PSD Owners with larger than stock tires

[timbuktu78]

Are there any Power Stroke owners out there running larger than stock tires? I have a 2006 F-350 6.0L SB 4x4 with 3.73 gear ratio and 33 inch tires pulling a 2010 Keystone Everest 345S (recently traded in the Monty for this). It's about the same size/weight as a 3400RL. I am considering re-gearing the axles with either a 4:10 or 4:30 for a extra low-end power for when I traverse the Rockies/Sierras very soon. Just wondering if anyone with a similar set up has put lower gears in? I already have a 4inch exhaust, intake, programmer, Firestone Ride-rite airbags, and aux fuel tank (all installed by the Ford dealership). I am running right at my max GCWR. The truck pulls the E great, but I have not towed it thru mountains yet. And going back to stock tire size isn't an option. Thanks!

Tim

[Art-n-Marge]

When you had the tires put on did you have the transmission retuned for them as part of the install? Those are some big tires, but I think if this has been done you should be okay. The exhaust, intake and programmer should help a lot as is. A higher diff might help improve things but not as much as what it would cost to do the conversion. You'll need an exhaust gauge to monitor if you push things too much!

If you have the Torqshift and the Tow/Haul mode, you'll need these on long downhills. Just keep the RPMs under 3500-3600.

Besides the GCWR you'll need to check the axle weights (I believe the RAWR is 7000lbs and front is around 6000). Even though the gross combined weight might be okay weight wise, you'll need to monitor how the pin weight, heavier wheels, hitch, & aux fuel tank affect your axle weights. The air bags will help level your truck but they don't increase the RAWR. If you are over on any axle, the higher diff WILL improve your TV's tow rating but I don't recall by how much and I don't remember if it improves your GVWR.

If all the weights are good, over time if you find the 3.73 isn't giving you the power you'd like then go for a 4.X diff (if you are going to change you may as well go with the 4.3). But if you are okay, your fuel usage especially when not towing will be much better not changing.

Best of luck with your decision.

Art

[PSFORD99]

I have the same setup as you other than I have the 7.3. Same size tires etc. I tow in the mountains( 3400 RL ) Utah ,montana ,and Idaho and there have been some grades that more power or different gearing would be nice, but seem to get over the top without problems. With you having the 6.0 you should be okay in the mountains having more torque and horse power than a 7.3. I think that 6.0 will do better than you think in the mountains,I would give it a shot before doing anything. Good luck

[stiles watson]

I agree with the above post. Unless you are just aching to spend the money, go check out how it pulls. I pulled my 2002 3670 Big Sky from Texas to Nova Scotia and back with an 2002 F250 PSD 7.3L and 3.73 rearend. Lots of mountains on that round trip. It did the job. Now I pull this Big Sky 340 RLQ with F350 6.4L 4.88. It pulls fine in the mountains too, but the mileage sucks big time.

[Tom S.]

Since you have a 4x4 and would have to change both axles, you might be further ahead to look into an under-drive unit. These mount between the transfer case and the rear drive shaft. Buying new would still be a considerable expense, but you might find one used.

[Farmhawk]

I live in western Montana and use an 2006 F250 with factory 18" (33" dia) tires and wheels and have absolutely no problem towing my 2955RL. I pull all over the west with it, there are a few grades where I wish I had more power but nothing serious. I know you weigh a little more than I do, but gear size is not your biggest problem, it is being maxed out on weight that I would be concerned with. It sounds like you are more psyched out about towing in the mountains than you need to be. The main thing is to keep an eye on your temp gauge and the tach and you will survive the mountains.