larger tires and allison 5th gear?

[mp5medic]

I have recently been to the allison web site and they are saying that there may be a problem with an allison shifting in to fifth gear while trailering with tires 285 or larger? has anyone experienced this?

[HK 3]

I have been using 285R75 16 BFG AT tires and have hauled a 6,500 lbs. boat and a 6,500 lbs. horse trailer and have had no trouble shifting into 5th gear with the Allison transmission. In fact, with the "Juice", I can hold 5th gear up any grade pulling either the boat or horse trailer.

[DmaxMaverick]

No problem with mine. I've been towing my 12K 5'er with 285/75/16's for about a year now. It will downshift a *little* sooner on a grade with the larger tires, but nothing unexpected. On flat ground, it runs just fine. With no load, it shifts fine. Better, IMO.

[NFLDMAX]

When I tow my boat down to the coast, I occasionally have a situation where the truck downshifts to 4th gear and won't come back unless I really speed up. It probably has to do with the 55 mph speed limit, and the shift point between 4th and 5th being in this area. Never notice this situation at higher speeds.