Hummer H3. Transmission or Transfer case?

[Hawkeye__8]

Hello, let me give you some background before I give you the heap of the problem. I have an '07 Hummer H3 base that Ive had since the summer of '08. She has close to 130,000 miles on it and has towed and made countless trips from Gilbert - Christopher creek Arizona. A few months ago the check engine light turned on, and naturally, we went to AutoZone so they could hook up their device to see what the issue was. Their computer said their was a malfunction with the TCC (Torque Conversion Clutch solenoid). Me and my father decided to change the transmission fluid and filter seems how it was due for a change anyway, we took off the pan and saw some deformed magnet with fine shavings along with many smaller shaving scattered across the bottom of the pan. We inserted the new filter with new fluid and also reset the engine light. About last September the light came on the dash again and it was the same code as before, at about this time we figured were on borrowed time on this transmission anyway and we'd just drive on it. Last weekend we were motivated to look at the pan again after the axle that runs from the Transfer case to the from wheels seal blew. After replacing that part, we decided to do matinence on the truck We rotated the tires, changed the engine oil and filter, changed the transfer case fluid, replaced all spark plugs, and changed out the transmission fluid and filter again. Very time consuming.

Ok now heres my issue. Last night me and a few friends went to go get a bite to eat and were on our way home. I was traveling at a constant speed of around 35 MPH and in my hummer I have to push the gas pedal just a tad to keep it going the same speed. Anyway, we were cruising and i felt the RPM's climb slowly and heard this grinding sound each time i would try to give it some gas. I pulled over as quick as I could and there was a loud grind as i put it in park. Also their was noise when the thing was idling in park. Seems how I was so close to my house I wanted to either push it or drive it back, so I tried the various 4 wheel drive settings. 4HI allowed me to drive it the rest of the way back. It has been sitting ever since..

Any tips on what happened?

 

[alrock]

Could be either, but I bet this time you find some good bits in the fluid. I'm leaning towards a transfer case that has a stretched chain since the change in drive modes allowed you to drive again

 

[Hawkeye__8]

Thank you for the tip. I'll be trying diagnose the issue within the coming weeks. I'll post updates

 

[4speedfunk]

If you got TC solenoid warning lights and metal dust in the AT pan...that's a totally separate issue from any T-case problems. I'm not saying you don't have t-case problems, its actually very common at your mileage. But, if something looks like poop...smells like poop...its usually poop.

The grinding noise while idling in PARK is very concerning and it eliminates the t-case and axles from the equation. Unlike the transmission, there isn't anything spinning in the t-case while sitting still...and thus, there shouldn't be any noises coming from it. Same with the both axles. Once you put the transmission in PARK...the rotating parts are pretty much limited to the motor and the input (torque converter) side of the AT. The output shaft of the AT is motionless and everything downstream of it will be motionless. So if its sitting there making a grinding (rotational) noise in PARK...it has to be the motor or transmission. A loose chain in the t-case could continue to make a rattling sound from engine vibrations but, it would be not be "grinding" while the vehicle is sitting still.

I get a tad confused on your story after you stopped last night. Are you saying the truck would not move in 4HI-street? And you had to shift modes on the t-case to move the vehicle? If so...that points to a t-case or front axle problem. Your description actually sounds EXACTLY like the typical ring & pinion failure on the front differential...however, it would never grind while in PARK. So that's why I think it must be the transmission. However, an AT problem would most likely show up in any transfer case mode, and changing modes would probably not have an effect....so I'm stumped on that.

So where do you go from here? Hmmmm. Not sure. Go for a drive...next time it starts making noise...put it NEUTRAL while rolling at 35 mph...and see if the noise changes. Also try coming to a stop in NEUTRAL...and rev the engine up to 2500 rpms to see if there are any changes in the noise. Take notice to see if there seems to be any lag or free-spinning when shifting from forward to reverse. In the past...I've had AT's not want to engage into reverse, only to have them completely die within a week. Lastly...a good tranny shop can plug into your truck and probably do a rough diagnosis on it without tearing stuff apart. Amazing what they can tell from via the OBD port.

 

[Hawkeye__8]

Let me clear up the street situation. Wording was a little off about that, my bad. The truck acted up on regular 4 wheel drive. After a couple minutes of having a what in the world happened event, I decided to mess with the other setting (4HI) and that allowed it to drive home without any abnormal noises. I did not try 4lo. I was also able to back it into the garage so I can work on it when I have the time and money to look and work on it. And im on the same page with you on the tcc warning along with the little shavings in the pan.

I'm just curious on how I could drive it back on 4hi.

 

[reaper]

When you say 4hi, do you mean 4hi lock? (4hi is the normal driving mode). 4hi lock locks the front and rear. This explains it: if you were to remove the front driveshaft, you would go nowhere in 4hi, as all the power would just go to the front driveshaft that's missing. However, if you put it in 4hi lock (with a missing front driveshaft) you would be locking the front and rear driveshafts, and you'd be basically in 2wd mode.

