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Discussion Starter #1
What is the current wisdom for the oil / fluid in the ZF6 6-speed transmission?

Yes, I searched, and I read a lot. This was a good thread:

https://www.thedieselstop.com/threads/zf6-atf-comparisons.645857/

So, the leading contenders For the ZF6 transmission oil are

Motocraft Mercon V

Redline MTL

Castrol Transmax Mercon-V 06068 not synthetic

Royal Purple Syncromax

And the RoadRanger recommends a synthetic mineral oil (PS-386) for their transmissions

So, what are people doing *today*? What is the current trend given the developments of chemical engineers?
 

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Discussion Starter #2
I have added a couple of fluids - Valvoline and Amsoil SyncorMesh
 

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mercon ATF is what i use in all ZF transmissions. that is what comes from the factory, so that is what i use.
 

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We used to put Mystic JT-7 in them.

Here's the results, when done in a new or near New transmission, it was fine, they ran forever, when done in a higher mileage transmission, it was horrendously stiff to get in gear.

If I was doing one again, I would stick with stock, or try the Mystic, in a 50W, that's available now.

Sent from my E6810 using Tapatalk
 

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Schaffers ALL Trans here, but you guys do what you want. It's 'Murica!
 

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I decided to go with Mercon V for the break-in period, and then go to a synthetic.
 

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What ever you do don’t use synchro mesh. It will eat the shift boot. I have it in mine now and I’m on the 3rd boot.
 

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I am thinking of this:
 

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amsoil is a waste of money.
there are much better oils out there for a whole lot less money.
when you buy amsoil, you are buying a name and marketing scheme
 

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amsoil is a waste of money.
there are much better oils out there for a whole lot less money.
when you buy amsoil, you are buying a name and marketing scheme
Which transmission fluid for a manual do you like?
 

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I’m going to put in redline or just standard synthetic atf.
 

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Jax,
Have you researched the various MTL lubricants? They are designed specifically for Manual Transmissions that call for an ATF. The right choice is dependent on the temperatures where you live and drive.

Although Mystic products are of excellent quality, the problem with the 50W mentioned above is it has a very thick Viscosity at operating temp 100*C and will be too thick for a ZF6. Also the PDS states:
"Meets API Service MT-1 performance requirements for use in non-synchronized manual transmissions used in buses and heavy-duty trucks. "

I have not researched this 50W extensively but I would not use a lubricant designed for non-synchro transmissions in a ZF-6 that has synchros. The concern is the EP additives might destroy the yellow metal. But I agree with BlueTruckNut's experience that a thicker fluid than the MERCON-LV is the way to go.

I am surprised to read about the Synchromesh causing shiftboot deterioration. That is the first report of that I have read and it would be great to get the specific details of which Synchromesh product is being used and how it was isolated as the cause and how quickly it destroys the boot? I am not doubting anyones personal experience, please don't misunderstand, I am just interested in the details. For comparison, GM also used a ZF6 and required Dexron fluid similar to original MERCON. GM also developed Synchromesh fluids and they are a popular fluid with GM owners of the ZF-6 (GM did not offer a Transmission cooler like the Ford SuperDuty).

I don't wish to contribute in an Oil War but there is absolutely nothing wrong with Amsoil products according to the science. They use quality basestocks and have excellent additive packages. Are there other quality synthetic lubricants? Yes. Does Amsoil have a terrible marketing strategy that makes guys distrustful? Yes. But their lubricants are very good.
 

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It was valvoline and it would cause to boot to be soft and rip at the bellows within about a month.

I changed the fluid. Month later I was leaking. This was the stock deal. Bought a new oem seal. About 2 months later I start to leak again. In a pinch I adapted an CV boot and its held since. I changed it last July. Also just an fyi. I only put 3k-5k miles a year on this truck.
 

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Jax,
. . . <snipped> . . .

I don't wish to contribute in an Oil War but there is absolutely nothing wrong with Amsoil products according to the science. They use quality basestocks and have excellent additive packages. Are there other quality synthetic lubricants? Yes. Does Amsoil have a terrible marketing strategy that makes guys distrustful? Yes. But their lubricants are very good.
Yes, I've been comparing data sheets, but some things you have to hear from the field . . . like melting shifter boots.
 

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It was valvoline and it would cause to boot to be soft and rip at the bellows within about a month.

I changed the fluid. Month later I was leaking. This was the stock deal. Bought a new oem seal. About 2 months later I start to leak again. In a pinch I adapted an CV boot and its held since. I changed it last July. Also just an fyi. I only put 3k-5k miles a year on this truck.
Very interesting.
Thanks.
 

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Very interesting.
Thanks.
Two points, one I was wrong, I was mistakenly thinking we were talking about the ZF5. I HAVE NOT TRIED IT IN A 6 SPEED. That was my mistake.

Second, I've heard that said, about the Mystic eating the syncro material, but as yet haven't seen it. In the heavy truck world, we've been cautioned about putting it in 10 and 15 speeds, because of the syncros in the high/low selector. However, there's currently 2 in the yard with at least a million miles that have had nothing but Mystic. One is 50W, one has 85W-140. Just for reference, not arguing, you make a good point!

Moral of the story, I goofed, I've run Mystic in the ZF5 speeds with good success, but cannot vouch for a 6 speed!

Sent from my E6810 using Tapatalk
 

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Jax, when i had the ZF5's in my trucks they had regular dextron ATF in them. worked fine for the 250k or so miles i had it in the 88, and it was still good when the flywheel fell apart and i switched to automatic.
as for the other trucks, i am not sure what the other guys did after buying the trucks from me, but i assume the stuck with regular dextron too.
i never had a ZF-6 so can't comment on what is good or not.
 

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Arctic, my problem with amsoil besides their price and marketing strategy is that they want everyone to believe their word.
when asked for testing data they produce their own data, not oil institute data.
that to me tells me they are hiding something and is reason enough to not use anything they sell.
i had a dealer up the road a bit years ago constantly pestering me to try their stuff.
he lost 3 engines in his personal vehicles, all due to amsoil oil.
once he switched to valvoline he never had any issues again. he also stopped selling amsoil because they absolutely refused to admit their oil had anything to do with the spun bearings, even though three different shops said it was oil issues.
 

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Arctic, my problem with amsoil besides their price and marketing strategy is that they want everyone to believe their word.
when asked for testing data they produce their own data, not oil institute data.
that to me tells me they are hiding something and is reason enough to not use anything they sell.
i had a dealer up the road a bit years ago constantly pestering me to try their stuff.
he lost 3 engines in his personal vehicles, all due to amsoil oil.
once he switched to valvoline he never had any issues again. he also stopped selling amsoil because they absolutely refused to admit their oil had anything to do with the spun bearings, even though three different shops said it was oil issues.
Ouch, Tom . . . . Good info!
 
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