I have an 03 HO 48re truck with 3.73 gears. Normally the torque converter locks up at ~49 mph in 4th gear and unlocks at ~45mph. This is with light load. However, sometime (about every 5K miles or so) the truck will lockup the torque converter in 3rd gear at ~35mph (~1600rpm). This has happened maybe 4-6 times since I have owned the truck. It generally does it under light acceleration while proceeding down a very slight hill.

What causes this? There must be some parameter in the transmission program to lockup the torque converter in this situation. Any ideas?

Are there any aftermarket products to force TC lockup in 3rd gear? I like this behavior in the transmission and would like it to occur more. While I love this truck, it really feels disconnected when the TC isn't locked up. And fuel economy plumets.

Thanks,

-Tom

 

If you drive with the OD turned off, it will lock up in third gear everytime. There are trans controllers out there where you control the lockup but they are expensive. Check out DTT or ATS.....

 

In this case, overdrive was on.

As I said, it's an odd occurance, I just wish it would happen more.

-Tom

 

You can lock the converter by backing off on the throttle for a few seconds and then easing down again. The slowest I have been able to do this is about 30. I use this when I am in town and the speed limit is 35 or 40. You will have to feel for it to get the timing right but it works.