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Front axle pinion angle seems wrong?

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Old 05-20-2011, 03:23 AM
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Front axle pinion angle seems wrong?

I have a 75 highboy, and noticed the front axle looks like the angle is off. I am guessing the pinion should be parallel to the frame, and not pointing toward the ground. It ends up putting the front u-joint at more of an angle than it really needs to be.

Why is it the front and rear axles dont just point to the t-case? That would leave virtually no angle for the u-joint to be fighting, right?
 
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Old 05-20-2011, 08:23 AM
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anyone want to drop some advice on me here? Should I just let it stay the same or think on fixing it?
 
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Old 05-20-2011, 08:43 AM
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im pretty sure it is supposed to be like that i cant rember and my truck is currentally torn apart to lift it... but the leaf pads on the axle are built into the diff(one of them is atleast) and you cant move your pinion angle without a shim so look to see if there is a shim in there otherwise its stock..
 
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Old 05-20-2011, 10:48 AM
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Sounds like a PO installed shims, and did so backwards.
 
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Old 05-20-2011, 10:53 AM
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Mine was the same way and had no shims. It's just the way they are.
 
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Old 05-20-2011, 11:08 AM
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Depends what the OP means by "pointing towards the ground", the axle is angled in that direction a degree or two, but to the naked eye it basically runs parallel to the frame, if the OP could post up a pic we could see how much angle he's talking about.
 
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Old 05-20-2011, 06:53 PM
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Stock 77 highboy low pinion D44 front.

-Jared
 
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Old 05-20-2011, 07:05 PM
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mine looked the same^
 
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Old 05-21-2011, 04:35 AM
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Thats pretty close to the same as mine too. So this can be fixed in part by adding some degreed shims to turn the axle? Is there any reason I cant relocate the leaf spring pads/blocks (whatever they are)? I am a very competent fabricar;

End result is I would like to have the pinion "pointing" at the t-case to reduce the driveline angle. I could have sworn that somewhere in my past I remember someone saying its a bad thing to do
 
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Old 05-21-2011, 07:06 AM
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As I understand it, if you have a two u-joint shaft front shaft, the output of the front differential has to be parallel to the front output of the transfer case. If you have a three u-joint front shaft, the output of the front differential has to be pointed at the front output of the transfer case.

Here are some pics from Tom Wood's website to help explain:





Even though these show rear shafts, fronts shafts would have to follow the same rules.
 
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Old 05-21-2011, 08:27 AM
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^100% Correct^

The front output on the t-case is either parallel to the earth or slightly north of parallel. The front pinion would then need to be either parallel or a slightly south of parallel to keep the yokes on the same plane. All of this being in the name of smooth, vibration free operation. I always felt that my pinion pictured above was exaggerated by the well worn front spring pack.

-Jared
 
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Old 05-21-2011, 01:46 PM
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Originally Posted by Deluxetruck
I always felt that my pinion pictured above was exaggerated by the well worn front spring pack.
I'm not certain that's the case, reason being, as the spring pack fatigues over time and the pack flattens out the pinion angle remains on the very same plane, its angle is not altered due do the worn springs.
 
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Old 05-21-2011, 05:38 PM
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And also, the front pinion might be down a couple of degrees to compensate for when torque is applied. When you put a load on the front drive shaft (i.e. 4 hi or 4 lo) the whole differential will want to pivot up. The angle might not look so wonky when in 4wd.
 
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Old 05-21-2011, 08:58 PM
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Front pinion will want to go down underload.

You should keep the angle at the tcase and front pinion the same = no vibration
 
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Old 05-22-2011, 07:31 AM
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Originally Posted by Greenhiboy
And also, the front pinion might be down a couple of degrees to compensate for when torque is applied. When you put a load on the front drive shaft (i.e. 4 hi or 4 lo) the whole differential will want to pivot up. The angle might not look so wonky when in 4wd.

Incorrect.

-Jared
 


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