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BCM Programing affecting the trans shift points?
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=8&t=42632		 Page 1 of 1
Author:  LibertyFever [ Mon Apr 27, 2009 9:23 am ]
Post subject:  BCM Programing affecting the trans shift points?
Can somebody tell me if the BCM controls the automatic transmission's shift points or does it function as a result of flywheel speed?

When I bought my 04 Liberty Sport it still had the stock wheel size of P215/75R16 tires and I'm assuming the BCM was programmed for that tire size. I've recently installed a set of LT245/75R16 tires and I'm considering having the dealership reprogram the BCM.

By the way initially I thought the bigger tires were drastically reducing my MPG however I've since realized that the odometer and speedo seem to be reading 5.7% low.
Author:  tjkj2002 [ Mon Apr 27, 2009 7:21 pm ]
Post subject: 
The TCM effects the shifting,the PCM is the one that tells the TCM when by using the speed signal(among other sensors) that is send from the BCM.The PCM is the one that needs to reprogrammed,some years can be reprogrammed and some can not.
Author:  LibertyFever [ Sun May 03, 2009 8:03 am ]
Post subject: 
Wow, thanks "tjkj2002" for explaining that point to me. I thought that perhaps that the transmission operation was complicated.

I'm on the fence as to whether or not to visit my dealership and have them reprogram the computers for the larger tires. I'm not positive it will improve the performance much. The inaccurate odometer/speedometer I can live with.
Author:  tjkj2002 [ Sun May 03, 2009 11:55 am ]
Post subject: 
LibertyFever wrote:
Wow, thanks "tjkj2002" for explaining that point to me. I thought that perhaps that the transmission operation was complicated.

I'm on the fence as to whether or not to visit my dealership and have them reprogram the computers for the larger tires. I'm not positive it will improve the performance much. The inaccurate odometer/speedometer I can live with.
It's a noticeable improvement since the trans will shift correctly.
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