Author Topic: Rear driveshaft angle??  (Read 719 times)


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Rear driveshaft angle??
« on: January 19, 2019, 10:03:11 PM »
Need some help and feedback, please.
I am installing the rear driveshaft, and I notice that there is about a 15-20 degree angle from parallel between the plane of the rear axle and the plane of of the emergency brake disc.  I know I can't shift the emergency brake disc, and not really sure how well I can rotate the rear axle.  (Note, the rear axle is lifted from below, not above).
Is this mating angle difference a big deal?  Will the rear driveshaft work with this angle? 
Advice?  Guidance?  Feedback?
Inquiring minds want to know.

« Last Edit: January 19, 2019, 10:05:13 PM by colkking »


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Re: Rear driveshaft angle??
« Reply #1 on: January 20, 2019, 07:42:02 AM »
Drive lines must have an angle to them. i am not sure what the HT is as I haven't looked at mine in a while, but they can not be straight.

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Ma Deuce

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Re: Rear driveshaft angle??
« Reply #2 on: January 23, 2019, 02:16:43 PM »
Working on my ht today put in another pto seal in rear output shaft. took these pictures. Mine looks pretty straight, a buddy thought he heard 3 degrees is recommended.
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Re: Rear driveshaft angle??
« Reply #3 on: January 23, 2019, 03:44:21 PM »
There are two driveshaft angle conditions that you have to be aware of.  The first is the angle between the driveshaft and the crankshaft /rear end pinion shaft centerlines.  This is the angle that causes the U-joints to articulate.  The greater this angle is, the more the U-joints move and the more power is sucked up by the driveshaft/U-joints.  Typically, the maximum design angle is around 5 degrees.  At 10 degrees, you are going to have lots of power loss and noticeably shorter U-joint life(ask your buddy about his lifted 4x4).
The second issue is that the crankshaft centerline and rear end pinion centerline angles have to be parallel.  This is because a driveshaft speeds up and slows down twice each revolution due to the U-joints.  If the angles are parallel, the U-joints are in phase and the speed up/slow down of each U-joint cancels the other so there is no drivetrain vibration.

When a driveshaft is used as a stationary jack shaft like on the Halftrack, the crank/pinion angles will be the same, but they will be slightly offset so that the U-joints will move alittle and then the U-joint needles won't wear in one spot only. 

I have not checked the angles and my halftrack, but I believe the flanges should be parallel.  The only time the pinion angle is different from the crank is on a drag race car.  The snout of the rear end is usually pointed down about 3 degrees.  This is because the power level of the car and the suspension geometry causes the snout of the pinion to rise when under power going down the track.  Sorry about the long explanation for a short question.