What's the real skinny on Manual tranny fluids and choosing what's best?

Curtis said:

More on why I originally suspected the slave/master:

Let's say that clutch pedal travel is on a scale from 1 to 10; 1 being all the way to the floor disengaged, and 10 being all the way out/engaged.  During all of my operating, the clutch starts to engage at 4, and is fully engaged at 7 (these are random guessed numbers).  So, if the clutch is engaged (10) at a stop and I push it in (1) and go for first gear, it takes a bit more effort than I'm used to.  Shifts through the rest of the gears take slightly longer than I'm used to with an M5R1.  So I did some experimenting.  If I sit at a traffic light and leave it in gear with the clutch disengaged (1) and then take off when the light is green, it still engages at 4-7 which tells me that the slave/master is not failing.  Also if I disengage the clutch (go from 10 to 1), put it in first with that little extra effort, then take it out of gear for a few seconds (or even a minute) and back in, it slides right with no effort in which tells me the clutch isn't dragging.

This leads me to think it is something internal; either worn synchros or a poorly chosen fluid.  Hence why I want to try a better fluid and see if the problem changes/improves.

That sounds an awful lot like what my M50D is doing in my Ranger. Slave was sugested to me on the forums, but I'm wondering about just doing a fluid change now. Definitely cheaper to just change fluid. 

You did read about steam cleaning but that was mostly confined to body and frame.  The engine oil pan and trans didn't get steamed as I did notice grime on them

Thanks for the tip.  I'm on therangerstation and when I posted there a few days ago, all I got was one reply that said "nice rig dude"

So, flatlander... if I'm following your tech... I should choose something maybe a little thicker for shift quality, but not quite as high as the 10.xcSt MTL?  Looks like Pennzoil's synchromesh is in the 9.x area.

Scroll down to the third post on this page and help me pick one.  Is it just the cSt, or are there different additive packages that make it better/worse by application?

In reply to wvumtnbkr : You said: First, in miata and rx7 trans, the best fluid I have found is the idemitsu fluid.  It rocks.  Only thing I have found that will keep synchro happy while road racing.

Never heard of this stuff. Please  elaborate..Sorry don’t mean to jack thread.

In reply to Curtis :

I'd try either Pennzoil Synchromesh or Redline MTL.

Yes I'm primarily looking at the kinematic viscosity in cSt.

Unfortunately it seems some transmissions take certain lubes better than  others... You really just need to try one and see what happens. FWIW I doubt any of them will be as bad as ATF since ATF lacks the friction modifiers that help synchros grab onto the blocker ring conical surface and match speeds.

This video (a really well done 3d model) may help understand what I'm talking about:

https://youtu.be/0Bqs-oHBBQk

If it were mine I'd try the Pennzoil stuff first just because it's relatively inexpensive and available locally.

Ok, I've made a decision.  The Pennzoil is cheap, and results from others is mixed.  RP Synchromax is the same KV (7.5cSt) as the Mercon.  I have decided to try the Pennzoil (9.3cSt), but I ordered some Synchromax from Amazon as a backup since I knew they would return it.

Also ordered the bushing kit for the shifter.  Mine isn't too bad, but it sure will make refilling it easier. :)

My Thunderbird SC uses the M5R2 transmission which is basically the same thing. Pennzoil Synchromesh did wonders for the shift quality.  

I also have an M5R2 in a Supercoupe. I used the GM Syncromesh at one point, and it was fine, but I've also used Mobil 1 ATF. I prefer the Mobil 1.

Part of it may depend on which blockers you have in your transmission. Not positive about the M5R1, but the R2 has brass and fiber-lined blockers available. Fiber-lined are preferred.

Some SC guys I know and trust who use Syncromesh add 5 oz. of friction modifier.

Another issue to keep in mind for FWD vehicles which run an LSD: The oil has to play nice with both, and sometimes what's best for one isn't for the other. For example, PPG straight-cut gears work great with Redline Shockproof gear oil, yet the WaveTrac LSD I was running with that gearset demands ordinary OEM-type oil - with no friction modifiers.

rustybugkiller said:

..Sorry don’t mean to jack thread.

 

Please do.  I hope it gets hijacked for a few months.  This is good tech.

kb58 said:

Another issue to keep in mind for FWD vehicles which run an LSD: The oil has to play nice with both, and sometimes what's best for one isn't right for the the other. For for example, PPG straight-cut gears work great with Redline Shockproof gear oil, yet the WaveTrac LSD I was running with that gearset demands ordinary OEM-type oil - with no friction modifiers.

This is important to research. Redline MT-90 in my Mazdaspeed3 cleaned up shifts but now the diff makes a “wah wah” noise in low speed sharp turns. Apparently it’s not a problem but it is annoying. 

Idemitsu was recommended by mazdatrix.  It is available on their website.

I have found it a few other places, but that is the o my place I can find it reliably.  It's expensive, but magic.

They need to flow, and be slippery, but not too slippery. 

Viscosity, friction modifiers, friendliness to yellow metals used in synchros, lot of stuff goes into transmission lubricants.  It really is like voodoo, except there is no chicken involved, and the witch doctor is some German guy.  

