New/low mileage Granite with wandering axles

[timmer62]

I have a Mack Granite GR64B with Camelback suspension (44k).  The rear axles wander and show significant displacement from each other (see image) particularly in tight turns.  The pictures shown were taken at 20k miles, but the wander has been present since new. The truck is a concrete pumper, and 99%+ of its driving is on freeways or surface streets.  

Brought this up to my dealer some time ago who told me "this is a hallmark of camelbacks... they are designed to have lots of compliance". 

Recently after reading a few other threads, I am skeptical, particularly since none of my other 7 trucks (all supposedly identical) show this behavior.  The other 7 trucks have very little wander (inch or less).

The truck is quite drive-able (no complaints from any drivers) and the tires show no unusual wear, just looks strange as hell to me.    

The unit has brass bushings in the trunions and urethane isolators with isolator spacers (so-called "twinkies").  Both carriers have longitudinal torque rods.  Neither carrier has a transverse torque rod. 

I don't see evidence of loose fasteners on the trunions or boxes (u-bolts or bolts) such as gaps, abrasions, rubs, wear or exposed threads, etc.  I don't see evidence of the leaf springs shifting forward or aft on the top half of the trunions which makes me think the u-bolts are properly torqued, and the bottom three leafs are aligned and centered in the isolator boxes (which makes me think the isolator boxes are properly torqued). 

The only two observations I can make that might be clues are that (1) the third spring from the top of the driver's side leaf spring is twisted and is out of alignment with the other springs in the leaf by about 0.5 inch and (2) the isolator pads (twinkies) are loose and rattle from side to side in the isolator boxes.  I am very surprised that the isolator pads are loose... if the pads are extruding outward under the axle load, I would expect the twinkies to be pressed outward against the box and not be loose at all.  

What would be the root cause of 2-3 inches of axle wander on a new and/or very low mileage truck?
What would make the twinkies loose?
Why would one leaf be twisted out of alignment?

I appreciate your help.

[Swishy]

If the truck is still under Warranty/Guarantee

It is Macks problem and they should fix it

your mack sales branch may not kno the problem to solve

so they just fob you off hoping it will heal itself

You need to bring the problem to higher authority

your pix & full expanation the jokers in Suits should get it fixd

cya

[JoeH]

There should be a sideways torque arm from the right frame rail to the rear differential. The eyes on these wear out, but if the truck is acting this way from new I'd wonder if someone forgot to install it...

Reread, you stated it's missing the transverse torque arm.  There's your culprit. I assume all your other trucks have it. For shits, go to your dealer parts dept, and run the trucks VIN and ask for that torque arm. If it comes up as a part on the truck then I'd tell the dealer to file a warranty claim and install it on Macks dime, citing that it never had it from new so they must have forgotten it at the factory.

[JoeH]

Our 79 r686 has about 6 inches of wander.  It can get bad enough the slack adjusters can hit the frame rails...

[doubleclutchinweasel]

23 hours ago, JoeH said:

There should be a sideways torque arm from the right frame rail to the rear differential. The eyes on these wear out, but if the truck is acting this way from new I'd wonder if someone forgot to install it...

Reread, you stated it's missing the transverse torque arm.  There's your culprit. I assume all your other trucks have it. For shits, go to your dealer parts dept, and run the trucks VIN and ask for that torque arm. If it comes up as a part on the truck then I'd tell the dealer to file a warranty claim and install it on Macks dime, citing that it never had it from new so they must have forgotten it at the factory.

Boy!  That would be a pisser!  Wouldn't it?!!

[timmer62]

Thanks for the comments, JoeH.  

None of my eight 38 meter boom pumps (same as this one) have transverse torque/stabilizer arms.   The pump kit mounted on the truck sits between the chassis rails, and I was told years ago that the clearance between the carriers and the pump cylinders is insufficient for the transverse torque arms to be installed, particularly on shorter boom pumps.  It is noteworthy that all of my 38m pumps have axle stops to prevent the carrier from pushing up and striking the pump cylinders, which I am constantly inspecting.  This is the only one of my pumps that has this wander.  
 

