DCT Fluid for Transfer Case Service

[Joba27n]

This is a general discussion i'm hoping to open up but, in my particular case the application I have in mind is a 2021 Toyota Tacoma (6MT) which as far as I've read has a VF2CM transfer case. The Manufacture suggested fluid is 75W Gear oil.

A little back story is that for me, the Toyota juice is un-abtain-ium. My local dealer (which is terrible) says no such fluid exist. I've ran the Redline MT-LV with nothing to talk about in regards to it. Worked fine, came out as clean as it went in. Reason I didn't use it again is because I could only get it for $50 a litre and only after a month of shipping time. Presently I have Amsoil syncromesh fluid in there. My only concern with it is that the truck feels like it has alot more drag, the truck used to coast obscenely well but ever since filling with syncromesh fluid the truck noticeably slows down when off the gas. Cold weather shifting from a -40*C start is fine. You (usually) need to have a little wheel speed to get 4wd to engage but that's nothing new from factory nor other 4WD trucks i've owned/driven. I've noticed no change in fuel economy and within reason, fuel economy isn't a high priority for me... I don't think it's possible to drive a Toyota truck and have fuel economy as a high priority anyways but thats another topic.

Fast forward to present day, it's coming up on time to change my driveline fluid again. If I can find Redline's MT-LV for a more reasonable price, i'm interested in trying it again to see if the additional drag is just in my head or if the Amsoil syncromesh is actually that noticeably thicker. I am aware of the viscosity difference on paper. If Redline is out of the question then I was planning to just run Syncromesh again, until I got the Idea of running DCT instead. For me it would be the Amsoil flavour as it's the best bang for my buck.

(**TLDR**) As far as I can Understand, I see no reason why DCT fluid can't be used in place of 75W for this transfer case. It's closer in viscosity to the manufacture suggested fluid and for the most part a DCT is (kinda) like an automated manual transmission. Combined with the fact that a transfer case really doesn't see any load unless you're in 4WD, I feel like this would be closer to the ideal viscosity for it but much easier to source.

Barring a glaring reason that i'm missing, I'm planning to fill my transfer case with it to see how it does. I am a licensed mechanic so aside from the time and financial aspect of the transfer case being ruined I don't have much to lose. Curious to hear the thoughts of more savvy people than I

 

[D60]

It's almost impossible for the Synchromesh to cause any appreciable drag, esp the small qty in the t-case. I think you're delusional.

Can you get the Ravenol 75W? Or Amsoil has 75-85.

In the States I think 98% of indies and 85% of dealerships will cram readily available 75W90 in there and send you on your way.

Looks like Febi Bilstein also offers a 75W
https://www.fcpeuro.com/products/audi-vw-manual-trans-fluid-g052171a2

That said, I have no useful input on the DCT. It would present an interesting option if it works.

 

[kschachn]

There are threads on similar questions if you look around.

Perhaps @MolaKule may be of assistance.

 

[Joba27n]

It's almost impossible for the Synchromesh to cause any appreciable drag, esp the small qty in the t-case. I think you're delusional.

Can you get the Ravenol 75W? Or Amsoil has 75-85.

In the States I think 98% of indies and 85% of dealerships will cram readily available 75W90 in there and send you on your way.

Looks like Febi Bilstein also offers a 75W
https://www.fcpeuro.com/products/audi-vw-manual-trans-fluid-g052171a2

That said, I have no useful input on the DCT. It would present an interesting option if it works.

Aha it is possible that i've being delusional but it is an observation i've noticed with it. Not earth shattering or anything and I fully agree that 75-90 would also be fine and without issue but that "drag" is my observation.

I like experimenting and largely just started this thread with the main point being to explore using DCT fluid in the transfer case. I've already made up my mind on trying it and to me I see no reason why it wouldn't work or be bad but I haven't seen or heard of anyone else talking about it so I'm curious to hear thoughts.

 

[Joba27n]

There are threads on similar questions if you look around.

Perhaps @MolaKule may be of assistance.

I'm kinda green to the site still, I did try searching around but didn't really find much. I'm not asking you for links because that would be time consuming but any special keywords or phases that you feel would point me in the right direction?

 

[martinq]

My guess is you're looking for a GL5 or GL4 Gear/Transmission fluid?

Is there an OE spec or part number?

 

[MolaKule]

The Manufacture suggested fluid is 75W Gear oil.

75W what? That tells us nothing about the viscosity range. Have you ever had an analysis done on the OEM fluid?

Any fluid in cold weather is going to have more viscous drag than in warm weather.

