Ok guys I'm out of resources so maybe you guys can help. Here's truck info, 06 Cummins with basic add ons with Suncoast Master kit and Converter. 3 weeks ago truck strated having a 3-4 flare or shuttle shift when the Tow/Haul button is pushed. I could turn off the Tow/Haul and the symptoms went away. Finally got tired of not being able to use Tow/Haul so took truck to tranny shop. Direct drive clutches and band were shot along with lock-up clutches in converter. So freshly rebuilt tranny with all hardened shafts & fresh converter and truck still has the same issue. All pressures are good, no codes thrown and all solenoids are working great as well. Like i said you turn off the tow/haul and tranny shifts fine, just when the converter load is placed on the tranny while it is trying to shift is when the problem happens. Any Help?

 

have you called suncoast about it? almost sounds electronic in nature.

 

Called a spoke with Ernie and he had me put it on the scanner to see if anything showed up. We did that yesterday and couldn't find anything. All the solenoids and governors checked fine, even went through the accumilator circuit and checked spring and piston. Gonna call him back today and see if he has more advice? Thinking it could be in the valve body but I can't find anyone that's had this issue?

 

maybe measure the resistance in the wire for the TC lockup since it grounds the circuit to lock the TC if there is a real high ohm resistance i could see if causing a problem. just thinking out loud. maybe Ernie has something else you can try he's pretty slick on these things. he built my valvebody and i can overdrive any gear now....that option isnt on the website....