Correspondingly, my longer pumps (47 meter and 56 meter) have more clearance and all of them have the transverse torque arms.  They also have Hendrickson or Neway suspensions.  
 

I took the pump to the dealer who tells me the wander is due to shot trunnions and pads. This diagnosis makes no sense to me for the following reasons:

wander has been present since day 1 (new) 

The brass trunion bushings are only about 1/8 inch thick, and the play from worn bushings would be way less than 3 inches (closer to 1/4 inch) 

springs are snug in the boxes with no extrusion of pads

I will be opening up the trunnions myself tomorrow to inspect them.  

The only thing that makes sense to me as a cause of the wander is that the u-bolts are loose and the springs are rotating slightly from left to right on top of the trunnionsl during turns.  Only 3 degrees of rotation would be enough to cause 3 inches of wander, if I can still do geometry.    I’ll be trying out my new torque multiplier tomorrow.  
 

appreciate any other ideas anyone may have.  
 

 

 

[Joey Mack]

Another way to check the trunnion bushing wear without taking anything apart, is to use a magnetic base with a dial indicator.. stick it to the trunnion bar, and point it to the A-Frame saddle, then jack the rear wheels of the ground under the center of the trunnion bar, and record the measurement of movement.. 

we use to call .100"   'worn'.  Good luck sir...  JOJO

[fjh]

On 11/5/2023 at 4:43 AM, JoeH said:

There should be a sideways torque arm from the right frame rail to the rear differential. The eyes on these wear out, but if the truck is acting this way from new I'd wonder if someone forgot to install it...

Reread, you stated it's missing the transverse torque arm.  There's your culprit. I assume all your other trucks have it. For shits, go to your dealer parts dept, and run the trucks VIN and ask for that torque arm. If it comes up as a part on the truck then I'd tell the dealer to file a warranty claim and install it on Macks dime, citing that it never had it from new so they must have forgotten it at the factory.

A lot of times the pump manufacturer removes these torque rods to the frame to make room for the syringe rams the rear one is usually in the way! Specially on the mack diffs!  The only real way to correct this with Camel back or hard tail walking beams is to be sure you have the steel side blocks in the buffalo pad boxes! Its a dammed if you do dammed if you don't situation! Their only other solution is to move the  pump back on the frame which will throw of the weight distribution of the rig Also     If the unit has Greased trunnions the unit should be jacked up when being serviced ! Quite honestly a pump unit is ideal to do this it has legs! Lift the unit off the ground and Grease it it will last a log time if you treat it right! Additionally you need to keep an eye on the u bolts keep em tight! The problem with a pump truck is it is eternally loaded ! No rest for the wicked!

[timmer62]

Thank you Joey Mack, fjh, and JoeH.  

I lifted the truck with the pump outriggers and removed the trunnion caps, wiped out the grease and visually inspected the parts.  Both the thrust washer and notched D ring spin (normal?) and no evidence of abrasions or brass shavings were noted.

 

While lifted and open, I shot it with grease and grease came out the bottom side of the bushing.  I stitched it back together, dropped it back on the ground and shot it with grease again to get the top side of the bushing.  Some grease also came out of the backside of the trunnion

I backed the truck up on a tight radius to create about 2" of axle displacement, put the dial indicator on (see 2nd pic), and then used the pump outriggers to lift the truck.  Once lifted, the axle displacement dropped from 2" to about 0.5".  The trunnions only moved about 0.020" (well below the Joey Mack 0.100" threshold).  

Parked the truck after a hard right turn and inspected the springs, and again after a hard left turn.  I was able to confirm that the leaf springs are rotating on top of the trunions a few degrees (3 degrees of rotation turn into 3 inches of wander on a 48" wheelbase). 

