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Front end rattle

Enter Hummer

Well-Known Member
Messages
244
Location
Southwest
Ok so I picked up a new metallic rattling/rubbing noise when I go over 30mph. It is definitely coming from the front end. I thought it was my front driveline, so I took that off and noise gone. So today I got new joints on both ends of the driveline and put it back on the truck and when I took it out for a ride the same noise came back.

Awd = noise
2wd = no noise

Nothing is visibly wrong with the driveline (no bends, scrapes, gouges, or dents). I drained the front diff fluid ~ 500-700 miles ago and all looked good. Another interesting note is noise only happens while coasting and braking, not when applying gas. Noise also doesn’t change with speed, it’s just a consistant fast paced noise. What do you guys think this is?

And I don’t know if this relates but I found out my engine mounts are also bad today, that wouldn’t make a rattling noise when coasting would it?
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
Well, if your engine mounts are bad then your engine is shifting position when torque is applied and it's in a different position when coasting. That's a very likely culprit.

And pardon me, I don't know your H3's history, but do you have a different transfer case and front end setup? You mention 2WD and H3s don't have that option unless they have had lots of parts thrown at them.
 

Enter Hummer

Well-Known Member
Messages
244
Location
Southwest
Well, if your engine mounts are bad then your engine is shifting position when torque is applied and it's in a different position when coasting. That's a very likely culprit.

And pardon me, I don't know your H3's history, but do you have a different transfer case and front end setup? You mention 2WD and H3s don't have that option unless they have had lots of parts thrown at them.
I will order new mounts tonight and let ya’ll know what changed. What I meant by 2 wheel drive was I removed the front driveline and locked the transfer case, making it 2 wheel drive.

Heat shield or front diff pinion bearing. Either way...crank the stereo and ignore it until it explodes.
Will look at the heat shield and blast my stereo, gotta show these junker chrysler 300’s what a real sound system is like lol
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
That’s pretty much the same troubleshooting method I use.


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I did that a few times. Once, I ended up coating the underside with Dexron VI while I left pieces of the transfer case on the highway. But I did make it to my destination!
 

4speedfunk

Well-Known Member
Messages
4,212
Location
Tardville
Yeah. If it ain’t broke...don’t fix it! You’ll get real poor and real frustrated if you start trying to track down every little noise under an H3.

Quickest fix is to crawl under it with a socket set and just start tightening every bolt you see. Skids, shocks, diff bushings, crossmember, rack, exhaust, etc...are all famous for rattles, pops, & squeaks. After that, ball joints, cv’s, control arm bushings, blah blah blah. It’s a mechanical symphony under there!
 
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Enter Hummer

Well-Known Member
Messages
244
Location
Southwest
Well something really weird happened today. I was driving in a parking lot and I turned the wheel almost all the way left with probably 1100 rpm and the truck shook like it was in 4wd! When I pulled into a spot I looked at and shook all the components underneath and nothing was loose, tires were torqued down, halfshafts were torqued down and everything looked fine. I drove home and it didn’t do it again.

On my trip home though, I swerved left and right pretty good, and when I turned right, the left ftont side made kind of a creaking/loose noise (sorry Im bad at explaining noises)

I jacked the truck up and shook the wheel, took the wheel off and visually inspected everything, put the wheel back on and everything looks fine, now I’m stumped. Is there a way to check the halfshaft without taking it out?

Does this sound like a problem related to my original purpose of this thread or different? No I haven’t got new engine mounts in, no skid plates are on, tires are weirdly worn (previous thing). I did notice the bushing around the torsion bar (where it connects to the LCA) was looking very old.

Other than a T-bar crank (23” high) the truck is 100% stock
 

Enter Hummer

Well-Known Member
Messages
244
Location
Southwest
Quickest fix is to crawl under it with a socket set and just start tightening every bolt you see. Skids, shocks, diff bushings, crossmember, rack, exhaust, etc...are all famous for rattles, pops, & squeaks. After that, ball joints, cv’s, control arm bushings, blah blah blah. It’s a mechanical symphony under there!
I will torque all those down tonight
 

RamRod

Well-Known Member
Messages
3,914
Location
AB, Canada
Perhaps your x-case plastic shift fork has worn (common issue) and it slipped into 4hi lock for a short bit?

What would be the test to verify this?

The good news is there is a metal one available to replace the plastic one if it comes to that - I bought one 3 years ago just in case and haven't needed it yet thankfully!
 

