I have a 06 duramax and my allison slips when shifting between 4 and 5 and from 5 to 6. I want to replace the tranny whats a better way to go? Should i rebuild my allison or go with a suncost tranny?

 

You can always go with a SunCoast Gmax6 Kit. That is what we use to build transmissions here. Matched with a Goeren torque converter they are really nice to drive daily.
If you are not feeling like jumping into a DIY transmission build, feel free to PM me, we have several customers ship us their transmissions to build here.