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As seen in “From the Bench” in TRANS DIGEST
Options By G.S.Carne
Electronic Pressure Control (EPC). What is it? What does it do? How does it work? The answers to these questions are crucial in order to fix the electronic controlled transmissions in today’s vehicles. Some shops have a better understanding than others do. Most shops understand what EPC is SUPPOSED to do, but you would be amazed how quickly an improper EPC command can cause an E4OD/4R100 CB. So, what IS the right line pressure RISE on any E4OD/4R100 unit? This article is not about the whys and wherefore’s of EPC, this article is about OPTIONS for solving those EPC problems. Lets look at three different scenarios:
#1. Your shop gets an early 90’s Ford pick-up in for service and the complaint is it ”SLIPS”. You pull the transmission and find that the forward clutches are welded together and intermediate clutches are black. Your builder says that you need to make sure the “ vehicle problems” are addressed. Your diagnostician checks the MLPS, the TPS, and the MAP sensors and they check good. You replace the MLPS because of known problems, but you really haven’t found any reason for the actual failure. The unit is replaced and your builder suggests a pressure gauge. GOOD IDEA!!! The gauge is installed and you do a typical in-shop test seeing 60 psi at idle and 195 at Wide Open Throttle (WOT). This looks great! Must have been that MLPS! Then you test drive the vehicle and find out that somewhere above 30 MPH your line pressure goes to minimum! At WOT it goes all the way up to 90PSI!! The shifts are sloppy. At 65 MPH the line pressure is 75 psi. Your diagnostician says, “ this will never last. Must be a bad PUMP”. Your Diagnostician and your Builder start the old argument about “WHOSE Fault it is”. Back and forth they go and all you can think about is that this vehicle has to go today!! What OPTIONS do you have?
#2. That 1996 F-250 diesel with the ”CHIP” is back! No reverse, AGAIN! Check codes and you find nothing. The fluid is black and you know it has to come back out AGAIN! The builder is PO’d because he has to do this problem child again, the R&R guy is PO’d because he’s done this one several times and you are stuck with several other vehicles that you could be making money on IF that “CHIP” truck wasn’t in the way. The unit is rebuilt again, and during the inspection
of the failed unit you find that the direct and low/reverse clutches are smoked, AGAIN. Your builder suggests a new pump, even though neither of you see anything really wrong with the one you have in front of you. Again your builder suggests a pressure gauge. The gauge is installed and you do a typical in-shop test seeing 60 psi at idle and 215 at Wide Open Throttle (WOT). This looks great! Then you test drive this vehicle and find out that somewhere above 35 MPH your line pressure goes to almost minimum! In Reverse you have 85psi at Idle and WOT it goes “All the up to 115 psi”!! No wonder this vehicle has no Reverse. At WOT in OD the Line pressure goes all the way up to 105PSI!! The shifts are sliddy, especially when that “CHIP” kicks in. At 65 MPH the line pressure is 85 psi. Your diagnostician says, “This will never last. I don’t know what to do”. Do you have any OPTIONS?
#3. A customer calls your Production Reman Facility with a 1992 F-250 farm truck that he needs to get out of his shop ASAP. You, as a production rebuilder, have the unit in stock and you ship the unit to the shop with all the proper installation instructions. The next day the shop owner calls and says the unit ”doesn’t work right”. You ask him to install a pressure gauge, which he be-grudgingly does, and find out that the vehicle Computer is commanding 65 psi at all times. Customer says “it must be in the transmission because we only changed it because of a leak”. Your headache is now getting severe because you know that the unit was dyno-tested. You confirmed that the transmission line pressure worked properly when commanded by the Computer Controlled Line pressure Commands you have on your machine. Getting that wholesale customer to do any diagnostic testing is almost impossible, “I don’t have any codes” he claims, “ there’s nothing wrong with the truck, it’s in your transmission, send me another one today! And by the way, my labor rate is $110.00 per hour for the R&R.” The bottle of EXCEDRIN is empty. You’re out of TUMS. Just another typical call for a Production Remanufacturer. OPTIONS?
You make a quick call to ATSG on the first two vehicles. They suggest you run an AMP test on the EPC ground wire to verify the command. You verify that the computer IS commanding the pressure you are seeing. Your AMPS are around .88 to .94 at anything above 30 MPH. TYPICAL you say? There is no chart to give you a “Specification” above stall tests. So what do you do? Any OPTIONS?
