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Discussion Starter · #1 ·
Good morning and happy New Year.

I had a quick question. In going to be changing trans fluid, as well as front and rear diff and the transfer case. Going to get on that seasonal interval.

The vehicle in question is a new to me 2002 Trailblazer LTZ with the 4.2. I see on the transfer case that the drain and fill plugs require a 10mm Allen wrench or socket. I have this. I'm looking to replace the drain and fill plugs with the more traditional hex head bolt.

Does anyone have leads on a replacement style, or thread size and pitch? Or maybe someone has done this before and have experience or a part number?

Any help would be appreciated. Thank you.
 

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IF you can actually get them out - it's usually best to stay with the original design because the hex type of plug is actually less susceptible to damage by a huge and ill-fitting crescent wrench.

ONE BIG THING .... make totally sure that you can remove the FILL plug before you take the drain plug out!

It is near impossible to turn the car upside-down to pour new fluid into the drain plug if/when you screw up the fill plug!
 

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Discussion Starter · #3 ·
IF you can actually get them out - it's usually best to stay with the original design because the hex type of plug is actually less susceptible to damage by a huge and ill-fitting crescent wrench.

ONE BIG THING .... make totally sure that you can remove the FILL plug before you take the drain plug out!

It is near impossible to turn the car upside-down to pour new fluid into the drain plug if/when you screw up the fill plug!
Thank you for the response. I had a feeling that was the way it was going to be.

As far as the drain plug before the fill plug, that's something I learned the hard way, WAY back in the 90's, when I did my first oil change. Drained the oil, couldn't get the filter off. Whoever did it before me never lubed the gasket and it bonded to the pan. Learned a few new cuss words that day.

Is it safe to spray the front diff and transfer case plugs with PB Plaster prior or do I risk some kind of contamination later on?
 

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Yeah you can spray some PB blaster on there prior to help get them out, also giving the plugs a tap with a hammer helps free them up. I just did this in preparation for the first snow and it’s a pretty straight forward process. Make sure to use Autotrak II for the transfer case. I also used the OEM GM fluid for the differential. I found the front diff is easiest accessed by removing the drivers side wheel then use a funnel inserted into some tubing to refill.
 

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Trailblazer 2008 LTZ (4.2L) (Destroed) :((. Now Trailblazer SS (2006)
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It is near impossible to turn the car upside-down to pour new fluid into the drain plug if/when you screw up the fill plug!
Yes, but if you really need to fill in oil, then it can be filled through the breather. ;)
 

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Thank you for the response. I had a feeling that was the way it was going to be.

As far as the drain plug before the fill plug, that's something I learned the hard way, WAY back in the 90's, when I did my first oil change. Drained the oil, couldn't get the filter off. Whoever did it before me never lubed the gasket and it bonded to the pan. Learned a few new cuss words that day.

Is it safe to spray the front diff and transfer case plugs with PB Plaster prior or do I risk some kind of contamination later on?
If you think about it for a minute .... where is the sealing gasket?

ANSWER ---> It's right under the face of the flange on the plug. Any attempts to get a solvent into the threads or even past the gasket won't happen.

I've seen guys spray goop on pipe threads too --- and the design of pipe threads is that they don't allow things from the inside to come out --- and therefore things on the outside don't get in either.

Fruitless endeavor, really.
 

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Yeah --- that's a possibility - but how can you tell when it's correctly - and sufficiently full?
Ask knowledgeable people here how much oil should be poured to the level of the filler plug.
 

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Just a quick suggestion when changing the transfer case fluid. After you loosen the fill plug, do not remove it. Leave the fill plug loosely threaded in, this keeps the air from rushing in as you remove the drain plug. I was surprised by how forcefully the fluid came out of the drain hole. Thought I had my work area all set up to catch the fluid from the transfer case, Not! The fluid came out so fast it over shot my drain pan, onto some card board I had positioned under the drain pan and some ended up on the drive way.
 

