Transfer case for 1995 (1 Viewer)

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Nov 19, 2006
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I know the oil in the diffs and the T/C is pretty dirty. I was thinking of doing a drain and fill on all three but I had two questions.
1) The dealer says I have either a model HF2A or HF2AV T/C in my 1995. One takes a GL-4 oil and the other GL-5. How can I tell which model I have?
2) I have the factory lockers in my diffs. Do I need to include any special additive(s) in the diffs or just any synthetic 75W-90 will do -- I don't do any towing or serious rock climbing at this point. so I assume I can get away with the factory weight of oil for the diffs.
 

spazzyfry123

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Don't overthink this.
Any analog or synthetic 75W90 for front diff, rear diff, and transfer case. Makes no difference which transfer case you have. Makes no difference if your diffs are locked or open.
Don't hit me too hard, but I'm overthinking this. :deadhorse:

FSM says SAE 75w90 for the transfer case and SAE 90 (>0°F) or SAE 80 / 80w90 (<0°F) for the diffs. I've read plenty on here to use 75w90 across the board - why the discrepancy? For me personally, it's six one, half dozen the other being in Florida as we don't get that cold. What about the rest of the folks - does it really matter? Regardless, I can't find "official" 75w90. I'm guessing it's close enough to 80w90 for the colder regions.
 

flintknapper

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Don't hit me too hard, but I'm overthinking this. :deadhorse:

FSM says SAE 75w90 for the transfer case and SAE 90 (>0°F) or SAE 80 / 80w90 (<0°F) for the diffs. I've read plenty on here to use 75w90 across the board - why the discrepancy? For me personally, it's six one, half dozen the other being in Florida as we don't get that cold. What about the rest of the folks - does it really matter? Regardless, I can't find "official" 75w90. I'm guessing it's close enough to 80w90 for the colder regions.

You're not overthinking it really, there IS a difference but not much of one, hence the advice (applicable to most situations) to just go with the 75w90.

The thing to remember about multi-viscosity lubricants is that it is preferable to stay with ones that have the closest 'range'. The reason for this is....there are fewer polymers and more of the lubricant (oil) in these mixes.

Polymers are added to the lubricant to control/prevent thinning as the lubricant heats up. At lower temps the polymers are coiled up....as the temperature increases they begin to open up and form long chains. The effect is that the lubricant will not 'thin' beyond the higher 'weight' number listed when heated.

An extreme example would be 20w50 motor oil. It is a 20 weight oil that will not thin more than a 50 weight oil when heated. BUT...that lubricant requires a lot of polymers to achieve those properties. Polymers can shear and burn which forms deposits. So wider range lubricants are more prone to thermal break down. So...Toyota has wisely made their recommendation.

I run 75w90 in my Tcase but 85w140 gear oil in my diffs since I live a hot climate. Diffs tend to see harder use than Tcases do.
 
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spazzyfry123

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You're not overthinking it really, there IS a difference but not much of one, hence the advice (applicable to most situations) to just go with the 75w90.

The thing to remember about multi-viscosity lubricants is that it is preferable to stay with ones that have the closest 'range'. The reason for this is....there are fewer polymers and more of the lubricant (oil) in these mixes.

Polymers are added to the lubricant to control/prevent thinning as the lubricant heats up. At lower temps the polymers are coiled up....as the temperature increases they begin to open up and form long chains. The effect is that the lubricant will not 'thin' beyond the higher 'weight' number listed when heated.

An extreme example would be 20w50 motor oil. It is a 20 weight oil that will not thin more than a 50 weight oil when heated. BUT...that lubricant requires a lot of polymers to achieve those properties. Polymers can shear and burn which forms deposits. So wider range lubricants are more prone to thermal break down. So...Toyota has wisely made their recommendation.

I run 75w90 in my Tcase but 90w140 grear oil in my diffs since I live a hot climate. Diffs tend to see harder use than Tcases do.
Interesting to hear you choose a 140 - that’s a first for me. I’ve picked up Redline 75w90 for all three. By your train of thought, a 80w90 would be better for the diffs than a 75w90 as they ask for straight 90 - the 80 has less of the polymers.

Waiting to come up with a breather extension plan before I do the changeout to get it all done at once. I know @NLXTACY is working on a manifold setup, but I may run the lines with fuel filters while I wait!
 

flintknapper

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Interesting to hear you choose a 140 - that’s a first for me. I’ve picked up Redline 75w90 for all three. By your train of thought, a 80w90 would be better for the diffs than a 75w90 as they ask for straight 90 - the 80 has less of the polymers.

Correct, but its a marginal difference. Easier to keep one product on hand for all three applications.

I'm pretty good about changing it out when needed as well.
 
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IIRC these gear oil recommendations go as far back as the FJ40. Lubrication technology advances somewhat in 40+ years.
Use what you want where you want to use it. I only use 75W90. Somehow my 1991 FJ80 with 300K+ miles is still running strong on the original drivetrain and my LX450 has over 230K. I'm not too concerned.
 

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