Manual transmission confusion

[SubieNate]

Hey All, first post here. Been lurking for quite a while.

I've got an FR-S with the Aisin manual. It calls for a 75w-90 GL4. Shifting varies from car to car, but the general consensus is that 1-2 and a few other shifts often leave something to be desired, especially in the cold. Some have reported good results on MT-85, others like Motul Gear 3000 in 75w-90. Still others are swearing by Pentosin MTF2, which isn't even close to factory spec viscosity wise. Comments such as "The engineers were asleep when they specced the factory fill" seem pretty common. I'm unconvinced.

Is it really a good idea to run a fluid so far off from factory spec, even if it's a high quality fluid?

Secondly, I'd like to clarify specs, if I can, on the Ford Motorcraft "Honey". On the Miata forums, they're adamant it's a 75w90 equivalent GL4 made by Fuchs in Germany. Big Jim here says it's made by castrol and closer to a 10w40 diesel oil. This disagrees with the ford spec sheet here:

https://www.fcsdchemicalsandlubricants.c...ion%20Fluid.pdf

So unless that spec sheet is outdated I am very confused. If it is up to date, I am inclined to give this stuff a shot as it seems to hit all the points (GL4, right viscosity per my manual, specifically formulated to improve syncro operation etc). That plus it's glowing rep on other similar transmissions has me intrigued.

For the moment I've ordered some Motul as my track driving buddies swear by it for this car, but for daily driving I'm not convinced it's gonna have the cold performance I'd like.

Thanks!
Nathan

 

[antiqueshell]

If the car is still under warranty do NOT use anything that is not the correct factory spec.

That being said in any case I would use a fluid that is close to the factory spec, a slight variation won't be a problem or cause potential damage, however using a product that is not close to factory opens up a whole new can of worms.

Especially important is the GL specification. If the manual clearly states GL 4 do NOT (NEVER EVER) use any other GL spec....
including those that say GL 4+5, GL 4+, or GL 4/5.

Only use GL 4 which has the correct friction modifiers, using something else could cause corrosion, and or rapid wear!

 

[MolaKule]

Welcome Nathan.

I would only add the following to what Antiqueshell has already stated.

Many MTs were speced for 75W90 for CYA purposes but customers found the 14.5 cSt@100C (75W90s) fluids shifted poorly in cold weather.

If your tranny is shifting ok in cold weather with a 14.5 cSt@100C (75W90s) fluid GL-4 fluid stay with it.

Sometimes you just have to experiment with different fluids to find the one that plays well with your tranny.

For new transmissions, the range of dedicated MT fluids below will offer plenty of AW protection and provide the proper friction modification for the synchro assembly.



Quote:
H. The next group of MTL’s are in the 10.x cSt range are:

1. Redline MTL 75W80

2. Amsoil MTL

3. GM Synchromesh’s

4. Volvo MTF 645

5. Ford Motor Craft XT-M5-QS
6. Fuchs TITAN SINTOFLUID SAE 75W-80 synthetic MTF (Carries a GL-5 rating as well)
7. Lodexol (Morris Lubricants) MTF

I. The next higher viscosity MTL would be:

1. Redline MT-85 – 12.0 cSt


J. The next higher viscosity MTLs in the 75W90 range would be:

1. Amsoil MTG

2. Redline MT-90

3. Castrol Syntrans Multivehicle 75W-90
4. Castrol Syntrans Transaxle 75w-90
5. Ford XT-75W90-QGT (Carries a GL-5 rating as well)
6. MOTORCRAFT® Full Synthetic Manual Transmission Fluid

 

[SubieNate]

Molakule and antiqueshell, thanks for your input. I personally have had a not horrible time with shifting, but not perfect either. Would you recommend against the Motul? From what I've read it's one of the better 4/5 rated ones for transmission operation but if there's a better option I'm all for it. I can always save the extra quarts for the diff.

Can you give any more into on the Mototcraft fluid I linked? Your 100C viscosity doesn't line up with what's in the linked spec sheet. Thanks!

Do you believe (off the record of course ) that the pentosin is thick enough to provide adequate protection for this tranny? The syncros are important but there is so much more going on. Good syncro performance is worthless if the actual gears or transmission bearings give out because of a lower viscosity fluid.

cheers
Nathan

 

[SubieNate]

Looking at your sheet, you have the XT-M5-QS listed under the ~10cP category and the "Motorcraft full Synthetic Manual Transmission Fluid" under the 75w90 section. According to this:

https://www.fcsdchemicalsandlubricants.c...mission%20Fluid

They are one and the same. What gives? This may be the source of my confusion. Amy thoughts on the quality of thosbfluid are appreciated as well.

Thanks!
Nathan

 

[MolaKule]

Originally Posted By: SubieNate
Looking at your sheet, you have the XT-M5-QS listed under the ~10cP category and the "Motorcraft full Synthetic Manual Transmission Fluid" under the 75w90 section. According to this:

https://www.fcsdchemicalsandlubricants.c...mission%20Fluid

They are one and the same. What gives? This may be the source of my confusion. Amy thoughts on the quality of thosbfluid are appreciated as well.

Thanks!
Nathan


Haha, I see what what you found.

Ford has changed the XT-M5-QS from a 10cSt fluid spec to a 15 cSt fluid. Also, Ford used to have three MT fluids in their stable. It appears they now have only two.

