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Transfer Case Slipping Under Power?


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Since I've owned the truck,, if you brake torqued it extremely hard, it would make a sound like an exhaust pipe banging on the frame or a broken motor mount that is wrapping up. I always thought it was my exhaust banging on the crossmember. Since I don't drive my truck like that it wasn't much of a concern. Well this past year after fixing the trans and leaning on the tune, I realized that noise was actually the transfer case slipping under heavy load. Basically, it sounds like the chain is jumping the sprocket. Where I noticed it most was if I tried to stomp it from dead stop. Usually, it would rap a couple or knock a couple of times as it took off. Well it got worse to the point that I could hardly even take off (normal) without it skipping. I swapped in another transfer case (30,000 mile unit) and it was driving normal again. Well maybe 10-20,000 later, it's back and getting worse. I've been noticing it a lot since I picked up the power this past few months (went from 12.60's to 12.20's) and with the cooler air. Just stomping it in 1st will usually make it pop away a few times as it takes off. A dead dig is horrible. Same noise, so I have to assume it's that damn chain again.

 

I'm just surprised I've never seen a post on here like this?????????? There are a lot of faster guys on here, some with even heavier rigs then me. What gives?!!!

 

P.S. One good point that I learned while dealing with these problems was that the back half of the t-case bearing pocket tends to wear out on these vehicles prematurely. In other words, you get a leak (usually) because the pocket where the rear output bearing goes gets oblonged or egg shaped from the constant stress of driving the front shaft. Basically the chain driving the front shaft is trying to pull the two shafts together constantly (AWD units anyways) and this tends to wear out the case half as a result. That happened to me and it got so bad that I couldn't get the rear seal to quit leaking even after replacing the bushing and seal and yoke. Makes sense if you think about it. I pullled the seal out and you easily see and move the shaft around in the bore and see the play.

 

Obviously, this play is going to bring the two shafts closer together which means the chain will get some slack in it. Add chain stretch and wear and I could see where I"m getting this skipping concern.

 

Anyone else experience this? A friend of mine that does axles and trans for a living initially pointed this out to me and sure enough he was right. He says he sees it all of the time (even on stock vehicles) and usually at 70-80K miles on up. Case halves aren't cheap either!

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Well, definitely a different noise then. Mine is dependent on the vehicle moving under heavy load. Yours may very well be the exhaust. Noises suck to isolate sigh.gif

 

Dude mines making the same noise! I always thought it was my exhaust as well. But where my story differs is that my truck only makes that noise at idle :question:

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I dont want to say this....but I think I have heard the same type of noise at milan, sounded like the exhaust was hitting on the drivers side, dont think much of it b/c I have headers and am loading the piss out of her at launch.

 

I know your truck has picked up a ton of power in this weather. I wonder if a new chain/rebuild would help?

 

Who is your axel guy? [email protected] detroitgear box?? I would love to figure out a high HP transfer case so guys could keep AWD when they get in the 1K HP range (chase comes to mind)

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I guess I am just "lucky" on this front as I still have the stock T-case (50K miles) and have had no issues with more power than most have thrown at it. The Questions I have are what fluid are you using, how often do you change it and how long have you been using this fluid?

 

Are you totally sure it isn't a U-joint?

Edited by Krambo
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I bet it probably is. Mine has done it since day one (i want to say I had 68,000 mile on it when I bought the truck). It didn't really change much until I beefed up the trans and went with a higher stall (it had a tb converter). When I cranked up the tune, it became an issue---lol! I launched it a couple of times in the last couple of days (2/3 3/4 throttle) and it is starting to sound like a ratchet --- lol!

 

Definitely, a combination of chain stretch, some sprocket wear I'm sure and maybe even some wear in that bearing bore. I'm going to rebuild this one in the next few months or sooner if it makes me --- lol!

 

Yes, Rich---he is excellent and willing to help out with whatever needs a guy has.

 

I dont want to say this....but I think I have heard the same type of noise at milan, sounded like the exhaust was hitting on the drivers side, dont think much of it b/c I have headers and am loading the piss out of her at launch.

 

I know your truck has picked up a ton of power in this weather. I wonder if a new chain/rebuild would help?

