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Discussion Starter · #1 · (Edited)
I'm currently reviving a 1968 Corvette 350 cu.in 300 H.P. currently having a TH400 transmission installed which shifts perfectly, but does not have the Overdrive gear or the Torque Converter Lockup.
I have already modified a TH700R4 for my 1934 SBC 350 cu.in. street truck, and it has shifted perfectly.
I realize I can install a base 4L60 or a TH700R4 with no problem, but I can get a great deal on a 4L60E.
Also, the 4L60E has the gear ratio I would like to have in the Vette, which only weighs 3500 lbs.

There are dozens of internet videos about converting the 4L60E to be shifted Manually by rewiring it for a floor shifter, but no one has been able to solve the EPC Force Motor rewiring problem.

THE MAIN REASON FOR REWIRING THE 4L6OE Force Motor IS TO AVOID RUINING/DESTROYING THE TRANSMISSION BECAUSE OF CONSTANT FULL LINE-PRESSURE WHICH CAN LEAD TO TRANSMISSION FAILURE OVER TIME BECAUSE OF HARD SHIFTS.

Problem #1 concerning the TCC PWM Solenoid(valve) can be solved by modifying the end of the valve body or the internal orifice diameter to a larger diameter so fluid can reach the Torque Converter Clutch at a faster rate which will engage the torque converter without "slamming the clutch" into full lockup (which would happen with Full Line-Pressure)

PROBLEM #2 IS MY HOLD-UP concerning modifying the EPC Force Motor. It DOES seem to require an in-vehicle computer to operate properly because of the low-voltage/ cycle-signal it receives from the vehicle computer. which causes the Force Motor to cycle On and Off about 30 times a minute in order to control shifting pressure.

My plan is to rewire the EPC using a relay/resistor/potentiometer to cause the EPC to function as though a in-vehicle computer is sending signals to the EPC.
MY PROBLEM is that I have limited knowledge as to how the relay/resistor/potentiometer can be wired to the EPC to make it operate correctly.

The Vette is "UNDER CONSTRUCTION" at the moment"

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168714



ANY ADVICE TO REWIRE THE EPC FORCE MOTOR WOULD BE GREATLY APPRECIATED !
 

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I am having my 4L60E remaned at a trans shop rite now. Its out of my 97 Silverado, with a Vortec 5.7 350. I have rebuild a few transmissions years ago. I will never do another one. It is something that I will pay an expert to do for me. They are doing a HD rebuild kit with hardened sun shell and corvette servos for about $2500. If I was trying to pull off what you are, I would be using a trans controller for the 4L60E. So here is the thing I have been asked, and will ask you the same. Why not a 4L80E. After all that is a new turbo 400 with OD and electronics as Im sure you all ready know.
 

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Discussion Starter · #6 ·
I am having my 4L60E remaned at a trans shop rite now. Its out of my 97 Silverado, with a Vortec 5.7 350. I have rebuild a few transmissions years ago. I will never do another one. It is something that I will pay an expert to do for me. They are doing a HD rebuild kit with hardened sun shell and corvette servos for about $2500. If I was trying to pull off what you are, I would be using a trans controller for the 4L60E. So here is the thing I have been asked, and will ask you the same. Why not a 4L80E. After all that is a new turbo 400 with OD and electronics as Im sure you all ready know.
It's a good idea to get a dependable rebuilder to do the nasty part. Basically, you are paying a little extra for the labor. All I will be saving is the labor charge because I will upgrade internal parts as needed, Why: I think the 4L80E has different gear ratio...I like the 700R4/4L604L60E gear ratios better...and the E-version won't be 30+ years old (which doesn't matter if you find a good rebuildable one)

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My plan is to rewire the EPC using a relay/resistor/potentiometer to cause the EPC to function as though a in-vehicle computer is sending signals to the EPC.
MY PROBLEM is that I have limited knowledge as to how the relay/resistor/potentiometer can be wired to the EPC to make it operate correctly.
You know you can now buy 5-12V input and 1 amp variable duty cycle output PWM DC motor speed controllers on amazon that has LED display for duty cycle. You don't have to build from scratch. The PCS (pressure control solenoid) is duty cycle controlled from 0-50% max by the PCM according to the manuals available online. 0 duty cycle is highest pressure (115 psi maybe) and 50% duty cycle is lowest pressure. Max amps is 1.0 amp. You can manually adjust the duty cycle to adjust the torque control on the hydraulic circuit. You will need to hook up a pressure gauge to the transmission and adjust the duty cycle and create a table for line pressures vs amperage on the PCS.
 

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Discussion Starter · #9 ·
You know you can now buy 5-12V input and 1 amp variable duty cycle output PWM DC motor speed controllers on amazon that has LED display for duty cycle. You don't have to build from scratch. The PCS (pressure control solenoid) is duty cycle controlled from 0-50% max by the PCM according to the manuals available online. 0 duty cycle is highest pressure (115 psi maybe) and 50% duty cycle is lowest pressure. Max amps is 1.0 amp. You can manually adjust the duty cycle to adjust the torque control on the hydraulic circuit. You will need to hook up a pressure gauge to the transmission and adjust the duty cycle and create a table for line pressures vs amperage on the PCS.
Thanks for the info bazar01...I'm adding this to my notes.
 

