V8 Engine/Drivetrain Vibration

[Jet Ski Puller]

I have a 98 5.0. Between second and third gear, from 2000-2500rpm, I'm getting this nasty resonant vibration I can feel under my feet. I noticed it a little before, but much worse since I changed to 31's. And, the more the engine lugs through this rpm range, the worse it is. If I really step on it, it moves through second gear in that rpm range without issue, but if I gradually accelerate, it's worse (that's probably why it's more noticeable with the larger tires because it now takes longer to move through that rpm range), and if I'm gradually accelerating up a hill, it's really bad. It's difficult to tell whether it's in the engine or drivetrain. I spool up the engine in neutral and it's smooth, but when I put a load on it, it's definitely there. And, it sounds like the engine kind of roughly gurgles, but it doesn't happen in other gears through the same rpm range.

Anyone have any suggestions or experience with this?

Thanks.

 

[Bill Kemp]

I would start out by changing the trans. filter & spark plugs & wires.

 

[99explorer5.0]

Mine seems to do the same thing at the same speeds but not all the time. Let me know if you ever find what it is. I thought maybe it was just vibration from my exhaust or something but it didnt do it when i first got it installed. I dunno.

 

[Jet Ski Puller]

I would start out by changing the trans. filter & spark plugs & wires.

Bill,

A few thousand miles ago, I did replace the plugs, wires, trans filter, and put in Amsoil trans fluid.

It's been getting worse since that time.

Thanks for the suggestions, though.

 

[Bill Kemp]

Transfer case? U joints on drive shaft? Thats just about all thats there.