Driveline vibration out of now where! Help!

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mopower440

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1972 dart swinger, 440/727, 3.23 geared clutch type 8 3/4 rear. I just got finished rebuilding the front end and doing the K-H disk swap. Finally got that all done and now noticed i have this pulsating vibration in the driveline somewhere.. Almost like swerving over onto the rumble strips back and forth..not quite that bad but... It had been fine and sits most of the time in the garage so i dont know where this came from all the sudden. I jacked it up and ran it through the gears on the jackstands and it still did it. I crawled under the car and grabbed the drive shaft and shook it and there doesnt seem to be any play in the u-joints..Im stumped. Like i said, its been fine and seemed to just develop out of now where.. any ideas?
 
1972 dart swinger, 440/727, 3.23 geared clutch type 8 3/4 rear. I just got finished rebuilding the front end and doing the K-H disk swap. Finally got that all done and now noticed i have this pulsating vibration in the driveline somewhere.. Almost like swerving over onto the rumble strips back and forth..not quite that bad but... It had been fine and sits most of the time in the garage so i dont know where this came from all the sudden. I jacked it up and ran it through the gears on the jackstands and it still did it. I crawled under the car and grabbed the drive shaft and shook it and there doesnt seem to be any play in the u-joints..Im stumped. Like i said, its been fine and seemed to just develop out of now where.. any ideas?
The driveline angle?!?! Angle of the trans vs rear diff yoke might be off.
 
So just to be on the same page.
Car drove fine.
You replaced many parts of the front suspension.
now you have vibration.
 
I will take a shot at this.

So you just finished putting on the Kelsey Hayes front disc brakes and all was well before that. To start with did you put in the proper "Distribution Valve with the Metering Valve" for the disc brakes? If you still have the drum brake Distribution Valve you need to change this out to the proper one for you discs in front and drums in rear setup, that includes the Metering Valve part of it to regulate the pressure to the front disc brake part of it. The Ram Man on youtube explains this well, Mopar Brakes.

Here is the deal with Discs up front and Drums in the back. Drum brakes take like 300 psi to activate and the front disc setups take like 3,000 psi. So if you don't change the distribution valve the rear brakes are coming on first and hard possibly causing your chattering from your brake drums, and the front disc are doing almost nothing when trying to stop with the pedal real hard.

OK, next down the line check your outer axle wheel bearings on the rear end to see if one them is binding up so much that it is making the Clutches in the Sure-Grip Differential chatter, because one wheel is trying to spin faster than the other. See if one side is getting hot when you take it for a short drive. Possibly one rear drum is set up tight to the shoes and the other loose causing the Diff Clutches to chatter because of the same above effect.

Kind of sounds like one axel in the rear end is doing the driving and the other is not for whatever reason causing the Diff Clutches to chatter. Brocken Parts in the Diff, Broken Axle although you woud probably hear additional contiunuous noises with this, bad outer axle wheel bearings. Sounds like something is not right with the axles and or the center chunk.

It's kind of like a Posi-Traction rear end going around a corner without the special additive in the gear lube, put the additive in and the chatter goes away.

Mopar recommends this same type of additives in their Sure-Grips along with the rear end grease. Some of the new rear end gear lubes already have the limited slip additive installed.

Hope this gives you some help to narrow down the problems . . .
 
So just to be on the same page.
Car drove fine.
You replaced many parts of the front suspension.
now you have vibration.
yes, at least i dont remember it vibrating like that. Its definately in the rear though, i jacked it up and ran it and it did it, even without the tires on it. I didnt touch anything in the back when doing the front suspension rebuild unless jacking the car up did something to it..?
 
Because there is no play in the u-joint does not eliminate the u-joints. Could be frozen up.
 
I will take a shot at this.

So you just finished putting on the Kelsey Hayes front disc brakes and all was well before that. To start with did you put in the proper "Distribution Valve with the Metering Valve" for the disc brakes? If you still have the drum brake Distribution Valve you need to change this out to the proper one for you discs in front and drums in rear setup, that includes the Metering Valve part of it to regulate the pressure to the front disc brake part of it. The Ram Man on youtube explains this well, Mopar Brakes.

Here is the deal with Discs up front and Drums in the back. Drum brakes take like 300 psi to activate and the front disc setups take like 3,000 psi. So if you don't change the distribution valve the rear brakes are coming on first and hard possibly causing your chattering from your brake drums, and the front disc are doing almost nothing when trying to stop with the pedal real hard.

