how many differential and transfer case boxes need gear oil change?

tyler

Original poster
Member
Aug 25, 2017
58
Boston
Hey guys,
I'm trying to change my differential fluid in the front and the back today. I tried googling and cant seem to find an answer. How many cases are there under the 06 trailblazer that need to be changed? I know there's one where it looks like its behind the drivers side tire and then the one in the back, in the middle of the truck with it looks like 6 bolts on the case. That's the only two I see. Is there a article or a link someone has where i could find out how many boxes do need the gear oil change for the 06 trailblazer?
It's the first time I'm doing it on my truck and I know it needs to be done, I don't want to ruin my truck by not doing it.

Thanks!
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
There's the transfer case. It uses blue Auto-Trak II fluid and has a 50k mile interval whether you use 4x4 or not. Then there are the front and rear diffs that use synthetic 75w90 gear oil. No additive needed. No maintenance interval for them but just a good idea to replace them when it starts to look dark.
 
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Reprise

Lifetime VIP Donor
Supporting Donor
Member
Jul 22, 2015
2,724
If you change both front / rear diffs, you'll need about 5 bottles of gear oil (2 for the front, 3 for the rear), and 2 bottles of the GM AutoTrak II fluid (NO substitutions on that).

Good idea to check your inner CV boots while you're there to see if any are leaking, etc. - and give them a shot of silicone spray lube to keep them pliable for the upcoming winter. Outers, too - but those are easier to reach :smile:

Before draining *any* of the three items - make SURE you can get the fill plugs off first!

The front diff fill plug can be difficult to get off (only supposed to be torqued to 24 ft/lb, IIRC, but it tends to rust in place the longer it's not disturbed, especially where it snows). Use a six-sided 18mm socket or box wrench; the bolt is susceptible to rounding. And some PB Blaster a day or two before should be helpful.
 

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