Weird Thumping?

[willindsay]

Ok so I've been having this thumping somewhere in my drive line for a while. It started just happening at between 50-55mph but now it does it just randomly out of the blue at different speeds. It's not a real hard thump kinda like an intense vibration.

Now I was repairing a kinked tranny line the other day and I was shifting through all the gears sitting in the driveway to get it warmed up so I could get an accurate fluid level and I noticed that when I put it in drive from reverse there is a big thumb and the whole motor shakes same going from reverse to drive just not as bad.

Anyone have any ideas?

I have recently changed the Rear Diff and T-case to synthetic fluids. If that would matter.

Thanks in advance for your responses.

 

[atreyu]

maybe bad u joints? i know mine clunks when i put it into reverse and drive and hums on the highway. Also could be a tranny mount. Thats easy to check...

 

[willindsay]

maybe bad u joints? i know mine clunks when i put it into reverse and drive and hums on the highway. Also could be a tranny mount. Thats easy to check...

I was thinking U-joints but when I grab the driveshaft and try and turn it by hand it won't budge. Which from what I understand means they are fine. If I'm wrong correct please as I'm just going by what I've read on here and haven't searched very throughly.

 

[ranger-93]

I was thinking U-joints but when I grab the driveshaft and try and turn it by hand it won't budge. Which from what I understand means they are fine. If I'm wrong correct please as I'm just going by what I've read on here and haven't searched very throughly.

turning it might show worn u joints but pushing and pulling the drive shaft probably works better. try that

 

[willindsay]

turning it might show worn u joints but pushing and pulling the drive shaft probably works better. try that

Will do next time I'm under there.

 

[Tony H]

I was thinking U-joints but when I grab the driveshaft and try and turn it by hand it won't budge. Which from what I understand means they are fine. If I'm wrong correct please as I'm just going by what I've read on here and haven't searched very throughly.

To do this correctly, the car needs to be in Neutral. If it's in Park there's too much pressure on the shaft and joint so you can't get a 'read' on it. Chock the tires so the 'X' doesn't run you over.
In Neutral, Push and pull at the Joint to look for movement.