Rear axle: Welding on saddles at proper angle (due to lowering kit)

[eskimomann209]

I should really clarify what I did with the pinion at 0 degrees.

The axle is out of the truck on my shop floor. I blocked up the axle to get the pinion to 0 degrees.

Then I put the inclinometer on the spring perches and measured their angle, which read 9 degrees.

I only did the above so I could see what the perches were set at. I then cut off the perches.

The pinion seal leaks anyhow, so I have to replace it! The axle will not go in until this is done first.

Eeeessshhh pinion seals... not always as easy as google makes it seem. Getting the pinion preload correct is important.

 

[OldBlueDually]

Eeeessshhh pinion seals... not always as easy as google makes it seem. Getting the pinion preload correct is important.

Luckily my dad is a 35 year GM mechanic and remembers working on these trucks when they were new and has done many of them! He said the same thing to me also about the preload on them. He will show me what to do, and will bring the necessary tools too. I want to do the work myself on this, but want him to guide me on it. Will see what happens, I know he likes doing this stuff on these old beasts!

 

[Turbo4whl]

Like @Big Chip stated, don't tack anything until you set the truck on the ground, engine and trans in place. Fully weighted body and bed complete. You will find you may need to point the pinion up. The angles of the two "U" joints in the rear need to match. The front "U" joint needs to match it's second joint also. This is why if you move the carrier bearing, you will need to change it's angle to match the front joint.

Watch this short video:

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[OldBlueDually]

Turbo4whl, I do plan to put everything together with no welds, once all is set then start tacking things in place, re-verify everything then weld it up. Interesting video, have not seen that before, well then again I never looked! Thanks for posting.

 

[eskimomann209]

Common guys. Tack welds are for fitment tests. I would NEVER be afraid to tack and check. If it’s wrong, a tack weld is simple enough to grind off.

 

[OldBlueDually]

I suppose if I turned down my welder to the lowest setting those welds easily break on this kind of steel. If I get a good torque on the u-bolts however I should be good. Guess I will find out when I get there! Doing stuff like this I usually use a scratch awl to mark where stuff is, then test it out (aka set it all down on its own weight) and then check those marks.

The main test might be when I smoke the old tires off of it for kicks I mean, after all if it can't handle a burnout with crappy tires I probably shouldn't be driving it

 

[Turbo4whl]

Common guys. Tack welds are for fitment tests. I would NEVER be afraid to tack and check. If it’s wrong, a tack weld is simple enough to grind off.

You are right about easy to remove tack welds. Just an extra couple steps that are not needed in this case. Until the suspension is weighted, anything done is wrong. The "U" bolts will hold it fine. Then when checking the "U" joint angles no need to remove the wrong tacks. Just rotate the axle until it is correct, then weld.

 

[OldBlueDually]

Ok, so now I am back at this once again. I have the truck blocked up on all 4 corners under the tires. Tire pressures all the same.

My first driveshaft (from transmission) measures at +5 degrees (going downward). 2nd driveshaft measures at +1.5 degrees (downward), and the rear end is coming in at -9 degrees (with pinion facing downward, same angle as it was below springs prior to it being placed above springs).

The difference is the 455 Olds bolted up to the Chevy TH400, which I was NOT able to properly measure before the Olds went in due to the original engine being gone. I am not sure what the original angle of the 1st driveshaft was at one point.

With the above said, and with me having 0 experience with any of this, what would you guys do at this point? Weld the **** out of it and say eff-it?

 

[OldBlueDually]

@Turbo4whl @Big Chip I have read, and re-read this thread a lot here and posted my above message.

However, after trying to process this info, and what you stated Turbo (post #18 above), if I understand this correctly what I should really do is remove the rear driveshaft. Then, measure the transmission tailshaft/u-joint angle, then measure the angle at the u-joint coupling after the carrier bearing to be sure they match?

Then whatever that angle is I need to make that same angle at the rear-end?

Here are some pics;

At transmission;

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At the carrier bearing;

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At the rear-end (as you can see it is leaking...nice);

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[OldBlueDually]

Found this too......

