Negative. Fat end towards engine moves pinion down. Think about it, leaf springs don't move so putting a wedge between them and axle with fat part towards engine will push axle down.

 

my bad I had my mind on flip kit spring under axle. your right....scratch what i said and reverse it.

 

i have 4* shims with the fat end facing the roll pan, which pushes the pinion down.(flip kit) i had a vibration between 80-100. the shims helped, but didnt solve the problem. im battling a few flip kit issues right now...

 

did you have a nuetral (0*) pinion angle before you used the shims? if so, that will wear out the u-joint and also cause this... ask me how i know

 

You may already be doing what I’m about to mention, but there are quite a few that don’t really understand the driveshaft angles and the proper approach at setting them. Make sure that when setting the pinion angle that the tail-shaft/driveshaft/pinion angles are measured against one another and to not set the pinion angle degrees vs the ground. I see what seems like entirely too many people that just grab an angle finder and try to achieve just a certain pinion angle in relationship to the world.

 

well... yesterday i put it on the drive on lift at the shop, unloaded the caltracs and took these measurements down...front drive shaft slip yoke= -6*, drive shaft is -2*, and pinon angle at pinion yoke is -4*. the pinion is facing up, so I put s 2* shim fat end in front(s&h drop). it brought my pinon to -2*, I need 2* more to put my angle at 0* pinon, -4 driveshaft and -6 trans. I have 5* total shim now, i have found the 2* shims i used to be about .25* to .5* smaller than advretised. I think i will try a 6* shim and see how it works, but i will hae to find one. does this make sense?

 

oh, and i tested it, and it didnt take the vibration away. but it comes in at 95 now.

 

when i had my 4l70e i would have a vibration come in at about 100......it never really bothered me cause my truck only saw a max of 75-80 mph on the street .....


make sure your pinion is set at -2 , replace both your u joints, grease your slip yoke.. and you should check your tail shaft bushing

 

I think the 6* shim will bring it back to -2*. u-joints are new spicer, drive shaft was balance by a truck driveline shop so I may have to find a high speed balance shop.

 

ok **** it!!! I put the damn overload back in, its not worth the extra 1.5" drop. I have not tested the vibration yet, but it was not there before I took the overload out. oh and fyi there is not a 6* shim. 5* is the biggest they make.