ZF S6-40 shifting problem
Thread Starter
Intermediate
Joined: Dec 2010
Posts: 26
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ZF S6-40 shifting problem
I have a 94 coupe with 70k. When doing a fast shift first to second I get a crunch. This is not a problem with any of the other gears. I would never try a wot power shift. I am afraid I have a syncro problem but for now do not want to rebuild the trans since this is just a driver and I don't race.
I had mobile 1 10w30 in the trans but assumed it was too slippery so I changed to Pennzoil Syncromesh. Pennzoil says on the label compatible for GM 12345349. This helped very little. I was wondering if anyone has gone from the thin 5w-30 oils to the thick Castrol tws 10-60 and found this to help a 1-2 shift crunch.
Since I can fast shift any of the other gears I don't think it's clutch related.
I had mobile 1 10w30 in the trans but assumed it was too slippery so I changed to Pennzoil Syncromesh. Pennzoil says on the label compatible for GM 12345349. This helped very little. I was wondering if anyone has gone from the thin 5w-30 oils to the thick Castrol tws 10-60 and found this to help a 1-2 shift crunch.
Since I can fast shift any of the other gears I don't think it's clutch related.
Thread Starter
Intermediate
Joined: Dec 2010
Posts: 26
Likes: 0
Thread Starter
Intermediate
Joined: Dec 2010
Posts: 26
Likes: 0
2nd gear synchro
I have a 94 coupe with 70k. When doing a fast shift first to second I get a crunch. This is not a problem with any of the other gears. I would never try a wot power shift. I am afraid I have a syncro problem but for now do not want to rebuild the trans since this is just a driver and I don't race.
I had mobile 1 10w30 in the trans but assumed it was too slippery so I changed to Pennzoil Syncromesh. Pennzoil says on the label compatible for GM 12345349. This helped very little. I was wondering if anyone has gone from the thin 5w-30 oils to the thick Castrol tws 10-60 and found this to help a 1-2 shift crunch.
Since I can fast shift any of the other gears I don't think it's clutch related.
I had mobile 1 10w30 in the trans but assumed it was too slippery so I changed to Pennzoil Syncromesh. Pennzoil says on the label compatible for GM 12345349. This helped very little. I was wondering if anyone has gone from the thin 5w-30 oils to the thick Castrol tws 10-60 and found this to help a 1-2 shift crunch.
Since I can fast shift any of the other gears I don't think it's clutch related.
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
I have a 94 coupe with 70k. When doing a fast shift first to second I get a crunch. This is not a problem with any of the other gears. I would never try a wot power shift. I am afraid I have a syncro problem but for now do not want to rebuild the trans since this is just a driver and I don't race.
I had mobile 1 10w30 in the trans but assumed it was too slippery so I changed to Pennzoil Syncromesh. Pennzoil says on the label compatible for GM 12345349. This helped very little. I was wondering if anyone has gone from the thin 5w-30 oils to the thick Castrol tws 10-60 and found this to help a 1-2 shift crunch.
Since I can fast shift any of the other gears I don't think it's clutch related.
I had mobile 1 10w30 in the trans but assumed it was too slippery so I changed to Pennzoil Syncromesh. Pennzoil says on the label compatible for GM 12345349. This helped very little. I was wondering if anyone has gone from the thin 5w-30 oils to the thick Castrol tws 10-60 and found this to help a 1-2 shift crunch.
Since I can fast shift any of the other gears I don't think it's clutch related.
I've only used the Castrol TWS 10-60 but when I first used it, it did make a nice difference in the shifting. Our 94 with the TWS shifts nicer than our 2000s (the 2000s both use automatic tranny fluid).
Also, every lubricant has different additives and friction effects so since ZF recommends the TWS, suggest trying it, but be sure to give it a couple of thousand miles and maybe even another fluid change before deciding (don't forget to change it every 10-12k nonetheless).
