1. Looking for some input on a few things. I recently lifted my 06 PSD 4.5" and installed 35" tires. Has everyone that has gone this route lost 2mpg. I was getting almost 16 now I am around 14.

2. When towing a small 7X14 enclosed trailer I get a nasty shutter if I accelerate more than babing it off the line. It sounds like it is coming from the driveline/rear end. I did it stock and with the lift. The lift only added 1" to the rear of the truck. Any suggestions coments?

3. Just bought a 19' Weekend Warrior Toyhauler. I believe it is rated around 7K lbs. The first 180 miles the tranny would not shift into 5th and or lock up the torque converter and I was lucky to get 8 MPG. On the way back it seemed to be working better and I was still under 10MPG. This seems really low for this light of a load. My buddies 04 gets 10 pulling a 33ft toyhauler. Is this just what I have to except with my tires and lift?

Thanks in advance

 

Heres a question for you. Before the lift did you have any problems pulling your trailor Did you have that shutter? What ratio rear end do you have? The lower the better like 4.10s or 4.30s would help pulling a big load lift an tires. Does your buddy have a kift on his truck? A few basic questions to start.

 

Yes it did it stock. It does it pulling my toyhauler or the 7X14 enclosed trailer. This is not a big trailer. My buddies truck is stock. It sounds like driveline angle, but it shouldn't have done it stock.

 

I lost about 2mpg when I went to 35" tires from the stock 33's.

No lift

 

Any more replies guys. 83 lookers an only 3 replies. Help this guy out. The more help the better.

 

I've talked to a few performance shops about a 4 inch lift, and they said that there is a "shim kit" available to help with "drive shaft vibration"...I've heard that the steeper angle of the drive shaft makes it vibrate/ wobble on quick acceleration...Sounds like your problem, precisely... Ask around about a "shim kit" for your drive shaft that can be used when you do a lift.. I've heard it's about $50...
Regarding your mileage...I would think that larger tires (more rotating mass) and a lift (less aerodynamic) would definitely lower your mileage...

 

03 went from 31.5's to 35's and am at 15.5 now, averaged 16-16.5 before.... my best of 23 will never be repeated

cannot go up an 8% grade in overdrive at less than 60 mph unloaded now..on stock tires, no problem at 50 to go up the same hill in od.

i need 4.56's, and so do you it sounds.


good luck, sweet *** truck!

 

Well, one thing to consider is that after the bigger tires, unless you changed your computer to reflect the different tire size, you will get an error in your speedometer. The stock 16" tire height is about 31". Going from that to 35" is a 13% increase in circmference. Therefore your speedometer is going to read 13% slower than you were before (assuming it was 100% accurate which I would say few speedos are.)

Is it safe to assume you went to a wider tire? I would think so with a lift and 35s. There is a lot more mass to accelerate, there is also a larger tread patch and the associated increase in drag and there is also more wind drag due to the wider tire. All these things and more subtract from your previous efficiency.

I too have the driveline shudder and have been told about the shim kit. I have been adding shims (I am just using 3/8" washers) and it has lessened the shudder but not eliminated it. I guess I need to keep shimming untill it goes away or until the carrier bearing is dragging the ground.

As for the toyhauler, I think that the bigger wheels/tires need a numerically higher gear to help with that problem. 150Ford has it on the money - in my opinion. "Shorter" gears should help with pulling that big sail down the road. I will say this, though, I have pulled some pretty heavy loads of equipment down the road (say 12-18,000 including trailer) and my stock '03 with 3.73s and stock sized LTX M/S tires did great. I could pull that weight at 75 mph all day long with it only dropping out of O/D on long rolling hills.

Good luck and check out the tech folder and the sticky folders at the top of the forum. Welcome to FTE - the best site on the net for these 6.0 pigs!

Big

 

I agree with Big. Get the PCM re-programmed with the new tire size, and then follow the Torqueshift re-learning strategy thread in the Tech Folder. This should help with most of the issues.

 

8inch lift + 37inch tires on 22's = (-4mpg) 14.5 down to 10.5

 

Hey thanks for the replies. I figured the mileage thing was normal and am aware of the rolling mass etc. Just wanted to verify. I have also accounted for the tire size when calculating my mileage. According to my GPS it is 5% off. My stock tires were 32.5 so I think mathematically it is about 7%. I always add 5% to my mileage then hand calculate it. Before the tires my Lie-o-meter was always about 1/2 mile per gallon high. Now it almost always matches my hand calc. I forgot about the relearning strategy thread. I remember reading it last year before I bought my truck. I will go back and reread. As for the shim kit, I purchased the carrier bearing drop kit from Donahoe, but did not install it yet because it looks like it will drop it about 3-4 inches. Since I only lifted the back 1 inch I thought it was overkill. Guess I need to read the instructions to make sure. I have been planning on getting the speedo recaled so will get that done and install the drop kit and see what happens. Thanks again

 

Actually, the PCM uses the tire size for some vital functions, so it's important to get it re-calibrated for other than just the speedo. The bearing drop kit comes with a multitude of shims, but your only meant to use as many as you need to get both sections of the driveshaft to form a straight line, not all of them.

 

not sure if this pertains to your particular prob but my 03 psd had a shutter in first gear. ford had to realign my drive shaft to correct it.