driveline angle help

[jdp]

hey guys so i have a 78 blazer that im redoing with 12in lift but am wandering what size shim i need for the rear. it is 8in springs and a 4in block and i am going to have a zero rate machined at the correct angle for my shim. do you guys have any recomendation of what angle shim to use with the lift​

 

[4X4HIGH]

Don't guess, install the lift then measure what you need. I'm going to suggest that you just cut the spring perches off and then weld some new ones on at the correct angle over using any form of shim or tapered zero rate (unless you need that "extra" 1" or so).

 

[jdp]

well right now it has a shim that i am unsure of the angle but the kit was originally on a short bed and i put it under my blazer and it looks like it will work but i would like to correct the angle and just be sure of it all. what would you suggest to measure my angles with?

also what is the general rule of thumb when doing the anlge? i herd make both ends match within 3degrees. but m,y buddys k5 has his pinion pointing straight at the drivle line and the only angle is at the upper ujoint and his works great

 

[chulisohombre]

what scott said is spot on.install the lift and see where the angle is and redo the perches accordingly.with a lift that large im guessing the zero rate would be 12-15 degrees if you need that extra lift.you wont know til the lift is installed though.

 

[4X4HIGH]

well right now it has a shim that i am unsure of the angle but the kit was originally on a short bed and i put it under my blazer and it looks like it will work but i would like to correct the angle and just be sure of it all. what would you suggest to measure my angles with?

also what is the general rule of thumb when doing the anlge? i herd make both ends match within 3degrees. but m,y buddys k5 has his pinion pointing straight at the drivle line and the only angle is at the upper ujoint and his works great

You'll need an angle finder to check the angles. http://www.amazon.com/Great-Neck-GreatNeck-10155-Protractor/dp/B0002YQR3S

If you're running a standard driveshaft with a single u-joint at each end then you want the angle at the t-case to match the angle at the pinion. If you're running a CV shaft (2 u-joints at one end back to back) and a single u-joint at the other end then you'll point the pinion directy at the t-case output (2* down would be ideal) so that as you drive the pinion points directly at the t-case.

 

[jdp]

yea i deffenitly want to run the zero rate so i think machining it to the correct angle is the way i will go.

and that weird cuz thats what i thought the rule was but my buddys has a normal ujoint on both ends and his pinion is pointed up like that and he has no problems with it

 

[4X4HIGH]

I should have added that you want anywhere from a minimum .5* to 3* working angle on the u-joints which is damn near impossible to do on such a short wheel based vehicle while maintaining the parallelism between the t-case and pinion if you're using a standard driveshaft.