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post #1 of (permalink) Old 10-26-2002, 08:53 PM Thread Starter
 
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Drive shaft fell out...again..suggestions

I have a cj-7 304 with a t-18 and a amc 20 rear. Dana transfer case. I have now gone through 2 pairs of U-joints and 1 sliding yoke. I have made sure the u-bolts where on tight and had proper lock washers. I'm thinking of taking the shaft to check if it is bent or not, before having to shell out for a new one. I have 30 inch tires with no lift. I know the angle is important, but how does that come into play? Suggestions would be helpful.

Jeeprugger~
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post #2 of (permalink) Old 10-26-2002, 10:21 PM
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Re: Drive shaft fell out...again..suggestions

1. It's not a bad idea to have the driveshaft balance checked.
2. Do you have even a shackle lift?
3. Do you use thread sealant on the strap bolts?
4. What happens when the shaft goes flying?
a. What end comes loose?
b. Is the Yoke damaged?
5. The angle is important... and it wouldn't hurt to check it.
6. How are the motor mounts and the transmission mounts?

That'll keep ya busy a while!
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post #3 of (permalink) Old 10-27-2002, 01:41 AM
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Re: Drive shaft fell out...again..suggestions

7. Is it out of phase?
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post #4 of (permalink) Old 10-27-2002, 06:47 AM
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Re: Drive shaft fell out...again..suggestions

I had a simalar problem once and it turned out to be the yoke on the rearend!!
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post #5 of (permalink) Old 10-27-2002, 11:19 AM Thread Starter
 
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Re: Drive shaft fell out...again..suggestions

good ideas, I do have extended shackels, so it might gain a 1/2 inch there, Yes I did use thread lock on the u bolts, no straps. When you say out of phase do you mean the u-joints lining up straight with each other when the yoke and shaft are installed? The yoke end is the one that comes loose, and the yoke is new and not damaged. The sliding yoke was caught on my slide plate underneath, one time it did fly o the left. The drive shaft stayed on twice but this last time it was thrown up and caught between the frame and body. I do not know the proper way to check the angle. Any tips there would help. Motor and tranny mounts seem to be fine. Could it be possilbe that the yokes where the u joints connect to might be too loose? Would that cause this problem? Everything is properly lubed. Thanks
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post #6 of (permalink) Old 10-27-2002, 06:10 PM
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Re: Drive shaft fell out...again..suggestions

How about just a basic question: have you measured the distance from the rear end to the transfer case, to see what it SHOULD be? Then compare that to your actually driveshaft. Seems like the driveshaft would HAVE to be too short. That seems odd, with just extended shackles but that's where I would start.
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post #7 of (permalink) Old 10-27-2002, 07:58 PM
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Re: Drive shaft fell out...again..suggestions

1. I'd doubt 1/2" shackle lift would cause a problem.
2. If the thread lock is shakin' loose, yep, ya got a problem.
3. As a rule, there should be a small punch mark on.
a. the driveshaft
b. And the yokes.
4. Phasing: The punch marks should be aligned.
a. A U-joint has 2 yokes connected by a cross.
b. The yokes must be 90 degrees apart.
c. When you connect the slip joints together you make 2 parts into 1. Make sure that when you re-connect the shaft together the splines are alinged correctly.
d. On this shaft the yokes at each end need to line up exactly.
e. Look at the other shaft and see how they line up on it.
f. This minimizes end thrust introduced by U-Joing angle at developed by the 2 ends.
g. Endwise motion of the slip joint is minimized.
h. When the u-joints are in standard phase, the slip yoke lugs (ears) and the tube yoke lugs (ears) are in line.
i. This is the ideal for a smooth running shaft.
j. In simpler words, if the zerk fitting on the front U-Joint is 6 o'clock, the zerk fitting on the rear U-Joint should be at 6 o'clock.
5. If the Yoke's were bad then you sure could have a problem.
6. Double check the Yokes for
a. Scaring,
b. Out of position,
c. Smooth rotation,
d. No exessive in - out play from the Transfer case or diff.
7. Checking the angle is simple: The two angles MUST be withing about 2* of each other.

As example:

Measure the angle from the transfer case to the driveshaft and it's a - 11 degrees

Then to avoid vibration the angle from the driveshaft to the Diff must be betwen +11* and + 9*

By subtracting the two angles you get the result, so if the subtraction yielded a result of 4*, then the vibration occurs.

The larger the difference between the two angles, the more vibration. The more vibration the faster the destruction of the parts.

8. If your tires are large then there's more footprint applied the the earth surface. It's like more firmly planting your foot on the earth and now twisting... if the foot don't move, something's gonna give and it's likely the ankle or the knee and you're gonna fall, grab something and scream in pain. You're Jeep may not be able to scream and grab in pain, but it can sure scatter parts.
9. Same prolem happens with a larger engine and stock driveline parts. You can overpower the driveline parts and scatter U-Joints everywhere you go.
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post #8 of (permalink) Old 10-28-2002, 07:16 AM Thread Starter
 
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Re: Drive shaft fell out...again..suggestions

thanks leve, you the man. ill let you know what comes about. i didn't know about excatly lining up the shaft. and the yokes having to be matched also. I guess you learn as you go right? The only way to learn is to brake it first.. jeeprugger~
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