Enter Hummer

Well-Known Member
Messages
244
Location
Southwest
I had the GM dealership (they’re a pretty good shop) install a new transfer case last june/july so either they screwed something up or thats not the issue. I have an appointment next monday for the HUMMER to get looked at by them. Will let you know what they have to say.
 

4speedfunk

Well-Known Member
Messages
4,212
Location
Tardville
I had the same symptoms when my t-case ate itself. However a bad CV joint can cause the same issue. You might check for sticking t-case buttons on the dash.

No codes sort of points to a “dumb” part...like a shift fork, cv, front diff, or sticking buttons.
 
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JPaul

Well-Known Member
Messages
2,400
Location
Way up north, UT
I think it's possible to still bind up the drivetrain when doing really tight turns at higher than wise speeds even in 4hi unlocked. Seems to be the worst when you're plunging the nose down and to the side with a really hard turn. Protip: just don't do that.
 

Traxx

Well-Known Member
Messages
682
Location
PNW
Sure it's not one (or more) of the body mounts popping? The things love to make random creaking and popping noises.
 

Enter Hummer

Well-Known Member
Messages
244
Location
Southwest
I tightened all them down yesterday and the creaking is still present. Since I posted this thread the original rattle has gotton worse (I can hear it at 15 mph and now has a very slight vibration) and also the creaking developed a slight vibration. Also when I am doing 15 mph I can hear the rattle weather I’m braking coasting or on the gas.

So far I have:
Torqued all body mounts
Torqued both shocks
Double checked that the tires are not loose
Froze my butt off
Grabbed and shook everything in the front and nothing is obviously loose

This weekend I will:
Check heat shields
Check sway bar and bushings
Check transmission crossmember
Check steering rack bushings
Torque front crossmember
Drain front diff fluid (look for metal shavings)
Will spray WD40 (unless there is something better) on all the bushings to see if that makes it quiet

Monday it’s going in to GM for new motor mounts and I’ll have them look at it unless I find the problem before then.
 
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Enter Hummer

Well-Known Member
Messages
244
Location
Southwest
Ok so I got new motor mounts installed today! So here’s some good news, and some tragic news...
Good news is they know without a doubt what the problem is, bad news is its the front diff :gaah:
So I guess I will ride this one out ‘til it’s done, then upgrade to the cast iron diff (with a locker :) ) so not all is lost. They are a direct swap correct?

Does anyone got any good recommendations on where to get a new diff?
 

4speedfunk

Well-Known Member
Messages
4,212
Location
Tardville
Yes direct swap. Your best bet for a cast iron, locked diff is from a wrecked 09-10 H3. It won’t be “new” but you can freshen it up and swap it in for much less than the cost of a brand new one. All 09-10 Adv Paks will have the ci locked diff.
Brand new front lockers and the cast iron case are only available from GM ($$$$). Not sure if you are L5 or V8 but you must use the correct ratio.
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/382263116630
 
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Enter Hummer

Well-Known Member
Messages
244
Location
Southwest
Thanks 4speed, my truck is an ‘07 lux so I have 4.56 gears. I might shop around a little but if thats as good as its going to get, then thats what i’ll do.

When GM called and told me the diff was the problem, he told me that GM doesn’t really make “new ones” and had to source parts. He told me that would be entering the $4000 range. No thanks! I would much rather pay half that for CI with a locker.

Thanks again everybody for all the help
 

RamRod

Well-Known Member
Messages
3,914
Location
AB, Canada
If you are planning on running this til is breaks, just make sure you have the right tools on had to deal with the break (so you can get home)

Or get a membership to one of those clubs/organizations that includes towing so you don't end up paying too much!
 

rascole

Well-Known Member
Messages
2,580
Location
Bellflower, CA
I would at minimum remove the front drive shaft and run it 2wd so you don't destroy your T case. How much is it to rebuild your existing diff?
 

4speedfunk

Well-Known Member
Messages
4,212
Location
Tardville
I rebuild a lot of H3 diffs, and a typical fresh-up (new bearings, seals, setup) runs around $450. That’s assuming all of the internals are intact. That is also “axle on the bench” price. Pulling one out & reinstalling it is a couple hours additional labor.
Big ticket items like lockers, gears, and broken parts would also be additional. Usually they have minor wear, or they are totally smoked...not much in between.
 

4speedfunk

Well-Known Member
Messages
4,212
Location
Tardville
Also, you can easily diagnose diff problems by giving the yoke a feel, and pulling the cover to take a look. The drain plug is magnetic, and it will tell you if something major is going on. Fluid is cheap. Checking the magnet takes five minutes, a 3/8” drive rachet, and a drain pan.
 
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