Need help in understanding & correct choice of MTF

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busfreak

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Mar 21, 2013
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Germany
Hi Guys,

first of all the facts:

car: Hyundai H300 TurboDiesel van
HP: power enhanced from 170 HP to 200 HP
torque: 450 NM
mileage: 50.000km
rear axle driven, normal Diff, Manual 5speed transmission


At low temperature (down to -15°C) shifting from 1st to 2nd and 2nd to 1st was very hard and needed a lot effort. Furthermore it was notchy and grinding despite of slow shift act. Gear oil recommendation is 75W-85 GL4. I dont know what type and brand original fluid was.
So I began to try diverse MTFs like Castrol. No improvement.
After searching many many hours through many internet forum I came across Redline products.
Due to the mostly very positive feedback of users relating to RL MTFs I ordered MT85.

I changed the fluid (3 qts). After that and about 700km, coldshifting became better, when the gearbox is really warm (after 1/2 hour) it is very smoothy much better than the oils before. I'm struck the gearbox is more quiet. MT85 was an improvement but it is not as it should be and I think can be.

Facts observed:

- the lower engine rpms the worse shifting is mostly !!
- if gear oil is cold it seems too slippery and 2nd gear shifts need significantly more time and effort however are notchy
- rarely the synchronizers seems to break down completely and I feel the gearwheel chattering in shift stick.
- All other gears are unremarkable in cold and very smooth in warm
- 2nd gear in warm condition sadly is not always without edged engagement of collars

Although I studied a lots of threads here I have a gap in understanding what is responsible for smoothy and correct shiftability: viscosity or FM ?

In my case I'm wondering what would improve 2nd shiftability,

lower viscosity --> RL MTL or
lower friction and viscosity --> mix of MTL with 75W-90NS or
lower friction --> mix of MT85 with RL 75W-90NS or
whatever

Trying pure MTL I would be worried, if it is too thin in summer and there would be not enough EP/AW protection.

Who can help in understanding what the issue is and what MTF or mix would be worth a try ?


thanks a lot for answers
 
I would guess the heart of your problem is worn syncro rings, the lower gears rings get more wear than the higher gears.
Also, all transmissions will be slow shifting and notchy in Sub Zero temps until things warm up.

You might try another MTL, I have used Pennzoil Syncro ( which is yellow metal safe) and have been quite pleased.
 
One you could try might be Motorcraft xt-m5-qs., available at Ford dealerships and online.

https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2704747

This oil was developed in germany as a solution for a particular transmission that ford was having problems with. It's GL4 full syn.

It ain't cheap at around twenty bucks a quart but should be a lifetime fill if it works for you.

If you try it, report back in a couple years and let me know how it worked!
 
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A proper manual transmission lubricant can do wonders for shifting as you have noted. However, if synchronizers are worn due to abuse or some defect, no lubricant can fix the resulting slow or hard shifting, or grinds when pushed past the synchornizer's remaining ability. No lubricant, even synthetic is really thin enough when it gets really cold. MTL may be worth a try if the cold shifting is a real problem. It is still a GL-4 lube and will protect, and is only one small step down in viscosity hot, 80 vs 85.

Sometimes it is just best to be patient and take it easy on that box until the lube warms up a bit to allow for faster synchronizing/shifts. I have found that when it is cold, I must change the speed of how fast I push it into the next gear while accelerating. The thicker (cold) lube causes the gears to slow down more quickly on their own between upshifts, making it easier to grab the next gear faster actually than when hot. If you wait too long while shifting gears cold, then your synchronizer is actually having to spin the geartrain UP in speed to engage the shift collar.
 
A synchronizer is essentially a miniature brake cone, that when you attempt to engage a new gear, slows down or speeds up the intended next gear until the mating (synchronizer)cone is at the same speed, then the shift collar pushes over and engages the gear teeth. If you hear grinding in a certain gear often, then most likely that syncho is worn and will always grind when you push it past it's remaining friction ability. A good lube can help some with a worn syncro, but an experienced driver can drive a worn unit without grinding as his shifting adapts to the gearbox's remaining synchro ability in each gear. With a worn gearbox, the driver IS the synchronizer, essentially.
 
Originally Posted By: suspiciousmind
He's olnly got 31k miles on the unit. It could be worn i suppose but, i seriously doubt it.


A dragging clutch plate can do that in even less miles.

Could that be an Issue here?
 