OK, next down the line check your outer axle wheel bearings on the rear end to see if one them is binding up so much that it is making the Clutches in the Sure-Grip Differential chatter, because one wheel is trying to spin faster than the other. See if one side is getting hot when you take it for a short drive. Possibly one rear drum is set up tight to the shoes and the other loose causing the Diff Clutches to chatter because of the same above effect.

Kind of sounds like one axel in the rear end is doing the driving and the other is not for whatever reason causing the Diff Clutches to chatter. Brocken Parts in the Diff, Broken Axle although you woud probably hear additional contiunuous noises with this, bad outer axle wheel bearings. Sounds like something is not right with the axles and or the center chunk.

It's kind of like a Posi-Traction rear end going around a corner without the special additive in the gear lube, put the additive in and the chatter goes away.

Mopar recommends this same type of additives in their Sure-Grips along with the rear end grease. Some of the new rear end gear lubes already have the limited slip additive installed.

Hope this gives you some help to narrow down the problems . . .
Yes, i did install the correct proportioning valve. the brakes work pretty good now!
 
OK brakes are good, so you can count them out and go on to the next thing.

Could be something as simple as one of the outer rear wheel axle bearings going out, one of the roller cages could have broke apart and now the rollers are stacking up in the confined space of the axle and the bearing race.

You are talking a 440 power plant there, that is a lot of force on the rear end parts. Guessing it is an
8 3/4 rear end. Some of the High Powered B Bodies used the Dana rear ends cause they are a bit stronger than the 8 3/4. Next basic thing to look at after you do the heat temperature test of the outer rear end bearings after a short drive or up on the jack stands. One of those infra red temp guns work real good for this.

Then pull one of the axles out and see what that outer bearing rolls and feels like. They do get rust pitted badly over time and the bearings need to be replaced, and you were saying it sits a lot so that is not good either if there is any moisture in the rear end causing corrosion.
 
OK brakes are good, so you can count them out and go on to the next thing.

Could be something as simple as one of the outer rear wheel axle bearings going out, one of the roller cages could have broke apart and now the rollers are stacking up in the confined space of the axle and the bearing race.

You are talking a 440 power plant there, that is a lot of force on the rear end parts. Guessing it is an
8 3/4 rear end. Some of the High Powered B Bodies used the Dana rear ends cause they are a bit stronger than the 8 3/4. Next basic thing to look at after you do the heat temperature test of the outer rear end bearings after a short drive or up on the jack stands. One of those infra red temp guns work real good for this.

Then pull one of the axles out and see what that outer bearing rolls and feels like. They do get rust pitted badly over time and the bearings need to be replaced, and you were saying it sits a lot so that is not good either if there is any moisture in the rear end causing corrosion.

I had the axle bearings replaced back around 1998 or so, and it probably has not got 1000 miles on them now, but yes, it does sit in the garage a lot, so..I will check that..Tomorrow i am going to pull the driveshaft and make sure the u-joints are not frozen..The bad thing about that is that its been so long ago that i built this car, i cant remember what u-joints i used..I remember buying a driveshaft at a junk yard from a mid 70's big block cordoba to use. If i remember right, i had it cut down and had new u-joints installed at a driveshaft shop..but dont remember what size joints..
 
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Because there is no play in the u-joint does not eliminate the u-joints. Could be frozen up.

THIS!!! LISTEN!!!

You can NOT check U joints by "shaking" the shaft. YOU MUST remove the shaft. By hand, move the joint throughout it's full movement, both ends and check for roughness, play, etc. You can "feel" rough dry needles. Of course you can remove the two rear caps, but the other two can be dry. Also examine for obvious problems, missing clips, damage, etc
 
Check your transmission mount
 
I had the axle bearings replaced back around 1998 or so, and it probably has not got 1000 miles on them now, but yes, it does sit in the garage a lot, so..I will check that..Tomorrow i am going to pull the driveshaft and make sure the u-joints are not frozen..The bad thing about that is that its been so long ago that i built this car, i cant remember what u-joints i used..I remember buying a driveshaft at a junk yard from a mid 70's big block cordoba to use. If i remember right, i had it cut down and had new u-joints installed at a driveshaft shop..but dont remember what size joints..

OK 1998 that was 20 years ago, time flies when we are having fun. Unfortunately time and moisture and sitting can do more harm than the miles a person puts on.

Just curious if they were the new "Green Sealed Bearings" you installed in '98 or the Mopar-you-pack-em, open style bearings that came factory and end play adjust the axle on the passenger side. If you have ever taken Boat Trailer bearings apart that had water in them you will know how bad things can get just sitting. Rust Never Sleeps.

