ZF6 issues
Team Owner
Joined: Aug 2005
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From: Riverside County Southern California
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The ZF is an unique animal. It is noisy, and the stock shifter is weird. The ZF is one strong son-of-a-gun, change the oil with motor oil 5W30 or Amsoil Synchromesh, and it will serve you for a long time.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Sure. My ZF shifts better than any manual trans car I've owned, except for an Integra. If you're having issues, I'd be checking the hydraulic clutch linkage, and changing the oil.
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
The slave cylinders in these cars won't last forever, and this could be the cause of notchy shifting as well. The last slave I bought I got from NAPA and it help up better the previous two from Advanced Auto. But i wouldn't change it unless it's leaking.
Another possibility is the pivot stud for the clutch fork could be wearing out. These tend to groove on the sides and will cause the fork to hyper-extend, may nit be getting a full clutch release.
Worst case is bad synchros.
I would start with new hydraulic fluid and new oil in the trans. Amsoil Synchromesh was my favorite.
Safety Car
Joined: Aug 2008
Posts: 4,344
Likes: 48
From: San Marcos CA
The shifter may have an overly mechanical feel and be audibly clunky, but should shift up and down like butter when the trans oil is warm.
As others said check the clutch hydraulics and maybe the oil. I am also in the Amsoil camp as they sell a 5w-30 equivalent viscosity replacement oil (the synchromesh oil). I understand the original oil fill was of the same weight.
Others like the BMW 10w-60 oil as ZF recommended it when the GM oil became no-longer-available from the dealer. I found the 10w-60 took a lot longer to warm up and was sensitive to being notchy going into 3rd unless you really really pushed the clutch to the floor and shifted at exactly the right time (the synchros didn't work as fast basically). The upside is the heavier oil will probably last a little longer before it would need to be changed, but the Amsoil feels like stock (I've driven a few of these cars and know what they should feel like).
As others said check the clutch hydraulics and maybe the oil. I am also in the Amsoil camp as they sell a 5w-30 equivalent viscosity replacement oil (the synchromesh oil). I understand the original oil fill was of the same weight.
Others like the BMW 10w-60 oil as ZF recommended it when the GM oil became no-longer-available from the dealer. I found the 10w-60 took a lot longer to warm up and was sensitive to being notchy going into 3rd unless you really really pushed the clutch to the floor and shifted at exactly the right time (the synchros didn't work as fast basically). The upside is the heavier oil will probably last a little longer before it would need to be changed, but the Amsoil feels like stock (I've driven a few of these cars and know what they should feel like).
Last edited by mike100; Apr 13, 2015 at 10:03 AM. Reason: typos
Burning Brakes
Joined: Sep 2005
Posts: 993
Likes: 3
From: Iowa
Yeah I agree. I would check the hydraulics out on it and see if they are good to go. Then service the fluid; the Castrol BMW oil is trick oil but in my opinion not the oil you want in the ZF S640....especially if it's cold outside...ask me how I know...lol Just my .02
Pro
Joined: Jan 2015
Posts: 538
Likes: 36
From: Northern Colorado
Don't forget about CAGS one-to-four forced shift if you're driving it wrong !! Be Well !!
Team Owner
Joined: Feb 2006
Posts: 23,110
Likes: 117
From: San Antonio Texas
Are you sure you don't have an aftermarket shifter or do you know it is the original still in there?
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Melting Slicks
Joined: Jul 2011
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From: Trinity FL
Thread Starter
Instructor
Joined: Nov 2014
Posts: 104
Likes: 0
I can use just plain old 5w30? I have access to a ton of it for free. Maybe this is the easiest route to take first, before I start dropping dollars at something that may not make a differece.
And yes it has a very long throw, I really only feel the pass through "gate" into 3rd, everything else feels normal its just a very long throw and like I said feels kinda clunky, not like a little honda shifter thats like butter.
