here, ive posted this in the past....
Originally Posted by Jerry
First IÃ*ll cover the seperator plate changes in the transgo shift kit.
Hole #1 and 1A
Hole #1 is a damping orifice for the converter clutch control valve. This hole damps the
output of the converter clutch solenoid. That solenoid is only an On/Off solenoid, it
controls pressure output by tuning on and off very fast. The more on time, the more
pressure, the more off time the less pressure. This is called pulse width modulated,
or PWM. They recommend opening this hole to .067Ã® from itÃ*s current size of .050Ã®.
I do not recommend any change to this hole. As I said, this solenoid turns on and off
very fast and the output goes from 0 psi to 55 psi. This hole dampens the peaks and
valleys from the output of the solenoid to provide a smooth signal to the converter
clutch control valve. If this hole is too big, then the valve will start to respond
to the on/off pulsations, giving an unstable system.
Hole #1A is the feed to the solenoid. Currently itÃ*s .100Ã® in production, so there is
no need to change this (this hole was recently added).
This is the intermediate clutch feed orifice. I go over this in my article. I recommend
.081Ã®, .100Ã® and .125Ã® for low, medium and high power applications. They recommend .067Ã®,
.094Ã®, and .125Ã®. For the most part we are pretty close. The low setting, .067Ã®, isnÃ*t
much different than production. Starting in 1996 this orifice went to .063Ã®, I doubt
there is much noticeable difference in .004Ã®.
They recommend not changing this hole. This is the direct clutch feed orifice. They
recommend no change because they want you to remove the check ball. IÃ*ll cover this
This is the OD servo feed. It should already be at .150Ã® in production, and they
recommend no change and either do I.
This is the forward clutch exhaust. They recommend not changing this as well. I
disagree. You guys with 1994/95 cars want to open this orifice to get rid of the
sag, or hesitation, at the 3-4 shift.
This is the feed for the OD servo release. They recommend at least an 1/8Ã® or a slot
OK. Most all of your cars will already be a slot. This is not a problem.
These are recommend to be .093Ã®. Holes A and B in any 4R70W will already be this big
or bigger. The early AODEÃ*s (1992-1993) have some smaller holes. So these do nothing
for our cars. Hole C is the power off forward clutch feed. I recommend different sizes
based on power, but .093Ã® is OK.
AC1 is the backpressure feed for the 2-3 accumulator. This is used on 3-2 downshifts.
Most all should be .125Ã® already, and they recommend .125Ã®
AC2 is the 1-2 accumulator feed and itÃ*s never been smaller than .160Ã® so I donÃ*t know
why they even mention it.
AC3 is the bottom of the 2-3 accumulator. This is also used on 3-2 downshifts. Again,
most of your cars should be at least .200Ã®, they recommend at least .125Ã®, and I agree.
I think they meant this to be the reverse clutch feed, but itÃ*s not. ItÃ*s a feed to the
reverse clutch, but has never been less than .125Ã®. They recommend .093Ã®
EPC Relief Valve (Page 3)
They say this valve corrects (extreme line pressure due to electrical malfunction, stuck
EPC valve, or crossleaks.Ã® I would under no circumstances EVER do this. We have never
seen any pressure spikes that have caused any damage. ThatÃ*s not exactly true, in 1995
there were less than 50 failures from pressure spikes, but we fixed the problem. This
valve would not have prevented damage in those cases.
The reason I donÃ*t recommend this is that if that valve ever gets anything stuck in it
and opens, you will fail the trans. It will cause a large line pressure leak. It doesnÃ*t
solve a problem, but creates the potential for disaster. Again, I have never seen
pressure spikes that this would prevent damaged caused by them.
Valves (page 4)
Step 1 and Step 2
All these changes allow the trans not to upshift out of manual low into second and allow
you to get every manual gear.
This is much better accomplished electronicly than with these mods. First off, if you
pull the lever into 2 at 120 mph it will go into 2. This is a bad thing. There are
values in the EEC that allow this and those should be used.
