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2004 chevy trailblazer_lt
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Discussion Starter · #1 ·
I finally got an evening with nothing going on and time to change my rear diff. fluid. Not too bad, but not a great time either. Definitely get a pump that hole is in a butt suck place. Just a couple questions after doing it.
1. I didn't use all of the fluid in the two bottles I had but it was flowing out. Should I be nervous or is that plenty?
2. Will I need the pump to do the front diff?
3. Is there really no way in our technologically advanced age that they could make gear oil smell any better? My garage still stinks like that stuff.

Nate
 

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2007 chevy
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60 Posts
The question isn't as much how much you put in (if it was flowing over the fillhole), rather how much came out when you drained it...

How big were the bottles (qt or gal?)...

My limited slip TBSS rear takes between 2.75 and 3.0 qts (factory spec calls for 2.1 I believe...) before it will spill over

I would go back and check where the level is sitting (since you drove it a bit)

I finally got an evening with nothing going on and time to change my rear diff. fluid. Not too bad, but not a great time either. Definitely get a pump that hole is in a butt suck place. Just a couple questions after doing it.
1. I didn't use all of the fluid in the two bottles I had but it was flowing out. Should I be nervous or is that plenty?
2. Will I need the pump to do the front diff?
3. Is there really no way in our technologically advanced age that they could make gear oil smell any better? My garage still stinks like that stuff.

Nate
 

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Premium Member
2003 chevy trailblazer_lt_ext
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268 Posts
Just did my '03 last week
manual called for 2 qts, came up 1/2 inch below fill hole,
the pump will make the front easier, it just takes about 39 oz,
the garage smell is just starting to fade now
 

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2007 gmc
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159 Posts
Rear Differential capacity is 3.6 pints or 1.8 quarts. If it was leaking out of the fill plug you definitely have overfilled it. Per the GM service manual "The lubricant level should be between 0-10 mm (0-0.4 in) below the fill plug opening."

http://www.amsoil.com/scripts/runisa.dll?amsoiloaf:index
 

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2004 chevy trailblazer_lt
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Discussion Starter · #5 ·
Rear Differential capacity is 3.6 pints or 1.8 quarts. If it was leaking out of the fill plug you definitely have overfilled it. Per the GM service manual "The lubricant level should be between 0-10 mm (0-0.4 in) below the fill plug opening."

http://www.amsoil.com/scripts/runisa.dll?amsoiloaf:index
Thats a great site, nice to have all the info in one place! Thanks. Just ran out and checked and if I stick my finger in the fill hole and bend it down I am just touching the lube. So sounds about right. Thanks again
 

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2003 chevy trailblazer_ls
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1,236 Posts
That should be just about right...

Rear axle oil is not rocket science. As those who have changed it can say, it is all rather a crude affair. Just open the cover, dump the old, replace the cover, and fill with new to just below the filler hole.

A bit more or less won't really hurt a thing, unless you really over-fill.

Also, make sure that the vent line works properly. No vent means that as the axle heats from use, it will blow out a seal instead of expanding via the factory-provided vent. For off-road use, extending that vent higher on the vehicle (or replacing it with a bellows system) is advised so you don't suck up a bunch of water. We just had a discussion about that whole deal in another thread.
 

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Basic Vendor- Skid Plates
2007 chevy trailblazer_ls
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3,700 Posts
That should be just about right...

Rear axle oil is not rocket science. As those who have changed it can say, it is all rather a crude affair. Just open the cover, dump the old, replace the cover, and fill with new to just below the filler hole.

A bit more or less won't really hurt a thing, unless you really over-fill.

Also, make sure that the vent line works properly. No vent means that as the axle heats from use, it will blow out a seal instead of expanding via the factory-provided vent. For off-road use, extending that vent higher on the vehicle (or replacing it with a bellows system) is advised so you don't suck up a bunch of water. We just had a discussion about that whole deal in another thread.
I agree... Though I usually don't open the cover if the rear end doesn't have a locker in it (if it does, I want to clean better and inspect the locker, so I do pull the cover)... Having worked at a lube place for awhile in high school, I got used to using the vacuum to just suck the old fluid out, and then fill with new fluid, without having to take the rear cover off... I don't have the cool industrial oil vacuum at home, but I do have a Mighty-Vac, and a mayo jar that I made into a vacuum canister (to replace that little-bitty container that's provided with the unit)... Have to empty the mayo jar once or twice, but it's much less of a PITA (and cleaner) than removing the cover, cleaning the gasket and surfaces, and reapplying (and hoping it seals)...

