Is it possible it's misfiring and you're mistaking it for a vibration?

 

anything is possible i suppose
its a new motor from ford with about 4k miles, and it did this before and after the motor swap
it happens both accel and decel and coasting, and its only around 20-30 mph than above 60 plus it just doesn't feel smooth, like it has resistance. it is def speed related and not RPM dependent.
i guess i need to log the vehicle running and look for misfires.
vacuum leak that sort of seals when is cooler outside?
thanks
matt

 

I was just thinking I know people sometimes mistake misfires for transmission shudder so maybe that's what you've got going on, but with a new engine I'm not sure that's likely unless it's a coil problem and they put the old ones back in which is possible. I don't know what they put in with a new engine, but I wouldn't be surprised if they have to reuse the harness and maybe the coils.
If you have the ability so monitor for misfires I think it'd be worth doing. Misfires are more likely to show up under load so I don't know how that would explain that it vibrates both speeding up and slowing down though.

 

i thought i had the problem solved. i changed the transfer case fluid about 3 weeks ago. the fluid was only 10-11k miles old, but it kind of felt when the problem would go away while driving i was feeling something in that area or the tranny. The fluid that came out was burnt looking and i found shavings in the fluid. I replaced it with Valvoline transfer case, same as last time. Drove great for about 2 weeks. than about 1 week ago, the same vibrations began to creep back when the truck was warmed up. I wonder if the fluid is breaking down in the transfer case and if the transfer case is bad?

thanks
matt

 

I could be wrong, but if your transfer case was going I think you'd have noise more than vibrations since the tolerances and bearings inside there should be pretty tight. That is unless you can wiggle your output shaft a lot, however I think it it was sloppy enough to cause a vibration you'd also be losing fluid out the rear output seal.
I just changed the front seal on my transfer case and when I drained the fluid I saw some brass looking metal particles in there, but I guess I'm just going to keep running it until it starts making noise.

 

Yesterday I read an article on the nhtsa website whose subject included vibration. Believe it or not, the third brake light function was somehow tied into and causing the brakes to drag ever so slightly. As I remember it occured when one or more bulbs were burned out. Check your bulbs, who knows? Brake shudder is tied to temperature.
I tried to find the article before I wrote the above reply but could not find it and it may not apply to your model year. I will see if I can find that article but the nhtsa website is hard to navigate. Lets us know what you find

 

about a year ago, I had similar problem, thought the road was messed up or my tire was out of balance, turned out to be a sticking caliper, boot was torn. Truck had about 180k miles on it. this week, i had a slight shudder on acceleration, thought it was coil and plugs, changed them out, but turned out to be transmission shudder, pan drop and filter changed fixed the shudder