preventable rear suspension failure

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rustystud

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OK, what if we added this phrase:...."but if you pump in grease normally (by using a REGULAR HAND PUMP) you will get grease coming out the back, without damaging any seals"...

Think about this, Rusty: how else would the operator be able to "flush" any old grease out of the inner bearing?


Just for fun, I did some (greasing) "tests", today... (I got curious and wanted to see how hard (or easy) it was to actually "blow out" one of those rubber seals/ shields...:smile:)
The parts shown in the following pictures all felt very tight, with no play at all. And all of them had the newer, rubber type shield...
Of course, I did not loosen the cap, on purpose and just pumped grease in, from the bottom.

1st one took a while (to compress the obvious air pockets), but what finally came out at the back side was some dark stuff with the consistency of chewing gum (!) Talk about old grease...! I could actually feel the resistance in the pump, but the thing is, that gum did squeeze out, without doing anything to the shield and washers.
I stopped when it started leaking (fresh grease) at the front. So maybe I blew the cap gasket, but not the rear seal.
View attachment 748318 View attachment 748319


2nd one, after about 20 pump strokes, just clean grease (no old stuff) started coming out the back, with very little resistance. After wiping it off, the seal looked as good as before. So, again, no sucess... (in popping the seal)
View attachment 748320


Of course, isolated test results don't prove anything. And I do acknowledge that things can go wrong, eventually. One single case is proof enough.
Every case may be a bit different. Brand new parts - which most of us don't have - might be a tighter fit, shield to housing?
(as always: "your mileage may vary...")

Again, my humble opinion - after years of working on these things: the whole design is far from ideal, and there is very little we can do to improve it.
One thing I always did was to move that grease zerk out of harms way and place it where everyone can see it - easy to reach and inviting" at least... People in my country don't read TMs, not in English, not in Spanish. But even a moron knows what a grease zerk is for, so there is a slight chance at least that they do add some fresh grease, from time to time!
It has yet to happen that one of those seals popped out, almost like exploded, as seen in Rusty's picture..
OK, I agree that my "pressure greaser" was more then likely the culprit here. But it can happen. Also my system did not have that felt washer you mentioned. Maybe it was decided by the military to delete it, or the last soldier putting it back together forgot it. Who knows. The whole point of this was it can happen and you must admit your message to me was totally different in how you've addressed others in the past who you thought where in the wrong. You usually say something like "well in my opinion that cannot happen due to this or that" not "think before you post" . That implies the person is stupid or something worse. Of course Doghead will give me another infraction for bringing this up. He basically told me to play nice or leave like I said I would. ( Of course I never said I was going to leave just never post any of my modifications like my "power steering project" and "transmission project" and on and on). I thought I've been pretty reasonable considering I was basically being called stupid. We will see what happens. At this point I don't care. After my heart attack I've realized there are many other things more important to me then posting here.
Rant over.
Now about the zerk fitting. I agree with you Gerhard. I personally like have the zerk on the hub. Much easier then crawling under the truck to grease. Maybe it will not allow the grease to go everywhere, but it will inject enough good grease to keep things from seizing up. That is the main thing anyway. Also this is a bad design. It would have been far better to have roller bearings (like it used to have but larger) and a oil bath system. With a good modern seal there is no way water would ever get in, and the oil would keep those bearings going for thousands of miles. Just look at the modern trucks with front oil hubs.
So my final thoughts on this subject is grease the zerks carefully. You never know what can happen. Also the relief valve works fine in my system. :wink:
 

Floridianson

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Think that's the way I feel sometimes when you post. Do believe most people are not stupid just misinformed lets say. Do believe sometimes real stupid people don't live that long.
As for the old rubber seal bet when it was new it would open up and let the grease out easer. Older maybe harder and till it finds the weak spot and squeezes out going to fast it might pop. Bet if you go slower at first with hand gun till you feel pressure build stop for a second or two. Then once it opened you could use a power grease weapon to get the good change out but still pumping one shot at a time. One shot in one shot out may let the pressure stay lower.
 
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gringeltaube

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Sorry Greg, the way you responded to Orren's post #52 made me believe that you did not take your time to think about it...? But its OK, it happens to all of us.

