Rear Spring Trunnion Service

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mudflap
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Rear Spring Trunnion Service

Post by mudflap » Fri Nov 17, 2017 8:20 pm

The TMs all recommend regular maintenance of the rear trunnion bearings and spring seats. In looking at the condition of these parts on my truck, it seemed like this was long overdue. Additionally, the design of the spring seat accumulates moisture and debris in the recessed area where the U-bolts go through the spring seat. This was causing the U-bolts to corrode and they were actually beginning to neck down near their attachment points. So, it was time to tear into these, and set things in order.

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After raising and securing the truck, and removing the load from the suspension, the first step was to try to remove the U-bolts. Although the nuts came off relatively easily, the bolts would not budge from the spring seats. Years of grit had accumulated in the spring seat virtually cementing them into place. Even placing a jack under the end of the U-bolt only raised the truck off of the jack stands. It would not push out the stubborn U-bolts. So, they had to be cut off with an abrasive disc.

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Next came the removal of the 2 large 7/8” bolts that clamp the lower spring leaves in the spring seat. Three of the four proved to be equally impossible to budge, even for my trusty ¾” drive impact which has twisted off many a rusted fastener in the past. Out came the cut off wheel again and I sliced them in the area of the slot on the bottom of the spring seat – being careful not to nick the spring leaf.
The spring would not come out as an assembly, as there was not enough room to slide it far enough, either forward or aft, to clear the axle loops. Since I was planning on disassembling it and cleaning it anyway, I clamped it, and removed the alignment clip bolts and the center bolt, then took it out leaf by leaf.

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Anybody know how many leaves are in a CCKW rear spring? I do now! Each of the 13 leaves was cleaned of rust and scale using a die grinder and abrasive pad. They were given two applications of Permatex rust converter, which coated the spring surface along with any pits or rough areas that the abrasive pad could not remove. After the rust converter dried, some OD green was applied to the sides of the leaves, along with the ends and any areas were the leaves overlap each other.

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While the paint on the springs was drying, it was time to focus the spring seat, which was disassembled, and cleaned. The frozen U-bolts ends were pressed out. The seat bolt remnants were also extracted (details in a future post). The seat was then sandblasted, primed and painted.

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Upon removal of the spring seat, inspection of the bearings showed them to be severely pitted, so it was no loss to cut off the cage and rollers of the inner bearing. The race was then pushed off of the trunnion shaft with an air chisel.

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Next came the spring seat seal. Originally, I was going to try to replicate the felt sealing washers, but after seeing the later design which utilizes the rubber lip seal, I knew that this would be the best way to go. While I was able to purchase the seals, I was not able to get my hands on the complete seal kit, which contains a flange that fills the space between the OD of the seal, and the ID of the spring seat.

So… it was time to do some lathe work.

More to come in the next post....

Best Regards...


mudflap
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Re: Rear Spring Trunnion Service

Post by mudflap » Fri Nov 17, 2017 8:33 pm

As mentioned in the previous post, with access to only the spring seat seals and not the entire kit, some parts fabrication was in order...

Starting with a piece of 304 stainless steel, I bored it out to the appropriate ID. The OD was then cut down at each end .002”to .003“ larger than the 3.995” ID of the spring seat. Using a parting tool, it was then cut it in half so that I would have two flanges.

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The pictures that I have seen of the production flange show a hex pattern on the outer edge of the flange lip. Not really sure what this is for – maybe to facilitate removal ? I was originally going to replicate this design element, however in looking at the flange, I did not see any reason to make such a provision. The ID is small enough to allow future removal of the inner bearing cup, and I’m thinking the 304 stainless should last several lifetimes. If it ever does have to come out, I left a small gap at the bottom to allow a punch to be used to knock it out.

Installing the flange involved placing the spring seat in the kitchen oven at about 200 deg F. For safety (my safety that is) I waited until SHAEF had left for an afternoon of shopping, lest she catch me using her oven to bake truck parts. The flange went in the freezer. After an hour or so, they went together easily with a few taps from a plastic hammer. A little blue loctite went on as well, just for added insurance.



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Use of the flange requires a spacer to go behind the inner bearing cone, in order to provide clearance for the flange. This also would have come with the kit – if I had one. A piece of 0.035” stock cut in the shape of a large washer worked perfectly well for this as shown in my home made "kit", below.

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After that, the bearings and spring seat were greased, installed and adjusted. Not having a gasket also presented a challenge. However like anyone else who has worked on older vehicles, I am getting pretty good at making gaskets.


