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DRIVESHAFT TECH IN CHIT CHAT WANTS: 74'' 7K RPM

xr-nut said:
in that pic it was .006-7'' which the builder says is acceptable.
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I was thinking more the run out of the shaft at each end, 4 total.

Looking at the installation page it looks like the slip should be built into the driveshaft, not at the carrier bearing. Looks like a lot of leverage hanging way back there. That u-joint is like what 10" away from the bearing where if the slip was on the shaft it would be maybe 4"?
 
Steve300xcw said:
If you are getting .006-.007 under the truck, I'd say thats pretty good.

Is that the back shaft too?
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That's the blue part of the short shaft. Right behind the u joint and the yoke welded into the rear shaft it was .016 I think. I have it written down at the shop
[486] said:
is the pillow block bearing binding a little bit and making the crossmember flop as the shaft turns?

smack the pillow block around a little bit to try and get it relaxed in the angle you've got it at
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Well........ There may be more that
 
[486] said:
I dunno anything about driveshafts, I shorten them with a grinder and welder, and when they vibrate I toss a couple hose clamps on them to try and get them balanced better
sometimes it even works, other times I just say "eh close enough" and deal with the newfound 65mph speed limit
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Less road pirate attention rolling the slow lane with the swift trucks anyway...
 
[486] said:
all of mine have the spline poking through the carrier
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It's been 20 years since I owned anything with a carrier bearing so there's that... It just seems like a lot of leverage back there.

Watching the video you see it start to wobble then the bearing cross member starts to flex, maybe truss the cross member into the one above to stiffen it.
 
Oh shit, I think I got it

that pillow block is really rigid so the front joint needs to be really square

the joints needing to be in phase is because the shaft grows and shrinks as the joints flex
so as the front joint flexes it is trying to pull and push the carrier bearing in and out

usually they're rubber diaphragm mounted so they can wigglewaggle back and forth between the two in phase joints
 
xr-nut said:
That's the blue part of the short shaft. Right behind the u joint and the yoke welded into the rear shaft it was .016 I think. I have it written down at the shop

Well........ There may be more that
Click to expand...

Shit kinda pivots at the carrier. Being a touch out on that first tube can make an issue out at the slip yoke. Same for the rear tube causing issues

16 is a bunch.
 
Steve300xcw said:
Shit kinda pivots at the carrier. Being a touch out on that first tube can make an issue out at the slip yoke. Same for the rear tube causing issues

16 is a bunch.
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Any idea if the slip should be in that front shaft or the rear?
 
last night laying in bed thinking of all you ff's........:laughing:....... i remembered a cross member i took out. it was right in front of the tube the carrier is mounted on. it had caught on the lift driving it off one time and was a little bent. so when we were mounting the carrier I took it off to get it out of the way. stuipdly I looked at it thought to myself "this isnt doing anything" and tossed it in the scrap metal.

put it back on this morning and ran it up again. its better. not good, just better. kid reminded me we were still 90deg out on the center so I put it back how it was built. run it up to 90mph on the lift and its considerably better. so he took it out to drive it. he said at 40 you can feel it vibe like maybe a tire is out all the way up to 60. said it feels worse with more throttle. then clears up a bit to 90mph then it starts back in.

Im going to raise the middle back up that 1/4'' like action recommended and try to stiffen up the frame there in the middle even more. maybe run a square tube across welded in.

 
xr-nut said:
last night laying in bed thinking of all you ff's........:laughing:....... i remembered a cross member i took out. it was right in front of the tube the carrier is mounted on. it had caught on the lift driving it off one time and was a little bent. so when we were mounting the carrier I took it off to get it out of the way. stuipdly I looked at it thought to myself "this isnt doing anything" and tossed it in the scrap metal.

put it back on this morning and ran it up again. its better. not good, just better. kid reminded me we were still 90deg out on the center so I put it back how it was built. run it up to 90mph on the lift and its considerably better. so he took it out to drive it. he said at 40 you can feel it vibe like maybe a tire is out all the way up to 60. said it feels worse with more throttle. then clears up a bit to 90mph then it starts back in.

Im going to raise the middle back up that 1/4'' like action recommended and try to stiffen up the frame there in the middle even more. maybe run a square tube across welded in.
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This is kinda funny, I was jokingly going to suggest reinforcing the frame and cross member until the shaft could no longer vibrate it.:laughing:
 
Glad you are making some progress.
This is also making me dread a long driveshaft in a station wagon project I have. I may do a 1 piece carbon fiber one.
 
greenlion said:
Glad you are making some progress.
This is also making me dread a long driveshaft in a station wagon project I have. I may do a 1 piece carbon fiber one.
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I'm a ways away from actually pulling the trigger, but I've been thinking about finding an aftermarket one that's close and finding somewhere local to shorten accordingly.

other option was try to just get a custom front section + bearing setup made to mate up to a stock 1-piece rear shaft (in my case Explorer)

like this
1721838893393.png
 
That 2 pc looks like a good option if you can find one with the yokes you want/can use.
The one pc may have too low of a critical speed, depending on what you are trying to do. Which led OP down this path.
 
greenlion said:
That 2 pc looks like a good option if you can find one with the yokes you want/can use.
The one pc may have too low of a critical speed, depending on what you are trying to do. Which led OP down this path.
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good point. i don't think my 68 IH pickup with a crown vic frontend hacked in by me is gonna see near the speeds OP is doing in his ride. I'll definitely have to do the calcs when I get to that point

seems like there's a ton of OEM type options for longbeds out there. finding the "right" one could take some time but save a fair chunk of $$ if possible
 
Got an email from action after sending them the first video. he told me everything has to run downhill, basically. so I raised the tailshaft up a 1/4'' or so and raised the center bearing up a total of 5/8''. turned the links in the rear to bring the pinion back down. current numbers are :
trans output 3.2 D
front shaft 1.5 D
rear shaft .9 D
diff yoke 0.0

all measured on the driver side of the shafts and from the top. didnt change a thing how I held the angle gauge, measured multiple times, so the numbers are close.(ish)

according to the spicer info, we need to be within 1.5 on the front shaft and diff yoke. its there. and its all "falling" downhill. from the trans ouput to the read diff, its pointing down now. still bad vibes.

called machine shop in topeka, they can spin it up. going to drive it down there tomorrow. I guess.

watch the bounce in the middle of that back shaft.

 
the front shaft is supposed to run 1.5 deg operating angle on that joint. its there. then the next number was to be the pinion angle to the front shaft. within 1.5 deg. its there. the operating angle on the joints on the rear shaft are with .5 deg of each other. and both shafts are angled down from the trans back. idk what else to do.
 
I don't like the slip on the mid shaft. Let's it do too much wiggle me thinks having the joint way out from the carrier bearing.
 
Dethmachinefab said:
I don't like the slip on the mid shaft. Let's it do too much wiggle me thinks having the joint way out from the carrier bearing.
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Ya, yoke seems pretty far out on the slip. All the two piece shafts I remember messing with had little to no blue showing outside.

OP, how far forward will the rear shaft go on the slip splines if you unbolt it from the diff?
 
SLOWPOKE693 said:
Ya, yoke seems pretty far out on the slip. All the two piece shafts I remember messing with had little to no blue showing outside.

OP, how far forward will the rear shaft go on the slip splines if you unbolt it from the diff?
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I can go check that. with though in mind, I do not have the rubber bushing and cap back on it. :confused::homer:
 
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