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Discussion Starter · #10 ·
I'm back after watching about 30 ore youtube videos concerning the 4L60Electronic transmission. My rookie opinion is the 4L60E has been over-engineered to please the new generation of vehicle owners "who don't want to feel a thing when the transmission shifts". That's fine, but I don't fit in that category. Those of you who are having your 4L60E and 4l80E transmissions rebuilt to make them stronger seem to be doing the right thing by eliminating the "wimpy/weak" parts in the "E" transmissions. There seems to ne too many "built-in flaws" in the 4L60E PWM transmissions.

I will be concentrating on the later-year1989-1992 TH700R4/Locking Torque Converter including the 4L60 Base Transmission. Even though 1989 thru 1992 versions could be considered "Dinosaurs" because of their age, they seem to offer much more in reliability and upgrades.
I will post my future progress for anyone interested..
 

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Discussion Starter · #11 ·
I'm checking in to let everyone know I appreciate ALL the info and advice. Emergency spine surgery has postponed any heavy lifting but I will still try to buy a 1989 thru 1992 A/T...preferrably the Overdrive version to be used on 1,000-2,000 mile roadtrips in the '68 Corvette once I am released from the Dr.'s care.
 

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1988 C1500 Silverado, 5.7L with some go fast parts.
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Discussion Starter · #14 · (Edited)
qman....I'm from Loo-z-anna....we doesn't know how to spell big words.

TBI....I hope you are right about the extra years of production...that will give me more choices....I can always look at the case connector to see what version the transmission is just to be sure. As long as it has a T.V Cable it will be much simpler to rewire.

"Peter - I'm retired but work part time as a pain in the ass."

You do your job well
168901
 

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Discussion Starter · #15 ·
UPDATE! My friend bought one of those built 700 h.p. 4L80E trans to replace his 4L60E in his GM truck. They offered him $100 for his 4L60E. He decided to give it to me in exchange for a boiled Crab/Crawfish dinner (we like our food down in Louisiana). So....I will buy a box of relays /resistors/whatever it takes to have a functioning automatic. Pics as I start the rebuild.
 

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UPDATE! My friend bought one of those built 700 h.p. 4L80E trans to replace his 4L60E in his GM truck. They offered him $100 for his 4L60E. He decided to give it to me in exchange for a boiled Crab/Crawfish dinner (we like our food down in Louisiana). So....I will buy a box of relays /resistors/whatever it takes to have a functioning automatic. Pics as I start the rebuild.
where on Louisiana are you from, Im in Lafayette.
 

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Discussion Starter · #18 ·
You know you can now buy 5-12V input and 1 amp variable duty cycle output PWM DC motor speed controllers on amazon that has LED display for duty cycle. You don't have to build from scratch. The PCS (pressure control solenoid) is duty cycle controlled from 0-50% max by the PCM according to the manuals available online. 0 duty cycle is highest pressure (115 psi maybe) and 50% duty cycle is lowest pressure. Max amps is 1.0 amp. You can manually adjust the duty cycle to adjust the torque control on the hydraulic circuit. You will need to hook up a pressure gauge to the transmission and adjust the duty cycle and create a table for line pressures vs amperage on the PCS.
I just got around to Amazon and bought one of those PWM programmers.
THANKS FOR THE INFO.....(scrap the relay idea.....yep...I’m slow!)
 

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Discussion Starter · #20 ·
You know you can now buy 5-12V input and 1 amp variable duty cycle output PWM DC motor speed controllers on amazon that has LED display for duty cycle. You don't have to build from scratch. The PCS (pressure control solenoid) is duty cycle controlled from 0-50% max by the PCM according to the manuals available online. 0 duty cycle is highest pressure (115 psi maybe) and 50% duty cycle is lowest pressure. Max amps is 1.0 amp. You can manually adjust the duty cycle to adjust the torque control on the hydraulic circuit. You will need to hook up a pressure gauge to the transmission and adjust the duty cycle and create a table for line pressures vs amperage on the PCS.
Now I need to take a lesson on programming. Installing a pressure gauge is about my speed!


Below by about 5 miles or so. Ive been through Gonzales many times, well on I 10 anyway. I used to work offshore, but now I work in a machine shop in town. Ive been all over the Gulf cost chasing those oil drilling rigs around.
I did the SAME things...now I'm a retired machinist. I need to make a trip to Lafayette to Pull-A-Part soon. What's the name of the bakery that makes King Cakes year 'round/I haven't been there in 10 years.

**
Update: My new-to-me 4L60E needs a few parts to get it 100% again. Front seal/rear seal/shifter shaft seal/piston seals/etc.
....a new separator plate ( 3 of the steel check balls have nearly hammered their way thru the plate)
....a new/wider Intermediate band
.....all the steel parts / gears /bushings /pump parts look new
.....a new 1600-1800 stall torque converter

I will need an adapter to connect a TH700R4 Tailshaft housing to the 4L60E case.....
......add a plastic speedometer Drive gear to the output shaft
......add a speedometer gear assembly with plastic Driven gear in order to keep my cable-driven speedometer
......add a transmission in-line cooler with built-in 180* thermostat

Fabricate a simple test-stand to make sure the trans shifts correctly before installing it (it will shift sooner because there will be NO load on the output shaft sliding yoke)
......use the pressure gauge to make sure the pump is capable of producing max pressure & to program the controller
I will work out the details on the shift controller after I learn how to program it.

More later...........Thanks again Everyone.

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169091


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