By hand, I attempted to wiggle/move the spring bolt on each leaf both when the truck was lifted and on the ground, and could not detect any play, so suspect that the spring bolts are intact.  

The springs are rotating in the isolator boxes, minimizing tire scrub when the axles are displaced (no unusual tire wear on this truck).  Isolator pads look good and there is no play front-to-back, side-to-side, or up-and down when the truck is on the ground or jacked up.

I ran out of daylight before I could tighten the u-bolts, so will tackle today.  

So a few questions

• are the thrust ring and notched ring in the trunnion supposed to spin?
• was my dial indicator set up correctly?
• was my spring bolt test adequate, or is there a better way to test for bolt shear that does not involve disassembling the leaf?
• one spring is rotated out of alignment from the other springs (see pic) by about 0.5".  Any risk of leaving this as is, or essential to realign?
• thoughts on re-torquing the existing u-bolts, or replace? 

Thanks gents, greatly appreciate your experience and expertise on practical repairs.

 

 

 

 

[MACKS]

There should be zero movement or twisting of the springs,if u can back the nuts off and oil the threads u can re torque other wise new u bolts..

Edited November 11, 2023 by MACKS
Mistake

[fjh]

On 11/8/2023 at 8:33 AM, timmer62 said:

Thank you Joey Mack, fjh, and JoeH.  

I lifted the truck with the pump outriggers and removed the trunnion caps, wiped out the grease and visually inspected the parts.  Both the thrust washer and notched D ring spin (normal?) and no evidence of abrasions or brass shavings were noted.

 

While lifted and open, I shot it with grease and grease came out the bottom side of the bushing.  I stitched it back together, dropped it back on the ground and shot it with grease again to get the top side of the bushing.  Some grease also came out of the backside of the trunnion

I backed the truck up on a tight radius to create about 2" of axle displacement, put the dial indicator on (see 2nd pic), and then used the pump outriggers to lift the truck.  Once lifted, the axle displacement dropped from 2" to about 0.5".  The trunnions only moved about 0.020" (well below the Joey Mack 0.100" threshold).  

Parked the truck after a hard right turn and inspected the springs, and again after a hard left turn.  I was able to confirm that the leaf springs are rotating on top of the trunions a few degrees (3 degrees of rotation turn into 3 inches of wander on a 48" wheelbase). 

By hand, I attempted to wiggle/move the spring bolt on each leaf both when the truck was lifted and on the ground, and could not detect any play, so suspect that the spring bolts are intact.  

The springs are rotating in the isolator boxes, minimizing tire scrub when the axles are displaced (no unusual tire wear on this truck).  Isolator pads look good and there is no play front-to-back, side-to-side, or up-and down when the truck is on the ground or jacked up.

I ran out of daylight before I could tighten the u-bolts, so will tackle today.  

So a few questions

• are the thrust ring and notched ring in the trunnion supposed to spin?
• was my dial indicator set up correctly?
• was my spring bolt test adequate, or is there a better way to test for bolt shear that does not involve disassembling the leaf?
• one spring is rotated out of alignment from the other springs (see pic) by about 0.5".  Any risk of leaving this as is, or essential to realign?
• thoughts on re-torquing the existing u-bolts, or replace? 

Thanks gents, greatly appreciate your experience and expertise on practical repairs.

 

 

 

 

I can see by the pic the ubolts are not as tight as they should be! These are to be torqued to 1600 ft pounds I also notice the spring packs apear to be non antisway packs which doesn't help the situation ! Anti sway have more and  thicker leaves above the three bottom leaves and have less give to them! For some Dam reason the pump manufacturers use or spec the cheapest chassis they can get their hands on ! Springs to small not enough brakes 24/24 brake pots ect !  you also have the cheapest spring saddle for the job there ! Your saddle has know ears athe very outsid of the saddle !  It kind of angers me in away that they are allowed to build stuff this way! Something that is eternally loaded gets built to such  low standards! Putzmeister ,Concord and others all guilty of doing this! There seems to be no rules in place for these units! check out the different styles here are some examples !  Mack Truck Trunnion Seats, Mack Truck Suspension (autoandtrucksprings.com)

[timmer62]

Thank you FJH and Macks.  I will be checking my other trucks to see if they have the same saddle config.  Maybe that is why only one of my trucks has this issue.  Waiting on delivery of a torque multiplier to attempt tightening the u-bolts.  I don't have enough umpfh to use my 3:1.  

