4L60E - Blocking the 3-2 Downshift and Control Valves?

[jamyers63]

I understand the logic behind blocking the 3-2 downshift valve inboard (inwards) with either a heavy spring or a 5/16" bolt - you 'cut out' a long and torturous path with lots of places to bleed off fluid / pressure. I see some places that say just block the downshift valve, and some say block both the downshift valve and the 3-2 control valve.

Couple of Questions;
Is it best to block off both, or just the one?
Does the Solenoid then become a deadweight plug to hold the control valve in place?
I assume that the transmission will still downshift from 3-2 when either coasting down or manually shifted, am I correct?

 

[ctechbob]

This is an @clinebarger question if he has the time.

 

[clinebarger]

Really depends on what you're doing & how much power being put through the unit.

 

[jamyers63]

Really depends on what you're doing & how much power being put through the unit.

Okay, are there rough parameters?

I'm building a 4L60E to go behind a currently mostly-stock 350 in a daily driver 1969 Chevy C10, but we plan in the coming years to build the 350 to maybe 400-425hp and the truck to become a weekend street/strip machine.

Should we block the downshift valve only now, and maybe do both in the future?

Or is blocking the control valve for manual-only use?

I'm reading the GM manual and looking at the fluid flow diagrams but can't wrap my head around the 3-2 control valve and solenoid...

 

[jamyers63]

Ahh, I figgered it out, after re-reading the GM Technicians Guide... the 3-2 Solenoid and Control Valve are for controlling the timing of the 3-4 Clutch release relative to the application of the 2-4 Band, and is controlled by the TCU programming
based on vehicle speed.

 

[clinebarger]

Correct, Blocking the 3-2 downshift & control valves puts complete control of the Band Release & 3-4 Clutch Apply Timing during a 2-3 Upshift along with Band reapply & 3-4 Clutch Release Timing during a 3-2 Downshift in the Builder's (You) hands, Meaning..........

*Band Clearance & 3-4 Clutch Clearance are now ultra critical.
*Spacer Plate Orifices #12, #13, & #28 Sizing is now ultra critical.

In reality, There's no one size fits all type recipe like I developed for 4L60E's with active 3-2 downshift & control valves, Though I can give some experienced educated starting points.

Be prepared to drop the Valve body & adjust the 3 feed/exhaust orifices listed above.

Spacer Plate detail....Orifice ID numbers circled.

 

[jamyers63]

Thanks, clinebarger! You just made me take a deep dive into the tech manual's electronic and hydraulic control sections, and now my head is spinning again, LOL. I do know that if I ever feel the need to block both valves and control it via those orifice sizes, I'll be dropping it off at clindbarger's shop before I pick up a drill.

So, back to the basics...
1. on a daily driver pickup, should I even block the 3-2 downshift valve, or leave it active? How big a concern are the "downstream leak points"?

2. If I do block the 3-2 downshift valve, then I'm supposed to either swap the oem spring for a much stiffer (TransGo) one or a bolt/spacer that will keep the valve inboard and in what the Service/Tech Manual refers to as the "2nd gear position", correct?

3. Blocking the downshift valve inward now means that the 1-2 accumulator is only fed via the orifice, BUT since the 1-2 accumulator is fed in all gears / shifter positions except when in 1st gear, that's not an issue, correct?

 

[clinebarger]

You have the basics down, With the 3-2 downshift valve in the 3rd gear position, The 2nd Servo can come on faster because 2nd feed oil can bypass Orifice #16 during a 3-2 kickdown.

With the 3-2 Control Valve regulates flow through Orifice #12. The Activated/Inboard position forces 3rd feed through Orifice #12, Deactivated/Outboard position bypass Orifice #12 & 3rd feed oil is routed through Orifice #13.

Orifices #12 & #13 are 3rd feed Exhaust Restrictors (For lack of a better term). During 3rd Apply they are bypassed making Orifice #28 the actual 3rd feed orifice......Like Orifice #16 is the 2nd feed Orifice.

Hope this helps explain how the downshift & control valves help control Non-Synchronous 2-4 Band & 3-4 Clutch Timing.

Calling them leaks isn't very accurate nomenclature, They're more exhaust routing control devices.

At your current & expected power levels.....I would leave both active.

I'll give Orifice Sizing recommendations on your other thread.

 

[jamyers63]

Thank you clinebarger! I live just south of Abilene, if you ever get out this was let me know and Ill buy you a coffee, ice tea, and/or beer! Next time I get over to Ft. Worth I owe you the same.