A number of years ago I tested part number XT-M5-QS and the viscosity was 10.7 cSt. My neighbor was replacing the fluid in his Ford 5-speed manual (MTF came from the local Ford Dealer) which called for a 5W30 MTL. We had about 5 oz. left over so I sent in a sample for analysis.

It is not unusual for a manf. of trannies or oil manf. to change viscosity requirements in the intervening years.

The corrected list is below:

Quote:
H. The next group of MTL’s are in the 10.x cSt range are:

1. Redline MTL 75W80

2. Amsoil MTL

3. GM Synchromesh’s

4. Volvo MTF 645
5. Fuchs TITAN SINTOFLUID SAE 75W-80 synthetic MTF (Carries a GL-5 rating as well)
6. Lodexol (Morris Lubricants) MTF

I. The next higher viscosity MTL would be:

1. Redline MT-85 – 12.0 cSt


J. The next higher viscosity MTLs in the 75W90 range would be:

1. Amsoil MTG

2. Redline MT-90

3. Castrol Syntrans Multivehicle 75W-90
4. Castrol Syntrans Transaxle 75w-90
5. Ford XT-75W90-QGT (Carries a GL-5 rating as well)
6. Ford MOTORCRAFT® Full Synthetic Manual Transmission Fluid XT-M5-QS


Since I have experience only with the 10 cSt version fluid, I cannot tell you how well the 75W90 shifts in various temps. Since Ford specialty lubricant products are usually first rate, IHMO, I would assume it would protect as well as any.

I do know many people have replaced their FF 75W90s with either Amsoil MTL or Redline MT-85 and have had better shiftability in most temps.

 

[MolaKule]

Quote:
Sometimes you just have to experiment with different fluids to find the one that plays well with your tranny.



Quote:
Do you believe (off the record of course ) that the pentosin is thick enough to provide adequate protection for this tranny? The syncros are important but there is so much more going on. Good syncro performance is worthless if the actual gears or transmission bearings give out because of a lower viscosity fluid.


On the record, try the Pentosin.

One way you can determine if the fluid is too thin, use it for about 250 miles. If the transmission feels "loosey-goosey" or sloppy, or if the tranny makes new noises, then change to a higher viscosity fluid in about 5 cSt increments until you find one that plays well.

 

[SubieNate]

How far from factory fill cSt can one safely go when trying different fluids? What is the potential for permanent damage?

Thanks!
Nathan

 

[MolaKule]

It dpends on the original spec and tranny design.


I don't think you should go more than about minus 8 cSt from the current viscosity if the tranny is speced for 15 cSt.

I have supplied dirt track racers with my 7.5 cSt MT fluid which was speced for 15 cSt and have had no failures related to lubrication.

 

[SubieNate]

Considering warranty and it's success in the Mazda world, would the ford fluid be worth a shot before switching viscosities or do you believe that 15cSt is just too high for syncros?

I'm curious about the GM 75w90 gl4 synthetic as well but it's like $30 a liter online.

Thanks!
Nathan

 

[MolaKule]

I don't know a whole lot about Mazda's warranty claim reputation, but try the Ford MTL. If you do have a warranty claim, at least you will be using the speced viscosity.

And since you live in a mild climate, I doubt you will be having any shiftability problems at -25F like we do here.

 

[SubieNate]

Thanks! I'll try it and update the thread for reference at a few different mileages.

Cheers
Nathan

 

[SubieNate]

I'm bumping this up super late because I'm putting MTF in my new car and just realized I never updated this.

I liked the Ford stuff about 80% of the time but occasionally it felt a little stiff when cold and I wasn't super keen on that. I ran it for about 10k and then switched out for Motul Gear300 which I stuck with for the rest of my ownership of the car. Good stuff.

 

[MolaKule]

Does this SUbie have the common sump for the transmission and differential?

 

[SubieNate]

No. It's a standard Aisin transmission. I wanted to try the Ford before the Motul because it's a GL4 only (Not GL4+5 like the Motul), but I didn't really like the feel and had friends that tracked frequently that swore by the Motul. It seemed to work out well so I can't argue with the results.

 

[kr_bitog]

Originally Posted By: SubieNate
No. It's a standard Aisin transmission. I wanted to try the Ford before the Motul because it's a GL4 only (Not GL4+5 like the Motul), but I didn't really like the feel and had friends that tracked frequently that swore by the Motul. It seemed to work out well so I can't argue with the results.


You may also try Redline, they have very specific spec for trans oil. You may find a better option based on your application.

 

[zeng]

Originally Posted By: SubieNate
No. It's a standard Aisin transmission. I wanted to try the Ford before the Motul because it's a GL4 only (Not GL4+5 like the Motul), but I didn't really like the feel and had friends that tracked frequently that swore by the Motul. It seemed to work out well so I can't argue with the results.


I'm thinking aloud Motul 300 has more consistency than Fords MTF oils , never mind Motul's GL5 status.

Could it be caused by additives or base oils ?

 

[SubieNate]

My overall impression was that on a good day the Motorcraft felt better than the Motul, but that when cold and on bad days it felt worse. The Motul just felt "good" all the time, where as some shifts with the Ford were buttery smooth and some made me cringe.

Some of the Miata guys (where I got the Motorcraft idea in the first place) claim that it really starts to make the shifts better after the second fill. But waiting 30k miles to feel a difference seems ridiculous to me.

I don't own the car anymore so it's a bit of a moot point.

My new car is loving some Pentosin MTF2.