In addition to this, the pressure coming out of the solenoid pressure regulator valve
is raised (Step 1) to a higher pressure. This pressure should not exceed the 55 psi
from the factory. The shift solenoids, which this valve supplies fluid too, do not work
the way you would think. There is always fluid flowing through the solenoids and the
solenoids must exhaust the fluid that goes to them when the solenoid is off. When the
solenoid is turned on, the exhaust path is stopped. If you provide too much pressure
to the solenoids, they will not be able to fully exhaust, especially cold. This could
cause the shift valves to start to drift one way or the other. I realize they change
the 1-2/2-3 shift valve spring, but they donÃ*t change the 3-4. Both shift solenoids
supply pressure to the 3-4 shift valve. Each solenoid alone doesnÃ*t have enough pressure
to move the valve, in production. But since the pressure is raised, the 3-4 shift valve
This is the converter clutch control valve. This is a very sensitive control system
and requires a very fine balance between all itÃ*s parts. I doubt they have done the
development we have to make a good control system. I wouldnÃ*t mess with the valve at
all. I do recommend the stiffer spring for 1995 and older cars. (I didnÃ*t put this in
the Thesis because springs arenÃ*t serviced seperatly)
The main regulator valve has the land removed that regulates the flow/priority system.
If you go to my article, I donÃ*t recommend this for the reasons mentioned in the article.
The main regulator valve spring raises line pressure across the board about 20 psi.
This change is OK and doesnÃ*t pose any problem.
More Valves (page 5)
I havenÃ*t actually seen the new manual valve so I donÃ*t know what it does.
The Taper spring (step 3) is a further mod to override the EEC and give you the gear
you select. See above for my opinion.
The 3-4 capacity modulator valve spring. They include a stiffer spring. This will make
the 3-4 shift softer. In production starting in 1996, we actually lowered the load of
Low Valve. This is a higher spring load than production. This wonÃ*t really accomplish
too much other than making the manual 2-1 firmer. It will still have the delay (or
neutral feeling), but will be firmer when it comes on. This change is not a problem.
IÃ*ll only address the new style piston. I donÃ*t know the spring loads so I canÃ*t really
comment on much, but IÃ*ll give it a shot.
As you add spring load to the bottom spring, the start pressure of the accumulator
lowers, making a softer shift. They have you put a washer in the bottom, in my opinion
the wrong way. The solid spring is similar to taking the spring out. I suspect that the
solid springs limits the accumulator stroke (or travel). This is something that I do not
recommend. Your better off with a light spring load or no spring.
The ball removal
This ball removal makes the direct clutch feed orifice .160Ã®, the size of the ball hole.
Like I said in the thesis, leave all the balls in. Taking this out will give you firm 2-3
shifts, maybe too firm for some (IÃ*m getting older) but the backout or partial backout
shifts will be very harsh. This harshness could result in driveline damage (U-Joints)
For firmer 2-3 shifts your better removing the spring and drilling the hole.
Overall I think the kit has some good things and some bad things. I donÃ*t like the major
reworking of the shift valve/solenoid pressure regulator stuff to give you every gear
manually. IÃ*d much rather do this in the EEC, you can still have protection from
over-reving and not have the compromises. And, every once in a while, I see a car
with this kit that just does not work due to all the valve replacement.
I donÃ*t like the main regulator valve, again gets back to the priority circuit.
Most of the holes are OK but if you have a 1996 or newer trans, you wonÃ*t be changing
many of them anyway.
If youÃ*ve put one in your car, IÃ*d like to see the production main regulator valve put
back in, the ball put back in and the feed orifice opened. You donÃ*t have to remove the
manual shift stuff as long as you donÃ*t move the lever when you are too high of a speed,
sometimes that lever is tempting. IÃ*d also like to see the EPC relief valve removed, but
that requires a whole new valve body to fix.