Engine/Transmission (1994 - 1998) need help with mystery knock

[LVJUNIOR]

I have a knock somewhere in my truck that sounds like a broken motor mount. It only shows up when I first start moving from a stop. It makes 3-5 quick knocks. I thought it was a motor mount or a trans mount but they both appear to be in good shape and still have rubberin them. The u-joints in the driveline apear to be tight and the trans and converter only have a few thousand miles on them. Any suggestions on where to look?

 

[DRAG DIESEL]

I have had cab mounts make noise as the frame twists when leaving a line or accelerating through a turn.

 

[LVJUNIOR]

did you have to leave pretty hard or would it do it under lite acceleration also

 

[LVJUNIOR]

checked the cab mounts and they all look good. any other ideas?

 

[ewcmr2]

Check the center carrier bearing mount on the driveshaft.

 

[LVJUNIOR]

I grabbed ahold of the front and rear driveshafts and tried to move them to check for u-joint slop and the rear driveshaft was solid as a rock even at the carrier bearing.

 

[fest3er]

• Any rust on any of the ujoints (propeller or axle)?
• Does it happen in 2WD and 4WD?
• Does it happen in forward and reverse?
• Does it happen under varying degrees of powerbraking (no boost, 5# boost, 10# boost)? (That is launching while controlling acceleration with the brake... )

 

[LVJUNIOR]

• Any rust on any of the ujoints (propeller or axle)?
  
• Does it happen in 2WD and 4WD?
  
• Does it happen in forward and reverse?
  
• Does it happen under varying degrees of powerbraking (no boost, 5# boost, 10# boost)? (That is launching while controlling acceleration with the brake... )
  

I live in the desert so the only rust is very light surface rust.

I have not checked 4wd but it is happening in 2wd

I have not heard it in reverse only in forward but it doesn't appear to make a difference if I am going straight or turning.

I have tried to power brake it in the driveway but the noise was either not present or not loud enough for me to hear. I have not tried a rolling power brake but I will try it when I leave work today.



I really need to find out what it is so I can find out how much it is going to cost to fix because I want to get a new exhaust housing for my turbo and I can't afford to do that and another expensive fix.