Kyosho UM706 Rear Upper Bulk

The Kyosho UM706 Rear Upper Bulk is the genuine upper rear bulkhead for the Ultima RB6. It caps the rear end of the chassis above the gearbox, tying the rear shock tower and gearbox together into one rigid structure. This component carries load in two directions at once: it takes the compression from the rear dampers on every landing and it resists the twisting force the gearbox generates under acceleration, which is why it is a common casualty in heavy rear-end impacts.

A cracked upper bulk lets the rear end flex more than designed, which changes rear traction and makes the car inconsistent from corner to corner in a way that gets blamed on shocks or diff settings. This is the direct factory replacement, using the kit hardware with no modification required. Package includes one rear upper bulk. Check the gearbox halves and shock tower for damage at the same time, as they usually take the hit together.