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

How far in the yoke do the splines run? All the way down or is there a big void at the top before the splines start?

I'd want that rear shaft slid in more at ride height personally, but it's probably just my OCD talking.
 
I just think the joint to carrier distance is to far on the midshaft. Let's the assembly get all out of sorts with the slightest imbalance input. (gear shift, angles, alignment,etc) The changes your making have an effect on the initial imbalance that causes the wobble. Hard for me to put to words. I don't think you can fix this setup.

I'd put the slip on the rear shaft and carrier right next to the joint.
 
SLOWPOKE693 said:
How far in the yoke do the splines run? All the way down or is there a big void at the top before the splines start?

I'd want that rear shaft slid in more at ride height personally, but it's probably just my OCD talking.
Click to expand...
all the way down, splines start at the very end of it.
 
Dethmachinefab said:
I just think the joint to carrier distance is to far on the midshaft. Let's the assembly get all out of sorts with the slightest imbalance input. (gear shift, angles, alignment,etc) The changes your making have an effect on the initial imbalance that causes the wobble. Hard for me to put to words. I don't think you can fix this setup.

I'd put the slip on the rear shaft and carrier right next to the joint.
Click to expand...
it sure looks like thats were all of the wobble or vibes start from. right there at the joint behind the slip. then it radiates both directions.
 
Lumberjack said:
Runout of the shaft behind the joint, not slipyoke side?
Click to expand...
.037''

right behind the weld on the front of the rear driveshaft.

IMG_20240724_160511734_HDR.jpg
 
That style driveline is on a pile of rigs without issue. Getting them both balanced together can be a PITA sometimes though...


xr-nut said:
.037''

right behind the weld on the front of the rear driveshaft.
Click to expand...

Hard to say which driveline is throwing it out that much though. Either way, that doesn't work.

Get it on a balancer
 
Steve300xcw said:
That style driveline is on a pile of rigs without issue. Getting them both balanced together can be a PITA sometimes though...




Hard to say which driveline is throwing it out that much though. Either way, that doesn't work.

Get it on a balancer
Click to expand...

tomorrow is 32 years with the same old broad. so she says were going in to the city to eat. I'll haul it down to T-town tomorrow.
 
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xr-nut said:
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.

Click to expand...

Is the pinion not pointing UP in reference to the rear shaft?
 
Dethmachinefab said:
I just think the joint to carrier distance is to far on the midshaft. Let's the assembly get all out of sorts with the slightest imbalance input. (gear shift, angles, alignment,etc) The changes your making have an effect on the initial imbalance that causes the wobble. Hard for me to put to words. I don't think you can fix this setup.

I'd put the slip on the rear shaft and carrier right next to the joint.
Click to expand...
Seems like two bearings and two yokes might be a good solution. That would isolate the shafts from each other pretty well and support them both much better too. Someone in the offroad world sells a bling kit to DIY one and there's a bunch of threads on the old site.
 
Dethmachinefab said:
I just think the joint to carrier distance is to far on the midshaft. Let's the assembly get all out of sorts with the slightest imbalance input. (gear shift, angles, alignment,etc) The changes your making have an effect on the initial imbalance that causes the wobble. Hard for me to put to words. I don't think you can fix this setup.

I'd put the slip on the rear shaft and carrier right next to the joint.
Click to expand...

arse_sidewards said:
Seems like two bearings and two yokes might be a good solution. That would isolate the shafts from each other pretty well and support them both much better too. Someone in the offroad world sells a bling kit to DIY one and there's a bunch of threads on the old site.
Click to expand...
I don't like how it looks either but the resident driveshaft guy thinks the config is normal so I'm inclined to think my opinion is a little opinionated.:spam:
 
CarterKraft said:
I don't like how it looks either but the resident driveshaft guy thinks the config is normal so I'm inclined to think my opinion is a little opinionated.:spam:
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I'm sure it's "normal" but going 140 isn't "normal" :laughing:

Is there even any vehicle that has an equally long shaft that operates at any noteworthy angle and is expected to go 140+? Vette is torque tube. Challenger, Mustang, Camaro are all way shorter and use IRS that doesn't travel. Likewise for the police 'sploder.
 
arse_sidewards said:
I'm sure it's "normal" but going 140 isn't "normal" :laughing:

Is there even any vehicle that has an equally long shaft that operates at any noteworthy angle and is expected to go 140+? Vette is torque tube. Challenger, Mustang, Camaro are all way shorter and use IRS that doesn't travel. Likewise for the police 'sploder.
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But he's having problems at 40 not 140
 
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.

Click to expand...

It got so much better with the other crossmember back in, it seems building a beefy one for the bearing would be the obvious answer.

Especially if the balance checks out.......
 
2big bronco said:
I assume the driveline wasn't cheap. Has action commented on the runout?
Click to expand...
No, it cost plenty. not sure its the problem and not something Ive done yet. we'll see here soon.
Thatg9659 said:
You know sometimes a car will shake at 60 but not at 90. Maybe it’ll be fine at higher speeds :flipoff2:
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its bad enough Im scared to go above the shake for fear of breaking something under there............:eek:

like the extrememracecarguyJ says......if this doesnt resolve itself before the 7th, Ill toss the 1-piece back in and slow down a couple classes for the sorc and only run the half mile shoot out. or maybe even skip the shootout all together and go find some dog towns to plink at. thats been in the back of our minds from the first time we went out there 4 years ago.
 
It still seems to me that the angles are not cancelling. Could you try taking all angle off the middle joint so that the trans output is down 3.2, the middle joint has no additional angle on it, and point pinion up close to that 3.2 degrees?
Basically treat it like a one piece. Could add a degree to the middle joint later for u joint rotation if the vibes smooth out.
Of course it may also have too much runout or be out of balance too.:mad3:
 
greenlion said:
It still seems to me that the angles are not cancelling. Could you try taking all angle off the middle joint so that the trans output is down 3.2, the middle joint has no additional angle on it, and point pinion up close to that 3.2 degrees?
Basically treat it like a one piece. Could add a degree to the middle joint later for u joint rotation if the vibes smooth out.
Of course it may also have too much runout or be out of balance too.:mad3:
Click to expand...
here is where its at as of last night. still bad vibes, the 3rd video. on pickup accel or decel the shaft shakes like the pencil did when you were a little kid showing you friend how you could bend a pencil just by shaking it from one end. :laughing:

transmission: 3.2 D
front shaft: 1.5 D
Rear shaft: .9 D
pinion: 0.0

just got an email from action saying those numbers look better. "decent" they said.
 
xr-nut said:
here is where its at as of last night. still bad vibes, the 3rd video. on pickup accel or decel the shaft shakes like the pencil did when you were a little kid showing you friend how you could bend a pencil just by shaking it from one end. :laughing:

transmission: 3.2 D
front shaft: 1.5 D
Rear shaft: .9 D
pinion: 0.0

just got an email from action saying those numbers look better. "decent" they said.
Click to expand...
How's the trans mount? If what I think is going on is correct as a test see if it gets better by trying to lock that down because that is what's keeping the midshaft straight.

Grab the joint at the slip end and move it in an orbital motion and see. Like this pic, the carrier is the center.

fig_r_05f.gif
 
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