Hello everyone. I just bought a 2004 Ford F-150 supercrew and I figured this is a good way to find out some things about my truck. You always seem to have good information on here. Anyway when I stop at a stop sign and step on the accelerator it feels like the tires are slipping but they are not. It doesn't do it when I go straight ahead, just when I'm turning and usually to the left. It feels just like the tires are slipping and it vibrates a little bit like the tires are somewhat grabbing. Like I said I stuck my head out the window when I take off and they are not slipping. Can anyone tell me what this is and how much to fix it.

 

Welcome to the site..

How many miles on the truck?

The rear differential as a limited slip (posi trac) has a clutch pack inside the carrier that needs to release as the truck makes tight turns. On a hard turn, one tire/axle has to turn faster than the opposite side to make the turn. If the clutches were bad, or sometimes if the lube is in need of a change the clutch will 'chatter' as you make the tight turns. You might take a sample of the gear oil and see if it is overly dark, or has a lot of suspended metals in the lube. Some is normal, and you may see it collected on the fill plug, but if excessive in the lube it may need to come apart. As a first step (especially if the lube has never been changed, or is moderately holding metals ect.) you may try and have it changed and a fresh fill of lube and friction modifier. If it were changed at some point, and modifier not added, or not enough, it could create the chatter. See if it corrects the problem, or makes any improvement.. Also, check to see if the pinion yoke (were the drive shaft attaches) has any up/down play. Sometimes if the yoke has excessive play it will mimick a clutch chatter even with out a leak point there...

 

Does the truck have 4 wheel drive? Sometimes when the front hubs are in the manually locked position and the driver is not aware it's in 4 wheel drive at the transfer case I have had them chatter on turns on dry pavement.

 

The truck has 100,00 miles on it. I just had the wheel seals replaced on the rear end about 2 months ago. So gear oil was just changed. I was driving it last night and it seems to do it some going straight ahead too.