1992 Skylark GS V6 w 3spd auto, converter lock up schedule
red88jeep
01-02-2008, 10:57 PM
Hello again, The question is what are the paramaters for the converter to engage/disengage lockup?. Now that it has gotten cold (as in 30 to 40 degrees F, not real cold like everyone else who get real icy winters) I have noticed an interesting transmission issue with the 92 Skylark GS 3.3 V6 with the 3 speed automatic. (before they went to the 4 speed). When the car is cold, the torque converter does not lock up like it normally does from about 45 MPH to 60 MPH until we have driven the car about 4 miles or so. Is there a programed schedule for the car that does not activate the lock up feature of the torque converter until specific paramaters are reached like coolant and or transmission temp? Once the car has reached operating temp, everything seems to work normal. Unless the load is low enough the temp drops to about what I would guess to be 130 to 160 degrees. (Thermostat seems to be working, because it opens up and the temp drops fast, then closes and it goes back up slower because of light engine loadlng and heavy heater use.) I have not found any real solid info on this. This is not an issue with the converter switches as they are working. normal lock up is around 60 mph (2000 rpm locked) on the highway and sometimes as low as about 45 (about 1400 to 1600) mph in urban conditions with light engine loading. It unlocks quickly when the throttle is pushed and will very lockup engagement with speed and road grade. The activation and deactivation is smooth so I do not think there is a mechanical problem. Thanks, Ron (PS, the coolant level is within the hot/cold marks on the tank) Maybe I should check its specific gravity and see if I have the right mix for proper sensor function?)
Blue Bowtie
01-19-2008, 08:45 AM
Since I don't have your PROM here to scan and hack, I can't be certain, but most of the other GM binaries I have hacked have a coolant temperature and closed loop flag in the TCC logic. That would require coolant to reach a specified parameter, as well as the OČ to be warmed and active (or after an OČ time delay). In a hydraulically controlled transmission (or even in most electrically controlled transmissions) shifting is a function of hydraulic line pressure. With cooler oil, line pressures are higher, which is usually interpreted by the mechanisms (accumulators and valve springs) as higher loading, thereby delaying engagement of subsequent gears. In other words, upshifts take longer with a cold transmission.
As a side note, if you really want to maximize your engine and transaxle life, you really should be limiting load until the assemblies are warmed to normal operating temperature. As a rule, I limit myself to light acceleration to about 45 MPH until the coolant is in the normal range. After startup, it takes time (even on a warm day) for all the components to heat up and expand to their normal dimensions, for lubricants to thin out and flow properly, and for latent moisture to be liberated from surfaces and the lubricants. Castings which are not at operating temperature are not at their design dimensions, and any extra stress imparted from loading in that state can be a real strain on sealing . I'm guessing that 90% of head gasket leaks are started by overloading a cold engine, allowing combustion gasses to start burning away at unsealed areas. It wouldn't be surprising if most of the notorious intake gasket failures start the same way. I'll bet that almost ALL of main and rod bearing failure which aren't directly attributable to incorrect oil level or type are caused by overloading when cold, when clearances are higher. Instead of blaming the design we should perhaps blame the type of driving. The wheel bearings and CVs are also operating with lubricant which has drained to one side and is not warmed. Other components and assemblies operate under stress when cold, such as power steering pumps with the thicker oil running at near line-bursting pressure, gaskets, water pump seals which are cold and stiff, allowing a rapidly rising coolant pressure to force leaks before the seals can actually seal, and discrete bearings like those in idler sheaves and alternators running essentially dry until they warm a little and start moving their lubricant. HVAC blowers suffer the same problems until they've been run slowly for a while, and rear drive cars have just about no carrier bearing lubrication until the axle has been driven for a few miles. Even the tires need to be warmed and flexed a bit before they can perform to their design, thus the reason for COLD tire pressure specifications.
You probably don't expect yourself to spring out of bed in the morning and head out to run a marathon before having your first cup of coffee. You shouldn't expect any more from your vehicle.
As a side note, if you really want to maximize your engine and transaxle life, you really should be limiting load until the assemblies are warmed to normal operating temperature. As a rule, I limit myself to light acceleration to about 45 MPH until the coolant is in the normal range. After startup, it takes time (even on a warm day) for all the components to heat up and expand to their normal dimensions, for lubricants to thin out and flow properly, and for latent moisture to be liberated from surfaces and the lubricants. Castings which are not at operating temperature are not at their design dimensions, and any extra stress imparted from loading in that state can be a real strain on sealing . I'm guessing that 90% of head gasket leaks are started by overloading a cold engine, allowing combustion gasses to start burning away at unsealed areas. It wouldn't be surprising if most of the notorious intake gasket failures start the same way. I'll bet that almost ALL of main and rod bearing failure which aren't directly attributable to incorrect oil level or type are caused by overloading when cold, when clearances are higher. Instead of blaming the design we should perhaps blame the type of driving. The wheel bearings and CVs are also operating with lubricant which has drained to one side and is not warmed. Other components and assemblies operate under stress when cold, such as power steering pumps with the thicker oil running at near line-bursting pressure, gaskets, water pump seals which are cold and stiff, allowing a rapidly rising coolant pressure to force leaks before the seals can actually seal, and discrete bearings like those in idler sheaves and alternators running essentially dry until they warm a little and start moving their lubricant. HVAC blowers suffer the same problems until they've been run slowly for a while, and rear drive cars have just about no carrier bearing lubrication until the axle has been driven for a few miles. Even the tires need to be warmed and flexed a bit before they can perform to their design, thus the reason for COLD tire pressure specifications.
You probably don't expect yourself to spring out of bed in the morning and head out to run a marathon before having your first cup of coffee. You shouldn't expect any more from your vehicle.
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