The first "Hawk-Rod" resurrection, Roadkill style

[HawkRod]

Just my 2cents here in reference to the isolators I don’t see how those could create the vibration because they are really sandwiched in around the springs plus the weight of the car.
I am thinking something back there that is in motion is creating this vibration and those rubber isolators don’t turn or spin.
Still working on this with you.

My father in law agrees with you. Only possibility I have is that the vibration started at the time I quasi-restored the car, at which time I added the non-stock Hemi suspension. If that screwed up the pinion angle, could that cause the vibration?

I don't know, but I gotta cross that off the list as a possibility.

Thanks for continuing to brainstorm this with me!

 

[64fury74charger]

My father in law agrees with you. Only possibility I have is that the vibration started at the time I quasi-restored the car, at which time I added the non-stock Hemi suspension. If that screwed up the pinion angle, could that cause the vibration?

I don't know, but I gotta cross that off the list as a possibility.

Thanks for continuing to brainstorm this with me!

I have been going through my mental Rolodex and I am not sure if you already did this but my question is when you had the axle shafts out of the car did you check each shaft to make sure they are straight? I have run across wobbly shafts in the past, mostly on Fords but as I recall I really chased my tail around trying to find the problem.

 

[HawkRod]

I have been going through my mental Rolodex and I am not sure if you already did this but my question is when you had the axle shafts out of the car did you check each shaft to make sure they are straight? I have run across wobbly shafts in the past, mostly on Fords but as I recall I really chased my tail around trying to find the problem.

You know, I didn't check them for straightness. But I agree I should check that too. I'll do that once I swap rears again.

 

[64fury74charger]

You know, I didn't check them for straightness. But I agree I should check that too. I'll do that once I swap rears again.

I was hoping you did check the shafts and I thought I may have just missed it following along on your posts here. The shaft definitely does spin or rotate and has not been swapped out and you still have the vibration. 3rd member and drums are different. Running out of moving parts back there.

 

[Don Frelier]

I could have a bent rear axle

This would certainly make more sense.
Kind of thought you had ruled that one out already.

You might try putting the front wheels on a 4"X 4".
Jack up the rear 3" and run it in drive with the wheels on.
Then try with a wheel off on each side.
It might help you find something.

 

[JDmac72chrgr]

Might have missed this is your write-ups, are the brake drums "true" & balanced?

 

[HawkRod]

This would certainly make more sense.
Kind of thought you had ruled that one out already.

You might try putting the front wheels on a 4"X 4".
Jack up the rear 3" and run it in drive with the wheels on.
Then try with a wheel off on each side.
It might help you find something.

I can try that on the lift. I did have the axles on my stainless benchtop, and they were rolling easily, so I didn't see anything obvious. I can try that and also pull the axles quickly and double check them.

Might have missed this is your write-ups, are the brake drums "true" & balanced?

I have swapped out brake drums from my 70 Road Runner (that has no issues) with no improvement in the vibration, so that does not seem to be the issue.

 

[HawkRod]

I agree with some of your posts above about my axles shafts and/or the whole axle being possibly bent. I have to check that.

Having said that, I am still moving forward to delete my worn ISO bushings in the rear. All I could find was a 2.75" round stock of steel. Overkill and too big, but all I found, so you gotta work with what you got.

Here it is after I cut it down and drilled a hole to accept the top of the leaf spring bolt.

So this leaf spring bolt...

...indexes into the adapter I made, and in turn into the spring bracket.

To test install it, I first had to remove the old leaf spring bolt

Then I installed the new bolt and the adapter

Here is a picture with the bracket on

Here is the axle lowered on to the assembly. You can see the adapter in the mirror.

So it looks like this will work. I now need to cut the lower part of the brackets off and fully install them. I also have 2 degree shims in case I want to play with those.

Unfortunately I need to take a 3 day trip, so I won't be able to get back to this until the weekend. While on my trip, I'll also try to brainstorm a way to check the straightness of my axle housing (the shafts are easy once removed).

Thanks for following along...

 

[64fury74charger]

I agree with some of your posts above about my axles shafts and/or the whole axle being possibly bent. I have to check that.

Having said that, I am still moving forward to delete my worn ISO bushings in the rear. All I could find was a 2.75" round stock of steel. Overkill and too big, but all I found, so you gotta work with what you got.
View attachment 1268790

Here it is after I cut it down and drilled a hole to accept the top of the leaf spring bolt.
View attachment 1268791

So this leaf spring bolt...
View attachment 1268792

...indexes into the adapter I made, and in turn into the spring bracket.
View attachment 1268793

To test install it, I first had to remove the old leaf spring bolt
View attachment 1268794

Then I installed the new bolt and the adapter
View attachment 1268795

Here is a picture with the bracket on
View attachment 1268796

Here is the axle lowered on to the assembly. You can see the adapter in the mirror.
View attachment 1268797

So it looks like this will work. I now need to cut the lower part of the brackets off and fully install them. I also have 2 degree shims in case I want to play with those.

Unfortunately I need to take a 3 day trip, so I won't be able to get back to this until the weekend. While on my trip, I'll also try to brainstorm a way to check the straightness of my axle housing (the shafts are easy once removed).

Thanks for following along...

Looks good and no bushings to look at. When you get back to this have a real close inspection on those shafts. As you know all it takes is a small area that is out of line to make a consistent problem.

