I'm wondering if anyone has pulled a Rockwood/Flagstaff Roo/Shamrock with their F150? I'm looking at a 21SS model that weighs about 3700 pounds empty. It is one of those expandable TTs. I'm wondering about the impact on fuel mileage and whether there is any hope of towing this thing in OD. Right now I'm pulling a 2,000 pound PUP tent trailer. That is an easy pull in OD and I get about 16 mpg @ 70 mpg towing it. I'm thinking that the 21SS will require OD being locked out and that I'll be looking at more like 10 to 11 MPG. What do you guys think?

 

P.S. It's a 5.4L Auto w 3.73s.

 

You might be OK but its going trial and error. I tow a 6700lb TT. I keep the OD off. It shifts to much with OD on. I found it easier to leave it off. I got 5.4, 3.73 gears and xcal2 kit(AF1 3.5, SISO exhaust.) Now I'm looking into 4.56 gears since I'm running 35" tires

 

I wonder if there is any hope of a "test towing" before buying. I'm guessing that insurance and liability concerns would put a nix on that. I don't think that weight is too big an issue here but, since this trailer doesn't collapse like a PUP, that wind resistance is going to be much higher. I notice that when I kick out OD, my mileage instantly drops by a huge amount, even when not towing. I have a ScanGauge II that gives me instantaneous readout so I know this is true. So I'd really like to avoid locking out OD if possible just because gas is so damn expensive. On a 3,000 mile towing trip, the difference between 16 mpg and 11 mpg will add up.

 

I tow a 26 foot, 6,500 lb.(actual) travel trailer just fine with my 06 F150 super crew XLT 4x4 with 3.73 gears. Expect 9-10 MPG towing due to wind resistance. Towing a 21 foot should be cake. I leave OD on and my truck does fine. You should leave it on if you can, it helps mileage and lowers your trans temps.

 

05extcabflare, do you have any problems with the 35's rubbing in the rear? I have a 30ft TT.. and im debating the 33's or 35's and thats one thing im worried about. thanks

 

that information is false. OD with cook a tranny so fast if you have a big load. If your towing, OD should be off. If you dont believe me, ask dad how his tranny is holding up in his f150. He used to tow the racecar before I got my truck, and his tranny is toast. I tow twice as much as he did (with overdrive off) and my truck is fine. If you dont believe me, call a trailer shop, they will more than likely tell you the same thing, tow with OD off.

 

Not so. I monitor the trans temps with my Edge and they are lower when it is in overdrive than when it isn't. Argue all you want, but those are the facts.

 

I have an 07 Rockwood 8317 SS thats 33 feet long & weighs just under 6K empty.
I have towed over 1500 miles this past summer, my best MPG was 9 going down hill with the wind at my back.
I have the Edge and a Maganflow but I didn't seem any difference in mileage when I added them. As KD4CRS stated the Edge is most useful for keeping an eye on the temps.
Unhooked the Edge and Magnaflow are great but when pulling a brick you won't feel much if any difference.

 

I got pictures in my photo gallery of the modifications were done. Or are you talking about REAR of truck. I use sway bars and torsion bar when towing so it keeps the truck level. The only time I moved the camper without the sway bars was in the driveway. It was close to inner fender. 35s definitely fill rear wheel wells. No I haven't had any problems.

 

My truck shifts alot when its in OD. In PA is known for its hills. When I hit a hill shift down even the smallest hill. Wouldn't that raise trans temp, shifting alot. I'm going to get a trans gauge this summer. It runs about 3000 rpm up hills.

 

Frequent shifting in and out of overdrive is good reason to lock it out, the manual says this. I will occasionally lock mine out if it shift in and out a lot on hills. My Edge consistently shows lower trans temps with the overdrive on than with it off, though. Hence, I leave my OD on as much as I can.

 

Heat is the enemy of transmissions. Unlocked torque convertors and shifting heats up the transmission more than locked in any gear. It is always trial and error for any truck/trailer combo. Either monitor the tranny temp with something aftermarket or keep an eye on what the trans is doing (locking/unlocking torque convertor or shifting frequently). That's when you know to keep it in a lower gear.

As for your proposed new RV, go for it! Check out the 23SS as well, which is a little larger and not much heavier. A couple key differenes is the 23SS has more counterspace, but the 21SS has a flush slideout vs. a step up. I remember reading @ RV.net about some of the 2008 Roos specs not being correct. Like the width is now 8' vs. 7.5' and some of the GVWR's went up accordingly. I've been eying the 232 for the front deck for bikes and an ATV.

As for fuel consumption, wind resistance will be the difference causing 8-10mpg for any full sized RV, hybrid or not.

 

I do think that the posts about transmission heat are on the mark. I have a ScanGaugeII with which to monitor transmission fluid temps. I will test OD and then with OD locked out. Whichever provides the lowest temps will be my strategy. The only caveat might be if OD is lower temp but shifts too much, then I'll probably lock it out. I think the key there is if it starts shifting on level ground, it is crowding the engine and trans too much. I would expect it to downshift on any kind of significant hill though. Rolling hills might be a time to lock out OD just to stop the up and down shifts. I don't know if that is particularly harmful though.

 

And thanks for the RV input. It's always nice to get another perspective. I think you are right about the wind resistance. I expect that to be a bigger factor on fuel consumption than the weight; at least with the lighter RVs around 3 to 4 thousand pounds. It makes me wonder whether to go with a larger high wall PUP tent trailer instead of the 21SS or 23SS. The weight is about the same but they are pushing a lot less air. The trade-off is additional setup time. And they are probably colder/hotter and noisier because of the additional canvas.