Still unclear to me: In this post you emphasized that it had to be a "high pressure grease relief valve" and yes, there are some that go up to 80 psi or more. (like this one)
But then in post #22 it appears that what you bought are only 1/4 - 1 PSI vents?
With such low range, how could you possibly get any fresh grease all the way through the inner bearing, and even some out on the back side, to confirm everything was "flushed"?
 

rustystud

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Think that's the way I feel sometimes when you post. Do believe most people are not stupid just misinformed lets say. Do believe sometimes real stupid people don't live that long.
As for the old rubber seal bet when it was new it would open up and let the grease out easer. Older maybe harder and till it finds the weak spot and squeezes out going to fast it might pop. Bet if you go slower at first with hand gun till you feel pressure build stop for a second or two. Then once it opened you could use a power grease weapon to get the good change out but still pumping one shot at a time. One shot in one shot out may let the pressure stay lower.
I'm sorry if I ever made you feel stupid floridianson, that has never been my intent. In fact you are one of the most knowledgeable ones here on the fuel injection pump I've come across. Especially considering you never had factory training on pumps like I have had the opportunity to do. You just have a natural ability to understand the thing which is rare.
About the seals getting hard, that probably had something to do with it also. A new flexible seal might have just let the grease pass and then reseal itself.
 

rustystud

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Sorry Greg, the way you responded to Orren's post #52 made me believe that you did not take your time to think about it...? But its OK, it happens to all of us.

Still unclear to me: In this post you emphasized that it had to be a "high pressure grease relief valve" and yes, there are some that go up to 80 psi or more. (like this one)
But then in post #22 it appears that what you bought are only 1/4 - 1 PSI vents?
With such low range, how could you possibly get any fresh grease all the way through the inner bearing, and even some out on the back side, to confirm everything was "flushed"?
I was referring to the ability of the relief valve to handle high pressure to relieve the system of the high pressure grease, thus preventing blowing out the seal. As far as the ability of the grease to go all over the bearings with the low pressure of the relief valve. It is no different then having the plug "removed" and greasing the system like the TM says to do. This way I don't have to worry about replacing the plug to prevent junk getting back in there.
The relief valve does that for me. It would be the same as unscrewing the cap. "Six of one and half a dozen of the other" as the old saying goes.
Also this is not the first time I accidently pushed out a seal greasing a system. There are a ton of fittings on the busses I have worked on that had a relief valve that got plugged up and I didn't notice until the seal popped out. They are usually in the "turntable" system where you do not want extra grease floating about, (due to electrical wires and hydraulics) so the extra grease is channeled outside and under the bush.
 
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Maverick1701

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In all my years of owning an m35a2 (and constantly reading the lubrication TMs) I totally missed these zerks. thanks for sharing the info. I went out and lubricated mine trunnions on monday (along with the rest of the trucks lubrication points)
 

dmetalmiki

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Thanks for all the information and pictures, (Dang it!)..Now I have added another "thing to do" on the wall 'Naughty pad'.
 

HDN

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I am greasing my truck and I'm about ready to tackle the rear spring seat bushings. This includes checking the torque of the trunnion nuts.

However, I'm having trouble finding the rear spring seat assembly in my TMs, especially an exploded view of the assembly. Can someone please share the book and section I should be looking through? Also, how big are the trunnion nuts? If they're as big as I think they are, I'll have to go socket shopping.
 

gringeltaube

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............. I'm having trouble finding the rear spring seat assembly in my TMs, especially an exploded view of the assembly. Can someone please share the book and section I should be looking through?
http://www.steelsoldiers.com/upload/M35/TM9-2320-209-34P.pdf . Fig. 127 shows the later (bushing)bearing style.
Spring seat, bushing bearing type.PNG
And this is the early (tapered roller)bearing style, from the parts book ORD 9 SNL G-742 (Jan1955):
Spring seat, roller bearing type.jpg

Also, how big are the trunnion nuts?
Same size as the spindle nuts: 3", 8-sided.
 

HDN

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Thank you for posting that! For some reason those views are absent from my M35A3 PDFs. It looks like I'll have to get gasket paper before I pull the covers.
 

HDN

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Why does the trunnion have a plug, instead of just leaving the grease fitting in all the time?
I wondered this as well when looking at the instructions to remove the front axle u-joint housing plugs to install a zerk in one. Like @rustystud said, they could get damaged either off-roading or during jacking.

I talked to my dad about this too, who experienced this on his M38A1 and M37. From what he learned through his years of collecting, some grease points were plugged to keep Pvt. Parts at motor pool from overgreasing sensitive components, like places where seals could be damaged or where motion could be impeded by lots of grease.
 

Blitz Omenz

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What's the torque for the inner and outer nut on the trunnion? Is it the same as the hub? I can't find it anywhere. I have trouble finding stuff in the TMs. I tried but I just don't see it. I took the outer nut off and the locking ring. When I took a rag to wipe the grease off the inner nut it was turning with just me wiping around it. I tested the outer nut with my torque wrench and it was about 120 ft lb.
 
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