preventable rear suspension failure

[cattlerepairman]

I tackled the trunnion rebuild today. Nothing difficult just time consuming. I filled the rust creation sump with silicone, maybe that will prevent the u bolts from rusting away again.

That is a fine piece of service work. The rear springs look like new.

 

[hndrsonj]

So who is selling the seals ETC to do the trunnions?

 

[NDT]

So who is selling the seals ETC to do the trunnions?

The grease seal is the same as the hub, so any number of suppliers carry that. I found the felt dust seal "kit" by Googling the NSN (see above picture or TM for the number) which brought me to an ebay seller. I am sure the usual suspects like Memphis Equipment would have that as well.

 

[gringeltaube]

I found the felt dust seal "kit" by Googling the NSN (see above picture or TM for the number) which brought me to an ebay seller.

Here it is: https://www.ebay.com/itm/5X614-Meritor-Felt-Washer-5310-00-693-0623-7521646-/303507346704



(Note: Rules have changed and posting eBay links is allowed, now.)

 

[Jeepsinker]

I filled my u-bolt pockets with plasti-dip. Easy to pour in with no air pockets.

 

[Lovetofix]

I also used plasti-dip. I have had too many problems with silicone not adhering well and peeling loose. After almost two years the plasti-dip has held up very well to the elements and pressure washer.


Sent from my iPhone using Tapatalk

 

[NDT]

I did the Plasti-dip today and I agree that is the way to go.

 

[HDN]

I haven't done the trunion lubrication yet since I've been deep in my tire project. However, I'll get to replacing the rear tires soon and will want to attempt the LO and nut maintenance while I have easy access to the trunion covers.

One question, though: Do I need to jack up the entire back end of the truck to properly adjust the nuts, or can I do one side at a time instead as long as there isn't a load on the leaf springs? The TM doesn't make that clear to me.

 

[cattlerepairman]

Here is my view of the world:

No, you really want the weight off the trunnion to assess/adjust and also grease properly. That means jacking up the frame until both axles are hanging free. Yes, it is a bit of a pain.

What you CAN do with the wheels on the ground is to take the covers off and check whether the nuts are ridiculously loose (i.e. falling off or can be turned by hand). If they are not, it would suggest they are "tight enough". In the absence of any debris, fractured bushings etc. one could call it good at that point. I do not believe that it is possible to set the preload accurately with the wheels on the ground; you don't know how much side loading there is on the assembly.
In a pinch, driving the truck forward and backward "straight" before attempting to tighten the nuts might remove sideloads as to be close enough with torque? Others might chime in.

 

[gringeltaube]

Do I need to jack up the entire back end of the truck....... ?

No, not the entire back end..... With truck on firm and level ground (and front wheels well chocked!) - place a bottle jack in the center of the spring seat bracket (#18 in the attached diagram) - plus one jackstand to each side of it. Then lift up until the spring ends on both sides are just free to move up-and-down in their respective pockets mounted to the axles.
For your own safety, don't rely on the bottle jack, but have it resting on the jackstands, before going further!

(Eventually, the tandem is out of alignment, so one- or even both axles have to be lifted a bit and shifted back to center, to allow the springs to move freely).
Now grab each spring pack and try to rock it sideways. There should be absolutely no play, horizontally! If so, you are a lucky man and good greasing is all it needs.
Otherwise, the spring seat bearings and related parts need to be disassembled/ inspected - even if you felt very little play, only.

Side note (and I know that this has been posted before): Older trucks - not been overhauled by the military - most likely still have the early style, tapered roller bearings in there. Inner and outer are the same p/ns (#3920 cup & #392 cone, same as outer wheel bearings).
Chances are that these are shot and need to be replaced.
In later production years, there has been an "upgrade" to this design, to have solid (steel) cones riding in those same 3920 cups (#8 in diagram), instead of the roller bearing cones. While this seems to last a bit longer, that setup still has its flaws IMHO, because the original keyway in the spindle remained unchanged, so only the outer cone can have its key (#7), to prevent it from spinning on the shaft. Guess what happens with the inner cone... instead of remaining stationary it slowly-but surely eats the spindle! Good thing is that it is the outer bearing which sees the greater load, in this system.