We all are aware of the after-market companies that have Valve Body “FIXS” or Re-calibration systems. Some of these work Ok and some don’t, but none of them can “FIX” the Computer Commanded Pressure control issues you normally face. If the Computer doesn’t command the proper line pressure, you have a problem! Most of us have used or tried to use the resistors for modifying the Pressure command. These work OK on some vehicles, but they do not”FIX” the Computer Command, they only modify it. Any OPTIONS yet?
You could try to sell the vehicle owner the necessary sensors and vehicle components to attempt to solve the real electronic problems you suspect are causing these computer commanded line pressure issues. Sometimes this works and sometimes it doesn’t. But the real chore is getting that customer to break loose of another $500.00 to $2000.00 for these repairs. Sometimes this costs you the whole job! So, let’s say you sell that customer the electrical repair, which sensors-computer-wiring-grounds-connectors-alternator-battery……..do you start with? Your scanner and you DVOM say that none are out of specifications, but the pressure gauge tells you without a doubt that you’ve still got a problem. No OPTIONS?
All three of the scenarios above most of us have seen. Any body who has consistently put a pressure gauge on units knows that line pressure must go up during acceleration and it cannot be at minimum pressure while driving down the highway at 75 MPH. Line pressure must increase during WOT down shifts. Line pressure cannot be at maximum for an extended period of time or pump outer gear damage will occur. The problem we all have is that there is no real specification for what line pressure is SUPPOSED to be during these actions. And we have nothing to say the EPC command from the vehicle computer is right or wrong!
Over the past 15 years I’ve accumulated specific hands-on data that defines what is good line pressure on good working vehicles, and what is not acceptable line pressure during test drives. I’ve found that the stall test in a shop, though informative, does not give you REAL information about whether or not that transmission is going to live through your warranty and beyond. This data is from hundreds of vehicles, good working and those that don’t work so well. And let me tell you, it is amazing how similar the pressures are on good working vehicles. Those units that worked good, nice smooth shifts that are not bumpy or sliddy, are with-in 5 to 10 psi of this graph. These readings are at specific TPS voltage and vehicle speed. The following graph is from the past 8 years for E4OD/4R100 transmissions. Transmissions that fall in the specific problem areas described in the 3 scenarios at the beginning of this article usually fall well outside of these graphs for line pressure. Remember, these pressures are during the test drive, NOT sitting in the shop.
It is not unusual to see the computer command 55 to 60 psi at 65 mph or to command 55 psi during a shift. These are the vehicles that are almost guaranteed comebacks!
SO, do we have any OPTIONS YET? YES!!
As of the writing of this article, you really do have an OPTION.
ESE. Short for Electronic Systems Eliminator Patent Pending
This ESE system is designed so that you do not have to worry about the problem vehicles, Chips, or whether the Computer Commanded Electronic Pressure Control (EPC) is working properly. As long as you have built these units using good transmission building techniques and specifications, you’ve replaced the typical worn valves and valve sleeves, and you have a good pump, the pressure control system WILL work properly. Common sense here folks, those worn out Boost valves MUST be replaced and those outer pump gears cannot have more clearance than factory specifications. If you do the basics, the pressure control system will work properly. No sloppy or sliddy 1-2 shifts. No harsh shifts from drilled Valve Body Plates. No delay in reverse. No double bump in reverse. No harsh engagements. Bottom line, you have now installed an internal pressure control system, based on engine RPM and pump volume!
This system installs in about 1 hour, if the transmission is still in the vehicle. On the bench it takes about 10 extra minutes during a standard build. This system gives you and your builder easy options for…Big Tires, Towing heavy loads, Chips, Hot Rodding, Tug-of War, etc. This system will let you and your builder decide what works best for the units you’re building. This system also gives you OPTION’S for re-calibrating while in the vehicle. This takes about 10 minutes more time than a filter change would take. In that 10 minutes you can go from nice smooth Lincoln Navigator to Power Stroke killer shifts. To do these easy calibrations, make sure you follow the OPTIONAL instructions while building these units and you can count on having OPTIONS.
What about the computer showing codes? A simple resistor, installed during the build or with the solenoid pack removed, in place of the EPC solenoid wiring works just fine. This takes about 5 minutes during the build. Just make sure you completely disconnect the wires from the solenoid to the computer.
What about the Accumulator system changes? Does this take a lot of work?
During the rebuild this takes about 5 minutes. And this is where the OPTIONS come in for making each unit shift correctly for the designated use for that vehicle, Towing, Big Tires. Etc.
Do I have to drill the valve body plate or the pump? No. We recommend that NO DRILLING is done in the valve body plate or in the pump. Again, common sense here, the pump is the heart of these units, it must be in good shape and the boost valves cannot be worn out.
OPTIONS. In today’s repair market, having options are an absolute necessity. With ESE you now have pressure control options.
