67 Rear axle bounce

[broey]

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

[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 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?
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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?

[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

[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!

[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

[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]

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

[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

[oldman3]

OK guys, I'm bringing up this old thread to update on the rear axle bounce.

A short story first, this thread is about 18 months old, Jimbo's wife had their baby, and has since had another, so his time as been limited to doing anything with the truck. We also had to change the engine (posted in his build thread today, last 2 pages). While we did that we also change part of the drive shaft alignment. I talked with several different drive shaft makers and they all said that it was possible that the 2 piece drive shaft could set up a wobble to cause the bounce. What we did was knock out the rivets from the carrier bearing bracket, and turn it upside down. Took a string from trans to rear axle pinion to make a straight line. Moved the bracket up till drive shaft was it line. Marked and drilled 4 holes, installed grade 8 bolts and tightened down. After breaking in the new engine, we when out on the four lane and man what a difference. We pulled a couple hard throttle pulls to 5,000 rpm in drive (3rd gear) and was smooth. Got up to 90 mph and still smooth. We still have a little vibration, so he is going to take the wheels and tires to a new shop in town that has a laser balance machine and works alot with large wheels. Here's a few before and after shots of the change..Jim

[oldman3]

In the old pictures above you can see how the bracket was mounted above the drive shaft. In the after pictures you can see were we moved it down, and is now under the drive shaft, making a more straight line for the drive shaft.
First pic is looking from rear toward engine
2nd pic is looking from front toward rear axle
3rd pic just a little different angle.
You can see were the old holes from the rivets where.

Hope this may help someone else. Thanks everyone for all your ideals and suggestions. Glad we final got this taken care of...Jim