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My first heavy truck xm215

tburk49760

Member
398
10
18
Location
spokane washington
That did make me smile, thanks. I've only driven it on my 1/2 mile driveway up to about 40 mph. Seems fine. As to the dog bones, as much as I've played with various suspension systems, to include a samurai coil/ triangulated 3 link install, the only reason I see for the dog bones is to prevent axle housing wrap. This can be problematic on spring over applications, especially with over zealous application of torque. Not a safety issue in any way though. I will take a look at the backing plates to see if the other side is similarly installed. Can't think of any issues this could cause either. The pinion angle issue could indicate camber and therefore steering centering issues and perhaps death wobble. Neither was apparent in test drive mode. I'm not sure there is an easy or other solution to that so let's hope no driveability issues crop up.
 

hendersond

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Galesville, WI
People often incorrectly jump to the conclusion that the dog bones are to prevent axle wrap under the severe torque of the engine or braking forces. I suppose they do serve that function to a point. But take a closer look at how the suspension actually functions in this truck.
This truck was designed to spend a lot of time moving off road with heavy loads. Regular leaf springs are very limited as to how much flex is allowed. They only go up and down a few inches. Over and over we see guys parking trucks on big stuff. I'm tralking about the guys who take a picture or post a video of the drivers side tire up on some foreign car. I'm amazed at how much flex the suspension has and the left front tire stay on the ground. Most pick ups would have the other tire hanging out in the air.
The M211/M135 trucks do this because it has 2 things. Dog bones... and 4 sets of spring shackles. Count them if you don't believe me. The dog bones hold the axle from shifting forward and backward. If you took the dog bones off and stepped on the brake while moving, the axle would shift backward. Take only the left one off, and step on the brake while moving and the left side of the axle shifts back and the truck pulls to the left.
This truck has 4 sets of spring shackles. Yep, shackles on both ends of the springs. It allows the springs to have more drop. It keeps the other front wheel in contact with the ground, good for both traction and braking. We incorrectly assume the trucks have only shackles on one end and the other end fixed like most leaf sprung pick ups.
So to recap, the current suspension is designed for more articulation. The springs are not fixed on one end and have shackles on both ends to allow for more drop. The dog bones or torque rods control front to back movement of the axle. Those huge spring rear spring mounts and the stabilizer bar running to the other side controls the side to side movement.

I'm wondering if they changed the rear shackles to a fixed mount?

If not maybe you should consider the fixed mount in the front. I rember an old CJ jeep when I was a kid. It had a "lift kit" (6" shackles) on the front. Here is something an old mechanic told me about what end of the spring pack to put shackles on:

"If the shackles are on the back, the axle would track. If the shackles are on the front axle will hunt." And it rhymes! :-D
 
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tburk49760

Member
398
10
18
Location
spokane washington
I always say, learn something new every day! Indeed looking at the TM I can see that there are shackles on the front and rear of the leafs, so now I need to go look at mine and see what changes were made. I see now there is definitely more need for the dog bones assuming that there is still moving shackle on the rear of the spring. Thanks so much for the detail and explaining it the way that I can understand.
 

Section8

Member
503
6
18
Location
Little Fort, B.C., Canada
Thanks so much for the added info on the suspension and the purpose of the dog bones.
My question is why three dog bones? I wanted to remove the top one for swapping my 6BT and was told not to.
The two lower ones should control the forward and back rotation of the axle under braking and the overblown axle wrap issue shouldn't they??
 

hendersond

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Not true. If you remove the top dog bone ,the bottom ones then become the center of the pivot point (where they attach to the axle) and the springs will still "rotate" backwards and forwards. The top one is needed as well or you need to anchor one end of the springs. I'm cutting some apart right now. I'll try to catch a pic or two.
 

hendersond

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Supporting pic-umentation...
 

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tburk49760

Member
398
10
18
Location
spokane washington
Took a look at my strangely modded front suspension today. Seems that the passenger side backing plate was assembled strangely. Also the rear shackles were removed and the front shackles lengthened. Effectively meaning that the suspension upfront is like a typical older Jeep would be. I wasn't able to put a angle gauge on the knuckle to see if an appropriate amount of caster was still retained but looking at it I would guess that it has been. I will probably have to pull a wheel off to get an accurate take on that.ImageUploadedByTapatalk1363923407.104601.jpg The top Dogbone mount on the axle housing doesn't seem to exist anymore neither does the frame end for that one. The bottom dogbone mounts are all in place and intact.ImageUploadedByTapatalk1363923427.287815.jpgImageUploadedByTapatalk1363923444.337231.jpgImageUploadedByTapatalk1363923461.953916.jpgImageUploadedByTapatalk1363923477.904316.jpg
 

hendersond

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Aaaaaah, so they must have lengthened the shackles to keep the same caster. The springs are mounted lower in the rear since the rear shackles removed. You should be good to go!
 

tburk49760

Member
398
10
18
Location
spokane washington
Put my new master cylinder on as well as two more new wheel cylinders and found one brass adapter at one front wheel cylinder was plugged. Rather, a restrictor washer was plugged. Cleaned it all up, bled the system and test run ho! Stopped crazy well, but releases a little slow. As in one must wait a second or two to begin moving again. Still thinking I should rebuild or replace the airpac. If NAPA can still get it, about $400, otherwise about $700. A little nervous about rebuilt parts availability. Then my son showed up for a pre deployment visit with the granddaughter and the deuce will get ignored for about 10 days til they head back to the east coast.
 

topo

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908
251
63
Location
farmington NM
When I rebuilt the brakes on my M211 they would hang or release slower then I though they should . I ajusted them again and they where fine . With 12 wheel cylinders the more the the shoes have to traval to stop the truck it takes time for that much more fluid to return to the master cylinder . Good luck
 

tburk49760

Member
398
10
18
Location
spokane washington
Took the old girl for a tour around the property and she fired right up! Still have a few minor leaks. Trans, dump hyd valve and pto all have slow leaks. Part of he deal I guess.
 

hendersond

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Location
Galesville, WI
The list is long. Not-cracked exhaust manifolds, carb, airpack, Transmission...

I think there is a thread on spare parts for the GMC series about 9 months ago?
 

tburk49760

Member
398
10
18
Location
spokane washington
Drove Olga the 4 miles to the fire station last nite and was able to get her up to nearly 45 before hitting the given er at 2800 rpm! Handled just fine. A little more speed would be nice, plenty of power just no more revs. Taller tires will help, singles are the dream. Noticed on the way home in the dark that my brake lights weren't working. Opened the housings tonite to discover both bulbs had failed. Time to begin paint prep. Yippee!
 

Gunfreak25

Well-known member
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620
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Location
Yuma, AZ
I had some catching up to do. Took me about 30 minutes to read all 14 pages. I had stopped at page 6. Very happy to see you've stuck in there brother. Oh yeah...

BOO

Here I am. :D
 

Section8

Member
503
6
18
Location
Little Fort, B.C., Canada
Great googily moogily!!
Glad to see your still around GF!
O boy o boy! Paint time!!
Can I suggest a nice robins egg blue or maybe a hot pink?! LOL
The blue on mine bugs me!
OD green?!! Or where you thinking of possible other colors?
 

SturmTyger380

Active member
482
30
28
Location
Easley SC
Talking about NAPA and the airpack, when I asked one store a few months ago they said they could not order it. It was on their web site still though. I might try asking another auto parts place.

Let us know if you find where you can order it.

Alan
 
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