So last weekend on the trip to deer camp, about halfway there (out of a 200mi drive), i could feel a vibration/shake in the truck. doing 65 mph, didn't really transmit through the steering wheel. felt like out of balance tires...but normally if out of balance... the shake will always be there.

I pulled over and stopped to inspect tires thinking one was going flat. nope. I got back in and continued driving. Don't think I noticed it any more after stopping, or it disappeared quickly after that so i didn't think about it anymore.

Return trip home... it didn't do it at all.

FF to this weekend, drove all the way up again. On the return trip, very shortly after getting going, I noticed the shake...and much more prevalent this time...really noticeable. even felt it a bit in the wheel. after about 100 mi, the shaking stopped.

I've read other threads here, and am trying to figure out what would give me this kind of on and off problem.

I've seen U-joints, e-brake cable... but am not sure what's the likely culprit. I've got a friend whose similar truck hangs on wanting to jump into 4wd mode because of an issue...but wouldn't think that's what's going on here.
Short of hitting a dealership, what's the best plan of attack?

 

What are the make of the tire's...on the rear?

 

BF Goodrich, Rugged Trail T/A.

Talked to friend with similar truck... he mentioned coil packs going out could feel like this.

 

What motor do you have and is it 4WD ?

 

5.4 and 4wd

 

Could be a mis-fire your feeling.. any DTC's present ?

 

no CEL, and i don't have my own computer reader.

it needs an oil change, i can probably pay for a code read at the same time.

 

If you're going to pay for a "computer read," take that money instead and buy this and the Torque Pro app.

 

If there is no CEL then don't waste your time.. you can get codes read for free at auto zone or Advanced auto.

 

had the oil done today and let them take a guess... they believe it's time for plugs (still on the originals at 113k)