how to measure front driveline angles?

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I am currently running about 3" of lift in the front, with 3 degree caster correction bushings. At first I had only a slight vibration on deceleration, but it grew worse with time. I pulled my front driveshaft and the u joints look and feel good. I am trying to decide whether to replace them anyway and see if it helps with the vibe, or just bypass the whole step and do Landtanks caster plates with a DC shaft. What is the way to measure pinion and t case angles in order to see if the stock shaft has any chance of running vibe free with the current set up?
 

landtank

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You will need to get a protractor from Sears or similar. It's one that has a needle that hangs down with degree marks around the outside.

Then rotate the drive shaft so that one of the cups of the u-joint points straight down. Now using a socket as a spacer place the socket against the cup and then the protractor against the socket and take a reading. My protractor has a movable marker so I mark the first spot.

Then rotate the shaft 90* and take another reading on that cup and compare the two. The difference is the angle that the joint is working in.

A stock shaft wants the angle at both joints top be the same. There is a tolerance but I don't know it.

A DC shaft wants the angle at the pinion of the Diff to be 0* +/- 1*
 
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That's a gravity protractor you are looking for. They cost about $10.

A standard u-joint will tolerate about +/- 3 degrees of difference between the operating angle of the t-case and axle u-joints. The 80 series configuration operating out of phase appears to be able to tolerate closer to 5 degrees, which is a tremendous variance.

What I found was the Slee blue bushings corrected fully for a DC shaft. When I measured with OME bushings, I only had 2 degrees of operating angle on the axle end, so I expected to correct within range of a DC shaft, and it worked.

I haven't checked caster, but there is decent resistance to turning at speed, so I wouldn't want any more than I have.

LT's plates are a great solution - I only went with the bushings because there was no way I was paying $42 per bushing to go back to stock rubber to then buy the plates. But I had measured my angles and was taking a educated risk that if the stock shaft vibrated with the extra mis-aligment (it did) that I could do DC (I did, with a Taco shaft).

Good luck :cheers:
 
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Nay, am I correct in saying you are the first person I have ever heard about that corrected for a DC shaft with slee blues? It was my understanding you had to go back to stock bushings and then install plates. I used Frankie's blue bushings so I wonder if I will get lucky enough to already be set up for a DC shaft.
Are these protractors both basically the same:
Harbor Freight Tools - Quality Tools at the Lowest Prices
Craftsman Magnetic Universal Protractor - Model 39840 at Sears.com


And, is this a correct statement regarding angles as well?:
You need an alignment machine to measure castor. Your protractor is exellent for measuring the pinion angle. For a stock drive shaft remove it and measure the angle on the axle output flange and the transfer case output flange. They should be parallel. For a double carden driveshaft stick the protractor to your driveshaft and note the angle. Remove the driveshaft from the axle flange and put the protractor on the axle flange. The two angle should make 90 degrees.

I think I understand the procedure to measure the angles, just want to make sure I have it straight. I know I saw a post where it showed pictures of measuring the angles, but of course I can't find it now.
 
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I doubt I am the first, but maybe the first to recognize it. We always talk about caster correction, not pinion angle alignment for a DC shaft. You align for angles, caster follows. Generally speaking, at 3" of lift, Slee blues with LT template should align perfectly for a DC. 3.5" and you are pushing the positive angle a bit, but for me still in tolerance.

Landtank has the right method for measuring angles, you can't do it with the driveshaft disconnected.

Just take a look at your driveshaft. Does the pinion look aligned with the driveshaft? If so, you are close, so measure as LT described.

Here is what mine looks like - you can see visually it is lined up for the DC style shaft. I could probably use plates to gain another degree of caster and take it slightly below zero degrees operating angle, but there is no reason given how it is driving.

Your link to the Craftsman gravity protractor is the one I use.
Taco Shaft Pinion Angle.jpg
 
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sleeoffroad

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Landtank has the right method for measuring angles, you can't do it with the driveshaft disconnected.

For the front U Joint, measuring the shaft and then the flange itself with the driveshaft removed should also tell you if you have 0 degree operating angle or not.
 
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For the front U Joint, measuring the shaft and then the flange itself with the driveshaft removed should also tell you if you have 0 degree operating angle or not.

Good point, that would absolutely work, and would be very accurate - not sure why I didn't read it that way in the post. You might even be able to read the flange without pulling the shaft, in which case that is the simplest method.
 

landtank

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I only suggest the cup method as it's easier for people to follow along with the instructions. It's a single setup done twice. I did however have one guy rotate the shaft 180* instead of the 90* I specified. Just trying to keep things as simple as possible for the newbies out there.

But y'all can go ahead and impress people with how many ways you know how to skin a cat!:flipoff2:
 

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