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

xr-nut said:
Yesterday's fun in the shop

IMG_20240731_091001188.jpg
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I think you're working on the wrong truck
 
CarterKraft said:
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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did you see the current numbers?

3.3
2.3
0.0
1.5

other than the back shaft and pinion not going in a down angle together, the numbers are right where its supposed to be. Im not going to fret over those today until i get the x-member sturdied up. could just be beating my head on a wall. which might feel better than working on this shitpile today. :laughing:
 
Maybe this sketch will help. Circles are u joints. R is rear, T trans.
The top pic is no vibe condition. Shafts rotate on an axis down the center. Bottom pic is during vibe, the entire shaft is going off center from the dotted line representing the rotation axis.

1000002885.jpg
 
Dethmachinefab said:
Maybe this sketch will help. Circles are u joints. R is rear, T trans.
The top pic is no vibe condition. Shafts rotate on an axis down the center. Bottom pic is during vibe, the entire shaft is going off center from the dotted line representing the rotation axis.

1000002885.jpg
Click to expand...
do you do driveshaft fab/sales or just a bunch of experience?

asking for future me. I know you're somewhat close to my parents in NJ, not exactly sure how close
 
budget76 said:
do you do driveshaft fab/sales or just a bunch of experience?

asking for future me. I know you're somewhat close to my parents in NJ, not exactly sure how close
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Na, fab shop and build/install process equipment. Might have an eye for how things work and do alot of troubleshooting on equipment.

Your always welcome to stop by. I'm 20 mins from north east corner of jersey.
 
Dethmachinefab said:
Maybe this sketch will help. Circles are u joints. R is rear, T trans.
The top pic is no vibe condition. Shafts rotate on an axis down the center. Bottom pic is during vibe, the entire shaft is going off center from the dotted line representing the rotation axis.

1000002885.jpg
Click to expand...
and that could easily be caused by that old cross member flexing even just a tiny amount. thanks that helps make sense.
 
where it sits for the night. lamb legofroastthing in the crockpot all day. kid coming out to eat. good times indeed.

that has to be a much sturdy mount set up. numbers as it sits are about where they were before I pulled it all apart. the front shaft and pinion are less than 0.5 apart. the front joint operating angle is 2ish and the rear shaft flat. I'll tack that mount up in the morning and go drive it. fangers crossed.


that .250 2x2 goes through both the outer frame and that thin wall on the inside. welded up good on the main outside frame and best possible on the inside. run a gusset forward and backward. I cant imagine this thing moving now?

IMG_20240731_171924773_HDR.jpg
 
xr-nut said:
that has to be a much sturdy mount set up. numbers as it sits are about where they were before I pulled it all apart. the front shaft and pinion are less than 0.5 apart. the front joint operating angle is 2ish and the rear shaft flat. I'll tack that mount up in the morning and go drive it. fangers crossed.
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The new crossmember looks like it will be a big help. But as far as numbers go, while the mid joint and rear joint sound like they cancel, it doesn't look like there's anything to cancel the oscillation from that 2* on the front joint, so it still may not be perfect.
 
Beefing up the x member is a good thing. But I still think it's not a great design with a carrier at the shafts mid point. Maybe you can get away with it and a stiff trans mount to lock down the front of the shaft.

If you grab the joint on the slip end, can you move it up/down/side/side easily? Does the trans move when you do? That's really all you can change with this set up to try and keep things in line.
 
Is your trans mount crossmember solid mounted where it attaches to the frame, or does it have bushings?
 
Dethmachinefab said:
But I still think it's not a great design with a carrier at the shafts mid point.
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trying to follow. you're thinking the front portion of the shaft is too long and creating the wobble? AKA make the front short as possible to be able to get the rear shaft within acceptable length?

i know the OEM front shaft I pulled out of my pickup was pretty short and seems to jive with that thought.
 
Dethmachinefab said:
Beefing up the x member is a good thing. But I still think it's not a great design with a carrier at the shafts mid point. Maybe you can get away with it and a stiff trans mount to lock down the front of the shaft.