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Just a quick suggestion when changing the transfer case fluid. After you loosen the fill plug, do not remove it. Leave the fill plug loosely threaded in, this keeps the air from rushing in as you remove the drain plug. I was surprised by how forcefully the fluid came out of the drain hole. Thought I had my work area all set up to catch the fluid from the transfer case, Not! The fluid came out so fast it over shot my drain pan, onto some card board I had positioned under the drain pan and some ended up on the drive way.
Good point!

There also is a vent that allows air in too .... if you really wanted to control draining it.
 

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Discussion Starter · #11 ·
Just a quick suggestion when changing the transfer case fluid. After you loosen the fill plug, do not remove it. Leave the fill plug loosely threaded in, this keeps the air from rushing in as you remove the drain plug. I was surprised by how forcefully the fluid came out of the drain hole. Thought I had my work area all set up to catch the fluid from the transfer case, Not! The fluid came out so fast it over shot my drain pan, onto some card board I had positioned under the drain pan and some ended up on the drive way.
Thank you for the great tip. I hadn't thought of that.
 

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2004 GMC Envoy SLT 4.2
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I usually do not fully remove any drain plug , at first . I hold it in the opening until the flow is more 'reasonable' . Sure my hands might get the drainage on them , but , that's exactly why shop rags were invented . And , I generally have gloves on anyway . ;)
 

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I usually do not fully remove any drain plug , at first . I hold it in the opening until the flow is more 'reasonable' . Sure my hands might get the drainage on them , but , that's exactly why shop rags were invented . And , I generally have gloves on anyway . ;)
Most vehicle lubricants are good for your skin. All except 90wt --- which just smells bad and makes your lunch taste funny.

Mechanics also never get infections in their hands - <anecdote time> and I've torn finger pads off, stuck them back on with masking tape and went back to work.

Masking tape is the BEST first aid bandage --- it won't stick to the big skin flaps as you take the tape off at home in the showier either! That's a good thing!

But yeah --- no infections 'cause germs can't live in stuff like that!
 

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I see on the transfer case that the drain and fill plugs require a 10mm Allen wrench or socket. I have this. I'm looking to replace the drain and fill plugs with the more traditional hex head bolt.

Does anyone have leads on a replacement style, or thread size and pitch? Or maybe someone has done this before and have experience or a part number?
Subscribing because I need a replacement plug, and I'd love to find an aftermarket solution. Does yours have a gasket? Mine didn't.

My '97 K2500 had drain and fill plugs with a 10mm Allen recess. Of course, Previous Owner beat-up the drain plug by attempting to use a 3/8" Allen tool. By the time I got it out, it was totaled, and in anger it found a new home "somewhere" on my side yard. Which was a mistake, 'cause I can't find a proper replacement.

Best I can tell, the original is tapered pipe thread with a metric pitch--M22 x 1.5. The local parts stores have gasketed plugs with a similar thread pitch, but not tapered. Therefore...leaks even with the plug as "tight" as I dare.

O'Reillys says this is correct, but they're wrong.
 

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Subscribing because I need a replacement plug, and I'd love to find an aftermarket solution. Does yours have a gasket? Mine didn't.

My '97 K2500 had drain and fill plugs with a 10mm Allen recess. Of course, Previous Owner beat-up the drain plug by attempting to use a 3/8" Allen tool. By the time I got it out, it was totaled, and in anger it found a new home "somewhere" on my side yard. Which was a mistake, 'cause I can't find a proper replacement.

Best I can tell, the original is tapered pipe thread with a metric pitch--M22 x 1.5. The local parts stores have gasketed plugs with a similar thread pitch, but not tapered. Therefore...leaks even with the plug as "tight" as I dare.

O'Reillys says this is correct, but they're wrong.
That's the drain plug I have - so I wonder what has transpired on your plug ....!

If someone used a 3/8" Allen on it --- then they should have their knees capped.

The last guy there was mumbling" You want fries with that" as he applied for the job at Quickee-Lube-&-Screw.
 
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