[Thickey92]

I’m having an issue with my trans in my 1999 f250 7.3 ,when my trucks in a tune that puts out more power then stock my trans will slip only while the converters locked while doing 45+ under load getting on it a bit , it’ll be pulling good and then just feel like it’s in neutral and Rpms shoot up until I let off the throttle then it catches again, if i drive the truck “normal” it won’t do it, also I tried this with OD on and off and it happens in both,it does shifts perfect through all gears,Trans was rebuilt 30k miles ago it has a BD valve body, and the converter is about 3 years old and has about 45k miles on it, my question is does this seem like the converter is going bad since it’s only during Lock up ?, I want to

 

[Mark Kovalsky]

The converter can't make it seem like neutral. If the torque converter clutch completely lets go RPMs should only jump by around 500 RPM. If you get more slip than this I suspect one of the clutches in the transmission is letting go. This can happen from a tune that adds power without modifying the transmission pressure to handle that added power.