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I've been able to do this for a long time
Circa 2017 I have separator plate drawings dated
It's a different method to feed the overrun clutch.
Study the circuitry and you'll see how it's possible.
but it can be done without the HD 2-3 valve.
The gist is: Feed the overrun clutch with D4 oil, and shut that feed off anytime you'll be in 4th gear. If you don't shut them off in 4th, you'll burn stuff up immediately
Also, beyond just shutting off the feed, you need to open an exhaust path
the 60e factory valve body lends itself very nicely to achieving this with just a couple simple changes
There are actually several ways to achieve both of those Hydraulic changes, and are actually rather simple to do.
If you looked at the Separator plate, the Case and a Valve-Body, you would easily see what they did.
If this interest you...
You can look at one example that we (GM) created for the Corvette with Paddle-Shifting on the 4L60E.
There are complications with the GM design for use of M1 and M2 positions (D3 and D4 Only)...
But can be further modified to allow for M1 and M2 use.
Last edited by vorteciroc; Jul 27, 2022 at 06:30 PM.
thanks for the input! as a first timer for *this* mod I'll have to spend a lot of time & study the circuit quite closely. Modifying the circuit specifics off of my own assessment for something like this isn't really my forte'.
Your post right there is exactly why the HD 2-3 shift valve is/was so popular
it's a simple modification with instructions anybody can follow and it just requires a drill bit.
This stuff is really not difficult if you take the time to look at it.
I do not want people to be afraid of it...
Give it a try, if you don't quite get it (understand it), who cares? ...it can't do you any harm!
Maroon Monster (who is excellent at all of this now) picked up all this stuff in very little time, with no formal Training/ Education.
He has a BS or MS in Engineering or Science, and taught Himself in a few Years!!!
Many of these Hydraulic Modifications were first realized by looking at a Transmission that was Malfunctioning from a Cross-Leak.
Kind of Happy Accidental Discoveries.
If you look at what the Sonnax HD 2-3 Shift Valve actually is...
It just removes one function of the Valve, leaving the rest intact/ identical to the OEM Valve.
It blocks off a Connection between 2 Passages; the D3 Circuit into the Valve Bore...
and the Overrun Circuit out of the Valve Bore.
The OEM Valve Opens this Connection if the Gear-Selector (Manual Valve) is in the D3/ M3 Position, operating in 3RD-Gear ONLY (NO 1st or 2nd).
Which is the complaint with the Original Design/ Function of this Transmission.
The Sonnax HD 2-3 Shift Valve keeps that Connection permanently Closed.
And instead has a Hole Drilled (Cross-Leak Created) that allows D3 Fluid to enter the Overrun Circuit all the time (except in the D4/ OD Position).
The Sonnax GM054-HD Valve-Body changes things so that the Overrun Clutch is always ON except when the Transmission is operating in 4th-Gear
(Regardless of the Gear-Selector Position: D4, D3, D2, or D1).
Here is another Hint:
If you look at the Separator Plate, it will show you that D4 Fluid and Overrun Fluid are right next to each other in different places.
There is more to it, such as releasing the Overrun Clutch...
But that should get you started.
I do not want people (or Memebers) thinking that this is all Voo-Doo Pseudo-Science.
Last edited by vorteciroc; Jul 28, 2022 at 07:14 PM.
is the advtange of this that if the driver forgets (or doesn't know) to pull the lever into 3 position when beating on the trans?
The advantage of the Sonnax GM054-HD is that the Gear-Selector can stay in the D4/ OD Position and have the support of the Overrun Clutch for the Input-Sprag.
Otherwise using D3 with the Sonnax HD 2-3 Valve is the next best practice.
With the hints vortec has given...and the hint I'll give here...you should be able to easily figure out how this can be done.
You just need a hydraulic manual (available for free with the proper google search)
Some people hound builders for Information like what has been discussed here.
I find it hilarious just how few people will probably read it in this Thread.
Some people hound builders for Information like what has been discussed here.
I find it hilarious just how few people will probably read it in this Thread.
here is one source https://procarmanuals.com/pdf-online...repair-manual/
same manual I have but somewhere somehow I found a downlaod version long ago. printing some pages for weekend reading.
No way I'll have this circuit figured out before this weekend. I have a VB going back in tomorrow, so it will just have the sonnax 2-3 valve and drilled hole for now.
Some people hound builders for Information like what has been discussed here.
I find it hilarious just how few people will probably read it in this Thread.
I've read and have taken notes and will be doing some studding.
Is this mod nessesary for the high HP applications only or it's a good practice having overruns on, on stock application too?
Because i didnt do that in my pan drop VB rebuild.
this mod sounds like it's for higher HP and/or the owner is forgetful to pull the lever down to D/3rd (assuming Sonnax HD 2-3 valve) when thrashing on their vehicle. It also might be good for someone who tows all the time or is a fully loaded work vehicle or someone who only manually shifts (paddle shifters as mentioned). You'll have to remember the overrun clutch will now be on in all gears but 4th, regardless of lever position, which also means engine braking. I am also thinking it might affect milage in a stock/daily driver application but if you meet the criteria above probably a worthwhile trade off....
FWIW, sonnax makes a kit that is similar for the 4L80E.
maroon, I have been busy but will also tty and study the hydraulics. trying to learn more this might be a good puzzle to try and solve as an amateur.
There are actually several ways to achieve both of those Hydraulic changes, and are actually rather simple to do.
If you looked at the Separator plate, the Case and a Valve-Body, you would easily see what they did.
If this interest you...
You can look at one example that we (GM) created for the Corvette with Paddle-Shifting on the 4L60E.
There are complications with the GM design for use of M1 and M2 positions (D3 and D4 Only)...
But can be further modified to allow for M1 and M2 use.
I see this now, hole 35c/39 is gone. why did they block 12b? this would not allow low/reverse clutch pack to engage when in reverse?
2005 corvette but I was using Transgo plates to compare to the 4L60E Hydrualic manual. It's a lot of work to just use the manual without having a valve body and separator plate right in front of you to check stuff...
4L60E Overrun Clutches in OD (3,2,1)? 
