The support bars are needed because of the transfer case bouncing around without it's own support. All the force would be on the thin aluminum bellhousing where it bolts to the block. Aside form breaking the bellhousing it would probably flex for awhile and take out the trans shaft seal or fatigue the flex plate. I've had my trans pan off a couple times without removing the exhaust. In the last two months I've had the tranny out and in on my 99Tahoe and out and in twice on the 89 K1500, the exhaust will have to be dropped from the manifolds to get the convertor cover off. I was able to loosen and rotate the support bars without removing them.