'89 F350 Zf-5. ATF? Really?

[RedBowTies88]

I feel like here and now in 2024 there must better a better option(s) than Mercon for a heavy duty truck manual transmission, right?

I feel as though IF (reasonably) safe to step up to a 90 weight the Ford XT-MT-QS fluid would be the ticket. I've personally experienced the wonders of "Unicorn Tears" in a Miata. I've also recently used the Motul Gear 300 75w-90 in a Subaru manual trans and am quite happy with the improvement.

I've used both Redline MTL and MT-90 in the past on various cars as well as differing flavors of synchromesh options. While I've never been displeased using those, I did not see the staggering improvement that I did with the unicorn tears or the good improvement with the Motul. I have never personally used the D4 in either a manual or automatic, but I hear good things online from the Corvette/Tremec guys.

I get why they spec'd this truck/trans to use Mercon back in the day, 35+ years ago but that can't still be the best choice now?

 

[bullwinkle]

Something I know!! The actual MTF spec is “Mercon H”-but I have used Red Line D4 in my F-Super Duty ZF, and I have a spare parking brake unit that has gear oil in it (which would be bad in a brass synchro transmission). In my other Toyota manuals I have used LiquiMoly 75W90 (not the greatest), and Red Line MT-90 (best I’ve ever used).

 

[michaelluscher]

Something I know!! The actual MTF spec is “Mercon H”-but I have used Red Line D4 in my F-Super Duty ZF, and I have a spare parking brake unit that has gear oil in it (which would be bad in a brass synchro transmission). In my other Toyota manuals I have used LiquiMoly 75W90 (not the greatest), and Red Line MT-90 (best I’ve ever used).

I wonder if it was spaced for the even older A fluid
I saw this tidbit on a Ford MTF chart

XT-M5-QS or XT-4-QGL replaced SAE 80W manual transmission fluid F2ZZ-19C547-A for pre-1989 manual transmissions

Ford specifies Ford D8DZ-19C547-A Standard Transmission Lube for all Bronco and F150-F250-F350 transfer cases including the NP203. Ford specification is ESP-M2C83-C. In 1992, D8DZ19C547A was replaced by F2ZZ-19C547-A SAE 80w Manual Transmission Fluid which was later replaced by XT-4-QGL 75w90 GL-4 Conventional Gear Lube (Ford Specification WSS-M2C203-A1) AND XT-M5-QS 75w90 Full Synthetic Manual Transmission Fluid (Ford Specification WSS-M2C200-C)

Ford Transfer Case Fluid | Get The Right Type of Fluid for Ford Transfer Case on Your 1959-2022 Truck at Torque King 4x4

Explore our Ford transfer case fluid recommendations at Torque King 4x4. We’ll help you find the right type of fluid for Ford transfer case types that you need for your full-size 4x4 truck. Use our Ford transfer case fluid chart online so you can maintain your car’s long-term performance today.

torqueking.com

I'd just pony up for the FS MTF, my opinion

 

[CDX825]

You don't want to put 90 weight in a ZF-5. Way too thick! Most guys are using full synthetic atf in these now. Some use syncromesh fluid and some have used tractor transmission fluid (THF). Guys that have tried to used gear oil have reported the transmission being hard or impossible to shift.

 

[bullwinkle]

The Mercon H is NLA, if my ZF-5 has survived as long as it has on H & the D4 that’s in it now (in a 12,000 pound plus service truck) it must be good enough. My old Honda manuals got 5W30 dino juice motor oil for MTF, that was weak sauce!

 

[RedBowTies88]

I wonder if it was spaced for the even older A fluid
I saw this tidbit on a Ford MTF chart

XT-M5-QS or XT-4-QGL replaced SAE 80W manual transmission fluid F2ZZ-19C547-A for pre-1989 manual transmissions

Ford specifies Ford D8DZ-19C547-A Standard Transmission Lube for all Bronco and F150-F250-F350 transfer cases including the NP203. Ford specification is ESP-M2C83-C. In 1992, D8DZ19C547A was replaced by F2ZZ-19C547-A SAE 80w Manual Transmission Fluid which was later replaced by XT-4-QGL 75w90 GL-4 Conventional Gear Lube (Ford Specification WSS-M2C203-A1) AND XT-M5-QS 75w90 Full Synthetic Manual Transmission Fluid (Ford Specification WSS-M2C200-C)

Ford Transfer Case Fluid | Get The Right Type of Fluid for Ford Transfer Case on Your 1959-2022 Truck at Torque King 4x4

Explore our Ford transfer case fluid recommendations at Torque King 4x4. We’ll help you find the right type of fluid for Ford transfer case types that you need for your full-size 4x4 truck. Use our Ford transfer case fluid chart online so you can maintain your car’s long-term performance today.

torqueking.com

I'd just pony up for the FS MTF, my opinion

FS as in the FS40/50? This is the first I'm hearing of the stuff. Not finding much in the way of user reviews. I suppose the FS40 would be comparable weight to the Mercon? Price isn't really a concern, I just want the best feeling shifts and most protection.

You don't want to put 90 weight in a ZF-5. Way too thick! Most guys are using full synthetic atf in these now. Some use syncromesh fluid and some have used tractor transmission fluid (THF). Guys that have tried to used gear oil have reported the transmission being hard or impossible to shift.

I have heard a bit about hytrans tractor fluid. I'd be curious to find out more about that and the pros/cons of it vs either ATF or some "syncromech"

The Mercon H is NLA, if my ZF-5 has survived as long as it has on H & the D4 that’s in it now (in a 12,000 pound plus service truck) it must be good enough. My old Honda manuals got 5W30 dino juice motor oil for MTF, that was weak sauce!

Of course it would likely survive just fine on dyno ATF, but I'm looking for the best I can come up with for feel and toughness.

I mean a great many motors have survived just fine on straight weight ND 30 or regular old cheap dyno 10-30. Doesn't mean it's a good option anymore in this day and age.


Appreciate all the info so far, if anyone can broaden on some of the mentioned options or point me in a good direction for literature I'd appreciate it. Thanks!

 

[Chris142]

Iirc thick oil doesnt ube the needle bearings in those transmissions well

 

[RedBowTies88]

Iirc thick oil doesnt ube the needle bearings in those transmissions well

I'm honestly not really sure where old school Mercon falls on the weight chart.

Redline MTL isn't particularly heavy...