There is a big hubbub in the Toyota truck community about gl-5 wiping out syncros in W-58 boxes. I drove all over hell finding gl-4, only in a slightly thicker than spec weight. Didn't notice any improvement, or degredation in shifting. The original specs must work. The trans has 449, 775mi on it with no grinding.

In reply to Curtis :

Synchromesh was supposed to be the hot ticket backs when I had a m50d equipped f150

In reply to Curtis :

Transmission fluid can be a very tricky thing. 

Front wheel drive cars usually have the front differential sharing the trans oil thus the life of the diff is part of the fluid choice not just the transmission syncros and shifter. 

Syncros can be engineered to work best with this or that fluid. Material selection for the syncros is a long topic during the life of the transmission development. For instance the neon NV350 trans had a special fluid that worked beat with giving you a quick shift. Not using the special gear oil with the hypoid additive could reduce the syncro effectiveness. Thus causing the gears to just snap together when in sync. So it may seem line your syncroyare fixed or last longer but in reality you are kind of defeating them and transfer the stresses to the gears themselves. 

Rear drive transmission fluid can be changed up with less effect on other drivetrain. 

All that said, the service manual guidance  is probably the way to go. Unless you want to learn about your specific transmission material choice for the syncros. 

If dealing with the old hydraulic trans control modules then all the more reason to stick with what is recommended. I never had such a vehicle but I understood that the fluid is like the voltage and current into a modern electronic trans controller. You would not just change the voltage going into that so don't change the fluid in a trans hydraulic controller.

Main point is fluid for your trans is never a topic where we have "The Answer" for all vehicles 

Just finished the thread so far and had about 17 different transmission fluid questions in my head mesh together with answers at the same time. Thank you guys for your timely knowledge. Edit. Reached halfdork status on this post. Yay!

For my manual transmissions, I've had good luck going with the OEM fluids, or the equivalent spec from Redline.

ive owned a 91 ranger now for 17 years. I use mercon v with some lucas tranny fix stuff, huge, huge, HUGE difference in shifting. Its way smoother than it ever was with just mercon V.

None of what you say sounds like the slave cylinder, which is a total bitch in my year ranger since its inside the bellhousing. Mine wouldnt shift into first from a stop nor reverse, you would have to turn the car off to make it happen. I drove it for awhile with that going on until i ended up having to powershift always

I used Amsoil Synchro for 9yrs/65K in my ZX2SR which inclued track  days, ice  racing an hill climbs with no problem.   Seemed to shift nicer than the ATF.

In reply to Antihero :

The slave cylinder on my brother's was a PITA, but for some reason getting it bleed was worse.  it took far more time, swearing, and fluid than it should have.

Lots of good info in this thread. 

I use 20W50 motor oil in my mini's gearbox, since it sits in the oil pan and shares engine oil. I have a 2nd gear synchro that is not always happy. I wish I could just try some Penzoil magic beans to help it. 

Appleseed said:

There is a big hubbub in the Toyota truck community about gl-5 wiping out syncros in W-58 boxes. I drove all over hell finding gl-4, only in a slightly thicker than spec weight. Didn't notice any improvement, or degredation in shifting. The original specs must work. The trans has 449, 775mi on it with no grinding.

This is also the case with Nissan's fs5r30a tran that were in z31's, z32's, and pathfinders/hardbodies. It was said that gl5, although supposed to be backwards compatible, was not friendly to the syncros that were spec'd for gl4. I couldnt find anywhere that had gl4 local so i ended up just ordering some on Amazon.

Also i cant speak on the Ranger trans, but I know the ZF5 in my f250 is waaaaay happier with ATF (that it's spec'd for) then whatever gear oil was in it from the previous owner, slides into each gear on upshifts and downshifts much easier.

Its your clutch wearing out.  I have a 97 Ford Ranger with the 5 speed manual.  I did all the stuff you are writing about including changing the clutch master cylinder.

I ended up changing the clutch and its slave cylinder and all was well.  I think the internal slave cylinder runs out of travel when the clutch wears out and you get to the point where the clutch does not fully disengage.  At that point, on mine at least, I could barely get it into first gear at a stop light.

I have put about 80,000 miles on the truck since then and its starting to do it again.  The first clutch lasted about 90,000 miles but I was doing a lot of highway driving then.

jharry3 said:

Its your clutch wearing out.  I have a 97 Ford Ranger with the 5 speed manual.  I did all the stuff you are writing about including changing the clutch master cylinder.

I ended up changing the clutch and its slave cylinder and all was well.  I think the internal slave cylinder runs out of travel when the clutch wears out and you get to the point where the clutch does not fully disengage.  At that point, on mine at least, I could barely get it into first gear at a stop light.

I have put about 80,000 miles on the truck since then and its starting to do it again.  The first clutch lasted about 90,000 miles but I was doing a lot of highway driving then.

That is a common issue with M5ODs, but it doesn't appear to be the case with mine.  At a stop, if I push in the clutch and go for a gear, I feel the synchros and it goes in with a little more than normal effort.  Now, if I leave the clutch disengaged, pull it out of gear for a while, then go back into that same gear, it goes straight in without pause.  If the clutch were dragging, it would have to re-synch but it doesn't.

In the TKO for the truck, I asked the folks at Bowler what their recommendation was for it. I know Tremec recommends Syncromesh or Synthetic ATF. They use Dex VI ATF and that was their recommendation for me. I tried it and it shifts better.