Shuddering above 25 mph...

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Milkman357

Member
175
1
16
Location
Des Moines, IA
Ok My M-1009 has a shudder...

I took into the transmission shop, because I thought it was my second gear in the transmission.. but he says he thinks it engine related.

Researching this sight, I need to start off changing the harmonic balancer..

It's not the tires, they are ok, That was the first thing I checked..

Both driveshafts have been rebuilt/balanced..

When I first start off, engine cold, it doesn't shudder. After a few minutes I will get a vibration after 2nd gear shifts... under acceleration. The Transmission guy thought (knows nothing about diesels) first gear doesn't put much of a load on the engine, but second gear actually makes the engine work.. and that might be a cause.

I've ordered some rebuilt injectors, so I'll change them soon.... If the harmonic balancer and injectors arnt the culprits.. Would an injector pump going bad cause this? 99,000 miles, probably original IP.

My dash kinda vibrates on the passenger side.. I think the vibration is coming from the passenger side btw... It feels like passenger front is where the vibration is coming from.

I have a crate engine laying around from a HMMV.. But I think it's bad. I could use that injector pump as is.. or send it in as the core... I'm going to need an IP someday.. just a matter of time. Kinda sounds like I'm talking out loud, I am..

Just curious about other people's 2 cents....

Would an injector pump going bad, cause one side of engine to vibrate?

I see no gray or excessive smoke anywhere.. just at start up, first time in the morning. Starts pretty easy cold, starts real easy warm..
 

Barrman

Well-known member
4,399
50
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Location
Giddings, Texas
You said it isn't tires, yet you describe a tire related vibration. Does it do the vibration power on and power off? Does it stop above a specified speed? You have new drive shafts, what about the ujoints? Front wheel bearings ok? Brake rotors round with brake calipers that actually release? How are your tie rod ends and ball joints? Front axle u-joints? What about the lock out hubs, do they actually unlock? Have you raised the hood, put it in gear and while holding the brake, added a good bit of power gradually to check the motor mounts are actually holding, and then do the same in reverse for the other side mounts? Tried bench pressing the tcase to verify the transmission mount is good? Checked the transmission to engine mount bolts to make sure they are secure? Same with the transmission to tcase pedistal mount bolts?

Can you replicate the vibration by just slowly revving the engine sitting still in park?

Check your tires again for being round and in balance just because.
 

Milkman357

Member
175
1
16
Location
Des Moines, IA
more...

You said it isn't tires, yet you describe a tire related vibration. I thought it was at first.. tires were checked by tire dealer......

Does it do the vibration power on and power off? The throttle does seem to affect vibration... When shuddering starts letting up on throttle stops shuddering.

Does it stop above a specified speed? sometimes.. not real consistant. at highway speed shuddering is very slight, if at all.. this is at cruise.. or once you reach cruise speed.. 55 or 65.. same same

You have new drive shafts, what about the ujoints? I removed rear driveshaft and those joints are ok.

Front wheel bearings ok? no strange heat build up.. new bearings/cups last year.

Brake rotors round with brake calipers that actually release? I doubt its brakes.. Throttle seems have affect.. brakes are within 1 year of needing replaced btw.

How are your tie rod ends and ball joints? everything seems solid.. that's what I originially thought might be probplem.

Front axle u-joints? new when rebuilt.. shudders in 2 wheel drive.. havnt tried 4 wd yet.
What about the lock out hubs, do they actually unlock? newer lockouts.. Not problem
Have you raised the hood, put it in gear and while holding the brake, added a good bit of power gradually to check the motor mounts are actually holding, and then do the same in reverse for the other side mounts? Not yet. good idea.. But I don't think thiis is problem.. motor seems stable in mounts from general observation..

Tried bench pressing the tcase to verify the transmission mount is good? Transmission may have.. they think engine related

Checked the transmission to engine mount bolts to make sure they are secure? Same with the transmission to tcase pedistal mount bolts? Transmission shop DID do this.

Can you replicate the vibration by just slowly revving the engine sitting still in park? No I can't.. tried a break stand.. nice and smooth..

Check your tires again for being round and in balance just because.



The more i think about it.. I think Harmonic balancer is a good place to start.
This might be hard to explain.. When I start off nice and smooth.. accelerating..not turning- going straight.. if I ease the pedal just right I can get everything to work correctly. Maybe a smooth and steady power application keeps the Harmonic balancer stay tight.. ? Or when I accelerate smartly.. and the transmission shifts it causes a lag or hessitation.. that allows the Balancer to slip... WAG- yes.. But I have one on order.. It sounds like its a problem that needs replaced one way or another.. at 27 years old, it's preventative maintenance.
 

Milkman357

Member
175
1
16
Location
Des Moines, IA
Drive shaft Yoke

I drove until it failed!
or
Found the problem!

I was driving home today and the rear drive shaft separated from the vehicle on the way home.


