Real bad Vibration / Shake in rear end
 

Hi guys, I'm new to the forum. Just picked up a 2004 Lariat and bought it knowing it had an issue with a major vibration. I'll try and sum it up as simple as possible. It's not intermittent and it's not felt in the steering wheel other than vibrations from the major shake.

I bought the truck from a guy who said that the truck had a serious vibration that he had checked by a mechanic. The mechanic told him that it was a bearing between the drive shaft and the rear diff.... and that it was ok to drive on, it would just be annoying.

So, the truck drives great until you reach 60 km/hr, or roughly 40 mph. At this point it starts shaking almost like something right down the box and into the cab of the truck is rippling. This continues until reaching approx. 100 km/hr or 60 mph where it turns into more of a constant vibration with a bit of a hum. The only time is not evident is under 40 mph.

My gf drove behind me last night at highway speeds and she said she thought my licence plate was going to fall off. It's not a side to side type of vibration and the dash actually rattles when it gets going good. I don't believe it's a tire/balance issue as I've encountered many of them in my life but I'm not an expert either.

The truck had new plugs, coils, brakes, and a brand new transmission in January. I'm wondering if anyone can point me in the right direction so I know a.) should I bring it to have it worked on or b.) should I pack it in and sell it. The guy I bought it from drove it daily like this for a few months but I can stand another day of it but don't want to put much money into fixing it.

I do work at a different make dealership so I do have a decent labour rate if there are some hours involved or can do it myself if I ever get a weekend off. Any ideas on what bearing it is or what else I can look at would be greatly appreciated! Love the truck otherwise and have wanted this gen for a while now after driving many early 2000 F150's!

Just throwing out some ideas, but I'd check the drive shaft bearing as recommended and make sure it's properly attached. Make sure your drive shaft is securely bolted to the companion flange on the differential. Have a tire guy inspect your rear tires. Had a tire start to delaminate that created a crazy vibration once. It wasn't really that visible until he pulled the wheel off and showed me. Another very unlikely cause could be a bent axle. It's got to be something that spins, and those are about the only things in the back of the truck that do. Keep us posted.

Edit:
Could be an issue with the bearings in your diff, but I think it would have blown up by now if they were wobbling around that bad.

Perfect, thanks! I'll crawl under it tonight and take a look. I'm away for a week this coming week so I'm thinking I'll just leave it at the dealership while I'm gone.

I personally wouldn't want to drive it like that. All that shaking is going to start breaking stuff if it goes on too long. Good luck. Hope you find something easy.

Iit's either a hanger bearing if it's a two piece drive shaft or probably a u joint.

rear pinion bearing shot and made worst for driving it that way...

Seems you already have your answer " The mechanic told him that it was a bearing between the drive shaft and the rear diff.... and that it was ok to drive on, it would just be annoying."

So replace the rear pinion bearing and you should be good.

Finally got it in to the shop here at work. Ended up being a busted rear u joint. Replaced the entire drive shaft as that was the cheaper way to go here at a Toyota dealership. Drives like a dream now, 335,000 km's on it and nice and quiet very excited to own this truck!

Like I thought, something simple.

Pinion bearings I believe would have to be run without oil for a failure. not a common issue on any brand of truck I have owned ; especially not a ford 9.25.

My truck an 09 at 332k's with original diffs and transfer case. The rear diff is full synthetic very expensive oil.

Good call on the synthetic rear diff oil, do you think I should have that done or go with what I have right now?