Driveline vibrations

[Officer_sloppyjoe]

I just put a 14b sf that I bought from Fourwheelerjeff and a shackle flip on my blazer. According to the speedometer between 50-75 mph the truck vibrates. speedometer is way off as the truck came with 31" tires and 3.07 now it has 33" and 4.56. I measured the TC angle, driveshaft angle and pinion angle. The pinion points up above the Transfer case and it is the factory driveshaft.

TC= 5.5 deg
DS= 16 deg
Pinion = 20 deg

My question is what degree of shim do I need? 15 degrees seems like a lot.

 

[ChrisPerry]

Cut and turn the spring perches. Pinion needs to be at or close to the same angle as the TC output shaft for the u-joints to be happy. More work than shims, but that large of shims scare the crap outta me.

 

[Deuling]

What length shackles? Im running 6 inch and a cv rear shaft and zero vibrations

 

[ChrisPerry]

I'm assuming when he said "factory driveshaft" that meant it was a non CV shaft.

 

[Deuling]

I'm assuming when he said "factory driveshaft" that meant it was a non CV shaft.

I need to start reading the WHOLE post


But he didn't say what length shackle. If it is a six, it would point it up more, meaning a shorter shackle would help.



But yes I would cut the perches and re weld before running a radical spacer

 

[Blue85]

Another option would be to use some mild 3 degree shims and convert the driveshaft to C/V style.

 

[Officer_sloppyjoe]

I have the Factory shackles. Well Monday I will call Austin Drivetrain and see what they charge to convert my drive shaft to a CV style. If its a really high price I will buy a new 1ton CV then shim it to the right angles.

Thanks for the input.