I have a 2006 F-150 scab 4x4 5.4 triton v8. I have a six inch procomp lift with 325/65R18 terra grapplers. I just had 4.56 genuin gears put in the front and rear. I wanted to lock in 4 wheel drive to run the gears a little on the street with out making any turns or going super fast. When i give it gas i don't hear anything but when i let off the gas just a little i hear like a roar that gives alot of vibration from the front, if i let off all the way on the pedal i don't here anything either, is this a normal thing to here? After all you realy should not be running it in 4x4 on dry pavement but i was going easy.

 

just it only do it in 4x4?

 

yes only in 4x4 and it comes from the front. I asked our local modifications shop here about it and he said it was a normal thing to here when you are running it on dry pavement. I just don't see how!

 

Anyone?

 

Did you ever run it in 4hi on the pavement before the gear swap? Could be a bad ujoint in the front driveshaft...or excessive angle on the driveshaft causing a bad vibe only at a certain speed like what you hit on the pavement. Or new front gears are close but not quite the exact same ratio as rear ( like 4.56 to 4.52 ) for example. OR front gears are not set up properly, too much backlash? Check easy stuff first like the ujoints in the driveshaft!

 

Thanks for the reply. I never did try the 4x4 on pavment before the gear swap that's why i had asked if it was normal. I am going to call up the people that did the gear swap and let them take a look at it. It has only been a week since they did the gear swap for me so i still have there warranty. I just hope if there is something wrong it is an easy fix. It is a hassel going with out it for any period of time. To maybe explain it better only in 4 wheel drive coming from the front it whines when there isnt a load on the truck... not under accel or decel, just when you are crusing and you aren't putting anything under a real load.

 

Are your front and rear tires the same size and worn pretty evenly between front and rear?

 

Yes they are the same size and they are worn even. The tires only have about 6000 miles on them.

 

I just regeared to 4.56 from 3.73. Went with Yukons. Drove about 70 miles in 4x4 high during 1st week of break in on short trips. The Yukons make a little noise but not as loud as the BFG All Terrain tire tread patterns. Did a few 'shift on the flies' to 4x4 hi at 35 MPH during that week also. No problems engaging/disengaging. I've had to drive about 33 highyway, back road miles home from work in bad weather in 4x4 hi so a few 45 -55 mph 4x4 hi drives on straight roads will not hurt.

Check out info on Randy's Ring and Pinion site under FAQ for noise issues during acceleration or coasting for installation problems. Also, some gears just may be more noisy than others.

 

Good info on the faq section of randy's ring and pinion.. Thanks! I took it back allready and had them test it out with me in the truck and they felt and herd it and said they didn't know what it was because the front drive shaft was tight and there was no play in it after looking it over. They told me they didn't think it was a big deal and if it got worse bring it back to them. From what i read in the fact section was that it was either a bad pinion bearing or a loose pinion bearing preload. I guess i am going to take it back to them again and tell them what i read in this faq section....errr I hate being a pain in the *** but i want it right!

 

Well after talking to the guys at the shop that did the work they came to the conclusion that it was in the front drive shaft. They ordered a front drive shaft with a cv joint and instaled it problem solved no more vibration at all.. They had told me that some of the trucks do it after they have been lifted due to the angle that the front drive shaft is at after they are lifted and some don't it is a hit or miss. They said it was probably there before the gear instal and i just didn't notice it because it was probably a slight vibration and after upgrading to the 4.56 it was more pronounced dew to the front drive shaft spinning much faster and it showed its ugly face. Fixed now and i could not be any happier with the 4.56 I love them!