SO... if that is the case-- if you can only drive in 4hi lock and NOT 4hi normal-- in 4hi normal you may be spinning the front driveshaft but may see that it's not spinning the wheels, which could be the front differential?

 

[Hawkeye__8]

Yes reaper, after that event I drove it back on 4 hi lock. Not on the 4hi normal driving mode. Your statement would be something I would think to be if I didn't hear something spinning while I was in PARK. Although, I will add this to the list of things that could possibly be wrong after we look at the transmission. Thank you for adding.

 

[MaxPF]

Isn't that a classic worn fork symptom?

 

[4speedfunk]

Usually, if you have to use 4HI-Lock to move the vehicle...its almost always a smoked front diff. This happens because 4HI-Street mode is variable output. It will always send the majority of the torque to the axle that is spinning. When you have a front diff failure (or remove the front driveshaft)...the t-case senses this as "spinning", and sends it 100% of the torque to the front axle. Of course this means the rear axle gets 0% of the torque. The result is: You just sit there and grind the front diff into powder. So to move the truck...you must over-ride the variable torque split, by using the 4HI-Lock mode. This sets the output at a fixed 50/50 and then you will get some power sent to the rear axle. Unfortunately...you are still sending power to the front (broken) but, at least you can move the vehicle and hopefully get home to repair it. I have driven over 100 miles with a broken front diff, and there won't be much left of it by the time you get home. Also because the IFS hubs are fixed...pulling the front driveshaft doesn't do much to help but, it might prevent damage to the t-case if the front axle decides to jamb up and explode.

If the t-case cycles easily thru all three modes, then I would assume the shift fork is intact and working. Also, I think most guys with fork issues also get some "Service 4WD" warnings on the dash, and they usually get "stuck" in one mode. But there can be other things wrong beside the fork. My t-case went totally bonkers at 42K miles and I never once got a warning light and I never once got stuck in a single mode! So, t-case issues aren't always real obvious.

Based on Hawkeye's description...I can't tell what the issue is. Sounds like he had to put the truck into 4HI-Lock to move it, and that's almost always a front diff issue. But the noises in PARK don't match that, nor does the previous AT codes and dirty fluid. It could be any number of things...Motor, Trans, or T-case. Its one of em.

 

[CaseyS]

If there is a broken front drive line component and with the vehicle in 4hi normal, and the trans in a forward speed, the output shaft of the transmission will turn sending motion to the corner with the broken component but no vehicle motion. With nothing broken, when you apply the brakes to stop, everything from the output shaft of the transmission through the drive line is all motionless. With a broken component and a turning output shaft, when you shift to park, the park pawl grinds on the moving output shaft to get engaged. The metal in the trans pan is likely part of one of those components. Try shifting to neutral, wait an minute and quickly shift to park I bet the problem goes away. Now to find the broken component in the front drive train.

 

[Hawkeye__8]

Usually, if you have to use 4HI-Lock to move the vehicle...its almost always a smoked front diff. This happens because 4HI-Street mode is variable output. It will always send the majority of the torque to the axle that is spinning. When you have a front diff failure (or remove the front driveshaft)...the t-case senses this as "spinning", and sends it 100% of the torque to the front axle. Of course this means the rear axle gets 0% of the torque. The result is: You just sit there and grind the front diff into powder. So to move the truck...you must over-ride the variable torque split, by using the 4HI-Lock mode. This sets the output at a fixed 50/50 and then you will get some power sent to the rear axle. Unfortunately...you are still sending power to the front (broken) but, at least you can move the vehicle and hopefully get home to repair it. I have driven over 100 miles with a broken front diff, and there won't be much left of it by the time you get home. Also because the IFS hubs are fixed...pulling the front driveshaft doesn't do much to help but, it might prevent damage to the t-case if the front axle decides to jamb up and explode.

If the t-case cycles easily thru all three modes, then I would assume the shift fork is intact and working. Also, I think most guys with fork issues also get some "Service 4WD" warnings on the dash, and they usually get "stuck" in one mode. But there can be other things wrong beside the fork. My t-case went totally bonkers at 42K miles and I never once got a warning light and I never once got stuck in a single mode! So, t-case issues aren't always real obvious.

Based on Hawkeye's description...I can't tell what the issue is. Sounds like he had to put the truck into 4HI-Lock to move it, and that's almost always a front diff issue. But the noises in PARK don't match that, nor does the previous AT codes and dirty fluid. It could be any number of things...Motor, Trans, or T-case. Its one of em.

Isn't that a classic worn fork symptom?