Mike
 

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2004 gmc envoy_sle_xl
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When I did the front differential, I just took the wheel off to give a little more working room. Real easy job, just unscrew the large bolt toward the bottom and all the oil flows out. Replace and open the smaller fill bolt just above and to the left (I think...it has been awhile) and refill. 10-15 mins with the wheels off and a whole lot easier than the rear diff!!
 

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2007 gmc
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I always take the fill pull off first just encase......I have heard to many horror stories.
 

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2003 gmc envoy_slt
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:iagree: I don't want to empty it if I can't refill it.
 

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2007 chevy trailblazer_ls
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I always take the fill pull off first just encase......I have heard to many horror stories.
Yep, my '89 Blazer was that way... I went to loosen the fill plug before I drained it, and a good thing too... EZ-out didn't work or anything... Ended up having to weld an extension to the fill plug and hit it with an impact wrench...

Mike
 

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Northwest Chapter
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11,824 Posts
Yep, my '89 Blazer was that way... I went to loosen the fill plug before I drained it, and a good thing too... EZ-out didn't work or anything... Ended up having to weld an extension to the fill plug and hit it with an impact wrench...

Mike
Funny enough I couldnt for the life of me get the fill plug off my 02 (it has both a fill and drain plug, dont have to pull the cover or suck the fluid out). Ended up having to buy a breaker bar and wait a day for it to come in. Then it came out easily, but I would have been SOL if I had removed the drain plug first. This was back 50k ago when I was barely 16 and didnt have many tools.:duh:
 

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2007 chevy trailblazer_ls
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Funny enough I couldnt for the life of me get the fill plug off my 02 (it has both a fill and drain plug, dont have to pull the cover or suck the fluid out). Ended up having to buy a breaker bar and wait a day for it to come in. Then it came out easily, but I would have been SOL if I had removed the drain plug first. This was back 50k ago when I was barely 16 and didnt have many tools.:duh:
Yeah, the issue with this one was that not only was the socket hole rounded out, but it was also not as deep as it should have been, plus it was really rusted in there... cocked up a 3/8" easy-out trying to get it out, and endedup, like I said, having to weld an extension to it, and hit it with an impact wrench, and it finally came out... I've got a brass plug in it now, with a male 7/8" bolt head sticking out...

Mike
 

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Premium Member
2003 chevy trailblazer_lt_ext
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268 Posts
why dont they put bolt heads on them to begin with?
 

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2004 gmc
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I did some Googling to see if I could discover the history of the recessed differential plug design. Came up empty. Seems to be a consipiracy shrouded in automotive history.

Best guess I have is that in the really old days, when there were drain plugs on all diffs as well as fill plugs, the recessed design was better because a protruding head of any kind could get bashed on rocks and debris. The drain plug being at the bottom of the casting (or on the rear cover) was at more risk. The designers simply chose the same plug for the fill plug to keep the number of parts down.

When manufacturers ceased providing the drain plug, as they stopped also for auto transmissions, they just retained the old design for the fill plug.

That's my best guess, and I love studying engineering history. Any other data out there, or other guesses?
 

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2005 chevy trailblazer_ls
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Guess 1. Component designers are an anti-social lot who love to see others twist and contort into unnatural positions, usually resulting in copious amounts of profanity and/or blood.

Guess 2. Component designers are in league with tool-makers and will come out with a part that requires a special tool that you do not have.

I'm leaning toward #1.

:x
 

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2003 chevy trailblazer_ls
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Let me add #3. Because it is a stupid pipe plug, available anywhere for 25 cents and, depending on size, any 3/8" or 1/2" extension made in the world will fit it. No special tools required.

They've been around since the 1800s with the same technology. Be thankful they didn't swap out to a Torx or Torx Plus version.
 

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2004 chevy trailblazer_ls_ext
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Differential Fluid Change Out

I am changing my differential fluid (front and rear) for the first time. I read the earlier posts in that I remove the fill plug first then the drain plug. Is the rear more difficult due to placement and is there anything I should know prior to starting?
I also changed my transmission fluid and filter for the first time at 108, 623 miles. That was a small bear getting the screws back in.
I have an EXT with separate AC control unit in the 2nd row. All it does is blow hot air even when the AC is on, should I just replace the module or what should I do?
 
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