And yes it has a very long throw, I really only feel the pass through "gate" into 3rd, everything else feels normal its just a very long throw and like I said feels kinda clunky, not like a little honda shifter thats like butter.
Safety Car
Joined: Aug 2008
Posts: 4,344
Likes: 48
From: San Marcos CA
I can use just plain old 5w30? I have access to a ton of it for free. Maybe this is the easiest route to take first, before I start dropping dollars at something that may not make a differece.
And yes it has a very long throw, I really only feel the pass through "gate" into 3rd, everything else feels normal its just a very long throw and like I said feels kinda clunky, not like a little honda shifter thats like butter.
And yes it has a very long throw, I really only feel the pass through "gate" into 3rd, everything else feels normal its just a very long throw and like I said feels kinda clunky, not like a little honda shifter thats like butter.
Burning Brakes
Joined: Apr 2009
Posts: 1,228
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From: That one city...you know that one. Idaho
Racer
Joined: Mar 2012
Posts: 456
Likes: 4
From: Columbus Oh
When I bought my 1991, the trans was very notchy/clunky. I changed to fresh oil and things got much better. When the engine was out, we converted it to crash through and put a hurst shifter in it and refilled it with synchromesh. Now it's much closer to what I expected it to be in the first place. The shorter shifter feels less clunky than the original did with old oil in it (or I'm guessing it was old oil, I don't know for sure).
Safety Car
Joined: Aug 2008
Posts: 4,344
Likes: 48
From: San Marcos CA
I think I paid $11-12-ish per bottle, but I had to pay for shipping for 3 bottles and probably the job cost around $40. Probably I got confused with my truck and mustang which use a little more oil... I'm using 4 qts Amsoil in my OBS(old body style) F-150 to replace the mercron atf that was the original fill.
I'm actually curious to try the GM Synchromesh because the Carquest franchise down the street stocks it and I bet I can get them for $9 a bottle. I only have 10k miles on this Amsoil lube though so I'm gonna go another year or two on it.
I'm actually curious to try the GM Synchromesh because the Carquest franchise down the street stocks it and I bet I can get them for $9 a bottle. I only have 10k miles on this Amsoil lube though so I'm gonna go another year or two on it.
Safety Car
Joined: Aug 2008
Posts: 4,344
Likes: 48
From: San Marcos CA
Thread Starter
Instructor
Joined: Nov 2014
Posts: 104
Likes: 0
One other thing I forgot to mention is sometimes it wont go into first unless I depress the clutch all the way and let it out a tiny bit, I can feel it go into first, same thing with reverse sometimes. Doesnt always happen just here and there.
Team Owner
Joined: Feb 2006
Posts: 23,110
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From: San Antonio Texas
Mine will do that every once in a while mostly for reverse. I just bump any other gear first and then it will go right in. I think it lines up the synchros on the gear shaft and lets things slide together better.
Thread Starter
Instructor
Joined: Nov 2014
Posts: 104
Likes: 0
Yeah I have noticed you really need to shift into 2nd to get into first if your at a light, and if you are rolling and try to put it into first it will make a god awful crunch sometimes, never had that issue before this car.
Pro
Joined: Oct 2012
Posts: 672
Likes: 2
From: Cheltenham, England
[QUOTE=lt4obsesses;1589404545]Agreed. Check the fluid level. You'll have to lift the ecm to get to the resevior, also check color. If it's black, you should change it. Bleeding is a pain, or you could use the 'ranger' method.
By far the easiest way is the 'reverse bleed' method, I did mine in a matter of minutes, you have to get under there anyway, so you might as well pump it in through the slave, guaranteed no air bubbles! why push the air down through the system when it wants to rise naturally..
By far the easiest way is the 'reverse bleed' method, I did mine in a matter of minutes, you have to get under there anyway, so you might as well pump it in through the slave, guaranteed no air bubbles! why push the air down through the system when it wants to rise naturally..