Fits '11-'19 Allison 4x4 Transmissions. This support can keep your Allison four wheel drive housing from cracking in the event of a driveline vibration (bad u joint, dented or bent driveshaft). Driveline vibrations from a bad u-joint or other factors can put stress on the 4x4 transmission housing and cause it to crack. Replacing housing can cost over $1000. Installing rear housing support can keep your four-wheel drive housing from cracking Our Rear Housing Supports are fabricated in-house right here at Merchant Automotive. Using 7/8 .120 wall DOM mild steel tubing for maximum support. The support installs using the factory bolts. This brace can be easily installed in the driveway or garage.