Ford / Mazda M5R1 manual transmission fluid

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masospaghetti

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I just rebuilt my M5R1 in my 2000 Explorer due to very notchy action, especially when cold. I've had other vehicles with the M5R1 and they were much smoother. Anyway, even with new synchros, the shifting is notchy. I filled it with Castrol Transmax Mercon V. Factory fill says Mercon.

I would like to try synchromesh fluid but they are much heavier than ATF. Thoughts on one quart of synchromesh fluid with the remainder Dexron VI ATF? Dex VI is thinner than Mercon V or Mercon, so the overall viscosity will be very close to factory.
 
Royal Purple Synchromax
Redline DCTF
BG Synchroshift
Ravenol and Pentosin MTF
Mazda 75w80
Toyota LV MTF 75w
Castrol BOT 303.... GM dealer
Castrol BOT 350.... Mopar dealer
 
Most 75w-80 and MTF's are much thicker than the original ATF, cSt 10.4-54 compared to 7.5-34.0 for Mercon V and 6.4-30.7 for Dexron VI. Even 0w-20 motor oil is thicker than ATF.

I've heard that regular Mercon may work better than Mercon V but why? As I understand it, Mercon (or Dex/Merc) is an inferior lubricant that shears more over its lifetime compared to Mercon V but with similar viscosity.

Edit: I see that Synchromax is actually pretty close to Mercon V for viscosity, it's thinner than the other MTFs. Maybe i'll try that.
 
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I had 2 rangers, on one I used all Maxlife atf, on the other, I used 50/50 Pennzoil Synchromesh and Maxlife ATF. The shifting in the all Maxlife one was unchanged, the shifting in the Synchromesh/Maxlife one was improved.

Next time I change the fluid, I will use 2 qts. Synchromesh or all Synchromesh.
 
Originally Posted By: Johnny2Bad
They say Motorcraft Brand and Mercon3 rather than IV or V for best shift quality.

confused2.gif
There's no such thing as Mercon 3 or IV.
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Check redline website for their recommendation. If it's just atf though, might try maxlife. It's synthetic and cheap enough. Use in power steering also. I have it in the ps on my 67 f250 and it works nicely compared to the regular type f that was in there.
 
I'm running straight Synchromesh in my 1994 Ranger's formerly neglected M5OD. It really improved shifting over the Dex/Merc I used as a flush.

Synchromesh isn't like 90 weight gear oil. You can use it for the entire fill and the trans will probably thank you for it.
 
My Honda Civic 5 speed was noisy with gm friction modified synchromesh when hot. It has intermittent hard shifting into first from a stop still, but rotella t6 in the trans now has really quieted it down. Shifting seems easier. I think my trans is kinda worn. Yours being freshly rebuilt could probably make better use of the thinner stuff like synchromesh or atf but mine seems to like it a little thicker. Worth the small investment to drain and fill with something different and see if it gets better or worse to figure out what might work better in your truck.
 
Originally Posted By: 01rangerxl
I'm running straight Synchromesh in my 1994 Ranger's formerly neglected M5OD. It really improved shifting over the Dex/Merc I used as a flush.

Synchromesh isn't like 90 weight gear oil. You can use it for the entire fill and the trans will probably thank you for it.


+1 I have a 2002 F150 with the Mazda manual tranny also and it was horrible shifting and grinding using the recommended ATF. I switched to Royal Purple Synchro Max and the shifting improved tremendously. The Synchro Max is around the same viscosity a the recommend Mercon ATF. It shifts easily, even in below 0 F temps.

Whimsey
 
There are thin MTFs similar in viscosity to ATF. Search Molakule's listings. DCT fluids would also be appropriate most likely.
 
I just put in GM Manual transmission Fluid, which is basically a Dex III weight MTF. Will report back results.

I was tempted by RP Synchromax and Pennzoil Synchromesh, but RP seems to have a bad reputation and the latter is quite a bit thicker than factory. Depending how the GM fluid feels, I may end up trying the synchromesh anyway.
 
Originally Posted By: Ramblejam
Originally Posted By: masospaghetti
RP seems to have a bad reputation


Synchromax has a bad rep?


Not sure on the bad rep, but, it almost destroyed my T56 when I tried it.
At least it was grinding every gear so badly it sounded like it was eating the blocker rings/synchros for lunch.
eek.gif


So I bit the bullet, and dumped almost $80.00 worth of fluid the next day, and filled it with plain old Pennzoil Dex 3 for that fill (it was $12.00 for a gallon jug back then).
 
The Rat has a M5OD Transmission. It is my first MT in 30 yrs. I periodically top it off with whatever ATF I have. My last BMW had a line leak, so I keep a few qts around. The truck is no cream puff , so I figured the missed shifts were me abetted by wonky shifter parts It will often grind going into reverse from a cold start. Thanks for the discussion.
 
Originally Posted By: andyd
The Rat has a M5OD Transmission. It is my first MT in 30 yrs. I periodically top it off with whatever ATF I have. My last BMW had a line leak, so I keep a few qts around. The truck is no cream puff , so I figured the missed shifts were me abetted by wonky shifter parts It will often grind going into reverse from a cold start. Thanks for the discussion.


There's a Dorman shifter bushing kit that runs about $20 and might improve shifter feel a little. The bushings get chewed up and fall into the transmission. Napa, Advance, and Rock Auto carry it, and I'm sure anyone else who sells Dorman.

If your transmission needs top off, it may be losing fluid through the shift rail plugs. There are three rubber plugs at the back of the shifter housing. If they haven't been messed with before, you may be able to pop them out and replace them from the bottom with a flat screw driver. I did that on my '01 2WD. Looks like you can probably get to them by taking off the shifter boot too, but it's still tight. Some people replace them with metal freeze plugs if they have the trans out. At some point someone took the plugs out of my 1994's transmission, gooped black RTV around them, and stuck them back in. Seems to be working...it doesn't leak.
 
Bushing kit might help if the shifter has a lot of slop, they are easy to install and cheap. Basically just remove the shifter consule with a few phillips screws, one hex bolt to remove the shift lever, three torx screws for the shifter seal. You will have to drive a couple rivets out with a drift and hammer.

So far the shift action has improved with the GM Manual transmission fluid. The notchiness has been reduced compared to the Mercon V. For about $20 for three quarts (the M5R1 takes 2.6 quarts) it seems worth it.
 
I like Mobil 1 ATF in the M5R1 in my Ranger. It quieted down the gear whine in 5th compared to the factory fill. One of these days I need to have the 2nd to 3rd grind looked at, but it hasn't let me down yet.
 
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