2010 Tiffin Phaeton 42QBH powertrain

Its bigger than my Cummins 5.9 6BT. But I prefer the mechanical engines, so I can only go as new as a '97 or maybe a '98. But the Cummins 8.3 ISC is a good dependable engine that you will also find on commercial over the road trucks. Know nothing about the transmission. My choice would be the Allison 3060, but my 19 year old Allison MT643 is still going strong. I think you can depend on any Allison transmission that can handle the torque of then engine. And no manufacturer is going to mate up one that can't.

Many manufacturers would put an 8.9L ISL in that big of a rig rather than the smaller 8.3L ISC Tiffin used...but it should work okay.

For comparison, I have a 2008 43 ft. Mandalay Presidio, 4 slides, tag. The setup is:
Freightliner XC-R;
Cummins 8.3 ISC, 360 HP, 1050 Torque, EPA'07;
Allison 3000

I'm about 34,000 lbs. fully loaded. I tow a 6400 lb. Chevy Traverse.
I've been through the Ozarks and Smokies so far with no problem. I'm comfortable and satisfied with my setup. I never worried about getting to the top of the hill. I'm not the first to the top but also not the last.

We had a 2009 Phaeton 40QTH with the same engine. We towed an Acura MDX. From a dead stop we could hit 55MPH at the end of most freeway onramps. No issues in the mountains.
Some issues you should have checked before purchase are the wetbay floor, the front driver's slide floor and the roof radius rails. A very good source for Tiffin info is tiffinrvnetwork.com.

pablo77 wrote:
For comparison, I have a 2008 43 ft. Mandalay Presidio, 4 slides, tag. The setup is:
Freightliner XC-R;
Cummins 8.3 ISC, 360 HP, 1050 Torque, EPA'07;
Allison 3000

I'm about 34,000 lbs. fully loaded. I tow a 6400 lb. Chevy Traverse.
I've been through the Ozarks and Smokies so far with no problem. I'm comfortable and satisfied with my setup. I never worried about getting to the top of the hill. I'm not the first to the top but also not the last.

I dont think the traverse weights that much closer to 4900 according to the 2014 dinghy towing guide.

Ted

I always felt that the tag-axle Phaetons were underpowered when they had the ISC, when everyone else seemed to be putting ISLs in their tag models. Apparently Tiffin heard that from enough people that they upped the engine to an ISL a few years ago. Remember that the 42-foot-plus tag axle model weighs about 10,000 lbs. more than the 40-footer with the same engine. Sure, it will get you there OK, but more engine is seldom a bad thing.

Tiffin (and all the others) upped their engines to the ISL when Cummins stopped producing the ISC.

To the OP, the powertrain you are asking about is perfectly fine and was used extensively in that time frame by multiple manufacturers. The powertrain should be the least of your worries.