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What Fluid is in your M5OD?

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Old 06-22-2018, 06:43 PM
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What Fluid is in your M5OD?

I've already changed the fluid in my M5OD with some super cheap Dex/Merc but decided to experiment with some additives and other fluids to see if they might smooth out the shifting. I read some people had success with a 3:1 mix of ATF to Lucas Oil Stabilizer. So I drained a quart of ATF out and put in a quart of Lucas. After 50 miles or so, it feels worse if anything. So I'm gonna drain that out and I think I'm gonna go with Valvoline Maxlife Synthetic multi-vehicle ATF next. Anyone running it? I was gonna try the Royal Purple Synchromax but at $16 a quart, I'll pass. Any other suggestions?

Also I'm not expecting any miracles by changing fluid. My transmission is just a but notchy going from first to second as it takes a second or so for the synchro to synch up, but otherwise it's fine. I'd just like to see if I can smooth it out even a tiny bit, even if it is just placebo.
 
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Old 06-22-2018, 07:27 PM
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Non synthetic Mercon. No issues other than it leaks.
 
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Old 06-22-2018, 07:47 PM
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Synthetic mercon V here, I'm about due for a change and I've heard many positive reviews about redline MTL and pennzoil synchromesh fluid that I will try next. Currently have an occasional grind on the 1-2 and 2-3 upshift especially when cold...
 
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Old 06-22-2018, 07:48 PM
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Mine is notchy as well from 1-2 and from 2-3. Can't tell if it's my shifting or something with the synchros. I changed 175K old fluid (guessing) with some Mobil 1 ATF and the shifting didn't seem to change.
 
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Old 06-23-2018, 11:02 AM
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I think the M5OD is a notchy transmission to begin with, so it'll probably never shift totally smooth. I've heard mixed results on people running synchromesh and people running Mercon V. I wish I could find a synthetic Dex/Merc, but the only synthetic I can find is Merc V or the Valvoline Multi-Vehicle, which I think I'm going to try.
 
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Old 06-23-2018, 04:06 PM
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I've got super generic ATF in mine and I change it every 40k or so. It's been fine for 120k that I've had it, short of replacing shift forks.. but, I think that's par for the course when it comes to the m5od.
 
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Old 06-23-2018, 09:03 PM
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Mobil 1 synthetic ATF. My buddy ran it in his zf5 for years and swore by it, so I gave it a shot. Only have about 1000 miles on it but it seems to be happy so far. Its always been a little glitchy on the 2-3 shift...maybe 1/50 times it will grind a little. The synthetic seems to have taken it away mostly. Still happens very rarely.
 
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Old 06-24-2018, 04:25 AM
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Originally Posted by miguel.in.az View Post
Currently have an occasional grind on the 1-2 and 2-3 upshift especially when cold...
I just installed a 1991 M5OD in my 1984, and came here looking for fluid upgrades (if such a thing existed). I bought this transmission used, and the seller claimed it had about 100k miles on it, and that it shifted fine. It's a bit notchy sometimes on the 1-2 and 2-3 shifts...probably more noticeable on the 2-3 shifts. It also doesn't like to be shifted fast. If I shift it nice and slow, it seems much smoother that way...but that's shifting it almost too slow if that makes any sense...lol. I thought maybe I was having clutch slave issues...but judging by what I'm reading in this thread, the M5OD is not a smooth shifter anyway...

In any case, I'm just replying so I can be subscribed to the fluid discussion. If there's a fluid that performs better, I'd gladly try it.
 
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Old 06-27-2018, 02:36 PM
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Originally Posted by Rembrant View Post
It's a bit notchy sometimes on the 1-2 and 2-3 shifts...probably more noticeable on the 2-3 shifts. It also doesn't like to be shifted fast. If I shift it nice and slow, it seems much smoother that way...but that's shifting it almost too slow if that makes any sense...lol.
Sounds like my M5OD. It's a little slow to go into second and third gear which makes it a little difficult to drive it really smooth or take off fast. I don't like jamming it into gear, so I just shift it slow, I'm not racing or anything. I drained and filled it STP Dex/Merc which is an improvement over the Carquest stuff that was in it, but it isn't anything to write home about. I may try the Redline or Synchromax next.
 
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Old 06-28-2018, 09:10 PM
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Originally Posted by Rembrant View Post
I just installed a 1991 M5OD in my 1984, and came here looking for fluid upgrades (if such a thing existed). I bought this transmission used, and the seller claimed it had about 100k miles on it, and that it shifted fine. It's a bit notchy sometimes on the 1-2 and 2-3 shifts...probably more noticeable on the 2-3 shifts. It also doesn't like to be shifted fast. If I shift it nice and slow, it seems much smoother that way...but that's shifting it almost too slow if that makes any sense...lol. I thought maybe I was having clutch slave issues...but judging by what I'm reading in this thread, the M5OD is not a smooth shifter anyway...

In any case, I'm just replying so I can be subscribed to the fluid discussion. If there's a fluid that performs better, I'd gladly try it.
I feel you on the slow shifts, but unfortunately I've got the dynamic duo of slow! Not only do I have to shift slow but I've also got to accelerate slow! Intersections are the worst, I'm tapped out in first halfway thru and then end up coasting the rest of the way through whilst shifting!

I can't complain too much - I'd like to see a newer pickup sit in the woods for 12 years and come back out running like a dream! Good ol' big six
 
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Old 06-29-2018, 07:06 AM
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Originally Posted by evan_nugget View Post
Intersections are the worst, I'm tapped out in first halfway thru and then end up coasting the rest of the way through whilst shifting!
Haha, I'm happy to know that there is at least one other M5OD shifting exactly the same as mine! That 1st to 2nd shift is the worst because of how slow I have to do it. 2-3 isn't so bad, and I have some momentum by then, so it carries me a bit.
 
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Old 06-29-2018, 05:20 PM
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Same here, I usually shift when it "feels right" and the 1-2 is clunky. But, I found pushing the revs around 500 higher, it seems to shift easier. So when leaving a red light I just blip the revs a bit higher and no coasting to get it into second.
 
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