A transmission: Can it be fixed?

Several points were brought up in a seminar presented at the Automechanika Chicago show in April about the frustrations that come with diagnosing transmission concerns. To determine if the cause of a malfunction is related to an engine management problem, an ABS issue or an actual transmission malfunction can be at times quite challenging. If the malfunction has been determined to be a transmission problem, the next step typically is to decide if it is a minor or major repair. Of course it is always nice when a cause to a problem has been discovered and is passed along to others saving them the grief it took to resolve it.

Through many years of experience diagnosing transmission concerns in shops and on ATSG’s technical help line, a general diagnostic approach has been developed to find that silver bullet as quickly as possible. The list begins with “Information,” meaning we look first to see if there are any bulletins or articles already covering the subject. The available diagnostic equipment as well as the ability to use the equipment is considered if handling the problem over the phone.

Understanding the codes received, checking power and grounds, doing a cursory view of the wiring and connectors while looking for cross connect possibilities are on this list. Checking into the four main critical PCM/TCM inputs (Engine load, Speed Sensors, Gear Shift Position Switches or Sensor and Temperatures) as well as how the signal is generated and delivered to the controlling computer and computer strategies (ABS, torque reduction, sport and economy modes, adaptations, manual tap shift controls, start/stop technology or neutral controls, etc.), transmission misapplication, transmission fluid and aftermarket programming, products and parts round out the list. Having this comprehensive overview goes a long way in determining which avenue one needs to take based on the problem at hand to get to the cause as quickly as possible. Of course it doesn’t completely eliminate every possible headache, but it sure can eliminate many of them.

One reason we are seeing frustration levels increase diagnosing transmission concerns are programming issues. The complexity of today’s vehicles brings a whole new dimension of diagnostics to the table. Shift strategies are becoming reliant on a multitude of inputs that if they become skewed, affect transmission operation. Put that together with a program not written well and you have malfunctions that cannot be totally corrected. Sometimes malfunctions are discovered and corrected through reprogramming, which is why the first step in our general diagnostic list is information. Nothing can be more frustrating than trying to fix a problem that can only be achieved via reprogramming.

A simple example of this was a call we took from a shop that decided to put its toe in the water to fix a CVT transmission for the first time. It was a 2007 Nissan Altima that arrived to the repair facility with a vehicle speed sensor code P1722. The shop had diagnosed it down to a problem with the tone ring and wheel bearing rather quickly. After repairs the code was cleared and they drove the vehicle. All was perfect for the exception of an approximate five-second delay into gear, both forward and reverse. Once engaged, the transmission drove flawlessly (as far as a CVT is concerned).

This particular CVT utilizes a torque converter allowing a forward or reverse clutch to apply like any other conventional transmission. This means all that is required to engage the clutch is to move the manual valve into the Drive or Reverse position. A select control valve in the valve body would then control the engagement of the clutch. Not only is the intention of the select control valve's function to provide a nice comfortable garage shift into gear, it primarily is used to prevent a damaging jolt to the drive pulley assembly.

For this reason the shop checked the manual valve adjustment and the transmission range sensor signal, which proved to be in order. The valve body was then removed to inspect the condition of the assembly and particularly the select control valve. In the process they noticed the fluid was still in good condition and the pan was fairly clean. The disassembly and inspection of the valve body revealed nothing. With the valve body removed, they checked the apply of the forward and reverse clutch with some compressed air and they applied nicely. So it all went back together with the sense that the transmission was in good shape.

The subject of initializing the EEPROM inside the transmission then came up. Part of the initializing process requires stepping into the throttle just enough so that the idle and wide open throttle signals are both in the Off state. For this reason, the wide open and closed throttle signals were inspected just in hopes that maybe something was amiss. But once these signals were verified, it then lead to the idea of performing an Idle Air Volume Learning procedure. This too did not resolve the delayed engagement problem. It was at this time the call came in to ATSG to see if we could help.

A delayed engagement into gear is somewhat of a fairly common call with this transmission, as it could have a two- to three-second delay and is considered normal. As much of a nuisance this slight delay might be, it is the result of the way the select control valve operates. But a lengthier delay is a problem and ATSG knew of a bulletin by Nissan that identifies specific Transmission Control Modules that have this problem (NTB 10-147). If the vehicle in question contains a TCM part number listed in the bulletin, there is a reprogramming procedure to fix the delayed engagement problem. Again, it is a simple example of trying to fix something only programming can fix. The bigger problem is a malfunction due to a programming problem without a reprogramming procedure available to resolve it. Unfortunately, this type of situation is on the rise beginning with some 6-speed automatic transmissions and increasing with some 8- and 9-speed transmissions.