...I've ran the Redline MT-LV with nothing to talk about in regards to it. Worked fine, came out as clean as it went in. Reason I didn't use it again is because I could only get it for $50 a litre and only after a month of shipping time. Presently I have Amsoil syncromesh fluid in there. My only concern with it is that the truck feels like it has alot more drag, the truck used to coast obscenely well but ever since filling with syncromesh fluid the truck noticeably slows down when off the gas. Cold weather shifting from a -40*C start is fine. You (usually) need to have a little wheel speed to get 4wd to engage but that's nothing new from factory nor other 4WD trucks i've owned/driven.

If I can find Redline's MT-LV for a more reasonable price, i'm interested in trying it again to see if the additional drag is just in my head or if the Amsoil syncromesh is actually that noticeably thicker. I am aware of the viscosity difference on paper. If Redline is out of the question then I was planning to just run Syncromesh again, until I got the Idea of running DCT instead. For me it would be the Amsoil flavour as it's the best bang for my buck.

(**TLDR**) As far as I can Understand, I see no reason why DCT fluid can't be used in place of 75W for this transfer case. It's closer in viscosity to the manufacture suggested fluid and for the most part a DCT is (kinda) like an automated manual transmission. Combined with the fact that a transfer case really doesn't see any load unless you're in 4WD, I feel like this would be closer to the ideal viscosity for it but much easier to source.

Okay, so DCT fluids are thicker than the MTL-V and DCT fluids are thinner than the Amsoil synchromesh. That is from higher viscosity to less viscosity:

Amsoil Synchromesh ~ 10cSt@100C, 49.4cSt@40C

DCT Fluids ~ 8cSt@100C, 40cSt@40C

MTL-V ~ 6cSt@100C, 38cSt@40C

So why would a DCT have any less viscous drag than MTL-V?
Why would Amsoil synchromesh have any less viscous drag than a DCT fluid?

In the general literature, a 75W without any numbers to the right is usually about a 6 cSt fluid.

High Performance Lubricants has an MTL (MTL Life), a 75W, that is about 6.2cSt@100C, 38cST@40C.

Bottom line, I don't see any advantage to the use of a DCT.

 

[Joba27n]

75W what? That tells us nothing about the viscosity range. Have you ever had an analysis done on the OEM fluid?

Any fluid in cold weather is going to have more viscous drag than in warm weather.

Okay, so DCT fluids are thicker than the MTL-V and DCT fluids are thinner than the Amsoil synchromesh. That is from higher viscosity to less viscosity:

Amsoil Synchromesh ~ 10cSt@100C, 49.4cSt@40C

DCT Fluids ~ 8cSt@100C, 40cSt@40C

MTL-V ~ 6cSt@100C, 38cSt@40C

So why would a DCT have any less viscous drag than MTL-V?
Why would Amsoil synchromesh have any less viscous drag than a DCT fluid?

In the general literature, a 75W without any numbers to the right is usually about a 6 cSt fluid.

High Performance Lubricants has an MTL (MTL Life), a 75W, that is about 6.2cSt@100C, 38cST@40C.

Bottom line, I don't see any advantage to the use of a DCT.

The spec is just 75W and according to a VOA I found Here, it has a viscosity of 5.68 cSt@100*C. I personally have never done an oil analysis though.

I do understand that cold viscous fluid is gonna have more drag, despite my time of year for posing this, I had summer time in mind for my possibly delusional comparison. I apologize for not stating myself clearly.

When I had MT-LV in my transfer case I noticed nothing different from factory, it's only when I jumped to the Amsoil syncromesh(MTF) that I felt this drag. My last service interval lined up in June. I also drive 30Kms one way to work on the highway so plenty of time to warm up the powertrain.

Albeit thin, MTF is almost "twice as thick" as the factory fluid at 100*C which I doubt the fluid actually reaches inside the transfer case so I imagine the fluid would be thicker than MT-LV by a larger margin (correct me if i'm wrong please, I want to learn).

My reasoning for wanting to try DCT is specifically because it's in between MTF and MT-LV viscosity wise. If I couldn't procure any MT-LV or DCT then I would happily stick with synchromesh or even if I could easily procure MT-LV (or HPL's 75w) without selling a kidney then I would use either without thinking twice.

Despite me posing the question, I don't know if there is any "advantage" to DCT other than it's easier to come by than Redline for me but it's also a little thinner than syncromesh.

Aside from sparking a conversation, the only question really i'm curious about is if there is a design factor of DCT that i'm not aware of that would make it not suitable for any transfer case that requires a similar viscosity fluid. For example as I understand it, CVT fluid has friction modifiers to make the fluid "sticker" so the chain/belt gets better traction. GL5 gear oil has friction modifiers to handle the loads of hypoid gears and GL4 to facilitate manual transmission synchronizer function.

 

[MolaKule]

The spec is just 75W and according to a VOA I found Here, it has a viscosity of 5.68 cSt@100*C. I personally have never done an oil analysis though.

