11-22-2022, 08:18 AM | #1 |
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ZF8 Jerk when shifting from 5th to 6th gear when cold ONLY
Hello,
I've been having a weird jerk for a while now, happens only when shifting from 5th to 6th gear. I could describe it as a punch, a kick. Occurs only when the trans oil is cold. As soon as the oil in the gearbox warms up above 60 degrees, everything is fine, you can't feel the change from 5th to 6th. The shifting of all other gears is perfect, cold/warm oil (no jerks, kicks, etc). The mileage at this moment is almost 200k km, during this time the oil was changed twice (at 100k km and at 192k km) - always everything from zf. Adaptation at exchanges done. The pressures and filling times are perfect. Anyone have any idea what I can do to improve the change from 5 to 6 on cold oil trans? |
11-28-2022, 04:50 PM | #2 |
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11-28-2022, 04:55 PM | #3 |
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Not a transmission expert, but that sounds like an issue with the 6th gear clutch pack. Clutch materials tend to be more "grippy" when cold.
Do you have xHP? Their software shows clutch pack delays/pressures which can help point to an issue. |
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11-28-2022, 05:32 PM | #5 |
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At 192 km, was there any issue?
If the issue is posted, a drain and fill of fluids, then I would be keen on checking fluid levels. Was the transmission pan/filter replaced at the same time? -This will make me sad if not. This jerk sensation, is it more noticeable when at a steady throttle input going from 5 to 6 and lessens with a more aggressive throttle input? i.e feels smoother when you apply more power. Let's start here.
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11-28-2022, 05:40 PM | #6 | |
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Oil level checked at 40*c. With the air conditioning on, the was car running, the gearbox in Park. Each gear thrown before. Was missing about 350ml. Filled with original Zf fluid for 8hp. |
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11-28-2022, 05:44 PM | #7 | |
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Sure, original pan/filter and zf oil at the same time. Feels smother when it changes around 2k rpm. When I apply more power, like you said. Is it normal? Other gears are great. |
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11-28-2022, 05:46 PM | #8 | |
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Currently running on bms stage 1. |
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11-28-2022, 06:21 PM | #10 | |
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How I can datalog? Don't Have bm3 etc. Is there any program on PC or android/iOS? I have enet & vgate obd. Edit. Found that testo should work with enet. Will check it later |
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11-29-2022, 06:22 AM | #11 |
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I have read that the problem may be related with BMS Stage 1. Will give some info soon.
Any other ideas? |
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11-29-2022, 11:27 AM | #14 |
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350ml Low on ATF is not great; however, not detrimental for a short period of time.
Since the rest of the other checks look fine. Seems like you might have an issue with clutch packs. Seeing how the rest of the shifts are fine. One possible solution is to perform another flush fill with a new pan/filter and use an ATF with greater cleaning properties like Motul. I personally use OEM ZF8 ATF, but the BMW performance shop I go to recommends Motul. Just an idea. If the 6th gear clutch pack is going, might as rebuild them all if that is the case.
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11-29-2022, 04:16 PM | #16 | |
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Just checked it. : |
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11-29-2022, 06:59 PM | #17 | |
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Can also run XHP since its great anyways and see if software helps |
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11-30-2022, 05:21 AM | #18 | ||
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I'm trying to shift into 6th gear with a little more throttle and it really seems to work. I'll unplug BMS in my free time. I also cleaned maf & map sensor yesterday. Will give more info soon. |
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