I can't confirm this, but I just switched to synchromesh in my fords 5 speed that calls for ATF. I feel like as I use the SM it keeps getting better the longer it's in there(6 months now) almost like its cleaning off the slick additives the ATF had left behind, thus allowing the syncros to work better and better as they get more friction.
It could all be in my head though.
 
Quote:
Trying pure MTL I would be worried, if it is too thin in summer and there would be not enough EP/AW protection.

- the lower engine rpms the worse shifting is mostly !!


That statement indicates to me that the OEM and other the second fluid in there did not have the proper friction modification, and possibly still a bit too viscous.

MTL 75W80 is about 10 cSt and has the correct Anti-wear and Friction modification additives, as does Pennzoil Synchromesh (9.3 cSt) and Amsoil MTL (10 cSt).
 
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thanks for answers !

@MolaKule: yes it is my assumption too. It is not a issue of worn parts, but a matter of the correct oil. I wasn't sure if viscosity is too high or low.

A few minutes ago I read a thread out of 2005 where scout wrote:

-----------------------------
quote:Originally posted by SamMan23:
Am I needing a thicker or thinner lube?

Noone has asked you the necessary question:
Two scenarios:
1. It slips through the "soft resistance" zone very easily, then grinds. (The lube viscosity is insufficient to "fill" or "load" the synchro sufficiently, and it squishes out before finishing its job.)
2. It hits the "soft resistance" as though it were a rubber barrier, and is hard to push through. (High viscosity lube is loading the syncro with a too-thick layer, that is too slippery to transfer torque through.)

At the coldest extreme of your operations, I think you should be feeling some "soft resistance", because your lube is thickest when its cold.
Are you feeling the "soft resistance" just prior to the grinding? Or not?

(Why should an older, worn transmission still be assumed to work best with the originally recommended lube? On the contrary, with no further expertise in the matter, it can be assumed to need a thicker lube, especially if problems appear!)

I have not mentioned friction modifiers, which can help both scenarios 1 and 2. I have experience changing viscosities, but not friction modifier.

-------------------

His toughts sound interesting for figuring out and drawing conclusions from deatils of shift act. Is his approach helpful ? If it is, I will pay attention on it next trip.

Apart from scouts post I understood, trying MTL purely is a good idea in terms of AP/EW additives, so there will be no risk in summer when the oil is getting thinner.
 
@mechtech2:

Sadly my car is used from my wife very often only for short trips.
In these cases the running temp of gear oil is never reached.
On top of that my wife has not really a technical feeling in order to stroke the gearbox in cold temps. So I think cold temp shifting is more important for me than for others, sadly.
 
Originally Posted By: busfreak
@mechtech2:

Sadly my car is used from my wife very often only for short trips.
In these cases the running temp of gear oil is never reached.
On top of that my wife has not really a technical feeling in order to stroke the gearbox in cold temps. So I think cold temp shifting is more important for me than for others, sadly.


This is the main reason mfrs spec ATFs and other light fluids - cold shifting complaints.
So you have to do what you +have to do.
I'm sure this is not the first or last time a concession will be made to your wife's preferences!
 
Sounds like time to experiment with one of the lighter Synchromesh fluids or Redline MTL. Please come back and update this thread and let us know how it works out. Then we all can learn something more perhaps.
 
As a fluid in which to start your experimentation, I would recomend the

Pennzoil Synchromesh

since it has a viscosity slightly above an ATF viscosity (9.0cSt) but lower than some of the other fluids such as Redline MTL or Amsoil MTL or GM Syhcromesh.

After using that fluid you could go down in viscosity to a fluid such as Castrol Syntrans or the Pentosin fluid or the Ford DCT fluid of 6.X viscosity, or then go up to the Redline MTL or Amsoil MTL or GM Syhcromesh fluids of 10.X viscosity.

The ultimate choice of course is your's to determine.
 
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Originally Posted By: MolaKule
As a fluid in which to start your experimentation, I would recomend the

Pennzoil Synchromesh

since it has a viscosity slightly above an ATF viscosity (9.0cSt) but lower than some of the other fluids such as Redline MTL or Amsoil MTL or GM Syhcromesh.

After using that fluid you could go down in viscosity to a fluid such as Castrol Syntrans or the Pentosin fluid or the Ford DCT fluid of 6.X viscosity, or then go up to the Redline MTL or Amsoil MTL or GM Syhcromesh fluids of 10.X viscosity.

The ultimate choice of course is your's to determine.


Besides the viscosity differences, are there any other major differences between the various GM Synchromeshes, and the Pennzoil stuff (basestock compositions/add packs/etc.)??
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