If I elect to replace the u-bolts, can you advise if this installation procedure is correct:

1. lift truck
2. center the axles under the truck (match spacing between the rims and the frame on all four wheels)
3. torch off old u-bolts
4. align the springs in the leafs (can I tap them into alignment without removing the spring bolt, or is it necessary to remove the spring bolt?)
5. Install new u-bolts
6. Progressively torque the u-bolts

[JoeH]

If your goal is to eliminate the axle wander then you're going to want to replace the spring saddles. FJH is right, the spring saddle looks to be missing certain anti wander features. Take note of this saddle from his link:

The lower springs actually set down into the saddle, where part of the saddle casting captures the lower springs from any wandering. If you're not going to replace the saddles then just tighten up the u bolts and call it a day. It'll still wander though. 

Saddles are easy to replace.  Block up the trunnion bar, since you're a pump truck you can do this with the outriggers.  (The trunnion bar "hangs" from the camelback springs)

Take cover off end of saddle, remove spindle nut etc from trunnion bar, cut u bolts with a torch and drive the out, jack up the axles to lift springs off of saddle, slide old saddle off.

Generally easier to do with all the tires out of the way.

Assembly is pretty much reversal of order.  Note any shims that may exist between saddle and trunnion stand.  

Slide new saddle on, lower axles/springs into saddle, install u bolts, install the retainer nut assembly and cap, grease and done.

[mrsmackpaul]

But isn't this truck still under warranty?

If it is found to be missing parts your other trucks have then I would expect Mack should be sorting this issue not you

Once you have found whats wrong it should be up to them, if you start changing bits and pieces will that effect the rest of the trucks warranty 

But yes, it does appear to be have some wrong parts, thanks to everybofy that has picked this up, I didn't notice

 

Paul 

[MACKS]

Why do they even make saddles like that,I never even knew that type existed?

[mrsmackpaul]

I would be guessing  to allow oscillation at different points when a sway bar type of deal is used to the chassis rail

Maybe the whole deal gets to stiff and not enough movement is allowed

 

Paul 

[timmer62]

Good afternoon gents.  The trunnions shared by JoeH and FJH would clearly be superior, no doubt. 

I inspected my other trucks and they all have the exact same trunnion/saddle as my wandering axle truck, and none have this issue. 

Given this, I attempted to re-torque the bolts, but a few of the nuts would not turn smoothly and kept jumping when in the vicinity of the torque spec (hear a pop and the nut would rotate a few degrees), so I don't trust that I can torque them to the correct spec and also concerned the shock may damage the torque multiplier.  

I am going to replace the u-bolts next... hopefully then this issue will be behind me.

BTW, Mack says no warranty coverage as I did not re-torque the bolts "soon enough".  Never mind that it has been like this since delivery and never mind that the vehicle manuals don't articulate when they should be re-torqued.  

[Joey Mack]

what are your thoughts on lubing the exposed threads on the u-bolts, and loosen then re-torque each nut individually?  when you back them off you can squirt some oil between the nut and the washer to insure full torque is applied to the nut..  Jojo

[mechohaulic]

On 11/18/2023 at 5:21 PM, MACKS said:

Why do they even make saddles like that,I never even knew that type existed?

light weight highway hauling.????