 

[qkcuda]

Nice work on the adapters Hawk!

 

[MoparJimT]

Hey Hawk, Very nice work on the adaptor. The brainpower from the rest of the members is way beyond my level, so cannot add anything to troubleshoot wish I could. Just wanted to say good luck and keep me posted on your trip. Still want to hook up for that beer if we can.

 

[Nxcoupe]

You know, 20 minutes with my PICO NVH scope hooked up and we'd be able to localize the vibration. Maybe if you swing through the Cincinnati/Dayton area at some point we can hook it up to the car.

 

[HawkRod]

You know, 20 minutes with my PICO NVH scope hooked up and we'd be able to localize the vibration. Maybe if you swing through the Cincinnati/Dayton area at some point we can hook it up to the car.

First of all, Thank You. I may well take you up on that offer. If I can't get this vibration addressed in this last go-around, It may be worth a two day trip to see if I can get it diagnosed.

Time to head out to the garage and get the rear back together. I'll report back hopefully later today.

 

[zyzzyx]

We's be waitin!

 

[HawkRod]

So today I got the rear leaf springs put back together.

First I had to cut the shackles since I am deleting the rubber bushings around the leaf springs. You can see the cut line in the picture below.

The alignment pieces for this were shown in my post above. Here it is assembled without the rubber bushings.

I also used 3 washers to align the bottom plate as well. So now both the top and bottom plates are aligned to the axle bolt and shouldn't be able to move.

Here it is all put back together except for the sway bar end links. No more ISO rubber bushings. Everything seems to fit well.

I also have 2 degree shims if I want to try those. Initially, I put the leaf springs together without these.

So I threw it all together and went out for a test drive. I did NOT carefully measure all my pinion angles, I'll do that over the weekend. I also did not measure the wheelbase to ensure the axle is straight. It probably is close enough, and I have never had an issue with the car crabbing anyway. Plus, that wouldn't cause a vibration.

So, drum roll: Result???

...

Same ****, different day. The vibration is still there.

Time now to check the axles and housing.

 

[zyzzyx]

 

[64fury74charger]

So today I got the rear leaf springs put back together.

First I had to cut the shackles since I am deleting the rubber bushings around the leaf springs. You can see the cut line in the picture below.
View attachment 1270572

The alignment pieces for this were shown in my post above. Here it is assembled without the rubber bushings.
View attachment 1270573

I also used 3 washers to align the bottom plate as well. So now both the top and bottom plates are aligned to the axle bolt and shouldn't be able to move.
View attachment 1270574

Here it is all put back together except for the sway bar end links. No more ISO rubber bushings. Everything seems to fit well.
View attachment 1270575

I also have 2 degree shims if I want to try those. Initially, I put the leaf springs together without these.
View attachment 1270576

So I threw it all together and went out for a test drive. I did NOT carefully measure all my pinion angles, I'll do that over the weekend. I also did not measure the wheelbase to ensure the axle is straight. It probably is close enough, and I have never had an issue with the car crabbing anyway. Plus, that wouldn't cause a vibration.

So, drum roll: Result???

...

Same ****, different day. The vibration is still there.

Time now to check the axles and housing.

Well at least you know that the axle housing is firmly attached to the leaf springs and all the hardware is serviceable. The vibration sounds like it’s consistent even with all the housing clamps serviced and isolators removed. That’ll pretty much eliminate those parts as a source of the vibration.
I am curious to see how the axle shafts look on close inspection because it looks like you’re working your way down the suspect list item by item. You’ll find the problem and get everything resolved in short order.

 

[HawkRod]

Well at least you know that the axle housing is firmly attached to the leaf springs and all the hardware is serviceable. The vibration sounds like it’s consistent even with all the housing clamps serviced and isolators removed. That’ll pretty much eliminate those parts as a source of the vibration.
I am curious to see how the axle shafts look on close inspection because it looks like you’re working your way down the suspect list item by item. You’ll find the problem and get everything resolved in short order.

I don't regret getting rid of the ISO bushings. They weren't compatible with the Hemi leaf springs that I put on in the 90s. I think the leaf springs are mounted much better now.

So yes, now on to axles and/ or the housing. Heck, there is nothing else it could be!

 

[1 Wild R/T]

Then use a feeler gauge to check the clearance. You need about .004" per inch of bore minimum. So I needed .017" minimum for my bore.
View attachment 1134708

Hawk

First time reading this thread... Enjoying watching your build, Seeing allot of the same stuff I've done myself.... I know it's to late to mention this & I haven't read much past the post where you discuss ring gaps... Perhaps it's been discussed but I gotta mention this.... You were setting ring gap at .004 per inch of bore but your running Hypereutectic pistons and they absolutely need .0065 per inch of bore... Instead of .017 you should be up around .026...

 

[HawkRod]

First time reading this thread... Enjoying watching your build, Seeing allot of the same stuff I've done myself.... I know it's to late to mention this & I haven't read much past the post where you discuss ring gaps... Perhaps it's been discussed but I gotta mention this.... You were setting ring gap at .004 per inch of bore but your running Hypereutectic pistons and they absolutely need .0065 per inch of bore... Instead of .017 you should be up around .026...

Yup - too late! Engine has been in and has about 1500 miles on it so far.

I don't remember my final end gap; it was larger than that but I can't quote you a number. Hopefully the engine will last the trip - no digging into it at this point...