I have a 98f150 ext cab and I have been hearing a kind of grinding noise and the truck vibrates alot when I take off from a dead stop but only when I turn to the left or right. It doesnt do it when I take off straight. Does any one have any ideas.

 

Did this just start or has it always been like this??

 

Hi chalo and welcome to the forum
Does your truck have limited slip in the rear diff?

 

Sounds like you need new clutch pack in your rear diff. They will cause a quick vibration when taking off on a turn. Make sure you soak clutch dics in friction modifier for 24 hours and add one container to diff.

 

It hasnt always done it. it just started small and has progressed. but it hasnt gotten any better or worse in the last 2 months. Im not really sure if it has limited slip in the rear axel either. I will try the friction modifier this week and see if that helps if not I guess from what you all are saying its the clutch pack. I appretiate your help and suggestions.

 

I'm following up on this thread. I'm having the EXACT same problem, only it seems like it's getting progressively worse. I found a TSB that says that 98-04 f150's are known to have a clunk or a bad vibration during acceleration, but i'm in the same shoes you are. It really only does it when the fluid is warm #1, and #2 when I'm taking off and making a right or left turn. Did replacing the fluid and adding a friction modifier help??

 

It's could be just a u joint on your drive shaft goin bad. That would explane the vibration when pulling off while turning.

 

Hi. New to the forum. This problem is the reason I was browsing this site. I have been having this problem for a few months on my 98. Its driving me nuts. It always seems to be when accellerating and turning. Any more info on this would be appreciated.
Thanks
David

 

If it were the driveshaft or U-joints or pinion/ring gear, it would happen straight or turning. Turning is when the spiders work, and if limited slip, when the clutches have to slip.

 

Its most noticable when turning, for the very reason you just mentioned.

 

So, how do I go about fixing it? I'm not very familiar with differentials.

 

Changing your u joints compared to rebuilding your Diff is like touching up a scratch compared to painting your whole truck. Well almost anyways. Try the simple fix first.

 

From the sounds of it, it seems like its the spiders tho. I dont mind painting the truck.

 

no one else has had this problem or can provide input??

 

Sometimes changing the diff oil and adding friction modifier will work. If it doesn't then you'll probably need new clutches like CanadianFordTech said further up on the page.