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

Maybe crawl under a 2000’s Ford and grab a bunch of those dampers they stick on everything that moves?
 
Can you weld some captive nuts onto some shit and weld that to the mount so that they're captive you don't actually need to access the inside of the shit the carrier bearing sits on? That would go a long way toward letting you build an elegant solution when it comes to stiffening up the tube.
 
arse_sidewards said:
This would be a good start.

Screenshot 2024-07-30 at 10.31.53 AM.png
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one piece of 2'' wide, .250'' thick plate al the way across say on the front of the tube would accomplish the same thing. weld everywhere possible.??

that would leave one side(the rear) open to access the bolts for the carrier.
 
xr-nut said:
plate al the way across say on the front of the tube
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I don't like that because vertical forces can translate into fore-aft flex about the tube which translates into "some" vertical movement which will actually allow a fair bit of movement once it starts moving because of the rubber.

I think you'd be much better off running a flange over the top of the whole deal with 2"x.25 flat bar and then filling in the web with 1/8 or something.
 
xr-nut said:
Well it's in. Current numbers are:
Trans . . . . 3.5
1st shaft . . 2.0
2nd shaft . 0.9
Diff . . . 0.3


So we have the allowed 1.5 angle on the first joint. Are 1.7 apart on the 1st shaft to diff, which they wanted to within 1.
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I would try make your front shaft parallel to pinion shaft first.

1722354123406.jpeg
 
Anyway you could strap a gopro under there on the next test run?
 
xr-nut said:
I think the only way to do that is to crank the pinion up. everyone, and I mean everyone says the pinion must point down.
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What about to move trans mount up higher? As someone said in this thread, treat the first driveshaft as an ‘extension’ of transmission.


I’d shoot for figure 10 via zero to no more than 1 degree at transmission u-joint due to expected high speed operation. There are 3 u-joints the oscillations can’t be completely eliminated, so let’s try mitigate operating angle at transmission.

Move trans and carrier up to have the first shaft parallel (0.3) to pinion shaft & have second shaft’s front yoke to be in phase with its yoke at pinion as shown in figure 10 & go for test drive.

Alternatively, use this an excuse to get adjustable control arms to move pinion up to 3.5 & lower carrier bearing (and away from floor) to set front shaft to 3.5.

My $0.02

What do you think, Steve300xcw ?
 
TrailTamer said:
What about to move trans mount up higher? As someone said in this thread, treat the first driveshaft as an ‘extension’ of transmission.


I’d shoot for figure 10 via zero to no more than 1 degree at transmission u-joint due to expected high speed operation. There are 3 u-joints the oscillations can’t be completely eliminated, so let’s try mitigate operating angle at transmission.

Move trans and carrier up to have the first shaft parallel (0.3) to pinion shaft & have second shaft’s front yoke to be in phase with its yoke at pinion as shown in figure 10 & go for test drive.

Alternatively, use this an excuse to get adjustable control arms to move pinion up to 3.5 & lower carrier bearing (and away from floor) to set front shaft to 3.5.

My $0.02

What do you think, Steve300xcw ?
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I can move the transmission up more. 1/4 to 3/8'' before it gets difficult on the exhaust and other associated bits bolted to the motor. I cannot raise the carrier up, without cutting out the cab bracing above it.

I already have the trans up 1/2'', and the carrier is lower than that, give me the downward angle on the 1st shaft. maybe I lower the trans to get that shaft level. brb.
 
IMG_20240730_121640765_HDR.jpg


Pulled the spacers out. New numbers

4.7
0.6
1.9
0.4

So the front shaft and the pinion are very close. Trouble is that front joint working angle is bad now
Haven't driven it yet with this setup.
 
xr-nut said:
that made it worse.
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It may be worse but this is informative. I think it’ll improve/solve your problem if trans output shaft, first shaft and pinion are within 1* parallel. Whatever angle the second shaft end up at doesn’t matter as both mid & pinion u-joints’ angles should be very close to same.

Looking like cut up & redo carrier mount is inevitable?

Can you move trans mount up to set trans output shaft to/close to pinion shaft’s 0.4* to avoid messing with rear suspension?

Also make sure you have the slip yoke on second/rear phased on same plane, otherwise angles at mid and pinion u joints will not cancel each others’ oscillations out.



By the way I like how you go “brb” and came back with a result quickly. I did not expect that. But cool :smokin:
 
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xr-nut said:
Well it's in. Current numbers are:
Trans . . . . 3.5
1st shaft . . 2.0
2nd shaft . 0.9
Diff . . . 0.3


So we have the allowed 1.5 angle on the first joint. Are 1.7 apart on the 1st shaft to diff, which they wanted to within 1.

Drove it, it was good to 90/95. Then it started a vibration. I didn't go any faster.

Shop told me the front shaft, on the land where the carrier bearing mounts, it was .034" out. :eek:
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Did you get the brace done? I would go back to these numbers and start testing 1 change at a time. Maybe start by going down with the pinion a little more, test. Worse go up, better go down more.

I had a grand Cherokee I did a homebrew hack-a-shaft in, had an offset 8.8, way to many changes 1/2° at a time a time until it was right.
 
If your vibe is 1st order, (once per rev) it's not a joint angle issue which would be 2 times per revolution. If it's rumble strip frequency it's 1st order imo.

The small changes your seeing are just impacting it's ability to get into that 1st order vibe.
 
xr-nut said:
I think the only way to do that is to crank the pinion up. everyone, and I mean everyone says the pinion must point down.
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well ignore that particular everyone and do it anyways
you aren't going to run into oiling issues going a few degrees up, it ain't a BGTL lifted jeep with the pinion pointing 30 deg up with 7.17s
 
xr-nut said:
3.3
2.3
0.0
1.5

Still vibes. By 60 it feels like very light rumble strip. Up to 110 it gets worse. :frown:
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[486] said:
well ignore that particular everyone and do it anyways
you aren't going to run into oiling issues going a few degrees up, it ain't a BGTL lifted jeep with the pinion pointing 30 deg up with 7.17s
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I did, see the numbers above.
 
Dethmachinefab said:
If your vibe is 1st order, (once per rev) it's not a joint angle issue which would be 2 times per revolution. If it's rumble strip frequency it's 1st order imo.

The small changes your seeing are just impacting it's ability to get into that 1st order vibe.
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Splain it to me like I'm Lucy? :laughing:
 
The way I personally see what's needed (same as the reference examples, but simpler explanation) - you need two of the ujoints operating with the same angles so they cancel like a standard driveshaft, and the 3rd ujoint to have essentially zero (or up to 1*) operating angle so it's not inducing any of its own oscillation.

So I'd personally raise the trans as much as you're comfortable, drop the carrier bearing until the front shaft matches the transmission angle (so the front ujoint is like 0.5* operating angle), then point the pinion to be parallel to the front shaft slope. Maybe 0.5* below that angle to account for pinion wrap under torque. But that will automatically make the mid joint and rear joint the same angle so they cancel out, likt the reference examples

But I know everyone has an opinion and you're getting tired of trying shit, but that should work in my mind.
 
xr-nut said:
I think the only way to do that is to crank the pinion up. everyone, and I mean everyone says the pinion must point down.
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I actually saw a video of a f body or some other hot rod type car that had the pinion pointed up he said it was butter smooth.

If the extension (first half ) is level with the trans where does that put he rear and pinion?
 
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