09 Cummins 871 with ultrashift

[mikealike]

I've had my truck since 13 and it came with 500k miles. Recently it developed a rear structure leak. Took it to the shop, they pulled out trans, clutch, fw, rear structure and driveshaft. Truck has 1.3million on it. They replaced with new mounts, structure gasket and resurfaced the fw, new clutch, new xy shifter, inertia brake and driveshaft. Drove the truck for 16 days and got stuck in a truck stop, it didn't want to come out of drive, dash flashing f. Went inside the store and 20 min, came out was able to get the truck out into neutral. I got under the truck to check and found the 5 top bolts to be non existent. Placed a strap under trans and got it out of the fuel island and caught a ride to get (5) 7/16×16 bolts to find out that the threads was stripped out of the fw housing. Other than the bolts with washers not torqued to spec, what would cause this to happen? Thanks in advance.[/font]