 

[cattlerepairman]

My pics from a couple years ago, doing that very work (while replacing the dog bone ends). I can cheat when lifting, due to the massive trailer hitch on my truck.

 

[yolner]

While this seems to last a bit longer, that setup still has its flaws IMHO, because the original keyway in the spindle remained unchanged, so only the outer cone can have its key (#7), to prevent it from spinning on the shaft. Guess what happens with the inner cone... instead of remaining stationary it slowly-but surely eats the spindle! Good thing is that it is the outer bearing which sees the greater load, in this system.

View attachment 839475

Want to contribute some info I came across during my tandem rebuild. I had to replace my rear trunnion (part # 7700126) and I discovered that the NOS trunnion I got from easternsurplus had the keyway all the way down and not just to the outer bearing. So it looks like the flaw that allowed the inner bearing block to turn was fixed at some point.

 

[HDN]

Want to contribute some info I came across during my tandem rebuild. I had to replace my rear trunnion (part # 7700126) and I discovered that the NOS trunnion I got from easternsurplus had the keyway all the way down and not just to the outer bearing. So it looks like the flaw that allowed the inner bearing block to turn was fixed at some point.

I should check mine on my A3. I hope my truck has the improved design on it

 

[dmetalmiki]

Though I'm sure your fine with new roller bearings, The mil upgraded the trunions to solid bearings due to high failure of the rollers, do you have the grease fittings on the pivot hub?, if not did you add them? ( another upgrade )

Well....A huge thank you here...Your 'report' earns you (In my book anyway)..the steel soldier of the month award.
You have supplied the best tips ever (Or at least one of) on the deuce.
I WILL be checking those bearings.
I will NOT be looking to replace the taper rollers.
I WILL be buying..OR MAKING plain bearings,
And fitting grease gun points.
An amazing 'truck saving' modification'..And a completely logical (ERR no, necessary one).
Again, Thank you.
((Now to inform the 'kids'..they have some serious assignments coming)).
Safety, Maintenance, Dissembling, Modifications, Lathe work. Fitting.

On all four of the applicable trucks...So, Two each.

WHAAAT?, AND a full project presentation write up, essay, ..grammar, spelling, punctuation....

I bet they will be wishing you a 'happy exmas'.. >holidays!< too, . ...he he!.

 

[gringeltaube]

Want to contribute some info I came across during my tandem rebuild. I had to replace my rear trunnion (part # 7700126) and I discovered that the NOS trunnion I got from easternsurplus had the keyway all the way down and not just to the outer bearing. So it looks like the flaw that allowed the inner bearing block to turn was fixed at some point.

Thanks for that contribution! First time ever I get to see a full keyway there; just as it's supposed to be!
Interestingly, the part number remained the same.

So, what about the key(s) itself? Guess it should be one only and full length, accordingly. Certainly, not just two of the short ones (#MS20066-240), unless they had roll pins to fix them in position and avoid shifting, axially.

 

[yolner]

Well now I'm really glad I posted this because I was planning on using two short keys. The newer TM (2320-361-20)I was looking at seems to show one longer key though and I was just thinking that's probably for a reason. You think I should get one longer one?

 

[gringeltaube]

You think I should get one longer one?

Yes, absolutely!
Problem with two short ones is what keeps them from sliding out from under the bearing, towards the center of that spring seat. (?)

 

[yolner]

Yes, absolutely!
Problem with two short ones is what keeps them from sliding out from under the bearing, towards the center of that spring seat. (?)

Cool. Already ordered some 4" ones.

 

[V8srfun]

This seems to be a common failure that people find when it is already so far gone that it is unsafe. We really need a sticky with proper inspection and maintenance procedures to increase awareness.