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Once the spring seat was in place, the spring was reinstalled and re-assembled. I used a very, very light coating of oil rubbed onto the surface of the leaves, just to keep the soft paint from sticking the adjacent leaves together. C clamps were used to compress the spring enough to install the center spring bolt. Then the new clip bolts and spacers went on, followed by a set of new U-bolts. Lastly, new grade 8 spring seat bolts were installed.

Overall, spring trunnion maintenance is not too bad of a job except for: 1) Cleaning the spring leaves is extremely dirty work – dirt and rust everywhere, and 2) Once you’re done, you have to do it all over again on the other side. However the results are worth it, and the rear suspension should now be good for a long, long while.


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Best Regards.....

johnseidts
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Re: Rear Spring Trunnion Service

Post by johnseidts » Sat Nov 18, 2017 5:30 am

Great post! Thanks for the information!
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D.R.H.
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Re: Rear Spring Trunnion Service

Post by D.R.H. » Sat Nov 18, 2017 10:03 am

Well written and job well done Mudflap! Out of sheer curiosity, would you please expand on what the acronym SHAEF is? I have heard "Commanding Officer and Commanding General, even Chief of Oversight Office", but not shaef. :) .
I don't have access to a press or lathe at the present time and needed to replace the U bolts on the aft axle of my Chevy. After cutting the bolts on one side with a cut-off wheel, I used heat and penetrating oil on the "saddle" and my impact driver to pull what was left of the bolts through the saddle.
You are very correct about the accumulation of rust and debris in those holes, and the deterioration of the bolts in that area. SCARY!!
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Thank You BOTH for always being there.

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kw573
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Re: Rear Spring Trunnion Service

Post by kw573 » Sat Nov 18, 2017 12:04 pm

Hi Mudflap,
Thanks for the details and for going to the trouble to post the pictures.

I am particularly interested in the seal modification, as I am trying to reduce the oil leaks on the oil-filled rear trunion of my 4ton Diamond T 6x6, a similar arrangement to the GMC.
I have no clue how oil would have been retained with the original felt 'retainers' (maybe it wasn't!), so I have fitted 'O' rings. But they still leak a bit. I think that I have incorrect clearances and/or surface finishes. As you implied, I'll have to be in the right frame of mind to tackle that one again!

Once you get into it, the job is not that arduous. The thinking about it is almost worse than the getting started.
BUT, you still gotta have access to enough skills/equipment to do the job.

Again, thanks for the posts.

Sam, downunder.
1942 Script GPW (Daily driver).
MB-T trailer.
Diamond T 969. ('The Glorifier')
Diamond T 969, rusty, complete, for sale.
Kenworth M1A1 Heavy Wrecker x 2.
M2A1 white HT. ('Clarrie')
Light Recovery Trailer (Ford?).
3ton GS (Blitz) Trailer.
150gal water tanker trailer.
Air compressor trailer, 100c.f.m.

kw573
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Re: Rear Spring Trunnion Service

Post by kw573 » Sat Nov 18, 2017 12:19 pm

This is a link to how I removed some front spring U bolts using a jack and chain, a similar setup to what you have done. The U bolt was in about 4" of housing. Anyone using this method must take great care that everything is very well in alignment when the pressure is applied. Lest you get an unwelcome surprise! See pictures about 3/4 down the page.
http://g503.com/forums/viewtopic.php?f= ... &start=150

FYI.
Sam.
1942 Script GPW (Daily driver).
MB-T trailer.
Diamond T 969. ('The Glorifier')
Diamond T 969, rusty, complete, for sale.
Kenworth M1A1 Heavy Wrecker x 2.
M2A1 white HT. ('Clarrie')
Light Recovery Trailer (Ford?).
3ton GS (Blitz) Trailer.
150gal water tanker trailer.
Air compressor trailer, 100c.f.m.

mudflap
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Re: Rear Spring Trunnion Service

Post by mudflap » Sun Nov 19, 2017 6:16 pm

Hi DRH,

SHAEF (Supreme Headquarters Allied Expeditionary Forces) was Eisenhower's European command in WWII. Several of my pals and I occasionally use it (affectionately of course) :) when referring to our significant other.

Hi Sam,

With regards to your suggestion on using a chain with the jack to remove the U-bolts, I wish that I would have thought of that! I bet it would have worked well and would have saved some die grinder time. The recess in the spring seat is tapered, so once the U-bolts broke loose and started to move, they came out rather easily. Thinking about filling that recess with something (not sure exactly what) to keep stuff from accumulating in there again.

Best Regards...

