I've got a '98 F150, 4.6, 3 door, automatic trans, built in Canada. Great truck...perfect truck except for a Door Ajar problem, and a shudder that only happens while accelerating after a stop with the wheel turned.

I read the thread about the Door Ajar fix and I haven't had a problem since I squirted WD 40 in the latch. Thanks!

But the shudder seems to be getting worse. It only happens if I'm turning after a stop, and then only under 10 mph. It's hard to tell if the shudder is from the front end, engine, transmission or back end. I've played with it in the parking lot and know if it's shuddering and I straighten the wheel it quits, or if I ease up on the accelerator it quits. It doesn't always happen but it can/does show up sometimes first thing in the morning, or right after I get off the freeway from the light at the end of the ramp. One interesting thing, I've never noticed it in the rain, and it doesn't seem to be any worse or better when I pull my boat...and it doesn't happen when I pull my boat in the rain.

Nick in Spartanburg, SC

Sometimes I wonder if the front wheels aren't skidding forward some instead of following the true turn radius -- my tires within a few thousand miles of being worn down to the wear bars. Sometimes I think it's the trans, or maybe the serpentine belt chattering maybe because the power steering pump is loading it up. Sometimes I think it's the rear end...

Anyone else have this problem? Any suggestions?

 

You did not mention if you had a limited slip rear axle. If you do, (which it sounds like you do) the LS unit could be worn out. More than likely, the plates are worn and they chatter against each other. You could try replacing fluid and the friction modifier additive for the LS. It would only be a temporary fix. I would suggest just rebuilding the LS or replacing it with a stronger unit like an Eaton. That should take care of your problem.
By the way, the reason it doesn't do it in the rain is because the tire is able to spin because of the water on the road.
Hope that helps, and good luck.
Brian

 

Ditto on the limited slip... the symptoms you describe are EXACTLY those of the bum-limited slip. You can try adding the friction modifier to the gear oil, but odds are you need a new clutch pack for it. The install isn't that hard from what I recall reading, just time consuming. The other option is to find a reputable drivetrain shop in your area and have them do it... it's not very costly, but will ensure the limited slip actually works again.

-Joe

 

Thanks for the leads y'all.

I bought the truck used. Is there a way to tell if I do in fact have a limited slip rear end?

Would the look or smell of the rear end lube confirm a problem there? Ford changed the differential fluid at 36k (now at about 60k) and they didn't indicate any problem -- they get a fortune for that oil change!

What happens if I do nothing? Will I 'blow' the rear end, or just end up with no LS?

Anyone got any idea what a rebuild for the rear end would cost?

 

jeff,

i suggest you take the "cheap" approach first. you can always spend more money later if need be. first, put in some fresh friction modifier and see what happens. my s-crew started doing the shudder thing after only 3k miles on the clock...this was a brand new truck! friction modifier has solved the problem so far...truck now has 12k miles...

 

I sucked out enough rear end lube to get a bottle of the Friction Modifier in. Just towed the boat over 1,500 miles with no sign of the shudder. Thanks!