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Discussion Starter #1
Driving the past couple of days I noticed a distinct vibration. It is not jarring but is definetely enough to annoy. The most noticalbe time is when I first dirve the truck each day. Usually a couple miles to the highway and after a mile or so about 60-65 MPH the converter locks and I feel/hear a vibration immediately. It disipates when the load is removed but is present cruising and accelerating.


I tried it in T/H and noticed in most of the gears. I checked my fluid it was maybe a pint low but when filled it didn't make any diff. I question the level, after 20 Mi. on the highway tranny temp about 140-145. If does seem to lessen when warmed up but is still present. I am off to the dealer Monday to have my PS windshield leak fixed
and will have them look at it.


I had noticed a vibration previously when in T/H only and only between 2000-2200 RPM (early fall) and around Christmas when in 4WD at 55+MPH and am now wondering if they may all be related. Any input/experience would be appreciated. Thanks in advance for any replies.


MikeEdited by: HisDMAX
 

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Mine comes on very very slightly in T/H between 50 and 55, 4wd right at 60. I have an appointment next Saturday. Mine is an 01, but the problem sounds about the same. I'll let you know what they find if yours isn't taken care of on Monday. Would appreciate it if you'd let me know what they have to say on monday.


Thanks,
 

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The 01's had problems with lose bolts ... Mine had one that was finger tight ...


With the 03 has revised TC bolts .... Good luck Mike let us know what happens ....





Mac
 

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Thanks for the info on the 01. I'll be checking the bolts this afternoon.
 

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Discussion Starter #5
I took it to the dealer to listen to the trans. and at least they fixed the windshield leak. Of course I don't really know because the last thing we are going to see is rain at 5-10 degrees!!



Anyway, the tech drove my truck and didn't hear anything. Service writer wanted to drive and listen himself and takes the diesel tech with him. "nothing out of the ordinary" heard. The writer did check for TSB and GM and there are no others experiencing what I am and he said it is documented if it becomes a prob. I guess because 150 others don't have the same issue and there is no TSB then it isn't a problem????


I questioned if it was just me but it isn't!! I put the truck in T/H and I hear this noise just when the TC locks at about 1800 RPM it does seem to disipate when the RPMs are higher 2300RPM. The only time I notice it when not in T/H is once the TC locks until 70+ MPH (the majority of my highway driving). In the truck it almost sounds exhaust related but it correlates way to much with the TC.


I drove around in T/H letting it shift from 1st to 2nd to 3rd. Going from 2nd to 3rd is when notice a slight fluctuation in RPM and hear it start. It is bugging the heck out of me.
It seems to respond to load when in 4wd the other day it was quite noticable. I will fill my dump trailer with rocks or something this weekend and I am almost sure it will be louder.


Rant over! What is the chance that I can get a tech/service writer to accompany me some time? A snowballs chance in...... bad analogy.... but you know what I mean!!! Any thoughts?


Mike
 

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I have the same problem with my 03. Vibration comes on about 50 mph and goes away at about 70 mph. Is much worse in 4wd and like you said it goes away when I let off the throttle. So far I have balanced and rotated the tires with no effect. The dealer has had the truck on two seperate visits and has checked tires, driveshafts and torque converter bolts. They can't figure it out. On monday they are going to try swapping parts out with a new truck. I will post thier findings. My suspicions are that it is the front diff or driveshaft. Would you describe your vibration as like driving over small rumble strips?
 

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My 02 does the same thing. It started in the Spring last year, and vibration comes on from 55-65.
 

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Ditto my 01 complete w/ suncoast TC.


I don't think the TC causes the vibration, I think it is related to the front diff, only because is gets louder when in 4 wheel drive. The TC locking may transmit more of the vibration though the body of the truck but I think it is coming from someplace else.


My only thought is tire pressure, the front of the truck weighs almost twice as much as the back, yet I think my tire pressure is the same all the way around. Front tire diameter is probably significantly smaller.


Would this cause gears in the transfer case to bind slightly?


Just a guess.
 

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I think the theory of the transfer case binding slightly could hold true in 4wd. In 2wd however the front and rear wheels should be isolated from one another.


