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#1411406 - 03/22/09 05:45 PM 99 k1500 suburban transfer case bad?
jstutz Offline


Registered: 10/06/08
Posts: 1487
Loc: NC
Guys i have been fighting grinding problem with my truck that i thought was the front diff. If i jack the truck up and put it in gear so the wheels are spinning freely in the back, the transfer case is making an awful racket. it sounds like it is in the front where the 4x4 shaft comes into it.Could this just be the bearing? it sounds like gears rattling around to me. I have drained a little fluid and didn't see any metal in it. it has been doing this for a while and is getting worse and worse. It looks to me that the case must be split to do anything in there is this correct? I dont know much about them so any help will be appreciated.

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#1411416 - 03/22/09 05:52 PM Re: 99 k1500 suburban transfer case bad? [Re: jstutz]
PT1 Offline


Registered: 02/06/07
Posts: 5746
Loc: near the mistake
Check the price of a rebuilt swap versus taking it apart. It may be cheaper. If you have the 4wd with auto-4wd then that unit has a clutch pack so it could be a lot of things. It should be an NVG unit but check with a dealer off your build sticker that should be in the glove box. Have you cycled it in and out of 4wd a few times?


Edited by PT1 (03/22/09 05:54 PM)
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#1411419 - 03/22/09 05:56 PM Re: 99 k1500 suburban transfer case bad? [Re: PT1]
jstutz Offline


Registered: 10/06/08
Posts: 1487
Loc: NC
yes it is the auto 4wd version. what does NVG mean. yes, it cycles in an out of 4wd like it should. there is just a racket around where the front shaft goes into it.


Edited by jstutz (03/22/09 05:57 PM)

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#1411423 - 03/22/09 06:01 PM Re: 99 k1500 suburban transfer case bad? [Re: jstutz]
PT1 Offline


Registered: 02/06/07
Posts: 5746
Loc: near the mistake
 Originally Posted By: jstutz
yes it is the auto 4wd version. what does NVG mean. yes, it cycles in an out of 4wd like it should. there is just a racket around where the front shaft goes into it.


NVG is New Venture Gear which is the GM/Chrysler joint venture company formed in the early 1990's to unseat Borg Warner from their monopoly on some manual transmissions. NVG is now owned by Magna and goes by Magna Powertrain. Probably a bearing if it is growling at you.
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#1411428 - 03/22/09 06:05 PM Re: 99 k1500 suburban transfer case bad? [Re: PT1]
jstutz Offline


Registered: 10/06/08
Posts: 1487
Loc: NC
i dont know if i would consider it a growl or not it really sounds like loose gears slopping around when it is jacked up in the air. when im driving it it sounds like a growl that is getting worse. do you have to split the case to change this bearing? it looks like it to me.

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#1411429 - 03/22/09 06:05 PM Re: 99 k1500 suburban transfer case bad? [Re: PT1]
PT1 Offline


Registered: 02/06/07
Posts: 5746
Loc: near the mistake
Your turck should have the NVG 236 or 246 Tcase. But check. The NVG 136 is the AWD model for 1999.
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#1412534 - 03/23/09 07:02 PM Re: 99 k1500 suburban transfer case bad? [Re: PT1]
jstutz Offline


Registered: 10/06/08
Posts: 1487
Loc: NC
Okay, The truck is at the shop and it is a confirmed bad Xfer case. it is the 246 model. He is evaluating now to see if he feels it will be cost effective to try to fix it or just get a rebuilt. it looks like i can get a rebuilt for 1k. God i had when vehicles throw a fit and start breaking stuff.

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#1415822 - 03/26/09 05:32 PM Re: 99 k1500 suburban transfer case bad? [Re: jstutz]
jstutz Offline


Registered: 10/06/08
Posts: 1487
Loc: NC
Well here is the problem. There is a bearing that is completely out and the shift fork is worn badly. Does anybody know what wears out of you use the wrong fluid in this case. It had dex 3 in it and auto trac is called for. Mechanic said the clutch plates looked really good and the chain looked good so i guess there is no reason to replace them.

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#1418096 - 03/28/09 08:08 PM Re: 99 k1500 suburban transfer case bad? [Re: jstutz]
jstutz Offline


Registered: 10/06/08
Posts: 1487
Loc: NC
anybody?

