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Transmission, Rear End... Talk & Q&A! Tranny, rear end, drivetrain related stuff... shift it... grind it... pop da clutch!

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  #1  
Old 09-01-2017, 04:30 PM
serrata serrata is offline
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Default Driveshaft reconfig questions...

Here's the issue. My donor is a long bed 4wd F350 dually crew cab. My rat will essentially have the same drivetrain layout, but the engine will be slid much further back, meaning I need a shorter rear driveshaft and a longer front driveshaft.

I'm not a mechanic, so just assume I'm dumb.

1- For the rear driveshaft:
The rear driveshaft has 2 segments: A longer one in the back attached to a shorter one with a yoke in front of that. The shorter one is braced t the frame.
The length of the shorter one is essentially the length I need.
It has a fixed brace on it that originally attached it to the F350 frame.
Can I take that brace off and use the shorter shaft with the yoke?


2- For the front driveshaft:
The idea is to push the front axle out in front of the engine instead of under it.
I would like to add a segment with a fixed frame brace on it, like the original rear was, so that I can have a shaft from the transfer case toward the front and braced to the front of the new frame in front of the engine with a joint attached to the existing front driveshaft.

What are my options for doing this?
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File Type: jpg 20170828_222342.jpg (90.1 KB, 19 views)
File Type: jpg 20170826_114938.jpg (91.0 KB, 38 views)

Last edited by serrata; 09-02-2017 at 06:49 AM. Reason: misspellings
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Old 09-01-2017, 05:23 PM
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The way it's designed the drive shaft is fixed from the tranny to the carrier bearing, after that you have a slide to allow for travel of the rear end arc, as the rear moves up and down the shaft slides in and out. On a single drive shaft the yoke on the tranny does the sliding.
Here is how I did mine just for visual, I kept the front so I wouldn't have a big tunnel in the cab and then let the travel take place after the carrier.





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Old 09-01-2017, 07:52 PM
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How does this work, sneaky? Looks to me, like the shaft would leave the scene immediately...



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Old 09-01-2017, 08:38 PM
serrata serrata is offline
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Staring at this for a minute, my original on the f350 was the same, just much longer.
I assume the shaft goes the majority of the way into the yoke, so that the centripetal force doesn't fling the u joint out.
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Old 09-01-2017, 08:44 PM
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Quote:
Originally Posted by Dr Crankenstein View Post
How does this work, sneaky? Looks to me, like the shaft would leave the scene immediately...



.
I agree, U joint looks to be too far back from the slip yoke. On semi's, we have a short driveshaft from the rear of the front diff to the front of the rear diff, the shaft is about 3-4" long from the front joint, then there is the slip joint, then the rear section of driveshaft is 2' or longer depending on the axle spacing.

As to the original poster, You are going to have to change the yoke on the transmission if you can, if not, you may have to use the front part of the front driveshaft welded to the rear of the rear driveshaft, that way you can have a joint at both ends. Might have to build a custom shaft using the original ends.
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Old 09-02-2017, 10:18 AM
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Are those mock up pics that show the sitting heights of your axles and trans? Will you be using bags? If so, keep in mind that the distance between axle and trans will get shorter when you inflate. Usually tail shaft space is about 3/4" from the housing, but with a frame dragger, that has to be measured when fully inflated. (Yeah, the one thing I nearly screwed up when I did my air ride)

Pay attention to what your U-joint angles will be at ride height. Too tight an angle could cause grief.
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Old 09-02-2017, 10:43 AM
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Quote:
Originally Posted by Dr Crankenstein View Post
How does this work, sneaky? Looks to me, like the shaft would leave the scene immediately...



.
It works perfect, the slide allows for all the movement of the rear on bags, and at ride height the shaft is in line so no harsh angle. The front has a long spline that the slide slips up on so I don't see where you think it can jump out of alignment?

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Old 09-02-2017, 10:48 AM
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I cut nearly 3ft off the rear section of drive shaft.

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Old 09-02-2017, 11:04 AM
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[QUOTE=serrata;483420]


Have both shafts shortened, keep the slide. Mount the carrier so the shaft has a pretty straight line to the rear axle. Like above allow for full travel in and out of the shaft.
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Old 09-02-2017, 03:35 PM
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Or get a sliding yoke for the transfer case from a single shaft and use a short one piece shaft.
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