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New motor mounts. Still have a thud.

mohawkmike82

mohawkmike82

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Location
Cleveland, Ohio
Just like above states I have what feels like a bad motor mount, but they are both spankin new. If you are cruising at any speed and chop the throttle I get a nasty thud that definitely feels like a motor mount. Also happens when adjusting cruise control. I have not replaced the trans mount but tried jacking up the trans to see if the mount moved excessively and it hardly moves at all.:???: Its a 4L80E if I'm not mistaken. Anyone ever experience this? Fixes?
 
Several other members here have had new motor mounts go to hell almost immediately. The rubber is crap and the shells are way lighter gauge material than oe.
Is your truck a extended cab long box? They have a hanger bearing that can get sloppy and a splined driveshaft coupling that can get loose. A bad u-joint is a possibility also. Sometimes they are not easy to detect.
 
Maybe its a bad tranny, does it happen on downshifts? The pressure control solenoid can get sloppy controlling the pressure needed to shift or Torque converter may not be locking correctly. My tranny jerks on shifts when I put programming for 4WD heavy trucks in my truck.
 
Check the u-joints. Does this have a carrier bearing? If so check it as well. Then check the rear springs.
 
Buddy, it doesnt happen on down shifts or up shifts. Only happens when you go from zero load to med/high load quickly or if you're cruising and jump off the throttle. Feels EXACTLY like a bad motor mount.
No carrier bearing on this drive shaft but I do need to check the U joints. Ive just never had any of the "typical" U joint symptoms. Ill have to look at the springs too. Ill be working on it tomorrow so Ill take a look and let everyone know if I find the culprit.
 
Balancer and Crank pulley are good to go. If you felt it, you would say "Hey you have a bad motor mount." Someone stated earlier that guys have had brand new mounts be bad. Maybe I have a bad one. Maybe it is a trans issue. Hmmm. . .
 
Down there on the list of possibles is loose torque converter bolts. They would thud going from load to no load and back.
 
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