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#1418485 - 03/29/09 09:06 AM Re: 99 k1500 suburban transfer case bad? [Re: jstutz]
PT1 Offline


Registered: 02/06/07
Posts: 5746
Loc: near the mistake
DexIII will fubar an auto-trak Tcase in time but it's usually the clutch operation (which could explain the shift fork).
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#1418488 - 03/29/09 09:10 AM Re: 99 k1500 suburban transfer case bad? [Re: PT1]
jstutz Offline


Registered: 10/06/08
Posts: 1487
Loc: NC
thank you PT1. By the way i did not put the dex in there, it was in there when i bought it two years ago and what makes me mad is that the lady i bought it from showed me receipts for all shop work and the shop shows that they changed the xfer case fluid when they rebuilt the tranny. Why in the heck would a certified shop use incorrect fluids.

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#1418490 - 03/29/09 09:11 AM Re: 99 k1500 suburban transfer case bad? [Re: PT1]
PT1 Offline


Registered: 02/06/07
Posts: 5746
Loc: near the mistake
Do you drive the truck on dry pavement in "Auto" mode? If so here is what happens.

The AUTO feature was added for driver convenience so that the vehicle could be driven at highway speeds on varying types of road surfaces. With an ordinary transfer case, non-auto, driving on dry pavement while in 4WD is not recommended due to the severe stress placed on the drive train. As with a basic transfer case, the NVG 246 should not be driven on dry pavement in 4HI or 4LO, but AUTO may be used on any road surface. The AUTO mode was indeed designed for highway use, whereas either 4HI or 4LO should be used while off-road.

What makes the AUTO feature unique on the NVG 246 and other GM AUTO type transfer cases is the use of a clutch pack. The clutch pack is a stack of steel plates and fiber discs such as those found in an automatic transmission clutch pack, the difference being that the transfer case clutch pack is applied with a motor-driven lever rather than hydraulic apply. The clutch pack is modulated by the transfer case motor, based on commands from the transfer case control module (TCCM).

The TCCM monitors two speed sensors, one at each output shaft, front and rear. When in the AUTO mode, the TCCM can fully apply the clutch pack within 200 milliseconds to drive the front prop shaft in accordance to rear prop shaft slip. When the AUTO mode is selected, the TCCM commands the front axle to engage and the axle remains engaged while AUTO is selected. In the AUTO mode if no rear drive slip is detected, the TCCM does not apply the clutch pack and the transfer case operates as it would in 2WD, with only the rear output shaft receiving torque.

In the AUTO mode, if the rear output shaft speed increases at a higher rate than that of the front output shaft, the TCCM takes action by commanding the transfer case motor to apply the clutch pack. The TCCM modulates the clutch pack via the transfer case motor, until the rear shaft and front shaft speeds are equal, at which point the motor reverses and releases the clutch pack. The duration and force of application of the clutch pack varies with demand. The motor and lever have the capability to apply the clutch pack with a 2,600 psi force.

Problems with the system show up most often when the vehicle is driven in the AUTO mode, and all four wheels are not of equal rolling circumference. It is of utmost importance that all four tires remain equal with any 4WD vehicle, but is most critical with vehicles driven on dry pavement while in the AUTO mode. If one or more tires has unequal pressure or wear or has a defect in sidewall construction, then its rolling circumference will not match the others. This inconsistency will then cause the TCCM to continually cycle the clutch pack on/off in an attempt to compensate for the perceived slip. This repeated cycling overheats the clutch pack and transfer case fluid, resulting in clutch pack and/or transfer case failure.

To verify that the tires have equal rolling circumference: 1) Check and adjust air pressure of all four tires to specification. 2) Check and verify that all four tires are of equal wear. 3) Mark all four tires at 6 o’clock with a chalk mark. 4) Drive the vehicle straight ahead for 10 revolutions. 5) With one mark back at 6 o’clock, verify that the others are within one inch of 6 o’clock also.



Edited by PT1 (03/29/09 09:15 AM)
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#1418493 - 03/29/09 09:14 AM Re: 99 k1500 suburban transfer case bad? [Re: jstutz]
PT1 Offline


Registered: 02/06/07
Posts: 5746
Loc: near the mistake
 Originally Posted By: jstutz
Why in the heck would a certified shop use incorrect fluids.


1. they have a bulk tank of ATF which is cheap
2. too lazy to go to a GM dealer and buy the auto-trak fluid.
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#1418505 - 03/29/09 09:30 AM Re: 99 k1500 suburban transfer case bad? [Re: PT1]
jstutz Offline


Registered: 10/06/08
Posts: 1487
Loc: NC
wow, everything i wanted to know in one shot. thank you very much.

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#1418673 - 03/29/09 12:55 PM Re: 99 k1500 suburban transfer case bad? [Re: jstutz]
PT1 Offline


Registered: 02/06/07
Posts: 5746
Loc: near the mistake
No problem, when you get it back together drive it in 2wd mode unless you encounter poor road conditions. Also, check your tires as outlined above.
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