Loud cracking/snapping sound coming from 85 R model trunnion

[Jhitch]

Hi all. I’m new to the site and I’m looking for some help figuring out an issue with my 1985 R Model Mack Truck.    I Purchased the truck a year ago and have been working on it.   I only use it sparingly because it is pretty much my baby. I’ve been getting some snapping and popping noises when I’m driving it.   I am no mechanic but it seems like a lubrication issue. I’ve tried all I know how to do to get it lubricated.   I’ve tried greasing it when it was loaded. I’ve tried jacking the truck up and greasing it.  I also took the cap off and cleaned out the old grease and put two new trunnion end caps on.   I believe the other ones were damaged and allowing moisture in.   I don’t believe the bushings are bad.   The trucks sat for a long time and I don’t believe it was greased properly. I’ve tried all I know how to do and the problem is still not fixed. Has anyone experienced something similar to this?  Any suggestions are welcome. Thanks in advance for your time. 

Edited May 2, 2018 by Jhitch

[mrgumby]

Have you jacked it up by the frame so the weight is off the suspension. That’s the correct way to do it

[880joe]

Could be the peanuts wore out and slipping 

[Jhitch]

 I have jacked the truck up from the back and on the plate welded to the frame rails for pintle hook. 

[Rob]

Sounds like a rotating origination to me. Could be a "spalled" wheel bearing. Do you have the noise without a trailer? Have you jacked the truck up getting both drive axles off the ground and ran the truck? This I would suggest and if the noise still persists without the tires being on the ground, let them rotate and find where the noise is originating from while they are rotating. You may have to remove one set of tires at a time to drill down to the culprit but it could be something simple like rust buildup inside a drum. That truck being an 85 probably has outboard brake drums so really easy to check. 

 

[h67st]

2 hours ago, 880joe said:

Could be the peanuts wore out and slipping 

What are the peanuts?

[Lmackattack]

1 hour ago, h67st said:

What are the peanuts?

Its part of the power divider

How are the U joints?

does it make this sound every rotation of the wheel?

 

[Rob]

1 hour ago, h67st said:

What are the peanuts?

They are the rollers in the front rear differential. They are basically the interaxle differential in a tandem and they, along with their respective drum wear. Going in a straight line they are usually silent when worn out but during a turn noisy as all getout.

[mrgumby]

Had a stud pilot rim do that when it was cracked. Just another thought

[Rob]

That is a very good suggestion I'd looked over thinking the truck had hub pilot rims. Regardless, loose lug nuts will make sounds like those experienced also.

[Jhitch]

Thanks, Fellas. Your help is much appreciated.  We are extremely busy right now but as soon as I get some time I’m going to check out some of your suggestions. I’ll let you guys know what I figure out. 

[Jhitch]

 I had a little time to look into some of your suggestions on my 85R model This weekend checked for cracked rims all appear to be in good shape.   Checked all Lugnuts everything was good and tight   Jacked her up and got all drive tires off the shop floor and got her in gear and rotated the drive tires and forward  and reverse  truck was quiet as can be . The sound is definitely coming from the trunnion .  As you let the truck down off the jacks Trunnion  seems to be bound up making metal on metal sound   What you can hear in the earlier video  You can watch the trunnion  having a hard time getting back to level out  almost getting stuck in position  i’ve also noticed this while driving it over grade changes  I cannot get it lubricated and taking grease.  I guess at this point asking for suggestions could something be installed incorrectly or put together too tight in the trunnion? Or at this point should I go ahead and  have bushings replaced? Just don’t want to do further damage to an expensive component .  This truck has sat for almost 4 years before being put back into service  just trying to get some bugs worked out of her .  Sorry I try to explain what I’m experiencing the best I could I am no mechanic could I be missing something?  any suggestions would be helpful and thank you for your time in advance 

[j hancock]

If it isn't taking grease, I would say to stop using the truck.  All the old grease needs to be flushed out of the bushing and replaced with new grease.  Old filthy grease is just going to grind the trunnion bushing up.  After cleaning and inspection, you can see whether the bushing needs to be changed.  All the weight on the rear of the truck is being held by the bushing, it needs to be lubricated.

[Lmackattack]

I have never worked with the heavier Mack rears but I see it has a cap that can be removed. I would pull that off and then see what it looks like. If its possible to jack it up from the center tube or lift from the rear of the frame that will show if it has to much slop. it will also help push grease into the bottom of the bushings when the weight is off it.  Pull that cap and let us know what you find

 

[mrgumby]

[mrgumby]

That will give you an idea of what your looking   Like mack attack said pull the end caps get the weight off the suspension give it some grease and see if it gets to the bottom 

[terry]

3 hours ago, mrgumby said:

That will give you an idea of what your looking   Like mack attack said pull the end caps get the weight off the suspension give it some grease and see if it gets to the bottom 

If you read his first post, he has done this.    terry