What causes my driveshaft to "jump" in this video?

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RustyRatRod said:
Well that'll be a boat load of fun. I'm starting to get all the parts to put a World Class T5 in Vixen.
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I hope so. I never really cared for the three speed auto. I've always liked manual shift cars. I'm just hoping I can sell the 727 once it's out.
 
jcolman said:
I hope so. I never really cared for the three speed auto. I've always liked manual shift cars. I'm just hoping I can sell the 727 once it's out.
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Take plenty of videos with good audio and I'm sure it'll sell.
 
I bet if you put the emergency brake on you will be able to rotate the drive shaft a few degrees.

My stock 321,000 mile 7 1/4 can rotate quite a few degrees there is always a bit of a clunk when you first engage the trans.
 
I had a car here that made bearing noises. I swore it was the diff. But it was an axle bearing. Get a stethoscope at harbor freight and listen to it and locate the noise. That's how I found it. You'll hear what bearing it is
 
RustyRatRod said:
Noise on decel is either too much pinion depth or too little, I can never remember which. You might try dropping the drive shaft and see if there's any slop at all in the pinion yoke, as if the pinion nut is trying to back off. That's actually a pretty common issue. What casting is the case? I "THINK" I see "742" as the last three, but I'm not sure.
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Whine on coast is the pinion is too far away. Kim
 
RustyRatRod said:
I understand the concern now. I would check it out too in that case. It might be a pinion bearing going out and now's the time to catch it, before any other damage is caused.
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Pinion bearings make a whirring noise when ur picking up speed. Silent when off the gas. Kim
 
Check the diff fluid level>
 
Did anyone else see the pinion jump up sorta when first put into gear.....................or am I losin' it.

20 second mark.
 
It starts to rotate at 18-19 and at 20 it jumps up with a clunk. I would, at the minimum, check the pinion nut/yoke like Rob said.
 
jcolman said:
I saw it too but thought it was normal. But then again, I know very little about these things.
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If the pinion jumps separate from the housing, that's an issue. I didn't notice that. I'll go back and pay better attention.
 
You know, it's hard to tell. The metal dust cover is a "little" out of round and that makes it difficult to tell if the pinion has slop or not.......it sure could, though.
 
Your car must be loud or really good looking... You neighbor came out and checked things out (0:45)
 
jcolman said:
I'm trying to track down a "whining" noise I can hear when driving. I put the car on jack stands, lifted the differential, and ran the car up to about 40mph, trying to see if I can recreate the noise. I didn't hear the whining sound, but my driveshaft jumps at the :37 mark. Thoughts?

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every time your drive shaft jumps your wheels lock up. are you hitting the brakes? If you are not braking it might be the clutches in rear. did you change fluid? if so you need special lube additive for the sure grip clutches. Could be pinion don't worry about crushing anything the torque setting is 250 ft.lb. the clutches also make a whining noise if lube is not added. I would get the sure mopar sure grip lube and put it in it's only a few ounces but it is costly.
 
I agree with Joemish, but would like to add a couple thoughts:
Sure grips use a special fluid with proper level settings
Remove the chunk and check gear mating or any other internal issues
Noticed disc brakes added, possible bearing damage(check race for damage)
lastly, short yoke or short drive shaft. Trying to pull out of transmission. Balance seems good. I would not drive, without a correction, due to further damage.
 
jcolman said:
I thought it might be the 1/2 shift too but since the rpm didn't change, I wasn't sure. I guess the car has to be under load. Question. Is the driveshaft jumping normal or is the transmission mount the issue like the first reply said?
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A bad transmission mount would cause the front to move with the tail housing.
Mopars were notorious even from the factory for some gear whine. Usually this is the grar setup being off a little. This never seemed to affect reliability.
Watching, I note the yoke as well as the driveshaft jump. Could the pinion nut be loose allowing the pinion to flop around. Try pushing the yoke and driveshaft up and down with no load on the driveshaft, eg in neutral.
 
I have a slight whine under load too. Helical Detroit true trac so suspect pinion bearing but all is tight, unless it’s a trait of the helical gear set. Been like that for 10 years and has never changed...did have a bad axle bearing a while back but caught that right away and the diff whine never changed.
 
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