As I said above, from the literature a 75W hangs around 6.0cSt: "In the general literature, a 75W without any numbers to the right is usually about a 6 cSt fluid." This is considered a ULV fluid.

Albeit thin, MTF is almost "twice as thick" as the factory fluid at 100*C which I doubt the fluid actually reaches inside the transfer case so I imagine the fluid would be thicker than MT-LV by a larger margin (correct me if i'm wrong please, I want to learn).

Which MTF are you speaking to, MTF-LV or the Amsoil synchromesh?

My reasoning for wanting to try DCT is specifically because it's in between MTF and MT-LV viscosity wise. If I couldn't procure any MT-LV or DCT then I would happily stick with synchromesh or even if I could easily procure MT-LV (or HPL's 75w) without selling a kidney then I would use either without thinking twice.

I assume you meant Amsoil synchromesh? Pennzoil also has a synchromesh of the same viscosity.

Aside from sparking a conversation, the only question really i'm curious about is if there is a design factor of DCT that i'm not aware of that would make it not suitable for any transfer case that requires a similar viscosity fluid.

The difference, other than viscosity, would be the additive package and its friction modifier chemistry.

For example as I understand it, CVT fluid has friction modifiers to make the fluid "sticker" so the chain/belt gets better traction. GL5 gear oil has friction modifiers to handle the loads of hypoid gears and GL4 to facilitate manual transmission synchronizer function.

CVT fluids have "traction" friction modifiers to reduce chain/belt slippage.

GL-5 hypoid fluids have EP additives, and maybe LSD friction modifiers for LS differentials.

MTF fluids have AW additives and friction modifiers.

Friction modifier chemistry is different between all the above.

 

[Joba27n]

"Which MTF are you speaking to, MTF-LV or the Amsoil synchromesh?"

I was using MTF to signify Amsoil syncromesh fluid and MT-LV to represent the redline of that flavour.

"The difference, other than viscosity, would be the additive package and its friction modifier chemistry.

CVT fluids have "traction" friction modifiers to reduce chain/belt slippage.

GL-5 hypoid fluids have EP additives, and maybe LSD friction modifiers for LS differentials.

MTF fluids have AW additives and friction modifiers.

Friction modifier chemistry is different between all the above."

Thank you for the information. I'd like to ask the question then of what friction modifiers/additives would make a DCT fluid different than a gear oil for a manual. A 75w-80 seems like it would be quite similar to the DCT fluid on a surface level.

As I said above, from the literature a 75W hangs around 6.0cSt: "In the general literature, a 75W without any numbers to the right is usually about a 6 cSt fluid." This is considered a ULV fluid.

Which MTF are you speaking to, MTF-LV or the Amsoil synchromesh?

I assume you meant Amsoil synchromesh? Pennzoil also has a synchromesh of the same viscosity.

The difference, other than viscosity, would be the additive package and its friction modifier chemistry.

CVT fluids have "traction" friction modifiers to reduce chain/belt slippage.

GL-5 hypoid fluids have EP additives, and maybe LSD friction modifiers for LS differentials.

MTF fluids have AW additives and friction modifiers.

Friction modifier chemistry is different between all the above.

 

[MolaKule]

Thank you for the information. I'd like to ask the question then of what friction modifiers/additives would make a DCT fluid different than a gear oil for a manual.

The clutch material in the two clutches and their sizing (according to HP), and the gearing arrangement require an additive complement to match the friction characteristics of the clutches while providing sufficient Anti-Wear (AW) capabilities for the gearing and bearings.

"A 75w-80 seems like it would be quite similar to the DCT fluid on a surface level."

Not really. This is a different question that relates to viscosity and the range of viscosity within XXWYY SAE gear lubes. Similar viscosities DO NOT infer similar friction characteristics or AW capabilities.

It is recommended by one manf. that DCT fluids be changed at 25k intervals with a filter change at about 7.5k intervals.

 

[D60]

To be fair I'd have to see the internals of the '20 Taco t-case but unless there are frictions for "Auto" or AWD, t-cases are pretty crude and likely indifferent to additives or FMs.

So, this is kinda interesting:
https://www.tacomaworld.com/threads/‘16-newer-transfer-cases.636057/

-they claim the '16+ case is an Asin VF2CM, but I'm unable to find an exploded view, although they say it's similar to previous 'cases. Ebay listings would suggest this fits '16-23

‐there's some VOAs -‐albeit Blackstone-- in Post #12

-post #23 suggests additives are there for the sake of the potentially too-thin spec of 75W. I don't know enough to speak intelligently on this issue

-post #24 suggests that at least back in 2019 Motul's site recommended DCT fluid for this t-case

-it's a long thread and I went no deeper

 

[Pablo]

I have been using Amsoil MTF in my 2019 Tacoma TC since nearly day 1. I highly doubt the cause of anything you feel has a thing to do with fluid types in any range from 6-14 cSt hot.