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[Bextreme04]

@Turbo4whl @Big Chip I have read, and re-read this thread a lot here and posted my above message.

However, after trying to process this info, and what you stated Turbo (post #18 above), if I understand this correctly what I should really do is remove the rear driveshaft. Then, measure the transmission tailshaft/u-joint angle, then measure the angle at the u-joint coupling after the carrier bearing to be sure they match?

Then whatever that angle is I need to make that same angle at the rear-end?

Here are some pics;

At transmission;

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At the carrier bearing;

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At the rear-end (as you can see it is leaking...nice);

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This is what you need right here:
https://spicerparts.com/calculators/driveline-operating-angle-calculator#more

Select 2 shafts. Measure the transmission angle(driving member), driveshaft between transmission and center support angle(coupling shaft 1), measure angle of driveshaft after the u-joint after the center support(driveshaft), and then measure the pinion angle at the rear-end(driven member). The calculator will then give you all of the u-joint operating angles. Read the acceptable values notes at the bottom of the calculator and adjust your rear pinion angle accordingly(in the calculator to find an acceptable value) before you make the rear end match that value in real life.

My bet, after looking at your pics, is that you will need to raise the pinion a bunch. Your centerlines are totally off and you will either grenade a u-joint or have a horrible vibration the way you have it set up now.

 

[Bextreme04]

I think the biggest issue that I could see right now, and that you should verify before doing anything else, is whether the center support needs to be moved due to the different engine and engine mounts you fabbed. You need the first part of that driveshaft to be on the centerline of the transmission to make it easier to deal with the rear end angles. You don't necessarily NEED to do that, but it will make the harmonics much easier to deal with. Things get very complicated very fast when dealing with two members spinning in separate plains. If you have the first part of that driveshaft in line with the centerline of the transmission, then it becomes no different than setting up a one piece driveshaft.

 

[OldBlueDually]

@Bextreme04 I actually do have that calculator

Just now I went out and verified all my numbers, and here is what it is. As for the next step, should I adjust the rear-end up 10 degrees (to put it at actual 0) so it matches the transmission & 1st driveshaft?

****, I goofed....updated correctly....




This little bit of info helped....

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[Bextreme04]

@Bextreme04 I actually do have that calculator

Just now I went out and verified all my numbers, and here is what it is. As for the next step, should I adjust the rear-end up 10 degrees (to put it at actual 0) so it matches the transmission & 1st driveshaft?

****, I goofed....updated correctly....




This little bit of info helped....

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Because angle 1 is zero, I would think you want angle 2 and angle 3 to match. The way that works isn't going to be as simple as just raising it 10 degrees, because as you raise the pinion angle it will actually also raise the driveshaft angle at the same time.

You will actually need to raise it 15.5 degrees to be in line with the transmission and 1st driveshaft. That would make the angle of the driven member 5 degrees down slope and then the driveshaft would probably shift to being several degrees up slope. That should let the operating angles be very low depending on how much the driveshaft ends up sloping up. I'm assuming by the pictures this is all being measured with the axle as high up as it will go(truck as low as it will go)? That will be your worse angle(but don't forget to factor in a few degrees that will kick in under load). As the truck goes up a few inches the angle would get better.

 

[OldBlueDually]

Because angle 1 is zero, I would think you want angle 2 and angle 3 to match. The way that works isn't going to be as simple as just raising it 10 degrees, because as you raise the pinion angle it will actually also raise the driveshaft angle at the same time.

You will actually need to raise it 15.5 degrees to be in line with the transmission and 1st driveshaft. That would make the angle of the driven member 5 degrees down slope and then the driveshaft would probably shift to being several degrees up slope. That should let the operating angles be very low depending on how much the driveshaft ends up sloping up. I'm assuming by the pictures this is all being measured with the axle as high up as it will go(truck as low as it will go)? That will be your worse angle(but don't forget to factor in a few degrees that will kick in under load). As the truck goes up a few inches the angle would get better.

Ok, I see what you are saying, makes sense. I have the truck sitting on blocks right now, with tire pressures the same. No other weight on the suspension besides misc. stuff in the box, so the truck is sitting at it's normal ride height right now.