With shops being faced with such a dilemma, it becomes all the more important to have some form of an organized diagnostic routine as previously mentioned in an attempt to nail down a possible programming problem. Admittedly this at times will take skill, equipment and time that might be difficult to bill.

Sometimes programming problems can be quick to determine, such as an incident

that came up recently in a Miami shop. It was a 2010 Ford F150 4 wheel drive with a 4.6L engine and a 6R80 transmission (Figure 1). The customer concern was that when he tows his boat, the Tow/Haul switch located on the end of the column shift selector lever seemed inoperative (Figure 2).

The Tow/Haul feature delays up-shifts to reduce frequency of transmission shifting and provides engine braking in all forward gears when the selector lever is in the (D) position.

The Tow/Haul switch is a momentary contact switch, which when depressed will illuminate the words TOW HAUL in the Instrument Cluster indicating the strategy has been activated. Just press the button again to turn the light and strategy off. All of this was working yet the delayed shifts and engine breaking were not present.

The computer for this transmission is located inside the transmission. MY 2010 Ford trucks with 6.7L engines have the TCM mounted externally. MY 2010 4.6L and 5.4L applications have the TCM inside the transmission. In 2011, the TCM is external for 3.7L, 5.0L and 6.2L applications. This has caused quite a bit of confusion when looking for accurate wiring information.

With the TCM being inside the transmission with this 2010 4.6L F150 truck, the connector at the transmission contains power, ground, CAN BUS wiring, P/N signal, Back up light signal and a Tow/Haul signal input on terminal 1 (Figure 3). This is a 12-volt signal wire that the Tow/Haul switch toggles to ground. When this signal was checked with a meter Key On Engine Off 11.57 volts was observed (Figures 4, 5 and 6). When the Tow/Haul button was depressed, the voltage dropped to 0.01 as it should (Figure 7).Once the button was released, the voltage returned. This verified that the TCM was receiving the Tow/Haul signal. No response to the shift strategy when the Tow/Haul was activated indicates a computer strategy malfunction. No bulletins for a reprogramming fix have been published to fix this concern. The only option

would be to purchase a new computer with the hopes that it will correct this concern. Not a happy conclusion, but this was the reality and the customer chose not to go that route (no pun intended).

Another area of frustration can at times be related to aftermarket tuners designed to enhance engine performance. This does not come up too often, so when it does it can be elusive since it is not in the forefront of one’s thinking. We had experienced tuners burning out 6-speed Aisin Seiki transmissions in Dodge diesel incomplete chassis applications as it blocked shift adaptations. We now are seeing overdrive clutch burnout with the 68RFE transmission behind diesel engines even when you tell the tuner to return to street settings.

There are other possibilities for premature overdrive clutch failure, but when you put in a new pump, drum assembly, valve body, solenoids and line pressure transducer, if you still burn out the clutch, the tuner is pushing it past the clutch assemblies holding capacity. From seeing how some of these trucks are outfitted and modified without any tuners, it doesn’t look like it would take very much to take out the transmission in the first place. Pump up some more horsepower and you'll find the weakest link in the chain. In this transmission it could be the sprag and/or the overdrive clutch.

Many new Dodge and Jeep vehicles now have 8- and 9-speed transmissions experiencing programming issues affecting transmission function. Someone who I know personally purchased a 2015 Jeep Rubicon with a 9-speed transmission that went down in 1,500 miles. After a new transmission and reprogramming, it now takes off in third gear and he has to go down a hill doing 60 mph for it to finally shift into ninth gear.

An interesting article concerning the front wheel drive version of the transmission appeared in the Feb. 16, 2015, issue of Automotive News entitled “Honda to offer ZF 9 speed in Pilot” by Lindsay Chappell. A quote from this article reads, “Fiat Chrysler officials said last month that they were making software improvements to address some complaints about the transmission's performance.” This transmission is also in the Acura TLX and MDX.

I think I said previously that nothing can be more frustrating than trying to fix a problem that can only be achieved via reprogramming. I need to correct myself. Nothing can be more frustrating then trying to fix a problem that cannot be fixed. Hopefully many of the programming issues will be resolved before they come into shops for repair once out of their warranty period.