67 Rear axle bounce

[oldman3]

Other info I forgot to post
#6569RACK 5 lug rear axles, complete kit (new drums etc) from CPP.
#6372SBK Heavy Duty sway bar kit (front and rear) from CPP.
The 3/5" drop kit we ordered came with the short adjustable trac bar not the long one.
If I find anything else I forgot, I will post it....Jim

[broey]

I may have missed where you said this. But has the drive shaft been balanced?
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[ulakovic22]

Have you tried driving it loaded and unloaded over the rear axle and then in front and behind? Also like Broey mentioned, carrier bearing and driveshaft balance.

[oldman3]

Originally Posted by broey

I may have missed where you said this. But has the drive shaft been balanced?
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Drive shaft was cut down to work with the 4l60 trans and was balanced, with all new u-joints installed and new carrier bearing....Jim

[oldman3]

Originally Posted by ulakovic22

Have you tried driving it loaded and unloaded over the rear axle and then in front and behind? Also like Broey mentioned, carrier bearing and driveshaft balance.

Talked about this last night with a group of club members. I will try to get with owner and schedule a time to try this. Will cover the bed with lots of blankets and see if we can find bags of sand or something to use. Will post up something as soon as i can. This might tell us if the springs or shocks are wrong....Jim

[Hart_Rod]

I have a similar problem, so I'm going to tag along if you don't mind.
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[oldman3]

Originally Posted by Hart_Rod

I have a similar problem, so I'm going to tag along if you don't mind.
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Don't mind at all. If you have tried anything not mentioned so far, let's hear it, the more info the better, can't ever have to much.....Jim

[Hart_Rod]

Originally Posted by oldman3

Don't mind at all. If you have tried anything not mentioned so far, let's hear it, the more info the better, can't ever have to much.....Jim

I did everything you tried. I'm not sure where to go from here. Maybe bent axle tubes? Rear drums out of balance?
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[oldman3]

Originally Posted by Hart_Rod

I did everything you tried. I'm not sure where to go from here. Maybe bent axle tubes? Rear drums out of balance?
Posted via Mobile Device

That's something that could be looked into, will let you know...Jim

[WBarlow]

I had the same problem out of a 72 swb that I owned in mid to late 80's while in High School and in the military. Had a 350 with muncie four speed and had a drive shaft custom shortened by a "profesional". My truck did the same thing at high speeds around 70. I changed the drive shaft out and it stopped. I was told it was balanced, but there is no way it could have been. Are you running a straight drive shaft or swing bearing?

[WBarlow]

You'r problem may go away with a one piece drive shaft.

[jjzepplin]

Had this happen once and it was my driveshaft. Now I always have them balanced and mark them before I remove them.

[68_chop_top]

I just installed the shock relocator kit along with new KYB shocks. The ride was TERRIBLE! Bounced like a trampoline! I could not imagine the relocator kit was the problem so I swapped back to my old shocks. Problem solved. I am not going to bash the KYB shocks as the store refunded my money and returned them as defective. The old Nitto Drop 2 shocks I bought from CPP are back on and the ride is much improved thanks to the shock relocator kit.
May try and change out the shocks. The coil spring rear ends with drop spings and short shocks can sometimes work against each other and give you a bad ride. Easy enough to change out - try it.
You do very nice work!

[Hart_Rod]

Good points by all. Jim can you post a video of what you are seeing? Also, do you get the same bounce at 50 MPH? 60 MPH?

[oldman3]

It is a two piece drive shaft with center carrier bearing, all new parts and was balanced.

[oldman3]

Originally Posted by WBarlow

I had the same problem out of a 72 swb that I owned in mid to late 80's while in High School and in the military. Had a 350 with muncie four speed and had a drive shaft custom shortened by a "profesional". My truck did the same thing at high speeds around 70. I changed the drive shaft out and it stopped. I was told it was balanced, but there is no way it could have been. Are you running a straight drive shaft or swing bearing?

It is a two piece drive shaft with center carrier bearing, all new parts and balanced. Will try a few things, but may have to see about a one piece unit...Jim

[oldman3]

Originally Posted by 68_chop_top

I just installed the shock relocator kit along with new KYB shocks. The ride was TERRIBLE! Bounced like a trampoline! I could not imagine the relocator kit was the problem so I swapped back to my old shocks. Problem solved. I am not going to bash the KYB shocks as the store refunded my money and returned them as defective. The old Nitto Drop 2 shocks I bought from CPP are back on and the ride is much improved thanks to the shock relocator kit.
May try and change out the shocks. The coil spring rear ends with drop spings and short shocks can sometimes work against each other and give you a bad ride. Easy enough to change out - try it.
You do very nice work!

As soon as I can get with the owner, we are going to try putting weight in the bed, if this works, then we have to figure out the shock problem. I've been reading about mono and twin tube shocks, not sure what type is on the truck now. Thanks about the work....Jim

[oldman3]

Originally Posted by Hart_Rod

Good points by all. Jim can you post a video of what you are seeing? Also, do you get the same bounce at 50 MPH? 60 MPH?

It's been hard getting with owner to do all of this, but I would like to get a video, havent' checked it at 50 or 60, will have to do that also....Jim

[Slow Build]

Have you tried rotating the rear u-joint connection 180 degrees? Somewhere in the back of my mind I think I remember someone doing this and it helped.

Also it must be an optical illusion but it looks like your rear driveshaft is lower at the center bearing than at the rear end. I've never had a two piece drive shaft so I don't know what kind of considerations you would have for angles at the center bearing but since the angles between the tranny and the center bearing are basically fixed I would think the angle from the rear of the bearing and the rear driveshaft might be important.

I'm just throwing it out there. Don't know if it's relative or not

Good luck

[oldman3]

Slow build, think it is just the picture. Rear driveshaft is actually level from center bearing back to housing. Pinion angle is 3 degrees up. Can try rotation the drive shaft and see if it makes difference, thanks....Jim

[oldman3]

Just wanted to let you guys know that I still haven't been able to set up time with the owner. His wife is due real soon with their baby. As soon as we come up with anything I will post it up....Jim

[68_chop_top]

How about now?

[oldman3]

Originally Posted by 68_chop_top

How about now?

Nothing yet, he still hasn't been able to get with me for any testing, etc.. Hope to within the next month, his wife hasn't delivered yet....Jim

[Dunenutt]

Have you checked to see if the drums are balanced? I had a bad one on my dually, and it drove me crazy.

[oldman3]

Originally Posted by Dunenutt

Have you checked to see if the drums are balanced? I had a bad one on my dually, and it drove me crazy.

That's one thing I have not checked, will add it to this list, thanks...Jim