Low Throttle Lock-Up?..
Low Throttle Lock-Up?.. This issue is somewhat intermitent as it will only occur after an extensive highway cruise. Converter lockup on the highway in 4th will lock positively but after 30 minutes or so of highway at 65 or so at low throttle it acts like it wants to hover between locked and unlocked, and it seems like the lockup clutch is slipping...but if I roll into the gas it will engage very well and I can accelerate strong with it locked in 4th. Any ideas...? Some kind of partial throttle lockup thing?..Obviously the clutch is fine since it locks better at 1/2 throttle than 1/4. It only does this in 4th, so if it is in 3rd and I stay in 3rd it will lock up and never faulter...any ideas? It has been tuned by a couple different guys and it still does it. All TM is gone also.
That I do not know. I didnt even know about it when it was built. It has a shift kit, but I assume that the PWM is an additional process? Is there no other way to remove it besides the VB? Is it something I could do if I pull the VB or is it risky?..
You can mostly eliminate it in tuning alternatley , Im sure some of the tuner guys will tell you what to do there.
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I have/had the same problem. I think I might have fixed it tonight though. I have to drive it a bit more tomorrow. If you have hp tuners, put your TCC duty cycle maximum to 100 and the minimum to 90. I'm not certain if this is what burnt up my last converter, but I'll be damned if it happens again. The lockup clutches on my fuddle were burnt up.
Let me ask you this. How long have you had this converter in and what brand is it? Do you have a dyno graph of your current setup?
Let me ask you this. How long have you had this converter in and what brand is it? Do you have a dyno graph of your current setup?
PWM with a small diameter converter can defininatly wreak havock with the converter clutch. Heres why, The PCM is programed to allow a certain about of slip it does this by pulsing the converter regulator valve. But the percentage of slip is based on a given friction area in the converter clutch. (The stock area of the stock clutch) Now because the small converters friction area is much less, a given percentage of slip comanded lets say a command of 50 percent slip by the PCM intended for the area of the stock converter can end up being and actual slip due to the lower friction area of 80 percent and the converter clutch will fail in relativley short order under these conditions due to heat/wear and burning of the friction material.
I see alot of post about converter clutch failures with the small aftermarket converters and It my thought that this is why. Many people install the small converter in there stock trans and or a trans with PWM functional and fail to take any action either mechanically or through tuning to eliminate PWM and then when there converter fails the converter and the converter manufactuer is placed to blame.When in actuallity its not the product thats to blame but failure to set up the trans and or tuning to compensate for this change in area.
(This is not and issue with any of our transmissions as PWM is mechanically eliminated in all of them. Lockup can only be commanded full on or off when this is done.)
Most other vendors and sponsors here also from my understanding eliminate this fully or partially in there builds mechanially also. But in anycase it needs to be done in one of the two manors either mechanically or through software or you will at the very least shorten the converter clutch life of your expensive converter. There are exceptions such as the multi disk converters however though I havent experinced this myself as we dont sell those at present. It is my understanding that even with these converters though much less likley to suffer a clutch failure do have at times chatterig issues (noise and vibration) When in the partial lockup condition.So its still a good idea.
I see alot of post about converter clutch failures with the small aftermarket converters and It my thought that this is why. Many people install the small converter in there stock trans and or a trans with PWM functional and fail to take any action either mechanically or through tuning to eliminate PWM and then when there converter fails the converter and the converter manufactuer is placed to blame.When in actuallity its not the product thats to blame but failure to set up the trans and or tuning to compensate for this change in area.
(This is not and issue with any of our transmissions as PWM is mechanically eliminated in all of them. Lockup can only be commanded full on or off when this is done.)
Most other vendors and sponsors here also from my understanding eliminate this fully or partially in there builds mechanially also. But in anycase it needs to be done in one of the two manors either mechanically or through software or you will at the very least shorten the converter clutch life of your expensive converter. There are exceptions such as the multi disk converters however though I havent experinced this myself as we dont sell those at present. It is my understanding that even with these converters though much less likley to suffer a clutch failure do have at times chatterig issues (noise and vibration) When in the partial lockup condition.So its still a good idea.
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Last edited by performabuilt; Jan 1, 2008 at 08:47 PM.
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Now with the small diameter converters theres even less friction area so they would be even more prone to fail in that condition.
Think of it this way ever seen the area and the force of a manual clutch? Well in and auto locking the clutch at WOT your asking a clutch with a fraction of the surface area and even lower presure to do the same task. It may do it for a while but eventually doing this will lead to converter clutch failure.
Again not the converter manufactuers fault a matter of physics. Not enough room for the friction area and the presure not available to make it live. Its not a suggested practice except in the case of multidisk converters which were designed just for this purpose.
When you do this with a single fiction converter you are each time taking a risk. However you tuner running a dyno should be able to tell if its holding and if not should imediatley discontinue the test locked to avoid damage to the converter clutch. That said it still dosent mean theres any problem with the clutch, It just simply wasnt designed to do that.
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Another thing to consider is the late model vehicles with factory converters they used a woven lining. This lining required the pwm function because of the way it worked. Basically it was created for comfort of the tcc apply. People complained about harsh lockup and this is why it was created. Now take a converter that does not have this woven lining and you are still using a valve body that has a full pwm regulator valve in it, how long is the clutch going to last? Another issue to look at by totally eliminating it. In the late model OBII vehicles the converter clutch is used on deceleration. If the pwm function is totally eliminated, a harsh feeling can be felt when you let off the gas in 4th. This happens when the clutch is commanded to come back on. Just got to love this industry! I have had this conversation with the owner of PI and his feeling is that a bit of pwm needs to still be used. The issue is really with the deceleration. As far as tuning I personally do not want to see tcc slippage under throttle. We use the transgo regulator valve in our valve bodies and it has been working very well for us. Tuning and the way a valve body is set up can make or break you. Just some food for thought. Vince