 

Who is your axel guy? [email protected] detroitgear box?? I would love to figure out a high HP transfer case so guys could keep AWD when they get in the 1K HP range (chase comes to mind)

 

 

I'm truly jealous! There have been a few occasions in last few days where I was really wanting to launch it with a nice 4 wheel spinning launch, but restrained myself in the interest of getting a few more months out of the t-case..... I bought this t-case used. I think it came out of an escalade (stock) and had 30+K miles on it. I just installed it with a new seal and gm fluid (Manual trans fluid). It's been in there probably 15k.....It has new joints in the back and the fronts were good. No binding or looseness. The rears weren't loose either, but were binding and when I took them apart they were dry and brinelling.

 

I guess I am just "lucky" on this front as I still have the stock T-case (50K miles) and have had no issues with more power than most have thrown at it. The Questions I have are what fluid are you using, how often do you change it and how long have you been using this fluid?

 

Are you totally sure it isn't a U-joint?

Edited by slowfive0
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Oh for god sakes --- LMAO! Ok, the driveshaft felt notchy when I rotated the joints (d/s out of car) so I pulled the caps and they were FUBAR! crackup.gif

 

But they were brinelled.... closedeyes.gifblahblah.gif

 

I personally like "FU*@#$ UP". I think it gets the point across better, but I was trying to be professional as it was......Thanks for the +1!!! smoker.gif

 

+1 to you.

brinelling....learned a new word today, thanks :)

 

you must be a forensic auto mechanic :)

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  • 2 weeks later...

you said you swapped from an escalade? didnt think they used the same transfer case did you happen to know the model number on the case your currently running?

 

 

I am pretty sure the 03 Escalade is the same unit. RPO codes for the Escalade are NP3 (NVG 149, BW 4473) or NR3 (BW 4476, 4481). So if the escalade was a NP3, it should be the same case.

 

With the change of company names, alot of the prefix's have changed as well. I have seen 3 prefix's for the same transfer case... NP (New Process) NV (New Venture) or NVG (New Venture Gear). There are even spots in GM service manuals that reference the NVG and the next line reference NP. I believe the key is to look at the suffix of the number (149).

 

So, I think the Denali, Escalade and GMC sierra C3 all share the NVG-149 case, depending on years.

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The 2001 / 2002 Yukon Denali and the 2002 Escalade used the NVG-149, while all later model SUV’s used the BorgWarner units. The trucks on the other hand did use the NVG-149 in the 2001 Sierra C³, 2002 thru 2007 Classic Sierra Denali and of course the 2003 thru 2005 ½ Silverado SS.

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  • 10 years later...

Hi Guys,

I am on my 4th transfer case ( new process 208 ) I have a 6in lift ,35 in tires 4.56 gears with lockers , it has a turbo 350 in front of it. Now on to the problem, every time I put it into 4 wheel drive ,I hear the a strange noise coming from the trans cases- clunk,clunk-clunk. So I pull the trans case apart and most of the teeth are chipped off the main shaft.

So what are your thoughts on this problem, 4 cases in three months. I have checked all the angles on the drivelines and they are in speck , this is enough to drive me nuts.

Any help from someone that has experience in these things would be great, cause I am about to scrap this truck

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  • 1 month later...

My '99 silverado 1500 4wd started making this grinding noise when I take off. Mostly just when under load or if I hit the gas too hard. Transmission is working good. I had it rebuilt a couple of years ago. The only thing I can think of it is the transfer case. I have talked to a couple of people and searched some forums. Maybe a slipping chain in the transfer case or I saw a post about some snap ring in the tail shaft breaking. Do you guys have any experience or thoughts about my truck?

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On 11/15/2021 at 10:58 PM, 88gmctruck said:

My '99 silverado 1500 4wd started making this grinding noise when I take off. Mostly just when under load or if I hit the gas too hard. Transmission is working good. I had it rebuilt a couple of years ago. how to test tcm duramax The only thing I can think of it is the transfer case. I have talked to a couple of people and searched some forums. Maybe a slipping chain in the transfer case or I saw a post about some snap ring in the tail shaft breaking. Do you guys have any experience or thoughts about my truck?

no response.

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