Alright... you guys may think I'm nuts, and I kinda am, but bear with me here. I've had my '05 EB expy for about 2mos now, love it, have been bitten by the mod bug and the car is starting to look great!
Here I go, try to follow along... driving down the road at approx 40mph, car going straight, the steering wheel straight, fine. Give it some gas to accelerate up to 50mph, the car pulls noticeably to the right, stay on the gas... you'll be off the right side of the road by 50mph! You'll need to correct the pull w/the steering wheel. Now, we're up to 50, let off the gas, the car pulls even more noticeably back to the left!!! You again need to correct the pull w/the wheel.
I feel like I've been drinking! And before you ask... no, I have not. The speeds are just so you understand, you do not need to be at exactly these speeds, it does it faster or slower, but much slower and it's not really as noticeable.
I wouldn't know where or how to do a search on this, so if someone has heard of this... do tell. Otherwise, where will I even begin? I know these cars have IRS suspension, but if they didn't, I'd swear the axle was loose and shifting under acceleration, that's what it feel like.
Please help! Car is going back the dealer soon, but was wondering if anyone knew...
Rick

 

Does your truck have a limited slip diff ?? It's sounds like a problem with the rear end.

 

Sounds like you need to tighten the rear end back down or get new u-bolts. Call the dealer...maybe a service bulletin out for that problem too.

 

Yeah, it feels like something wrong with the rear-end... it does have the limited slip rear. Pulling one of my trailers is even worse!! I've owned all kinds of cars in my lifetime, I've had a few other Fords before, so there will be absolutely no Ford-basing here, I love this car... just hope she's a good work truck for the next four years!! Any body else have any insight?

Rick

 

It sounds as if the rear suspension is out of alignment. I would definantly take it back especially if you can reproduce the problem at will.

 

I'm assuming that the air pressure in all 4 tires is correct.

 

Air pressure was the first thing I checked, but that was a couple weeks ago. I should probably check again, but wouldn't the result of an under-inflated tire be a pull to the side where the low tire is? And if a tire where under-inflated, would the car track perfectly straight down the road? I will check again.
Does anyone know if this car has four wheel alignment? Some do, just not sure about the expy. Thanks for all the replies, anything else... tell me!
Rick

 

Edit... that would be Ford bashing, not basing. Regardless, we'll have non of either!