When you say 4hi, do you mean 4hi lock? (4hi is the normal driving mode). 4hi lock locks the front and rear. This explains it: if you were to remove the front driveshaft, you would go nowhere in 4hi, as all the power would just go to the front driveshaft that's missing. However, if you put it in 4hi lock (with a missing front driveshaft) you would be locking the front and rear driveshafts, and you'd be basically in 2wd mode.

SO... if that is the case-- if you can only drive in 4hi lock and NOT 4hi normal-- in 4hi normal you may be spinning the front driveshaft but may see that it's not spinning the wheels, which could be the front differential?

If you got TC solenoid warning lights and metal dust in the AT pan...that's a totally separate issue from any T-case problems. I'm not saying you don't have t-case problems, its actually very common at your mileage. But, if something looks like poop...smells like poop...its usually poop.

The grinding noise while idling in PARK is very concerning and it eliminates the t-case and axles from the equation. Unlike the transmission, there isn't anything spinning in the t-case while sitting still...and thus, there shouldn't be any noises coming from it. Same with the both axles. Once you put the transmission in PARK...the rotating parts are pretty much limited to the motor and the input (torque converter) side of the AT. The output shaft of the AT is motionless and everything downstream of it will be motionless. So if its sitting there making a grinding (rotational) noise in PARK...it has to be the motor or transmission. A loose chain in the t-case could continue to make a rattling sound from engine vibrations but, it would be not be "grinding" while the vehicle is sitting still.

I get a tad confused on your story after you stopped last night. Are you saying the truck would not move in 4HI-street? And you had to shift modes on the t-case to move the vehicle? If so...that points to a t-case or front axle problem. Your description actually sounds EXACTLY like the typical ring & pinion failure on the front differential...however, it would never grind while in PARK. So that's why I think it must be the transmission. However, an AT problem would most likely show up in any transfer case mode, and changing modes would probably not have an effect....so I'm stumped on that.

So where do you go from here? Hmmmm. Not sure. Go for a drive...next time it starts making noise...put it NEUTRAL while rolling at 35 mph...and see if the noise changes. Also try coming to a stop in NEUTRAL...and rev the engine up to 2500 rpms to see if there are any changes in the noise. Take notice to see if there seems to be any lag or free-spinning when shifting from forward to reverse. In the past...I've had AT's not want to engage into reverse, only to have them completely die within a week. Lastly...a good tranny shop can plug into your truck and probably do a rough diagnosis on it without tearing stuff apart. Amazing what they can tell from via the OBD port.

Could be either, but I bet this time you find some good bits in the fluid. I'm leaning towards a transfer case that has a stretched chain since the change in drive modes allowed you to drive again

If there is a broken front drive line component and with the vehicle in 4hi normal, and the trans in a forward speed, the output shaft of the transmission will turn sending motion to the corner with the broken component but no vehicle motion. With nothing broken, when you apply the brakes to stop, everything from the output shaft of the transmission through the drive line is all motionless. With a broken component and a turning output shaft, when you shift to park, the park pawl grinds on the moving output shaft to get engaged. The metal in the trans pan is likely part of one of those components. Try shifting to neutral, wait an minute and quickly shift to park I bet the problem goes away. Now to find the broken component in the front drive train.

Hey guys,

Tonight I'm going to go underneath the thing and swap out the old TCC for a new one. The engine light came on a year ago from it and if it works the cost is low or I rule it out. I will post the results tomorrow, may include pictures.

 

[Hawkeye__8]

First we unbolted the front drive-shaft to open up the bolts for the pan.

Some black shavings but nothing chunky.


*I tried uploading pictures showing the Valvebody and the location of the TCC was and I got a error message.

On the left in the old TCC and the right shows the pin along with the new TCC. I used a Fishing hook with a pair of plyers to wiggle it out.

We did start it up and she still runs fine on 4HI Locked and 4LO, but after we switched it to 4Hi and put it into D the spinning noise came back. Im more leaning toward 4speedfunks reply on the problem being a smoked front differential... If so it sucks because I just drained it and added new fluid..

 

[4speedfunk]

Its real easy to check for a smoked front axle:

Start it up.
Put the transfer-case in 4HI-Street mode.
Put the trans in DRIVE.
See if the truck will move forward.

After giving it some light throttle, and the truck still doesn't move (and you hear the spinning/grinding sound)...have someone look underneath to see if the front driveshaft (and input yoke on the front diff) is spinning. If so...it means something inside the front diff has let go. Its almost always teeth missing from the ring & pinion, or a broken axle shaft on the drivers-side (inside the tube) but, it could also be the spider gears inside the carrier. This type of failure is very common, and a diff rebuild is in order. You can pull the front diff cover to verify the damage...look for chunks or shavings inside it. The drain plug is magnetic, and when something inside lets go...it often looks like a steel Chia-Pet. I have acquired a pretty good stockpile of used AAM-7.6 parts parts if you need something. Let us know what you find.