However, I would not rule out a problem with the clutch system because it shifts ok between the other gears. Just a minor deficiency of the hydraulics can prevent the clutch from full disengagement, and generally most trannys shift easier between the higher gears than lower gears.
Suggest reading info on zfdoc.com and consider at least flushing/bleeding the clutch system to see if it helps before considering a rebuild.
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
rjrjs,
I've only used the Castrol TWS 10-60 but when I first used it, it did make a nice difference in the shifting. Our 94 with the TWS shifts nicer than our 2000s (the 2000s both use automatic tranny fluid).
Also, every lubricant has different additives and friction effects so since ZF recommends the TWS, suggest trying it, but be sure to give it a couple of thousand miles and maybe even another fluid change before deciding (don't forget to change it every 10-12k nonetheless).
However, I would not rule out a problem with the clutch system because it shifts ok between the other gears. Just a minor deficiency of the hydraulics can prevent the clutch from full disengagement, and generally most trannys shift easier between the higher gears than lower gears.
Suggest reading info on zfdoc.com and consider at least flushing/bleeding the clutch system to see if it helps before considering a rebuild.
I've only used the Castrol TWS 10-60 but when I first used it, it did make a nice difference in the shifting. Our 94 with the TWS shifts nicer than our 2000s (the 2000s both use automatic tranny fluid).
Also, every lubricant has different additives and friction effects so since ZF recommends the TWS, suggest trying it, but be sure to give it a couple of thousand miles and maybe even another fluid change before deciding (don't forget to change it every 10-12k nonetheless).
However, I would not rule out a problem with the clutch system because it shifts ok between the other gears. Just a minor deficiency of the hydraulics can prevent the clutch from full disengagement, and generally most trannys shift easier between the higher gears than lower gears.
Suggest reading info on zfdoc.com and consider at least flushing/bleeding the clutch system to see if it helps before considering a rebuild.
Pro
Joined: Feb 2003
Posts: 715
Likes: 21
From: Ontario California
I have a 94 coupe with the ZF 6-speed, and it shifted fine, until I had a Hurst short shifter installed in the car. Now I get a condition, every once in awhile...where the shifter hangs up, between first and second gear. I have to push and pull it in several directions, before it will go into second gear. The same condition has happened before in the 3rd to 4th shift, but not as frequent. I was told there is no external shifting linkage to adjust, so what ever is going on, happens on the inside.
I have looked a zf.doc.com site, and there they say that something like 80% of transmission problems are caused by the clutch. The master or servo wears, and isn't fully releasing the clutch between shifts. So now I'm wondering if I should replace the master and servo units first?
Any suggestions??
I have looked a zf.doc.com site, and there they say that something like 80% of transmission problems are caused by the clutch. The master or servo wears, and isn't fully releasing the clutch between shifts. So now I'm wondering if I should replace the master and servo units first?
Any suggestions??
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Verdad Gallardo
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Joined: Sep 2001
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From: NEwhere Ohio
rjrjs,
I've only used the Castrol TWS 10-60 but when I first used it, it did make a nice difference in the shifting. Our 94 with the TWS shifts nicer than our 2000s (the 2000s both use automatic tranny fluid).
Also, every lubricant has different additives and friction effects so since ZF recommends the TWS, suggest trying it, but be sure to give it a couple of thousand miles and maybe even another fluid change before deciding (don't forget to change it every 10-12k nonetheless).
However, I would not rule out a problem with the clutch system because it shifts ok between the other gears. Just a minor deficiency of the hydraulics can prevent the clutch from full disengagement, and generally most trannys shift easier between the higher gears than lower gears.
Suggest reading info on zfdoc.com and consider at least flushing/bleeding the clutch system to see if it helps before considering a rebuild.
I've only used the Castrol TWS 10-60 but when I first used it, it did make a nice difference in the shifting. Our 94 with the TWS shifts nicer than our 2000s (the 2000s both use automatic tranny fluid).