I think it is something to do with the front diff. as well. The fact that it is worse in 4wd points to the front end. Along with the diff, front axles theory maybe it could be a front wheel bearing problem.
 

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MIne has the same vibration... but only with the juice installed... I took out my juice, and after a few days the vibration was gone.... Put back in the juice, and after 100 miles, it was back..... Are any of you guys adding power?
 

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Discussion Starter #11
I am going to just run mine with a load this weekend and see what happens.


403 - The dealer was instructed to check the turbo bracket to see if it was cracked after "calling Detriot" (Oh man it sounded so official!!! Bear in mind his quoted comment was in the same breath when he "reminded me" of the satisfaction survey and it's importance LOL). Anyway, it is worth checking. As I have said it does have a sound like it could be exhaust related but on a cold morning like today at 0 degrees, hit the highway and when the TC locks there it is!


I'll monitor it. If it keeps up maybe a 4" Banks system might help neutalize it
.





Mike
 

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With the front dif, in 2wd, the front shaft is stationary and the outer axle shafts only spin the spider gears inside the carrier assy.

I don't see where that would do anything noticable unless you have something wrong with a wheel bearing or CV joint.
 

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Yes, it sounds a bit like going over rumble strips. Not quite as bad though. I do not have any of the power chips, completely stock. I'll be at the dealer at 0800 tomorrow. I'll let you know what this one says. I already have it arranged to have the tech take a ride with me so I know he'll get to hear/feel it.
 

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Ok, took mine in this morning. I took the tech for a test drive to make sure he knew what noise/vibration I was talking about. As soon as I hit 60 in 4H it started. he said he was pretty sure what it was, and he was correct, as the shop had taken care of sevrral with teh same symptoms. The front diff pinion torque was almost double what it should be. The bearing is now bad and has to be replaced and the T/C front output shaft bearing is starting to go. This is not a problem unique to mine, he has seen it on several others. I'd say have your tech drop the front driveshaft, and check the pinion torque and bearing. Good luck.
 

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Oldman did you have this noise even when not in 4WD?


Being the front diff pinon it should only be turning when in 4WD. Mine is more noticable when in 4Hi but also when its not, and it does seem to be worse when TC locked.


Just trying to convince myself that we have the same problem before I tell the tech to rip off the front axle @ $68 an hour.
 

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I have heard the noise in 2WD. You're right, it should not be there if it's coming from the front diff. I never really paid much attention to it, it may have been just after coming out of 4WD. I have to wait a week for parts to get up here - can't believe they've had this problem with other trucks and don't have the bearings and seals in stock!! Anyway, I'm not headed out again today but I will check tomorrow and let you know what I find.
 

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The dealer had another look at my truck today. (4th trip) They are still not sure what is causing the vibration but have heard of the problem. They are still waiting to hear from GM on a possible cause. I mentioned what your dealer found Oldman about the front pinion bearing. They are willing to try changing the bearing on Tuesday. I will keep you posted if this turns out to be the cause. It looks like it is a difficult problem to troubleshoot as there are so many possible sources of vibration.
 

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The dealer is done troubleshooting. They went through a process of elimination until nothing was left but the engine and the tranny. With the truck on the hoist and no driveshaft hooked up they had a vibration at 1900 rpm. This was in more than one gear but not sure which ones they checked. It sounds like at this point they disconnected the tranny and the engine ran vibration free. When I take it in next they are going to check for obvious causes in the tranny. It was indicated though that they don't actually fix the Allison's, they are replaced. I'll let you know how that goes.
 

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The early Ally has had failures at the stator support bushing(where the input shaft come out the front of the trans). This in turn will prematurely wear out the pilot bushing on the input shaft where it mates to the intermediate shaft. This can cause a converter shudder. I have not felt this in a truck yet and have not had anyone complain about it yet. The new stator bushings are teflon coated. The are the only ones i have seen on my customers trucks. I now have an Ally core donated by TTS and it's an early '01 and it has the early bushing and it's totaly worn out. This unit must have had a converter shudder.
 

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The vibration was there in 2WD but not much at all. An inspector is comiong by the dealership today to see if they will rebuild or replace the T-case!
 
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