Torque Converter Lockup Question
#1
12-25-2008, 02:42 PM
Torque Converter Lockup Question
On a 99 4wd with the 4L60E automatic, when does your torque converter lockup?
Ever since I had my tranny rebuilt, I think mine engages too early, and too low of an RPM/Speed. I notice it most at about 45 or 50 mph cruising on a flat road. It goes into lockup, the rpms drop a couple hundred maybe, and the truck bogs a bit. If I gas it, it drops back out but soon locks up again. It works fine, just a little annoying. If it really bugs me, I drop the shifter into 3rd to stop it from cycling so much. Any higher speeds are fine, it is just right at this point it is a little busy and it really isn't in a good point in the power band.
On the electronic tranny, the shift points and lockups are controlled by the PCM, so I can probably just get it reflashed or use a tuner to adjust it. The tranny shop is too far away to make that trip worth my while.
The shop updated not only the tranny hardware, but any outstanding software updates as well. It is possible they didn't get it quite right.
Just looking for your thoughts and experiences.
Thanks
Ever since I had my tranny rebuilt, I think mine engages too early, and too low of an RPM/Speed. I notice it most at about 45 or 50 mph cruising on a flat road. It goes into lockup, the rpms drop a couple hundred maybe, and the truck bogs a bit. If I gas it, it drops back out but soon locks up again. It works fine, just a little annoying. If it really bugs me, I drop the shifter into 3rd to stop it from cycling so much. Any higher speeds are fine, it is just right at this point it is a little busy and it really isn't in a good point in the power band.
On the electronic tranny, the shift points and lockups are controlled by the PCM, so I can probably just get it reflashed or use a tuner to adjust it. The tranny shop is too far away to make that trip worth my while.
The shop updated not only the tranny hardware, but any outstanding software updates as well. It is possible they didn't get it quite right.
Just looking for your thoughts and experiences.
Thanks
#3
12-25-2008, 11:59 PM
RE: Torque Converter Lockup Question
Yes, I'm sure. When does yours kick in?
I hope most anyone can tell when a tranny shifts, I counted them many times. And yes, it is in D. I mentioned I can change the behavior by shifting down to 3 to avoid it. This vehicle does not have the ability to disable it like some other vehicles.
It is also easy to tell when the lockup occurs. After the truck shifts into OD (4th) there is a second subsequent more subtle drop in RPM when the clutch applies. One way to confirm this is to keep the gas constant and VERY lightly apply the brake so that only the brake switch clicks on, which immediately drops a vehicle out of lockup (protects the clutch and other things). You will notice the tach jump up in RPM slightly to correspond to the TCC disengage. You can also confirm this with an OBD tool if you can read real time data.
It is a little harder to tell on quieter cars without tachs, but these trucks are noisy enough that you can hear everything, if you know what you're looking for.
Thank you, I appreciate your interest in my question.
I hope most anyone can tell when a tranny shifts, I counted them many times. And yes, it is in D. I mentioned I can change the behavior by shifting down to 3 to avoid it. This vehicle does not have the ability to disable it like some other vehicles.
It is also easy to tell when the lockup occurs. After the truck shifts into OD (4th) there is a second subsequent more subtle drop in RPM when the clutch applies. One way to confirm this is to keep the gas constant and VERY lightly apply the brake so that only the brake switch clicks on, which immediately drops a vehicle out of lockup (protects the clutch and other things). You will notice the tach jump up in RPM slightly to correspond to the TCC disengage. You can also confirm this with an OBD tool if you can read real time data.
It is a little harder to tell on quieter cars without tachs, but these trucks are noisy enough that you can hear everything, if you know what you're looking for.
Thank you, I appreciate your interest in my question.
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