Also, every lubricant has different additives and friction effects so since ZF recommends the TWS, suggest trying it, but be sure to give it a couple of thousand miles and maybe even another fluid change before deciding (don't forget to change it every 10-12k nonetheless).
However, I would not rule out a problem with the clutch system because it shifts ok between the other gears. Just a minor deficiency of the hydraulics can prevent the clutch from full disengagement, and generally most trannys shift easier between the higher gears than lower gears.
Suggest reading info on zfdoc.com and consider at least flushing/bleeding the clutch system to see if it helps before considering a rebuild.
I started by replacing my clutch hydraulics.
zfdoc told me id have to pay thousands to get my trans rebuilt.
I simply put the stock stuff (its recommended syncromesh replacement) back in and it fixed everything.
I dont care what zfdocs experiments try to prove. BMW motor oil is not whats meant to go into our transmission. It doesnt have the proper additives and is too slippery.
Race Director
Joined: Sep 2001
Posts: 14,679
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From: NEwhere Ohio
I have a 94 coupe with the ZF 6-speed, and it shifted fine, until I had a Hurst short shifter installed in the car. Now I get a condition, every once in awhile...where the shifter hangs up, between first and second gear. I have to push and pull it in several directions, before it will go into second gear. The same condition has happened before in the 3rd to 4th shift, but not as frequent. I was told there is no external shifting linkage to adjust, so what ever is going on, happens on the inside.
I have looked a zf.doc.com site, and there they say that something like 80% of transmission problems are caused by the clutch. The master or servo wears, and isn't fully releasing the clutch between shifts. So now I'm wondering if I should replace the master and servo units first?
Any suggestions??
I have looked a zf.doc.com site, and there they say that something like 80% of transmission problems are caused by the clutch. The master or servo wears, and isn't fully releasing the clutch between shifts. So now I'm wondering if I should replace the master and servo units first?
Any suggestions??
the hurst shifter is a high quality piece, so I doubt thats the issue.
Also consider bleeded your master/slave and replacement as well.
Thread Starter
Intermediate
Joined: Dec 2010
Posts: 26
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I tried to go to ZF.doc and it says account suspended. What does this mean? Is it suspended or am I suspended?
I have a 94 coupe with the ZF 6-speed, and it shifted fine, until I had a Hurst short shifter installed in the car. Now I get a condition, every once in awhile...where the shifter hangs up, between first and second gear. I have to push and pull it in several directions, before it will go into second gear. The same condition has happened before in the 3rd to 4th shift, but not as frequent. I was told there is no external shifting linkage to adjust, so what ever is going on, happens on the inside.
I have looked a zf.doc.com site, and there they say that something like 80% of transmission problems are caused by the clutch. The master or servo wears, and isn't fully releasing the clutch between shifts. So now I'm wondering if I should replace the master and servo units first?
Any suggestions??
I have looked a zf.doc.com site, and there they say that something like 80% of transmission problems are caused by the clutch. The master or servo wears, and isn't fully releasing the clutch between shifts. So now I'm wondering if I should replace the master and servo units first?
Any suggestions??
Race Director
Joined: Nov 2003
Posts: 12,221
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From: Overland Park Kansas
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You didn't do anything wrong.
Seems like there's been problems before...I even posted the phone number a few months ago when it happened. If I find it, I'll post it again.
Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
I have seen new ZF trannys for sale for $1500. I dont know if they are the blue or black label or what difference it makes.
My 4+3 second gear syncro occasionally grinds especially when its in OD. I just dont do a fast shift from 1 to 2 and really watch the OD. Just take it easy with yours and it should last a while.
I would put the lube GM recommends in the tranny. This could turn out to be another motor oil, gas grade or type of wax thread.
Good luck!
My 4+3 second gear syncro occasionally grinds especially when its in OD. I just dont do a fast shift from 1 to 2 and really watch the OD. Just take it easy with yours and it should last a while.
I would put the lube GM recommends in the tranny. This could turn out to be another motor oil, gas grade or type of wax thread.
Good luck!
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