This TC is not picky. People use 15cSt + SAE 90 range gear oils, people use ATF, MTF, etc. NO issues (would I use a gear oil? No.)

Would DCT work? Most likely, no problem.

I tend to think the Amsoil MTF is a great match based on customer feedback, viscometrics, additives and base oil.

 

[Hootbro]

Too bad you were not in the USA as I have two sealed liters of the Ravenol 75W I would send you for just the cost of shipping to just get rid of it.

 

[Joba27n]

To be fair I'd have to see the internals of the '20 Taco t-case but unless there are frictions for "Auto" or AWD, t-cases are pretty crude and likely indifferent to additives or FMs.

So, this is kinda interesting:
https://www.tacomaworld.com/threads/‘16-newer-transfer-cases.636057/

-they claim the '16+ case is an Asin VF2CM, but I'm unable to find an exploded view, although they say it's similar to previous 'cases. Ebay listings would suggest this fits '16-23

‐there's some VOAs -‐albeit Blackstone-- in Post #12

-post #23 suggests additives are there for the sake of the potentially too-thin spec of 75W. I don't know enough to speak intelligently on this issue

-post #24 suggests that at least back in 2019 Motul's site recommended DCT fluid for this t-case

-it's a long thread and I went no deeper

Thank you for the info, I am quite active on TW and partially read that thread a while ago but i've revisit it.

Also ya this is just a conventional electronically shifted part time two speed transfer case. Nothing special about it aside from it's oil recommendation but, with myself also not being educated in tribology I would say the additives are the make up for the lower viscosity. At the same time though, you could probably run canola oil in a transfer case and be fine. Unless you're in 4WD, it basically just serving as a solid shaft thats supported by bearing on it's ends. In 4WD is a different story but 2WD operation only needs an oil to lubricate the bearings spinning. This is an exploded view if you're interested.

 

[Joba27n]

I have been using Amsoil MTF in my 2019 Tacoma TC since nearly day 1. I highly doubt the cause of anything you feel has a thing to do with fluid types in any range from 6-14 cSt hot.

This TC is not picky. People use 15cSt + SAE 90 range gear oils, people use ATF, MTF, etc. NO issues (would I use a gear oil? No.)

Would DCT work? Most likely, no problem.

I tend to think the Amsoil MTF is a great match based on customer feedback, viscometrics, additives and base oil.

I agree with you that Amsoil's MTF is a great match and I still feel like it is based on this transfer case in a oversimplified way being a manual transmission with only direct drive and an under drive gear along with the viscosity of MTF. I've had MTF in my transfer case for about 80'000kms.

Curiosity now though has me wondering if DCT might be an even better match

 

[Joba27n]

The clutch material in the two clutches and their sizing (according to HP), and the gearing arrangement require an additive complement to match the friction characteristics of the clutches while providing sufficient Anti-Wear (AW) capabilities for the gearing and bearings.

"A 75w-80 seems like it would be quite similar to the DCT fluid on a surface level."

Not really. This is a different question that relates to viscosity and the range of viscosity within XXWYY SAE gear lubes. Similar viscosities DO NOT infer similar friction characteristics or AW capabilities.

It is recommended by one manf. that DCT fluids be changed at 25k intervals with a filter change at about 7.5k intervals.

Thank you and gotcha, I see what you're saying(I believe). Similar to a GL5 vs. GL4 75w-90 gear oil, although both may have the same viscosity, they both have different additives and both gear oils are made with a different purpose in mind beyond simply lubricating.

 

[martinq]

Thank you for the info, I am quite active on TW and partially read that thread a while ago but i've revisit it.

Also ya this is just a conventional electronically shifted part time two speed transfer case. Nothing special about it aside from it's oil recommendation but, with myself also not being educated in tribology I would say the additives are the make up for the lower viscosity. At the same time though, you could probably run canola oil in a transfer case and be fine. Unless you're in 4WD, it basically just serving as a solid shaft thats supported by bearing on it's ends. In 4WD is a different story but 2WD operation only needs an oil to lubricate the bearings spinning. This is an exploded view if you're interested.

Thanks. Looks similar to an MT with a chain in it. Do you know if the blocking rings use brass or pads for friction? An MTF or Hygard would work really well.

 

[Joba27n]

I'

Thanks. Looks similar to an MT with a chain in it. Do you know if the blocking rings use brass or pads for friction? An MTF or Hygard would work really well.

Yes and I don't know if the synchronizer is brass or has a composite friction surface

 

[tvaughn]

FCP Euro sells Liqui Moly 75w for $8.45, that's what I used in my transfer case on my GX460. It's GL4 and will be safe for any brass.