The normal hydraulic forces within the torque converter push the TCC piston toward the cover; the TCC piston reacts like a “normally on” pressure switch. It is normally pushed to the apply position and is released only when the flow of TCC-release/charge oil between the piston and cover floats the piston off the cover.
A mid-’90s Dodge Caravan came into the shop with the complaint of a rough noise/feel when driven above 45-50 mph. The van had been into a couple of other local shops in an attempt to find the noise with no success, and the customer was getting frustrated.
As normal, I started with a road test to see whether I could duplicate the customer complaint. Sure enough, upon reaching 45 miles per hour the van started to make a low growling sound and you could feel a little vibration through the steering wheel. It was time to get the van inside and do a visual inspection.
The sheriff wanted to be more competitive with his Charger so he could win more than one third of his races. The Charger – here in Metro Denver – ran the quarter mile in 15.9 seconds and averaged 88 mph with the stock 5.7 Liter Hemi engine, automatic transmission and 2.80 differential gears.
The motor vehicle is a combination of many separate components and operating systems that are mechanical, hydraulic, electronic, and air or vacuum operated. Successful diagnosis and repair can be accomplished only by viewing the problem with a systemic approach and careful consideration of the entire group of components that can influence or be the cause of the complaint.
The 604 was the first American computer-controlled transmission with adaptive shift strategy. The relearn process was not much different from what it is for today’s transmissions. For those of you who were not in the transmission industry back then, there was no quick-learn procedure for the 604. The quick-learn feature was not available until the mid-’90s. You actually had to drive the car at different throttle openings to relearn the shift adapts, and it could take 30 minutes or more of driving time to get it right.
In This Issue
2004 & later GM ‘T’ truck: 4L60-E TPD-model changes
4L65-E M33 partial-hybrid transmission: Auxiliary-pump filter
Allison 1000/2000 series: No forward movement
Many of today’s release bearings may not look like the original bearing that was in the vehicle. A large number of release bearings are now of the “self-centering” type.
Since the time of writing that article, it seems the Hall-effect style of sensor is favored among the manufacturers, most likely because of its reliability and the cost effectiveness of producing it. This sensor can be either a two- or three-wire design, with the frequency signal being generated by a magnetic wheel (ring) or by the teeth of a gear. The three-wire design consists of a voltage-supply wire, a ground and a signal wire. The two-wire design has a voltage-supply wire and a signal wire. For this two-wire sensor to work a resistor inside the TCM/PCM is wired to ground, allowing the voltage on the signal wire to drop when the rotating magnet is used to “chop” the sensor circuit and producing the signal pulse.
For a while now I have been interested in finding out what is causing third-clutch failures in Honda five-speed transmissions. An opportunity finally presented itself when a customer brought in his 2003 Honda LX with a 3.0L engine and a BAYA five-speed automatic transmission. We had overhauled this transmission three years ago when the vehicle had 60,000 miles. Now with 134,000 miles the vehicle had an erratic 2-3 shift and code P0780 “Problem in Shift Control System.” When we disassembled the unit the only problems we found were burnt third clutches (Figure 1) and badly burnt fluid.
A half-hearted attempt to make a sale leads to disbelief on the part of the customer: “Well, your brakes are pretty worn out. You may want to think about replacing them.” Does the customer need the brake job or not? If he does, tell him so. If not, tell him when he will. Being wishy-washy about it doesn’t do either side any good. The customer loses confidence and you don’t make sales.