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Driveshaft Angle Question

cuda joe

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I would not cut the floor what matters is the angle of the u joints trans down is ok with rear angled up. get rid of the lowering springs in the rear,, it works with my set up a 727 trans and an 8 3/4 rear
 

Steve Blair

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The trans is down 4.4 degrees, after I removed the 1 inch lowering springs from PST I noticed the arch in the PST springs were unequal (already!) so I ordered a set of springs that were made for a 440 6 pack or Hemi, the passenger side has an extra leaf (I don't believe its a full leaf). I'm pretty sure the 1 inch lowering leaf springs from PST are not great since their arch is already different from one another, and when they were installed the passenger side rear looked like it was bending downward with a slight twist by the shackle. After the new springs are in I will try and move the rear of the GV unit up as much as I can without making contact with the floor and adjust the angle of the pinion so it is opposite the angle of the GV unit (GV down, pinion up) in a parrallel line and see if there is any vibration.
 

heminut

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I would not cut the floor what matters is the angle of the u joints trans down is ok with rear angled up.
This is true up to a certain point and when both u-joints are at the same approximate angle. Once you get to a certain angle the chances of driveline vibration increase exponentially, and the life of the u-joints are severely reduced. 4X4'ers and rock crawlers all know this. Any rock crawler guy will tell you that the more severe the angle on the u-joint, the less torque it takes to snap it. Pole vaulting your classic car on the highway would not be a good experience!
 

cuda joe

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the angle between the trans angle and drive shaft angle should be between 1 and 3 degrees . that would be the u joint angle not the angle between the trans and floor. same for the rear i had the best luck measuring the ends of trans and rear with driveshaft removed
 

Steve Blair

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I removed the bolt from the transmission mount and raised the GV unit until it hit the tunnel and the angle finder said 2.60, when I get the rear springs installed I will see if I can duplicate the angle on the pinion so the GV unit and pinion run parallel and hopefully the driveshaft will run at least 1/2 degree between the two. I will make sure to remove the driveshaft when I measure the angles.
Thanks
 

cuda joe

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great wright back with the angles after new springs. happy wrenching
 

Steve Blair

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So with the new Hemi or 440 magnum rear springs installed my Pinion angle is 8.6 degrees down (not good but better than the 11 or 12 degrees down that I started with when I had the 1 inch lower PST springs in the car (no wedges just the spring perches that are welded to the rear end). Let's say my GV unit is 3 degrees down so to cancel any driveshaft vibration the pinion angle should be up 3 degrees (or within a degree if not the exact opposite). From what I understand opposite angles of the GV unit and pinion angle will cancel any vibration provided I start with no more than 3 degrees ). I have the rear end out of the car and the spring perches are welded to the rear end housing at the same angle as the pinion. The Dana was from a truck and I can see the axle tubes have been ground on, maybe a truck has a different location for the spring perches? I will stop and talk to a person who rebuilds rear diffs and transmissions before I do anything. As it is right now I could cut the spring perches off the diff, bolt the diff back into the car without new perches welded in place, set the cars ride height, raise the pinion so it is the exact opposite angle of the GV unit (3 degrees up), tack the spring perches in place, remove the rear end and do the final welds on the spring perches. None of this accounts for axle wrap but I'm pretty sure vibration should be eliminated during normal driving. Thanks for the info on your transmission angle.
Hope you have a great day!
 

MoPard

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I believe you now have it. Mock it up and tack new spring perches in place. I’m using Cal-Trac bars on factory replacement heavy duty springs for 550 HP street. I’m adding a GV soon and that’s my plan. Let us know how it works out
 

cuda joe

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yep that sounds right .as for the pinion angle you do have the jack stands under the rear so the springs are fully loaded ?
 

Steve Blair

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Yes, when I reinstall the rear diff with loose spring perches I will make sure the car is sitting on the front and rear suspension at ride height. I will also speak to the 4 wheel drive shop again before welding anything in place.
 

cuda joe

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I never welded a rear what is the procedure for that steve ?
 

Steve340

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I dare say the factory had a welding jig that would have held it close to true.
Weld on the spring perches are whatever brackets you are attaching to the housing.
The shop I use has a bar around and inch diameter and two tapering cones and he uses heat or weld opposite the warp to "pull" it back.
I pay to have this done as I do not have the gear or necessary experience.
I do know if the housing is out you can have trouble with axle bearings and differential noises.
 

brotow

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for the street you don;t want super stock springs. and to change pinion angle you use shims no need to move the perches
Super stock springs no shims just 2" longer front mounts.

20220902_184916.jpg
 

Dodgeboy

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Don't let the diff get to hot or it will warp, especially if your not using a jig, Control your heat that's going into the housing. You could do small welds, opposite corners with cool down time in-between welds. If you have a variety of welding machines too choose from then I would use a tig
 

heminut

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The welding will warp the rear axle housing. You will need to get it straightened.
Arc welding, maybe. MIG, I seriously doubt it! I MIG'ed mine and had absolutely no warping issues. I have done this to two Cuda's (put the narrower B body housing in both of them) and had no issues whatsoever.
 

Steve Blair

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I spoke to a 4x4 shop and they said I can weld 1/4 of the spring perch starting at opposite corners letting the weld and axle housing cool between welds, they said the Dana 60 housing is thick enough they have never had a problem. I will use a miller 200 mig welder and let the weld and axle housing cool between welds, I'm also going to lay a wet towel on the end of the axle housing to keep heat from transferring toward the axle seal and bearing.
Thanks for the advice and info!
 
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