I've done some research on this part and seen some problems with the dorman products, advance auto etc...
They are to tight on the shaft and with shatter under stress. Go to napa get the part number 6005567. It's 95 bucks but it fits like the original. I have no problem with most things from those box stores but with things like gears or internal stuff that can cause catastrophic damage i always use napa or car quest. Good luck

 

Hopefully NAPA's requirements on that part number are to a higher standard than the other box stores that Dorman makes that part for. 6005567 from NAPA is manufactured by Dorman.

The GM part numbers for the various pieces involved are listed in the 4wd Front Axle Clicking When in 2HI - Goes Away when in 4HI/4LO tech article; excerpt quoted below:
All that typically is required is the passenger extension gear & the collar, but the differential gear/stub-shaft should be inspected to make sure that it is not damaged.

 

Well, that sucks,,,,,,,,,,,, I just got it back together,,, I guess I will have to do a; 'do-over',, and get a different gear,,,,,, from a Chevy Store, or Napa,,,,,,,,,,,,, I asked a mechanic here about the problem, it said maybe the Dorman gear has a machined taper in it, to hold it tight,,,,,,,,,,,, I am wondering if it needs to have some wiggle room,,, or if being tight may not be a problem,,,,,, ?????????? I suppose the wiggle would help with engaging,,,,,,,,,,,ugh,,,,,,,,,,,,,,,,,,,,,,, start over I guess.

 

It is a splined connection, it should not have any taper to it and it should slide on, not press on.

 

Well that sucks Part 2,,, at least I could get a live that with Dorman,,,, looks like I am screwed with the Dorman kit.

Greg R.:
I have a Dorman gear kit 600-561. I purchased it for a 2000 Chevy Blazer 4wd. The old gear slides easily on the axle splines, the new gear in the kit is very tight, had to press it on axle. Being told the Dorma gears for this vehicle were manufactured incorrectly, the gear should not fit tight. GM #26047584
Have you come across this problem with this gear kit

Welcome Greg R.! Your request has been directed to the appropriate department. Please wait for our operator to answer your call.

Call accepted by operator Jim. Currently in room: Jim, Greg R..
Jim:
hello
Greg R.:
hello
Jim:
Sorry yes you are correct as these should not have to be pressed onto the shaft.
Jim:
we have heard of this before and they are looking into these as it is not all of them that fit tightly
Greg R.:
ok,, what next,, is there a different number or anything else available
Jim:
Sorry no this is the only one we offer at this time. do you you have any numbers off the part itself so i can log the data code
Greg R.:
there is a bar code # is that what you would like
Jim:
it will be a separate 5 digit code
Greg R.:
?? all numbers 12277 52508 bar code 0 19495 35632 s
Jim:
12277 should be the date code
Jim:
i'll have to let them know there was another call on this.
Greg R.:
there is another set of numbers 1A-AXX-00080 says replaces 600-561
Jim:
600-561 is our number. no idea on whose that 1A-AXX number is
Jim:
unfortunately if this didn't fit you'll have to get a GM one.
Greg R.:
ok,, thought so,,, thanks for the info,,,,,,,,,,,,,
Jim:
You're welcome, have a great day!

Also,,, maybe NAPA happened to get a good gear kit,,,, maybe all the NAPA kits are some good, some not,,,,,,,,,,,,,,,,,,,, Won't know until a guy gets it home,,, I guess take the axle to the store and test fit it,,,,,,,,,,,,,,,,, ugh,,,,,,,,,,,,,

 

It sucks, but it might be easier in the long run to take the passenger side extension shaft to the parts store with you to make sure that it will fit properly.

 

yup,,, need to take shaft along with,,, but it seems NAPA does not have this on the shelf,,, so it will be a special order,,,,, ugh,,,,,,,,,,,,, add to that, NAPA also used the Dorman Kit,,,,,,,,,,,,,,,,,,,,,,, jeepers ,,, this is like a tire fire,,,,,,,,, it just keeps burning,,,,,, may just have to go the Chevy Store, and get a OEM GM gear,,,,,,,, One last question,,,,,, are we sure things could explode if I just use the gear I have installed,,,,,,,is there a mechanical reason they would not work ?????? sorry had to ask,,,,

 

Am I crazy or what,,,, I thought the Blazer was a common, popular vehicle,,, easy to get parts for,,,,,, even NAPA live chat offers no info,,,, NAPA not-so-know HOW:

Welcome to NAPA KNOW HOW. An agent will be with you momentarily.


[Daniel B] Hello, my name is Daniel B. I would be happy to assist you today! How may I help you?

[Greg] You list a part 6005567 , which a gear kit for a 200 Blazer 4wd, correct

[Greg] It also says it is MFG. by Dorman,,,,,,,,,,,,, Dorman #600-561, I purchased a 600-561 from a different vendor, the gear is not correct, the gear has to be pressed on, it will not slide on.

[Greg] Have you sold many of these and have you had any customer complaints about this item.

[Daniel B] Unfortunately, we do not have information that detailed available online.

[Daniel B] We do not have any kind of database for that via NAPA Live Chat. I apologize.

[Greg] well, ok,,,,, thanks anyway,,,

So, looks like NAPA is out also,,,,,,,,,,,,,,,, arghhhhhhhhhhhhhhhhhhhh!

 

If you read my first response in this thread, I pointed out that the NAPA PN listed was manufactured by Dorman. The only saving grace might be if NAPA requires additional quality checks that other box stores do not.

As far as the availability of this part goes, it is far from a commonly replaced component and as a result not many manufacturers make the part.


Concerning the live chat thing, most of the people you talk to in this type of setting are just sitting in a room full of people at a computer and do not have access to any better information than what you can find on the website for said company. They are most definitely not mechanics or even remotely involved with the manufacturing side of things for that matter.

 

First let me say Thank you for all the help here,,,,,,,I was getting pretty down in the dumps,,,,, I have the axle assembly removed again , and will take a break,,, and do a parts search later,,,,,,,,,,,,,, thank you again, for your hints and tips,,,,