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Transmission shifting question.

J

JCircs

New member
Why would my auto 4T65e hd transmission shift fine while driving regular but at wot it shifts very late? Even with the PCM programmed to 1-2 shift at 43 and/or 5700rpm it still hits 53 and 6300rpm? Those numbers could be off a bit but the fact is its not shifting when the PCM tells it to, 1-2 and 2-3 at wot. It don't feel like its slipping or banging into gear in fact it feels great. Any help is greatly appreciated, thanks.
 


It will command the shift at those points, but by the time it select the next gear, moves fluid around and drops into the next gear it can increase rpm 200-400 and the vehicle speed can rise 2-5 mph.
 
Regardless of how low we made the shift points it still shifted at 6300rpm @ wot. The tuner seemed to think the transmission was slipping but I'm not feeling it, can this be caused by something else?
 
BillBoost37 said:
There are two tables. Are you looking at the Wot settings?
Click to expand...
Just to be clear I'm not the tuner. The car was originally tuned by 3800Chris and most recently by Tune Time Performance, both mentioned the same issue and both are very experienced with the 3800. Now I just want to know why, maybe just a sensor I hope....
 
Did either give you a copy of the file that you could forward over for us to look at?

There's often a slight lag from the commanded shift speed/rpm to when it actually occurs. The rpm are climbing and when it hits X it's told to shift..so the actual shift happens slightly later. Your difference seems too large though.
 




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