transmission shakes

[sabrediesel]

When I pull a trailer my truck shakes real bad in transmission. Mechanic said it was the clutch slipping in the transmission. It is an automatic. It runs and shifts great but terrible starting off. The truck has 61000 miles on it, 2003 7.3 stroke. I want to put a chip in it but don't know what it will do. Any suggestions?

 

[sabrediesel]

mechanic looked at it today ans said it was the carrier on the drive shaft. he recommended getting a solid drive shaft made.