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Driveshaft fun

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goochieman83

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So the shop is done rebuilding the transmission and transfer case on the K5, but they don't want to put the old driveshaft back in, it got thrown when the t-case broke free from trans. Am in the process of getting a new cv shaft for the rear but the local guy who builds them is apparently in Ireland for a week. Do you think if I put the old driveshaft back in it would be alright to drive back home, roughly 6 miles, without issue. The old, lengthened driveshaft isn't bent, it is just a single, non-cv, shaft. Don't want to leave the blazer sitting at the shop for another week but don't want to mess anything up after all that work either.
 
Is the old shaft balanced? How fast will you be going? Is the shaft binding at all?

If you keep it under 40 mph and its not binding then its ok. If its binding put a ****load of weight in the back lol.
 
The old shaft is balanced and no it was not binding, the vibration of the driveshaft caused issues with the t-case, which broke it. Just trying to figure out if I can get it back without issue. Like I said I will have a new cv shaft but looks like I might have to wait a little longer to get it.
 
I have to replace the front u joints first, the front driveshaft actually wasn't in it when it threw the rear shaft. Plus wouldn't the rear slip come out if I drive it home in front wheel drive anyway.
 
Make sure all the yokes are phased correctly. they should all be in line or you will get a lot of vibration.
 
The funny thing about all this is my cj7 had a regular lengthened driveshaft in it and it had 6" of lift, and I never had a problem with driveline vibration.
 
Driveline phasing

Reference: drivelinespeclist.com

http://drivelinespecialist.com/Tech1.htm#Phasing






Phasing:

Phasing is a term that describes the alignment of the single-cardan joints on opposite ends of the drive shaft. As discussed above, a single-cardan (or u-) joint does not rotate at a constant velocity if the operating angle is non-zero. The drive shaft speeds up and slows down slightly as it rotates due to the nature of the joint. One way to reduce this is to make sure the joints at each end of the drive shaft are aligned properly. If the yokes on each end of the shaft line up with each other, as seen in the figure below:

image.jpg


Then the affect will be that the two joints will tend to cancel out the speed variations from each other. In most 4x4 applications, the drive shaft will have a slip yoke in the middle to allow for changes in length. If the shaft is ever taken apart, it is important to get it re-aligned properly when it is re-assembled. One way to do this is to mark both sides of the slip yoke. However, you should check that the joints really do align properly, don't assume they are. The reason for the phasing is that the speed variation of the joint is related to its operating angle and its angle of rotation. In order to get the most effective cancellation, the joint yokes *must* be aligned exactly with each other and the operating angles must be identical. Any variation in either angle will show up as un-cancelled vibration, which will get worse at higher speeds.

image.jpg
 
Yes,a one piece shaft (with the slip yoke that goes in the transfer case or transmission),has the yokes welded in phase "permanently"..

Our "beater" ramp truck at the junkyard had a rear driveshaft that looked like a bananna after it was backed over a "hump" in a parking lot...we never used it to go far or very fast,at about 35-40 mph the rear of the truck started "hopping" pretty bad--felt like a bad retread tire ready to pop..
We tried bending it back in place (by lifting up on the shaft with the forklift gently..:D).. and it helped some,but it was fubared and could never be "saved" really..we just used it as-is..never could find one the right length and the right u-joints,and the boss was too cheap to have a new one made up..

I'd say you could limp home 6 miles slowly with no worries..
I have driven further with a dented shaft under 30 mph..once I drove my K5 home over 50 miles on just the front shaft only..rear one fell out when the u-joint came apart..:blush:..was lucky I found it and it was relatively unhurt!..
 
Do any of you happen to know the length of the rear output shaft on the np208, from the case to the end of the output shaft. Basically how much the shaft sticks out from the transfer case.
 
6d8a4c7429394f2f712b71a5637d8beb.jpg


Here's a pic from my thread.


It looks like about 1 1/2"
 
Cool, thanks. Getting my cv shaft built and took the measurement from the end of the shaft. He asked for the length from the end of the case to the pinion u joint mounting surface.
 
Well I picked up my cv shaft this morning and when I got there I noticed the slip yoke was not splined out to the end. So now I have a new driveshaft that has the incorrect yoke. I guess I could have the shaft lengthened to accommodate for the spline not having an extra 2" of travel or just see if they can order a new cv assembly.
 
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