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Username Post: 98 Tahoe NP 246 Transfer case Fill Plug        (Topic#266453)
Forum Newbie
Posts: 24

Loc: Wyoming
Reg: 10-26-09
07-20-11 08:46 PM - Post#2116322    

Anyone have suggestions as to how to remove the fill plug on the NP 246 transfer case. My 1/4" rachet is short and I tried to remove the plug but I fear the square hole is now round...

Is this why I've seen suggestions to replace the fill and drain plugs?

Forum Newbie
Posts: 24

Loc: Wyoming
Reg: 10-26-09
07-20-11 10:27 PM - Post#2116347    
    In response to archie1407

Really wasn't planning on replying to my own post but I've been doing some investigating. Here's what I've found:
GM Service Bulletin # 99-04-21-001

Use of Heat for Difficult to Remove Transfer Case Fill and Drain
Plugs #99-04-21-001 - (03/29/1999)
Use of Heat for Difficult to Remove Transfer Case Fill and Drain Plugs
1998-99 Chevrolet and GMC K1-2 Suburban, Utility Models

1998-99 Oldsmobile Bravada

with NV136/246 Transfer Case (RPOs NP4, NP8)

This bulletin is being revised to add the 99 model year and part
information. Please discard Corporate Bulletin Number 76-74-03 (Section

Some transfer case fill and drain plugs may be difficult to remove. In some
cases, the plug may be "rounded out" attempting to remove the plug. These
plugs are made of aluminum and have a 1/4 inch square hole designed to
receive a 1/4 inch square drive extension. Installation torque may have been
too high causing difficulty in removal.

To help avoid a fire, thoroughly clean the area around the fill and drain
plugs of grease build-up before heating and use only an electric heat gun.
DO NOT USE AN OPEN FLAME. If sources other than an electric heat gun are
used, the transfer case may catch fire and cause personal injury.

In cases where the plugs cannot be loosened, the use of an electric heat gun
may make plug removal possible. Heat should be applied to the case around
the plug, not directly on the plug, for one to two minutes. Use only enough
heat to loosen the plug. Also, fully insert the 1/4 inch square drive
extension onto the plug before turning the plug.

Do NOT use plugs made of steel or brass. These may cause a severe corrosive
reaction when in contact with the magnesium case, making future removal even
more difficult.

If the fill and drain plugs are damaged during removal and must be replaced,
use only aluminum replacement plugs. Replace the drain and fill plugs
(internal, square drive tool access design) with the EXTERNAL HEX DESIGN
plug, P/N 15032997.

When you install the transfer case fill or drain plug, tighten the plug to
20 N?m (15 lb ft).

Parts Information

Plug, Transfer Case Oil Fill

Senior Member
Posts: 3768
Loc: Northern MN
Reg: 10-27-04
07-21-11 06:06 AM - Post#2116399    
    In response to archie1407

I have done this before but complete forgot what the plug looks like. Is it the same as a 3/8 racket but you are saying the end isn't long enough to work? Could you use a 3/8 drive extension to reach?

98 Silverado k1500 4x4 350

Posts: 28656
Age: 48
Loc: Texas
Reg: 08-01-03
07-21-11 06:01 PM - Post#2116599    
    In response to 355Cheyenne

Haven't had to mess with one of these transfer case plugs myself, but if it uses a square drive plug, there are actually sockets meant for this job that work a lot better than a ratchet or extension. Typically referred to as pipe plug sockets. Can sometimes be difficult to find but make tight plugs easier to remove without stripping them out.


06 Silverado ISS / 06 Silverado SS / 06 300C SRT8

Forum Newbie
Posts: 24

Loc: Wyoming
Reg: 10-26-09
07-22-11 07:55 PM - Post#2116969    
    In response to someotherguy

Thank you...The square in the plug is 1/4". I tried using a "regular sized" 3/8 rachet with a 1/4" adapter...and broke the adapter from my allied tool set I got in high school 22 years ago. Will give it a go this weekend. I thought they made a socket for this kind of plug...local o'reilly and autozone didn't have them.

Forum Newbie
Posts: 24

Loc: Wyoming
Reg: 10-26-09
07-22-11 08:11 PM - Post#2116971    
    In response to 355Cheyenne

Sorry about not being too clear. When I put the 1/4 rachet in the square it was perpendicular to the ground, but the length of the rachet handle didn't go past the bottom of the transfer case...making it difficult to get a good grip to turn it. There is also a beam/brace that runs right in front of the fill plug...and I tried to use different 1/4" extensions but that beam/brace is about a 1/4" too tall and interrupts the proper seating of the 1/4" extensions. I did get a replacement from our local GM dealer. Was happy to see that it was an aluminum bolt(plug) and not a crappy 1/4" recessed fill plug. I'm glad I decided to try and get the fill plug out before I drained the fluid...The drain plug is the same 1/4" design, but of course, I was able to loosen it.

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