side before it will stroke the valve towards the left...aka it reduces the size of the exhaust path and slows the exhaust.
That's alot of words to just go back to what was said in post #14...the slower the piston strokes, the firmer the shift will be. I hope I've been clear in differentiating between the accumulator valve (in the valve body) and the accumulator piston (in the 1-2 accum. housing)
This can also be seen in the RatioTek kit for anybody that has installed these you will know that there is the patented 1-2 accum plate. Essientially what it does is uses a hole on the plate to meter the INCOMING oil. It also states that the smaller the hole (slower fill and travel rate of the piston) the firmer the shift.
So...blah blah blah...words words words. you can change a bunch of stuff if you want and make the shift feel however you want if you know what you're doing.
For what it's worth, The best combination for a performance minded build that I've come to use with the "corvette" servo is the #CX stamped accumulator valve sleeve, the white accumulator valve spring, the transgo hd2 over/under spring setup in the housing with NO SHIMS, and then use the 2nd gear feed hole to dial in the shift feel.
09-19-2018, 12:27 PM