Bob

kw573
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Re: Rear Spring Trunnion Service

Post by kw573 » Mon Nov 20, 2017 10:21 am

Bob,
How about a wax-like sealer, warm it up, pour it in and let it cool/harden. Maybe 'Tectyl'? Or even beeswax? But do it in the driest low humidity time of the year.

My 2cents worth.

Sam.
1942 Script GPW (Daily driver).
MB-T trailer.
Diamond T 969. ('The Glorifier')
Diamond T 969, rusty, complete, for sale.
Kenworth M1A1 Heavy Wrecker x 2.
M2A1 white HT. ('Clarrie')
Light Recovery Trailer (Ford?).
3ton GS (Blitz) Trailer.
150gal water tanker trailer.
Air compressor trailer, 100c.f.m.

mudflap
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Posts: 356
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Location: SE MI

Re: Rear Spring Trunnion Service

Post by mudflap » Mon Nov 20, 2017 2:26 pm

Hi Sam...

Hmmm... Thx!.. Those are all very good suggestions. :) Not familiar with Tectyl. Is that like the black stuff the spray on truck frames - almost like an undercoating?

I was also thinking about something along these lines...

http://www.americansealantsinc.com/asi- ... tadhesive/

It is self leveling product, so it should flow into the area all around the U-bolts. Would spray the cavity with silicone spray first, to keep it from bonding too well.

Will have to think about this one for awhile. I'm sure there is a good product out there somewhere for this application.

Best Regards....

kw573
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Re: Rear Spring Trunnion Service

Post by kw573 » Tue Nov 21, 2017 10:31 am

Bob,

Tectyl is an automotive rust proofing product. We used to spray it on/in new cars when the customers purchased "rustproofing" for their new car. Curiously, we sprayed it in some places that never rust, like the middle of the door outer skin instead of the bottom of the door! It dried to a hard wax like surface, seemed to be the 'business' to me.

I would not be inclined to use a product that is adhesive as this will cause great problems if it needs to be re-sealed or the bolts need to be removed for any reason. Similarly, using a release agent would, to my thinking, promote the ingress of moisture over time, defeating the purpose of the sealer in the first place.

What about a self-leveling grease?

Looking forward to seeing what you decide as I also want to protect this part of my trucks.

My 2cents. (That's 4 cents now!)

Sam.
1942 Script GPW (Daily driver).
MB-T trailer.
Diamond T 969. ('The Glorifier')
Diamond T 969, rusty, complete, for sale.
Kenworth M1A1 Heavy Wrecker x 2.
M2A1 white HT. ('Clarrie')
Light Recovery Trailer (Ford?).
3ton GS (Blitz) Trailer.
150gal water tanker trailer.
Air compressor trailer, 100c.f.m.

mudflap
Sergeant Major of the Gee
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Posts: 356
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Re: Rear Spring Trunnion Service

Post by mudflap » Wed Nov 22, 2017 2:21 pm

Thanks Sam.

I share your concern about anything with strong adhesive qualities such as silicone. Taking that joint apart someday might be as much of a challenge as it was this time.

Was just thinking about this product.

https://www.3m.com/3M/en_US/company-us/ ... 048&rt=rud-

Back in the day, we used it on vehicles that had windshields retained by a rubber channel (unlike now, where they are installed using urethane adhesive.) Sometimes there would be a gap between the rubber channel and the body, which would result in a water leak. We would pump this stuff in behind the lip of the rubber channel to fill the gap and stop the leak. It worked quite well as I recall, and although it would "skin over" it remained soft and pliable.

I also used it while installing metal wheel well moldings ( now I am showing my age :) ). Either the moldings or the screws that held them on were bound to chip the paint during installation, eventually trapping water and/or salt (Michigan winters, ya know..) rusting the fender. I used to put this stuff on first, to act like kind of a "gasket". The best part was that you could still easily remove them, even years later, because it would not harden or turn into a adhesive.

Might have to see if I can pick some up and evaluate it.

Best Regards,

Bob

kw573
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Re: Rear Spring Trunnion Service

Post by kw573 » Wed Nov 22, 2017 6:52 pm

I call that stuff 'mastic'. Messy, but effective.
Might be the "bee knees" for this job.
Sam.
1942 Script GPW (Daily driver).
MB-T trailer.
Diamond T 969. ('The Glorifier')
Diamond T 969, rusty, complete, for sale.
Kenworth M1A1 Heavy Wrecker x 2.
M2A1 white HT. ('Clarrie')
Light Recovery Trailer (Ford?).
3ton GS (Blitz) Trailer.
150gal water tanker trailer.
Air compressor trailer, 100c.f.m.


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