M1031 vibration when stopped

[TechnoWeenie]

OK, I picked it up, and noticed a vibration at all RPMs, suspected the harmonic balancer, so I checked, and sho nuff, it was wobbly..

Replaced it, and the vibration went away... for a bit... I now have probably 200 miles on the replacement balancer.

Now, at idle, in anything BUT park, and NOT moving, the truck feels like it's gonna shake itself apart... just above idle and it smooths out.. in P it smooths out, even at idle.. It's not a loping idle, or low like it's gonna miss... and it just started... The balancer looks good (as a brand new one should), and there is no wobble.

I did notice the lines to the power steering pump violently shaking, but everything looks bolted down/secured properly.

I did also notice that the power steering lines were burning hot, even after just a 5 minute drive... hotter than the coolant lines... whereas on my previous CUCVs they were warm to the touch, but not burning hot.. Dunno if it's related or not...

Thoughts?

 

[the skull]

Check your p/s pump and bracket. Mine was loose and was so loud
at idle you couldn't hear yourself think if you were in front of it. It had
1 nut missing on the bracket and 1 bolt holding the pump to the bracket.
After the repair, she's so quiet you can actually be under the hood while
it's running now.

 

[Drock]

Check your belts, loose belts slipping, or flapping around can also cause vibration.

 

[Recovry4x4]

I will offer 2 thoughts or things to check. Motor mounts can break down and you end up with the clamshell sitting on the frame. Secondly, the idle might be set too low. I find this alot. I enlist the services of soldier "B" and adjust the idle while in gear. Success rate on idle adjustment has been 100%.

 

[acesneights1]

What kind of Balancer did you replace the old one with ? There are a few horror stories floating around DP about the chinese made Dorman stuff. I personally will only use Fluidampr . I'd check that again. Also check the flexplate. They are known to crack. You could be missing a TCC bolt.

 

[TechnoWeenie]

I just noticed my gen1 light is flickering, and goes away when you hit the gas...

Methinks the idle may be off a bit.... Probably contributing, but not the sole cause.

Will work through the list of things you guys said to check.

Thanks.

 

[K9Vic]

I will offer 2 thoughts or things to check. Motor mounts can break down and you end up with the clamshell sitting on the frame. Secondly, the idle might be set too low. I find this alot. I enlist the services of soldier "B" and adjust the idle while in gear. Success rate on idle adjustment has been 100%.

Agreed on motor mounts, could be the issue. Idle may be an issue as well.

As for Harmonic Balancer, the Precision ones are made in Australia and are good. Been using those for years with no issues. Do not buy a balancer made in Asia.

 

[m1008chevy]

Can raising the idle have any negative effect on the transmission? I also have rough idle, but in my case it doesn't matter what gear I'm in.

 

[acesneights1]

Idle is not something that generally needs to be messed with. If it's idling rough, there is probably a reason for it.

 

[TechnoWeenie]

Well, I found out what it was....

So, you know there's FOUR bolts that bolt the power steering pump to the power steering pump bracket?

Wanna guess how many I had in there?

I'll give you a hint... It's less than 1...

opcorn:


Friggin awesome that it actually RUNS, and WITH power steering, and the alternator charging (mostly), with ZERO bolts holding the pump in there...

I have to remove the pump, remove the pulley, remove the bracket, bolt it back together, then reinstall it..

So... I'm just gonna replace it....

It's 30 years old. If I'm going through all the trouble of pulling it off, might as well put a new one in its place.

 

[scottladdy]

Glad you found it. When I picked up my M1008 I drove it almost 1,000 miles to get it back here. On detailed inspection I found only 1/2 the requisite number of bell housing bolts holding the transmission to the engine and they were grade 3.

 

[Recovry4x4]

The deuce is worse but still, the CUCV has a wierd harmonic vibration when the idle iis sub 800. Since bumping all of mine up to just above 800, I have had zero bracket failures and zero bolts loosen up. It's not from a rough idle but to calm the harmonics.

 

[the skull]

Well, I found out what it was....

So, you know there's FOUR bolts that bolt the power steering pump to the power steering pump bracket?

Wanna guess how many I had in there?

I'll give you a hint... It's less than 1...

opcorn:


Friggin awesome that it actually RUNS, and WITH power steering, and the alternator charging (mostly), with ZERO bolts holding the pump in there...

I have to remove the pump, remove the pulley, remove the bracket, bolt it back together, then reinstall it..

So... I'm just gonna replace it....

It's 30 years old. If I'm going through all the trouble of pulling it off, might as well put a new one in its place.

That was like my experience as well. I put the old pump back on.