If you grab the joint on the slip end, can you move it up/down/side/side easily? Does the trans move when you do? That's really all you can change with this set up to try and keep things in line.
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I will do that here in a few minutes. along with a test drive. brb
M92PV4U said:
Is the engine solid mounted? Are you sure that the engine & transmission aren't torquing one direction?
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No not solid mounted. I'm sure theres some twisting/torquing happening...not sure it would effect this much, if at all?
pcorssmit said:
Is your trans mount crossmember solid mounted where it attaches to the frame, or does it have bushings?
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yes, solid mounted.
budget76 said:
trying to follow. you're thinking the front portion of the shaft is too long and creating the wobble? AKA make the front short as possible to be able to get the rear shaft within acceptable length?

i know the OEM front shaft I pulled out of my pickup was pretty short and seems to jive with that thought.
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no, I think he's saying that the slip joint on the rear shaft is too wobbly. or has the potential to be since it is so far from the carrier bearing.
 
xr-nut said:
No not solid mounted. I'm sure theres some twisting/torquing happening...not sure it would effect this much, if at all?

yes, solid mounted.

no, I think he's saying that the slip joint on the rear shaft is too wobbly. or has the potential to be since it is so far from the carrier bearing.
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If the engine and transmission are torquing as an assembly I could see that throwing the driveline off ° at least at the transmission.

If the transmission is solid mounted, I would solid mount the engine to avoid breaking the transmission where the mount is.
 
M92PV4U said:
If the engine and transmission are torquing as an assembly I could see that throwing the driveline off ° at least at the transmission.

If the transmission is solid mounted, I would solid mount the engine to avoid breaking the transmission where the mount is.
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as of now both are OE style rubber mounts.
 
Dethmachinefab said:
Beefing up the x member is a good thing. But I still think it's not a great design with a carrier at the shafts mid point. Maybe you can get away with it and a stiff trans mount to lock down the front of the shaft.

If you grab the joint on the slip end, can you move it up/down/side/side easily? Does the trans move when you do? That's really all you can change with this set up to try and keep things in line.
Click to expand...
its hard to see in the video but lifting up and down on the slip joint ujoint makes the back of the trans move in the opposite direction. not so much side to side, but you can still hear the trans slip clacking in the there.

 
Last edited:
numbers for todays drive are

4.5
3.3
0.2
2.5

feels ok up to 70ish. starts to vibe north of that, enough that I let off at 95ish. on decel it got worse.
 
That trans slip yoke flops around to much for my liking in that video. I don't think you have an angle problem, I think you might have a parts problem.

Is the output shaft on the transmission tight in the housing?
 
SLOWPOKE693 said:
That trans slip yoke flops around to much for my liking in that video. I don't think you have an angle problem, I think you might have a parts problem.

Is the output shaft on the transmission tight in the housing?
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"Is the output shaft on the transmission tight in the housing?"

edit- that yoke feels loose to me.

huh? I guess I should pull it out and slip the oe yoke in to check its fitment?

In doing so I just realized I cannot run the one piece for race day as a last resort. the new cross member is in the way. ugh. fuck me.
 
budget76 said:
trying to follow. you're thinking the front portion of the shaft is too long and creating the wobble? AKA make the front short as possible to be able to get the rear shaft within acceptable length?

i know the OEM front shaft I pulled out of my pickup was pretty short and seems to jive with that thought.
Click to expand...
I think is doing a pivot around the carrier like you would row a kayak, the carrier being you and the ends of the oar the u joints. Imo it should be around 2x as long on the trans side compared to the slip side. Better yet would be the carrier right against the joint and the slip on the last shaft.
 
xr-nut said:
its hard to see in the video but lifting up and down on the slip joint ujoint makes the back of the trans move in the opposite direction. not so much side to side, but you can still hear the trans slip clacking in the there.

Click to expand...

So picture that entire shaft orbiting around the center line like that and how badly out of balance it would get.
 
i think the oe yoke is a tighter fit also. Notice how it is set up now there is 2.5-2.75'' of yoke on the new shaft inside the trans. with the oe yoke there is almost 3.75''

 
Dethmachinefab said:
I think is doing a pivot around the carrier like you would row a kayak, the carrier being you and the ends of the oar the u joints. Imo it should be around 2x as long on the trans side compared to the slip side. Better yet would be the carrier right against the joint and the slip on the last shaft.
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so flip the back shaft around and have the slip at the diff?

how does the shop attach the ujoint against the carrier then? weld a yoke to it and make the carrier permanent?
 
Dethmachinefab said:
So picture that entire shaft orbiting around the center line like that and how badly out of balance it would get.
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should I try to move the carrier closer to the trans, to engage more of the splines there and also then put the pillow block back on to make that shaft more rigid?
 
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