For the record...H3 "front diff issues" outnumber "trans issues" at least 50 to 1. Both are expensive repairs but front axle problems are far more common. Based on that along with your symptoms...I think you might be looking in the wrong place. Just a hunch.

 

[Hawkeye__8]

I just replaced the front drive axel a just before I began having problems. The seal went and grease went EVERYWHERE. I'm going to hold off on taking off that bottom magnetic plug so that if I decide to bring it to someone to rebuild the front diff I can.

 

[4speedfunk]

I just replaced the front drive axel

Whats that? The entire diff assembly?

 

[Hawkeye__8]

No, sorry I was a little vague on that description. The driveline from the transfer case to the front diff is what I was trying to get at. Theres a seal at the transfer case end of the drive line that tore from age it seems. Maybe the new part put enough stress on the front diff to break it?

 

[Hawkeye__8]

Whats that? The entire diff assembly?

No no, just the front driveline that runs from the transfer case to the front differential.

I started up my H3 a few minutes ago to check and see if the driveline would turn in result of a smoked from diff... and it didn't spin. The same noise is still heard as soon as i change it into gear. Now I'm completely stumped on what the problem is, may just take defeat in DIY and bring it to a mechanic depending on if I find an answer within the next week.

 

[alrock]

Are you driving it now? Perhaps a second, non-paid opinion would help. I could meet you this weekend and we could do some troubleshooting together.

 

[andyzed]

Its real easy to check for a smoked front axle:

Start it up.
Put the transfer-case in 4HI-Street mode.
Put the trans in DRIVE.
See if the truck will move forward.

After giving it some light throttle, and the truck still doesn't move (and you hear the spinning/grinding sound)...have someone look underneath to see if the front driveshaft (and input yoke on the front diff) is spinning. If so...it means something inside the front diff has let go. Its almost always teeth missing from the ring & pinion, or a broken axle shaft on the drivers-side (inside the tube) but, it could also be the spider gears inside the carrier. This type of failure is very common, and a diff rebuild is in order. You can pull the front diff cover to verify the damage...look for chunks or shavings inside it. The drain plug is magnetic, and when something inside lets go...it often looks like a steel Chia-Pet. I have acquired a pretty good stockpile of used AAM-7.6 parts parts if you need something. Let us know what you find.

For the record...H3 "front diff issues" outnumber "trans issues" at least 50 to 1. Both are expensive repairs but front axle problems are far more common. Based on that along with your symptoms...I think you might be looking in the wrong place. Just a hunch.

I just went through this, I would listen to this advice. In my case the half shaft pulled out of the carrier while driving on the highway, once it got out enough it sheared off the remaining splines and wore out the supporting hole in the carrier. I drove it home in 4hi lock. Extensive driving will tear up the front diff more because you can't disconnect it from the wheels, it's spinning as long as the car is moving.





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[Hawkeye__8]

I just went through this, I would listen to this advice. In my case the half shaft pulled out of the carrier while driving on the highway, once it got out enough it sheared off the remaining splines and wore out the supporting hole in the carrier. I drove it home in 4hi lock. Extensive driving will tear up the front diff more because you can't disconnect it from the wheels, it's spinning as long as the car is moving.





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My dad decided to get it checked out on Friday at this shop down the road from where we live. It had free diagnostic so he figured why the heck not. It turns out that it was the driveline that transfers power from the transfer case to the front diff. This was the replaced driveline, the old one had a deal that cracked and spewed grease everywhere. There were cheers when there wasn't a grinding noise when we put the transfer case into 4hi!

 

[andyzed]

Glad to hear it worked out for you. I just got mine back on the road too.


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[Hawkeye__8]

Thanks for wanting to help me out alrock, I appreciate it. Just shows how great this forum is to help out people. I would've went forward on meeting you if I didn't have a friend tell me about this free diagnostic thing at some shop nearby. Great place.

 

[Hawkeye__8]

So guys all in all, the snapped driveline cause the gears to whine in the transfer case. This is what made the sound seem like it was coming from the transmission. Same thing happened to a friend of mine last week who reached out to me today (little late). The stock drivelines seal blew which made me get the faulty replacement. Just washed and detailed her so now all is good! Thanks everyone who gave suggestions and opinions!

 

[Hawkeye__8]

Whats that? The entire diff assembly?

No just the front drive axle, the old one had a cracked book and grease flew everywhere.

 

[Hawkeye__8]

So guys,

Its been a while since this has been updated, however the issue was that a part of the front drive axle that I REPLACED broke where the transfer case and drive axle meet. Went back to oriellys and swapped it for another one. Then the SECOND one decided to snap in the same location. Worked it out with oreillys and they found an OEM front drive axle for me and has been fine ever since.