Thinking I should change the gear oil in the front and rear differentials, and the ATF in the transfer case. The owner's manual does not give a periodicity for the differential's. It does state 50,000 miles for the transfer case, but I think they are referring to the AWD models. Mine has a 4H/4L style transfer case. I plan to use Mobil 1 75W-90 both front and rear. My rear axle is a limited slip, and I noticed Mobil 1 gear oil has the LSD additive already added. Currently have 75,000 miles on "Thirsty" and hope to keep it for 75,000 more. Any suggestions?
Trailblazer transfer case, differentials.
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MolaKule
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The transfer case usually requires Auto-Trac II.
Valvoline makes an TC fluid that supposedly covers quite a few TC's.
I use a 75W90 for the front differential and a 75W110 for the rear differential.
Valvoline makes an TC fluid that supposedly covers quite a few TC's.
I use a 75W90 for the front differential and a 75W110 for the rear differential.
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You're in the top 10% of owners by even thinking about axle and transfer case fluids. "Most trucks go the junkyard with the factory gear oil", et cetera. I'd change those fluids once and figure the truck is good for life.
It looks like 75W90 is right for the axles. Auto-Trak sounds right for the TC, as mentioned.
It looks like 75W90 is right for the axles. Auto-Trak sounds right for the TC, as mentioned.
Originally Posted By: Ethan1
You're in the top 10% of owners by even thinking about axle and transfer case fluids. "Most trucks go the junkyard with the factory gear oil", et cetera. I'd change those fluids once and figure the truck is good for life.
That's why a lot of transfer cases randomly explode too.
You're in the top 10% of owners by even thinking about axle and transfer case fluids. "Most trucks go the junkyard with the factory gear oil", et cetera. I'd change those fluids once and figure the truck is good for life.
That's why a lot of transfer cases randomly explode too.
Mobil 1 is great for clutch type LSDs. Read the label, Several brands come with a friction modifier.
When I had Grand Wagoneers, if the pumpkins weren't leaking, it was because they were dry.
MolaKule
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Originally Posted By: MolaKule
The transfer case usually requires Auto-Trac II.
Valvoline makes an TC fluid that supposedly covers quite a few TC's.
I use a 75W90 for the front differential and a 75W110 for the rear differential.
BTW, I own a 2008 four wheel drive Trailblazer with the V8 and have had good service from the mentioned fluids.
The transfer case usually requires Auto-Trac II.
Valvoline makes an TC fluid that supposedly covers quite a few TC's.
I use a 75W90 for the front differential and a 75W110 for the rear differential.
BTW, I own a 2008 four wheel drive Trailblazer with the V8 and have had good service from the mentioned fluids.
Molakule, which brand gear oil you using? I'm trying to use up some Amsoil and Schaeffer gear oils I've had on the shelf for a few years....
MolaKule
Staff member
I use my own formulations with similar addpacks as used by the major's but if I were buying on the free market I would use either Amsoil Severe Gear, Redline, or Schaeffer Oil products.
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Originally Posted By: andyd
Mobil 1 is great for clutch type LSDs. Read the label, Several brands come with a friction modifier.
Somebody correct me if I am mistaken, but I don't think my L.S rear axle is the clutch type. Also, thank you all for your comments.
Mobil 1 is great for clutch type LSDs. Read the label, Several brands come with a friction modifier.
Somebody correct me if I am mistaken, but I don't think my L.S rear axle is the clutch type. Also, thank you all for your comments.
Look in your glove box for the rear axle code. There was a G80 option (made by Eaton) for the 4.2L chassis that was "limited slip" but it was a cam style that either locked the diff or didn't depending on conditions. If you have the G80 diff, you do not require an LSD additive, as the setup does not use clutches. I don't recall that Trailblazer platform having anything other than an open differential or the Eaton one.
Unless you have a clutch based LSD I'm not aware of, standard 75w-90 will work fine with either differential available in the Trailblazer.
I prefer Amsoil's Severe Gear 75w-110 for vehicles that are used hard (towing, off-road 4WD). It's been awhile since I've refilled my diffs, so I can't say for sure whether it's even made anymore.
Unless you have a clutch based LSD I'm not aware of, standard 75w-90 will work fine with either differential available in the Trailblazer.
I prefer Amsoil's Severe Gear 75w-110 for vehicles that are used hard (towing, off-road 4WD). It's been awhile since I've refilled my diffs, so I can't say for sure whether it's even made anymore.
I service my differential (2WD) every 25,000 miles because of operating conditions. Initially, I was using the GM grape scent 75W-90 before I made the switch to Mobil 1 75W-90. My last differential service was with Motul Gear 300 75W-90, which I've bee extremely happy with.
Auto-Trak-II for the transfer case, which is made by Petro-Canada. I would not deviate, because it has some sort of proprietary friction modifier.
Auto-Trak-II for the transfer case, which is made by Petro-Canada. I would not deviate, because it has some sort of proprietary friction modifier.
HM- I did the front and rear diffs on my 2005 Trailblazer shortly after I bought it used (this was years ago). Easy job. I had the open rear diff and it had a nice metal/rubber reusable gasket. The front diff was easy with that huge fill port hole, big enough to drop a golf ball in.
I am using Amsoil 75w90 in both on mine. Runs as good as any other gear oil considering I rarely tow with it anymore.
I am glad GM had the brains to incorporate reusable gaskets. Made taking the diff and trans pan off super slick.
I am glad GM had the brains to incorporate reusable gaskets. Made taking the diff and trans pan off super slick.
I would replace those fluids asap. I would definitely use OEM grape for the transfer case and whatever brand you prefer in 75w90LS for the front and rear diff.
MolaKule
Staff member
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I would replace those fluids asap. I would definitely use OEM grape for the transfer case and whatever brand you prefer in 75w90LS for the front and rear diff.
Originally Posted By: MolaKule
The transfer case usually requires Auto-Trak II...
The Auto-Trak II Transfer Case fluid is dyed Blue, not Purple.
I would replace those fluids asap. I would definitely use OEM grape for the transfer case and whatever brand you prefer in 75w90LS for the front and rear diff.
Originally Posted By: MolaKule
The transfer case usually requires Auto-Trak II...
The Auto-Trak II Transfer Case fluid is dyed Blue, not Purple.
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The auto trak II came to 16$ for 2 litres at the dealer. It was dirt cheap.
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