Mopar U-Joints come in the Small u-joint or the Large u-joint.

Here are the Moog Part numbers:
(Used on the 8 3/4 rear ends)
Small Mopar U-Joint 7260, 2 1/8"
Large Mopar U-Joint 7290, 2 5/8"

Moog also makes a combination U-Joint for the small U-Joint Drive Shaft that mates up to the large size yoke on the rear end. They just call it the 7260/7290 Combination U-Joint by Moog.
Some driveshafts are made with the Small 7260 joint up at the front by the trans, and Large 7290 joint at the rear of the shaft to go with Large Yoke rear ends. So it pays to measure and find out just exactly what you have got.

OK, will be interested to see what you find when you go at it again . . .
 
A couple simple next steps:

Drop the drive off the rear end, check the U-Joint at the same time. Then roll the Pinion Shaft Yoke over by hand, if there are bearing or differential problems in the rear end you should be able to feel it right here.

Also turn the passenger side brake drum/axle and see if you can feel any bearing roughness here, do the same with the driver's side. Good time while turning the brake drums to make sure the opposite side is turning in the same direction telling you the Sure-Grip is still engaged. If brake drums are turning in opposite directions then there is a problem with the Sure-Grip wore out or broke.

Next in line internally in the center Chunk, Pinion bearings and Carrier Bearings. These both get rust pitted on the used rear ends. If it was sitting for long periods of time it will rust pit on just one area of the ring gear possibly causing that rumble strip vibration.

Carrier bearings for the differential carrier can wear and rust, opening up the distance between the Rings Gear and Pinion Gear as much as .010" ths. causing things to make noise from misalignment. You should be able to feel this by rocking the pinion yoke back and forth by hand and listen for the clicks when pinion engages the ring gear. This is supposed to be like .008 to 012" ths.

Then finally the Sure-Grip, 4 spider gears in there with their cross shaft so something could go wrong here. And the Clutch Packs for the Sure-Grip too. Also there are supposed to be buttons on each side of the Sure-Grip where the axles bottom out against when you are setting the axle end play on the passenger side. They can sometimes drop out and fall into the bottom of the rear housing when pulling the axles. If you have the Green Axle bearings then you don't use the buttons, no end play to set.
 
no green bearings, still using the original adjustable mopar style axle bearings
 
OK good, I like the Ma Mopar bearing setup that are more resistant to side sway. Not hard to adjust when you have done it before.
 
I work in parts at a cadillac dealership and remember the techs talking about something called 'Phase Boom', where they would have to take the driveshaft loose at the rear chunk and rotate it 180 degrees to stop this very thing! Im just not sure why this started out of no where after i rebuilt the front end..?strange!
 
Could be one little thing that changed while you were working on it, even unrelated like jacking the car up at the front. Something could have gave at the rear end at the same time.

The Straw that Broke the Camel's Back . . .
 
Pull the brake drums too, blow out and clean up in there at the Brake Shoes. Could have a stuck open wheel cylinder causing the break to drag. Also want to clean up and put a little thin film of Anti-seize on the Brake Backing Plates where the shoes slide back and forth on, they rust right here too.

Want those brake shoes returning back to their "at rest" position where they are not dragging on the drums. The wheel cylinders rust internally being Brake Fluid draws moisture. Were you getting clean fluid out of the back brakes when you bled them after doing your disc brake upgrade?

If the rear brake fluid was quite dirty and not clear at the back, this could be a clue to faulty rear wheel cylinders.
 
Pull the brake drums too, blow out and clean up in there at the Brake Shoes. Could have a stuck open wheel cylinder causing the break to drag. Also want to clean up and put a little thin film of Anti-seize on the Brake Backing Plates where the shoes slide back and forth on, they rust right here too.

Want those brake shoes returning back to their "at rest" position where they are not dragging on the drums. The wheel cylinders rust internally being Brake Fluid draws moisture. Were you getting clean fluid out of the back brakes when you bled them after doing your disc brake upgrade?

If the rear brake fluid was quite dirty and not clear at the back, this could be a clue to faulty rear wheel cylinders.
yes, i use Dot 5 fluid and it was new coming out the back when bleeding..
 
OK sounds good, just have to continue on with the "Process of Elimination" one thing at a time until you find the problem.

You will get it . . .
 
Here are the actual Moog part numbers:

The small mopar 7260 U-Joint
Moog 315G

The Moog Combo Joint 7260/7290 part number:
Moog 347

The Moog Large 7290 U-Joint:
Moog 316
 
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