What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Driveline angles

R

rickdavis81

Newbie
Joined
Sep 17, 2018
Posts
4
Reaction score
0
Location
Rich Hill MO
I boughta m1009 with 4” of lift. Owner said it had just started to vibrate on take off. It vibrates most of the time the faster you go the better. Rear driveshaft had never been extended and was pulled quite a ways out of the tcase. I’m having it lengthened. And it wrecked the rear bushing and seal in the tcase. The tcase sets at 6 deg, pinion at 16 deg and drive shaft has a 23 deg angle. I’m thinking I need to stick the tcase adapter/mount in my mill and get the tcase angle around 14 to 15 deg. Does this sound acceptable?
 
most blazers i have read about in the 4" and up range need a rear shaft with a c/v joint . otherwise they vibrate . its due to the short wheel base length and short shaft .

but also you do seem to have a few angle problems . others who do this more will chime in soon .

and if you play with the rear angles by dropping / lowering the tcase mount / crossmember you also make the front angles worse .

and welcom to the site . :waytogo:
 
The t-case and pinion should be at the same angle, so if the t-case is 6 deg down the pinion should be 6 deg up. With a CV shaft the pinion should point straight up the driveshaft. That said, my Blazer rear, 4 inch lift, with 6 deg down at the t-case and 0 deg at the pinion is fine, no vibration. No CV, just a new 1410 driveshaft from tom woods. I was certain I would need to rotate my axle up 6 deg but for me things are OK. I have an SM465/NP205 so my driveshaft is longer than yours likely is.
 
ORD sells axle shims to rotate the pinion. You could try those and not have to cut your mount, this would also not affect the front shaft angles.
 
Its a bastard, some superlift softride 3/4 ton springs with a leaf removed and an AAM 10.5 axle. Just thought it is weird that I don't have a vibration when my numbers are so far off from theoretical alignment.
 
HankScorpio said:
Its a bastard, some superlift softride 3/4 ton springs with a leaf removed and an AAM 10.5 axle. Just thought it is weird that I don't have a vibration when my numbers are so far off from theoretical alignment.
Click to expand...
not you silly ... the o.p. of this thread .
 
I think tuff country. That’s what the front springs say. Rear is blocks. I was worried if I shimmed the pinion to match the t case the u joint operating angle would be too much.
 
The blocks should be tapered to realign the rear. Are they in right??
 
x2 on block install correctly .

short end of block to front of vehicle . tall end of block to rear of vehicle .
 
As you said the total operating angle becomes an issue and that is where the CV shafts come into play.
 
Yes the blocks are installed correctly. I tried to find a NP241 to install a sye and cv driveshaft but didn’t have any luck
 
you can do a slip c/v unit if you need to .

but as said drive line angles first .

need to get the rear down a bit closer to the t-case spec and try that first .
 
Why is your pinion up 16 anyways. How did it get like that.
Thats 17 degrees at the T/C and 7 at the pinion giving you
10 difference.
Moving the T/C is not the solution.

IMHO
 
If you are using a standard, 2 u-joint driveshaft, you absolutely need to get the angle of the pinion to within 2 degrees of the output of the t-case.
Your operating angles will be in the 13 degree range.
There will be a mild vibration on Accel or decel.
The blocks are in backward if your angles are that far off.
It will never be right.

Dropping the t case an inch will only get you less than a degree at the front u-joint.

You need to fix the blocks, use shims, or cut and turn the spring perches on the axle to get those angles within 2 degrees of each other.
Do that BEFORE you lengthen the driveshaft.
It will affect the measurement.

In my case I used ORD shackle flip brackets to get my rear lift of 4".
This tipped the pinion up over 6 degrees.
I used 6 degree steel shims and new spring center pins to point the pinion back down.
My pinion angle and t-case output are within 2 degrees of each other and there is just a faint hint of vibration when letting off throttle at highway speeds.
Yes, the operating angles of the u-joints will be in the 13 degree range.
They will still last a long time.
Take a look at Tom Woods site regarding lifespan vs angle.

Otherwise, have a CV shaft made for the rear instead.
But read up about that.
There can be issues with having a heavy CV hanging off the back of an np208 as well.
Call Tom Woods.
 
4" lift and a slip yoke t-case pretty much requires a cv rear shaft. The slip yoke eats up length that would ease those angles a bit.

My 75 K5 had a shackle flip (4") with a fixed yoke 205 and it had a perfect 2° difference on the angles. No vibes what so ever .

Now my 91 also with a shackle flip but having a slip yoke 241 had shitty angles on each end. Almost 10 degrees off . For me it was either SYE with a custom shaft or a slip yoke CV shaft, also custom. I had a driveline shop build me a slip yoke CV shaft and I pointed my pinon at the same angle of the shaft. No vibes up to 90 mph.


There just isn't enough length to cover the change in hieght from the t-case to rear axle on a K5 when it has a slip yoke. A 14b full floating axle hurts this too as the pinion sticks another 1-1.5" further forward than a 10 or 12 bolt axle due to the size.
 
You must log in or register to reply here.

Latest Posts

Top Bottom