Looks like the front yoke failed. It was still in the transfer case when I got stopped. I coulda drove it home but..... when all this happened it broke the transfer case housing. The case had issues and I had just taken my spare in to have it rebuilt.. so I'm not gonna cry about it.

Must have been a crack that only became visible at a certain speed.

I don't mind breaking weak parts! lol

I wanta take this truck on some outings with my sons, so I'm ok in the weak stuff breaking now!

I called the transmission shop to mention that I had some spare transfer case parts if he needed any for the rebuild.

Even he said He checked the yokes, they looked ok to him.

I wonder what a new Yoke costs?
 

Iceman3005

Member
876
8
18
Location
Jonesville, MI
I have a transfer case, PM me if interested. I see you have one that is being rebuilt so you might not be interested.

There is a drive shaft shop near me he rebuilt mine for $150, that was just for the tube and welding the yokes back on, add a new yoke about another $100-200, depending on what the shops around you charge for labor and materials. Hope this gives you an idea of what it will cost.
 

Milkman357

Member
175
1
16
Location
Des Moines, IA
2 cents

thanks Iceman.. but I'm good on Transfer Cases..

A friend has another driveshaft for me.. I will take it in and get it rebuilt, and balanced....
After thinking about it.. I'm not sure I want the one that came off my truck, and bounced down the interstate....It should work fine.. but I don't want the worry hanging around.. especially when I can get another one..

How to diagnose this issue?

I woul dthink you'd have to remove the driveshaft completely, they secure one end, maybe in a vise.. then use something to twist the driveshaft and then inspect the yokes for any cracks that might show up..

When A shop balances a driveshaft I have no idea if they can put a load on it, to check for cracks....

this driveshaft was rebuilt and balanced less than 15,000 miles ago, by a respected shop.
 

ganderle

New member
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0
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Location
Racine, WI
I have a 1986 M1008 and have a similar problem. It has been shifting 2nd -3rd under strain, when it gets to about 40 MPH, it sometimes goes into a violent shudder, when I brake and get down to 15 to 20mph, it stops and I can resume. I took it in to a mechanic who checked everything on the front end (I had a similar shaking earlier from a stabilizer arm on the steering and replaced that myself). The result was no problems. The mechanic said it that the rear wheels are freezing and releasing quickly which is causing the shudder. I need to get it in to a transmission shop but was wondering if it is likely transmission or rear differential? motor mounts are good and no obvious problems with transmission to engine bolts. Any suggestions would be appreciated.
 

2deuce

Active member
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Location
portland, oregon
I had a vibration problem with my M1009. I could rev the engine without vibs. Balanced the driveshaft and the shop that did it said it was within specs when I brought it in. I couldn't figure it out until I put it on jack stands and watched the vibration at the rear end. The yoke in the rear was bent. It would vibrate hard at 35 to 40 but go away to a buzz above 50. It was a very slight bend. I couldn't see the difference until I removed it after watching it moving on stands. Ganderie I think your is not the same and probably not a good idea to run it on stands. I didn't like running mine that way and it was not violent shaking.
 
Last edited:

edpdx

Member
743
7
18
Location
Oregon
The driveshaft once it starts to vibrate becomes worse and worse. Mine felt wrong about 20 miles into a 350 mile road trip home. I squeezed the last hundred miles, but made it home. It was the u-joint at the differential. I had replaced it less than 2 years back, but I hosed the pinion yoke trying to get the u-joint out- so the driveshaft became unbalanced. I got on it with a hammer and calipers to get it pretty close. I know I'll have to replace it with a new one though.

My M1009 had similar probs, vibrating and rattling in a bracket between 35 and 50 or so. I replaced the Harmonic Balancer- everything was great for a while, but I had vibration a few months later. The only thing left to try was the IP pump. Replaced it for about $1600. The last two were unrelated, but either may be your problem.
 

MarcusOReallyus

Well-known member
4,033
84
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Location
Virginia
I have a 1986 M1008
No you don't. You have a 1984 M1008. It doesn't matter what year it was built - it's a 1984. The Army didn't want the logistics nightmare of trying to keep parts for different years in stock, so all CUCVs have 1984 parts. You'll drive yourself nuts if you try to buy parts based on a 1986. Most will be fine. Some won't.
 

cucvrus

Well-known member
8,468
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Location
Jonestown Pennsylvania
Z3K_otfo5oyC V Joint adapter.JPGOn an M1009 the rear U joint needs the C clips attached to the trunnion caps to keep the U joint centered on the differential Yoke. No one is that good that they center that U joint tighten the bolts to keep it there. Keep that in mind. I have fixed a few that the drive shaft came loose, came off and just disappeared magically at highway speed. The disappearance was on a lifted m1009 and it was nasty on the exhaust, wiring and frame rail flanges. It was lost but not forgotten. It left it's mark. Also keep the front CV joint greased. That has been an issue on 2 plow trucks in the past week. 1/2 an hour saves a lot of destruction. Special grease gun attachment needed. Good Luck. Have a Great Day. Stay Safe and Warm.
 
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