When I take off from a stop I feel a brief 1-2 second vibration from somewhere in the rear of the truck. It feels like running over a washboard. At first I thought it was my shovel sliding on the bed liner but I took that out so the bed is empty. Not sure what else to check.
It is very brief and is gone after about 5-10 feet of movement. Shotgun start, turtle start doesn't seem to matter. Straight vs turning doesn't seem to matter.
It has been really nice here lately so I rolled the window down and I can hear absolutely no noise from anywhere. I only feel it.
I haven't towed anything with it yet as I have only had it since July. I am the second owner. I don't know if the previous owner towed anything with, I suspect not since I had to put in the relays for the trailer brakes but that doesn't really mean anything.
I guess I am concerned about something in the rear end. But that may be paranoia.
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Is it a vibration or a thump? I know I have a light thump from my driveshaft due to the slip joint design. Supposedly, greasing the fitting on the driveshaft will fix it for about thirty days. If its a vibration, I'm not sure what it would be.
-2004 Ford F150 Lariat Scab w/ 5.4l
-2005 Chevrolet Corvette M6
-1997 Pontiac TransAm M6 w/custom heads, custom cam, moser w/4.10's and lots of other fast mods
From what I've gathered, it has something to do with the internal clutch pack failing, or sticking together, for the LS rear end. I replaced the fluid in mine when I bought it, and put some friction modifier in it, and after about 10K miles the vibration has only gotten worse. I will probably just end up replacing the clutch pack, or the entire rear end.
Mine was doing this the other day. About 2 months ago I had Ford garage replace my axle seals and when the put fluid back in the diff. they apparently didn't put the Friction Modifier in. When I noticed it vibrating I came home and looked at the receipt and there wasn't anything on it about putting the modifier in, just 4 quarts of gear lube. So I go to the Ford garage and get the Friction Modifier, put it in and haven't had any problems since. I've put about 400 miles on since then and it's still smooth so I'm guessing that fixed it.
If you do try this make sure to do a couple figure 8s.
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