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      01-27-2019, 10:14 PM   #1
Canadian440i
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JB4 upgrade transmission slip?

I recently did the JB4 tune on my 440i Xdrive and sometimes on map 2 and always on map 3 it feels like my transmission slips? Misses shifts? and has a huge lag? It's Automatic and just has a afe intake mod. I'm running 94-96 octane. Anything I can do to help this? Any suggestions would be greatly appreciated!

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      01-30-2019, 02:25 PM   #2
eksigned
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Can you be more specific? Maybe a video? If your transmission is slipping, it'd be blatantly obvious. To test, you can throw it into a higher gear and get on the throttle without allowing the car to downshift. If it holds the gear, you're good. If not, you'll see the car rev freely. Highly doubt this. Haven't read a single post of anyone having their ZF slip, yet. If you're talking about the "pause" in the revs, that's normal. Engine speed just matching actual vehicle speed. JB4 likely just exacerbates this because more powa.

What do you mean by missed shifts?
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      01-30-2019, 02:37 PM   #3
Canadian440i
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Quote:
Originally Posted by eksigned View Post
Can you be more specific? Maybe a video? If your transmission is slipping, it'd be blatantly obvious. To test, you can throw it into a higher gear and get on the throttle without allowing the car to downshift. If it holds the gear, you're good. If not, you'll see the car rev freely. Highly doubt this. Haven't read a single post of anyone having their ZF slip, yet. If you're talking about the "pause" in the revs, that's normal. Engine speed just matching actual vehicle speed. JB4 likely just exacerbates this because more powa.

What do you mean by missed shifts?
I won't have a video until the snow is gone up here in Canada. Haha. It's hard to explain, it feels like a slip of a gear and if I lay off the throttle and press 60% of the way in the throttle it goes fine. Might be a transmission issue if no one else has ever had it. It's not gear specific either, car is auto and it doesn't matter if it's first,middle or last if I go full throttle it slips.
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      01-30-2019, 02:40 PM   #4
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Quote:
Originally Posted by Canadian440i View Post
Quote:
Originally Posted by eksigned View Post
Can you be more specific? Maybe a video? If your transmission is slipping, it'd be blatantly obvious. To test, you can throw it into a higher gear and get on the throttle without allowing the car to downshift. If it holds the gear, you're good. If not, you'll see the car rev freely. Highly doubt this. Haven't read a single post of anyone having their ZF slip, yet. If you're talking about the "pause" in the revs, that's normal. Engine speed just matching actual vehicle speed. JB4 likely just exacerbates this because more powa.

What do you mean by missed shifts?
I won't have a video until the snow is gone up here in Canada. Haha. It's hard to explain, it feels like a slip of a gear and if I lay off the throttle and press 60% of the way in the throttle it goes fine. Might be a transmission issue if no one else has ever had it. It's not gear specific either, car is auto and it doesn't matter if it's first,middle or last if I go full throttle it slips.
Actually, I think I kind of know what you mean. Frankly, it's likely from the JB4 unit itself. Driveability goes out the window with that thing, especially with how the car shifts. Try turning off the box, and do what you do...see if the problem persists
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      01-31-2019, 03:30 PM   #5
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There are quite a few things that limit acceleration that might feel like transmission slip. The most likely thing is fuel limits. The JB4 can only deal with a few of these to try to trick the engine into giving more power. The real answer is to take a few logs with the JB4 and go over to N54tech and post them there. They can tell you what is happening.
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      01-31-2019, 06:46 PM   #6
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Can someone post a video about what happens? I hear a lot of these types of issues and wonder what it looks like...
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      01-31-2019, 06:49 PM   #7
Canadian440i
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Originally Posted by GT500R View Post
Can someone post a video about what happens? I hear a lot of these types of issues and wonder what it looks like...
I will in spring. Too much snow up here right now.
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      01-31-2019, 08:41 PM   #8
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Could it also be the transmission computer due to over torque
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      02-11-2019, 11:17 AM   #9
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Quote:
Originally Posted by Brett530 View Post
There are quite a few things that limit acceleration that might feel like transmission slip. The most likely thing is fuel limits. The JB4 can only deal with a few of these to try to trick the engine into giving more power. The real answer is to take a few logs with the JB4 and go over to N54tech and post them there. They can tell you what is happening.
+1

Also would make sure these aren't traction events you are feeling.. With more power and the traction system fully engage anytime there is wheel slip the power gets cut back.

Mike
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      02-16-2019, 06:05 PM   #10
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Quote:
Originally Posted by Mike@N54Tuning.com View Post
+1

Also would make sure these aren't traction events you are feeling.. With more power and the traction system fully engage anytime there is wheel slip the power gets cut back.

Mike
This is exactly what I'd suspect is going on. I bet you are getting throttle closures due to wheel slippage.
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