TCCoA Forums banner

1 - 16 of 16 Posts

6,111 Posts
Discussion Starter #1
OK, so, I am NOT going to do any other shift kit other than a jerry mod on my 4R70W, however, I was wondering, could somebody explain to me why the j-mod is the only suitable recommended "shift kit" for this trans? I understand the part about "go with what the guy who designed it says" and I agree. But what is it about the other shift kits, B&M, Lentech, etc. that are "BAD" for this trans? What exactly are they hurting, and what about the J-mod causes it to NOT have the issues the other shift kits cause?


Super Moderator
12,076 Posts
Didya read through the transmission section of tech articles?

Super Moderator
12,076 Posts

PostWhore, The AFDB is on a lil tight.
3,868 Posts
If I remember a phrase that explains it....

Its trying to control something mechanically when it should be done electronically.

348 Posts
Baumann makes a good kit, very adjustable.

875 Posts
No point in debating it Earl, they'll just get nasty with the answers. Lots are running shift kits and are smart enough not to post cause they don't wanna get bashed. Even some of the trans gurus here are building transmissions with shift kits or a combo of jmod and shift kits. I asked a similar question a long time ago and got bashed because questioning the jmod here is considered sacrilidge. ;)

5,412 Posts
I'm interested in the Bauman stuff on top of the jmod I like the idea of being able to paddle shift. But I'd be paranoid of damaging something.

798 Posts
No point in debating it Earl, they'll just get nasty with the answers. Lots are running shift kits and are smart enough not to post cause they don't wanna get bashed. Even some of the trans gurus here are building transmissions with shift kits or a combo of jmod and shift kits. I asked a similar question a long time ago and got bashed because questioning the jmod here is considered sacrilidge. ;)
Maybe it's because the J-Mod is tried and true, while these BS 'shift kits' or 'shift improvers' do absolutely nothing. I find it strange that you can read plenty of posts, where the car ran fine till they installed one. Hmm. Strange.


6,111 Posts
Discussion Starter #12
I wasn't debating the j-mod...I was just asking why other kits are considered "bad" I got my answer today anyway ;)

348 Posts
I have no problem with the J-Mod, I've just never trusted myself to do one as for some reason I find the instructions confusing. If you can figure it out no problem go for it as it does sound like a good option.

The four 4R70W cars I've done Baumann kits on have all ran and shifted better afterwards. I've done two AOD cars with Baumann kits too and all was well. I contacted Baumann with some questions too on the last build as I was using a bunch of Sonnax parts with it and between the two I got great support. The guys at Sonnax were really helpful!
The only trouble I've had with any of them is quite a while ago when I installed a B&M stall convertor in one of the AOD's and the needle bearing went out of it, I was pissed as it was a fresh heavy duty build, and they did squat to help, nor did the speed shop that sold it to me and helped install it!

Almost every tuner I've talked to (6 out of 7 in the past few years) has said it's better to do changes internally to the trans instead of the tune, other than shift points and rev limiters etc... ;)

So imho, the best choices are Baumann or J-mod...

4,309 Posts
I wasn't debating the j-mod...I was just asking why other kits are considered "bad" I got my answer today anyway ;)
The "Kit" to avoid is the Transgo on the 4r70w. They added an external pressure regulator.

Lentech makes an excellent valve body for the AOD equipped vehicles - and Silverfox has a whole lot of information on modifying AOD's .. I just wish Jerry would have made an article on that also.

6,220 Posts
here, ive posted this in the past....

Jerry said:
First Iíll 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 .067î from itís current size of .050î.

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 itís .100î in production, so there is
no need to change this (this hole was recently added).

Hole #2
This is the intermediate clutch feed orifice. I go over this in my article. I recommend
.081î, .100î and .125î for low, medium and high power applications. They recommend .067î,
.094î, and .125î. For the most part we are pretty close. The low setting, .067î, isnít
much different than production. Starting in 1996 this orifice went to .063î, I doubt
there is much noticeable difference in .004î.

Hole #3
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. Iíll cover this

Hole #4
This is the OD servo feed. It should already be at .150î in production, and they
recommend no change and either do I.

Hole #5
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.

Hole #6

Hole BR
This is the feed for the OD servo release. They recommend at least an 1/8î or a slot
OK. Most all of your cars will already be a slot. This is not a problem.

Hole A,B,C
These are recommend to be .093î. Holes A and B in any 4R70W will already be this big
or bigger. The early AODEís (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 .093î is OK.

Hole AC1,2,3
AC1 is the backpressure feed for the 2-3 accumulator. This is used on 3-2 downshifts.
Most all should be .125î already, and they recommend .125î
AC2 is the 1-2 accumulator feed and itís never been smaller than .160î so I donít 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 .200î, they recommend at least .125î, and I agree.

Hole R
I think they meant this to be the reverse clutch feed, but itís not. Itís a feed to the
reverse clutch, but has never been less than .125î. They recommend .093î

EPC Relief Valve (Page 3)
They say this valve corrects (extreme line pressure due to electrical malfunction, stuck
EPC valve, or crossleaks.î I would under no circumstances EVER do this. We have never
seen any pressure spikes that have caused any damage. Thatís 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 donít 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 doesnít
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 donít change the 3-4. Both shift solenoids
supply pressure to the 3-4 shift valve. Each solenoid alone doesnít have enough pressure
to move the valve, in production. But since the pressure is raised, the 3-4 shift valve
could move.

Step 3
This is the converter clutch control valve. This is a very sensitive control system
and requires a very fine balance between all itís parts. I doubt they have done the
development we have to make a good control system. I wouldnít mess with the valve at
all. I do recommend the stiffer spring for 1995 and older cars. (I didnít put this in
the Thesis because springs arenít serviced seperatly)

Step 4
The main regulator valve has the land removed that regulates the flow/priority system.
If you go to my article, I donít 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 doesnít pose any problem.

More Valves (page 5)
I havenít actually seen the new manual valve so I donít 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.

Step 1
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
this valve.

Low Valve. This is a higher spring load than production. This wonít 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.

Iíll only address the new style piston. I donít know the spring loads so I canít really
comment on much, but Iíll 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 .160î, 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 (Iím 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 donít like the major
reworking of the shift valve/solenoid pressure regulator stuff to give you every gear
manually. Iíd 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 donít 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 wonít be changing
many of them anyway.

If youíve put one in your car, Iíd like to see the production main regulator valve put
back in, the ball put back in and the feed orifice opened. You donít have to remove the
manual shift stuff as long as you donít move the lever when you are too high of a speed,
sometimes that lever is tempting. Iíd also like to see the EPC relief valve removed, but
that requires a whole new valve body to fix.

6,111 Posts
Discussion Starter #16
thanks for posting that vic, excellent information there, that's an article I have never seen before...
1 - 16 of 16 Posts