'98 X- Mysterious Thumping sound when accelerating!

[mcpbud]

Greetings gents, long time follower/ first time posting. I need some outsiders thoughts as to what could be the issue-

The Beast-
Stock 98 exploder XLT V8 with 165,x.. miles.

The Problem-
Mysterious thumping sound when ACCELERATING only

Recently (past month or so) tried solutions (to no avail):

-Replaced both front CV joints and hubs/bearings
-Replaced all sway bar links/ bushings
-Rebuilt transmission ($$$)
-checked all brakes/ calipers etc.
-alignment
-ball joints and control arms are good
-tie rod ends are OK
-no mud flaps in the way

I am pretty handy when it comes to fixing my sickly explorer. But this one has me puzzled. She thumps when giving her some gas (moderate to heavy accel) and sounds like someone slapping their boots on the underside of the floor, shakes like granny on the freeway and I need to let off the gas because I'm too scared to see what would happen. It also sounds like it is going at the same rpm's as the axle/ driveshaft. The Camshaft. Pos. Sensor code has tripped and I am familiar with those problems/ symptoms, but this sounds like a drivetrain problem to me.

After ALOT of research via this forum, I was leaning towards either driveshaft/ driveshaft CV, transfer case, new tires.

I need some outsiders opinions or hopefully someone who has dealt with this problem. Any ideas gents??

 

[jremington59]

What shape are your tires in? Does the front driveshaft feel tight? Sounds like your propshaft could be shaking....

 

[Spdrcer34]

CV in your front driveshaft, if you are AWD...

Recently people have posted that there is a rebuild kit available for the front driveshaft. I have not seen one, but I also haven't looked.

Ryan

 

[JoeMahma]

Greetings gents, long time follower/ first time posting. I need some outsiders thoughts as to what could be the issue-

The Beast-
Stock 98 exploder XLT V8 with 165,x.. miles.

The Problem-
Mysterious thumping sound when ACCELERATING only

Recently (past month or so) tried solutions (to no avail):

-Replaced both front CV joints and hubs/bearings
-Replaced all sway bar links/ bushings
-Rebuilt transmission ($$$)
-checked all brakes/ calipers etc.
-alignment
-ball joints and control arms are good
-tie rod ends are OK
-no mud flaps in the way

I am pretty handy when it comes to fixing my sickly explorer. But this one has me puzzled. She thumps when giving her some gas (moderate to heavy accel) and sounds like someone slapping their boots on the underside of the floor, shakes like granny on the freeway and I need to let off the gas because I'm too scared to see what would happen. It also sounds like it is going at the same rpm's as the axle/ driveshaft. The Camshaft. Pos. Sensor code has tripped and I am familiar with those problems/ symptoms, but this sounds like a drivetrain problem to me.

After ALOT of research via this forum, I was leaning towards either driveshaft/ driveshaft CV, transfer case, new tires.

I need some outsiders opinions or hopefully someone who has dealt with this problem. Any ideas gents??

Does it happen only under hard acceleration?

 

[Turdle]

I Know you said it seems like a driveline issue-however I suggest you look at ignition. Try a new set of spark plugs.
Then, using a spray bottle, wet down the spark plug wires. Have someone put some load on it while braking hard, and look under the hood for arcing. ( it may help to do this at night time, while it is dark)
While doing this, pay close attention to the passenger side-listening for an exhuast leak.

An ignition misfire during load sure can feel like a transmission shudder--that is why I am throwing this in

If this is an AWD, the front drive shaft could be the issue. you might try removing it and go for a drive-this may tell you

 

[gijoecam]

It's the t-case engaging/disengaging under load. Perfectly normal, completely harmless. Mine's been doing the same thing for 13 years.

Either get used to it, or install perform the Brown Wire Mod to disable the t-case when it annoys you.

 

[mcpbud]

thanks for the advice guys, i'll take a look and try all those options and re-post when I find out what it is. it seems to happen only during medium to heavy acceleration and it makes a hell of a shaking/ thumping sound, not a sharp distinct banging that a bad bearing or rear-end would make. its never done this its whole life which has me concerned.

spark plugs are a year old but who knows the condition so I'll try that idea as well.

tires are evenly worn and just about time for new tires, so that could be contributing to the problem and could be a combination of that and a worn transfer case/ stretched chain/ crappy driveshaft bearing

 

[NoFear95]

Flat spot on a tire. Broken belt on a tire.