Lifted truck driveshaft questions.

[Nick88]

Howdy. I just mached up the rear of the 6 inch rough country lift kit on my 1986 gmc crew cab that I am restoring. It was a pain to get the pinion angle better, as the lift kit shim was angling it higher than the angle of the driveshaft. My questions are based off these pictures, do my angles now look good for the pinion and off the carrier? Should I change anything? Is my driveshaft far enough on the carrier splines or should I get a longer one? Thanks.

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[Nick88]

Here's the splines.

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[chief_shotts]

Hard to tell with pictures alone. I picked up a digital angle finder from Hoe depot for $30 +/- they had klein or milwaukee brand. Use that to measure engine/tran/tcase angle and rear pinion angle. The angles should match or the pinion angle should be a degree or two less. In my recent experience getting these angles matched or close is extremely important for high speed driving without vibes and odd noises. It also looks like you have a two piece driveline so you may want to drop that carrier bearing an inch or two.. so you dont have an excessive joint angle at the carrier bearing. For example i have roughly 8 in of lift and my carrier bearing is dropped about 1.5 inch maybe two. I have tried running it with carrier bearing in stock location and i picked up some weird rotational noises.

As for the spline contact. first clean that sheet off. Now droop the suspension out and mark on the splines where the yoke sits. now pull the driveshaft off and measure how much contact your splines have in the yoke. This will give you an idea of your spline contact at full droop and if its okay or not.

 

[Nick88]

Hard to tell with pictures alone. I picked up a digital angle finder from Hoe depot for $30 +/- they had klein or milwaukee brand. Use that to measure engine/tran/tcase angle and rear pinion angle. The angles should match or the pinion angle should be a degree or two less. In my recent experience getting these angles matched or close is extremely important for high speed driving without vibes and odd noises. It also looks like you have a two piece driveline so you may want to drop that carrier bearing an inch or two.. so you dont have an excessive joint angle at the carrier bearing. For example i have roughly 8 in of lift and my carrier bearing is dropped about 1.5 inch maybe two. I have tried running it with carrier bearing in stock location and i picked up some weird rotational noises.

As for the spline contact. first clean that sheet off. Now droop the suspension out and mark on the splines where the yoke sits. now pull the driveshaft off and measure how much contact your splines have in the yoke. This will give you an idea of your spline contact at full droop and if its okay or not.

I used a digital angle finder but I ended up confused. The slip yoke is about 1.5 degrees, the driveshaft is 10 degrees, and putting the angle finder on the face of the dif next to the pinion read 84, so about 6 degrees. Those numbers are obviously all very different but it looks kinda close. Also for the slip yoke, at full droop how much spline engagement do I need?

 

[Nick88]

Hard to tell with pictures alone. I picked up a digital angle finder from Hoe depot for $30 +/- they had klein or milwaukee brand. Use that to measure engine/tran/tcase angle and rear pinion angle. The angles should match or the pinion angle should be a degree or two less. In my recent experience getting these angles matched or close is extremely important for high speed driving without vibes and odd noises. It also looks like you have a two piece driveline so you may want to drop that carrier bearing an inch or two.. so you dont have an excessive joint angle at the carrier bearing. For example i have roughly 8 in of lift and my carrier bearing is dropped about 1.5 inch maybe two. I have tried running it with carrier bearing in stock location and i picked up some weird rotational noises.

As for the spline contact. first clean that sheet off. Now droop the suspension out and mark on the splines where the yoke sits. now pull the driveshaft off and measure how much contact your splines have in the yoke. This will give you an idea of your spline contact at full droop and if its okay or not.

Also, what can I space out the carrier bearing with? Can I use large bolts or washers to space it out like an inch or a pinch less?

 

[chief_shotts]

I used a digital angle finder but I ended up confused. The slip yoke is about 1.5 degrees, the driveshaft is 10 degrees, and putting the angle finder on the face of the dif next to the pinion read 84, so about 6 degrees. Those numbers are obviously all very different but it looks kinda close. Also for the slip yoke, at full droop how much spline engagement do I need?

Your objective is to get all operating angles to cancel out or come close to doing so, and secondly try to keep operating angles to a minimum. When setting the pinion angle ignore the slip yoke joint and the driveline angles. Your goal with the pinion(driven member) angle is to match it to the angle of the engine/ trans/ tcase(driving member). If you get the pinion angle to match the drivetrain angle all the operating angles will cancel out and in theory you should not have vibrations. Once your pinion angle is locked in you can then play with the carrier bearing location to reduce the operating angles of all the joints. By dropping the carrier bearing location you straighten the two piece driveline. Keep in mind you don't want it perfectly straight, because you do want some operating angle for u joints to properly lubricate. You can get the driving member angle in a number of spots: Rear or front tcase output yoke, front face of heads if accessible and a flat surface, harmonic balancer, could even use the top of carb too id imagine.

useful calc for drivline angles:

Spicer Driveline Operating Angle Calculator

Measure the angles of each component in your drivetrain, then use the Spicer Driveline Operating Angle Calculator to find the operating angle of each u-joint in your drivetrain.

spicerparts.com

 

[chief_shotts]

Also, what can I space out the carrier bearing with? Can I use large bolts or washers to space it out like an inch or a pinch less?

i would and have done that for testing purposes because you can add and subtract washers easily but for final assembly use a chuck of steel.. i have a piece of square steel tubing used to drop my carrier.