[mrsmackpaul]

On 11/23/2023 at 8:37 AM, Joey Mack said:

what are your thoughts on lubing the exposed threads on the u-bolts, and loosen then re-torque each nut individually?  when you back them off you can squirt some oil between the nut and the washer to insure full torque is applied to the nut..  Jojo

I know nothing about anything worth knowing

But this is exactly what I would do

And not just the thread, also the surface on the end of the nut

How accurate is a torque setting if it is binding up, I would think not very accurate at all

Think about doing up head studs, they don't jump or bind, even when I have done them on my D7 they are a long gentle smooth turn, I can't remember what they were but they were pretty high 

My point is if the nut is jumping, I would undo and make it spotless and lube it up and then torque the studs up slowly keeping them even and in steps

Paul

[JoeH]

I think dealer is being lazy.  

[R.E.D]

In my opinion, you should replace the u bolts and torque them to proper specs.

I think JoeH is right, a transverse torque arm is needed for this application.

You can add one to the front diff, the torque arm bracket has a circular hole in order for the drive shaft to pass through it.

Most front diffs aren't threaded for this ,therefore you would need to remove it and have a machine shop drill and tap for you.I had this done on my rd that has 38k Camelback suspension with rubber bushings and did not come with the transverse torque arm.Granted I did it to the back diff but it would be the same procedure.

[timmer62]

Gents, 

finally have this resolved and thought I would give a summary update.

Dealer advised that trunnion bushings, isolators and u-bolts would need to be replaced.

After lots of investigation, and guidance from this expert forum, concluded that only the u-bolts needed to be replaced (maybe even only tightened, but given the amount of twisting they had experienced I opted to replace them).

Found that the u-bolts could not be installed without lifting the axles off of the springs due to an interference with the frame rails.  Being able to rotate the springs forward and aft around the trunnion along with a very slight tip of the leaf spring to the side (away from the frame rail) gave just enough clearance.  So in the end, I replaced the isolator pads too since they had to be removed to raise the axles anyway.  However, once I removed the isolator pads they looked quite good.

For those who might chose to do this, thought I would point out a few tools that you will definitely need:

• torque multiplier.  I picked up a used Williams unit with a 13.6:1 ratio.  No way to get to the prescribed u-bolt torque without a good torque multiplier, and the 3:1 multiplier I already have just did not have enough juice.  Not cheap, but figure I can use it to re-torque going forward.
• porta-power.  I did not plan on using one for this job, but found I needed to use it three times.  I did one axle at a time, and when I lifted the driver side axle off the springs the axles shifted a little bit since the passenger side axle was still attached to the spring.  I used the porta-power to get the driver side axles positioned over the top isolators once they were placed back on the spring.  Without the porta-power I could not get the isolator boxes and isolators aligned properly.  Had to do the same on the passenger side.  The third time I used the porta-power was to align the springs parallel to the truck frame before re-tightening the u-bolts so the wheels would run true.
• Plenty of pb-blaster or equiv, applied liberally the day before you start.  This may seem obvious to the experienced, but I struggled mightily to get a few bolts loose (specifically, the passenger side isolator box bolts that thread directly into the top half of the box).  Even my 2000 ft-lb impact could not break them loose.  I sprayed these bolts down mid day with PB-blaster, and still couldn't break them end of day (when I applied PB-blaster again before heading home).  Came in the next day committed to using heat, but they broke free easily without any heat.  Patience is a virtue, and so is planning, so plan to put lots of pb-blaster on early so you don't have to be patient.

Doing this my first time, this repair took about 24 hours, but it took me quite a while to solve the alignment issues (see porta-power comments above) and break those bolts loose (see pb-blaster comments above).  To save time, I would do both axles at the same time.  Hopefully, I won't have to do this again, but if I do I think I could probably do it in about 12-16 hours.

Axles wander is now gone!

I appreciate everyone's help and input, and hope that these comments will be helpful to others in the future.

 

 

[mrsmackpaul]

Thats a fantastic out come I feel

Even though Mack didn't offer much help it must feel good to have it fixed

 

It really is a great feeling to achieve this type of result

 

Well done 

 

Paul 

[JoeH]

Atta boy!