All The Reasons Why/How Your Transmission Might Be Slipping (And How To Fix It)
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- Опубликовано: 9 дек 2023
- ►The ZF 6HP, found in tons of BMW, Land Rover, Audi, and Jaguar vehicles, has a reputation for being largely reliable. However, any issue they have is likely caused by a pressure loss within the mechatronics, which will trigger some annoying symptoms. Everything in the video here will diagnose the possibilities related to the hydraulic side before getting into the more costly and labor-intensive mechanical side.
Symptoms of a Failing ZF 6HP Hydraulics
Delayed Shifts
Hesitation
Slipping under acceleration
Automatic transmissions use a combination of a hydraulic system and several large mechanical components ( physical clutch packs, cogs, and gears) to turn engine power into forward motion. Tying the two together is the mechatronics unit. It controls both systems, determining hydraulic pressure and to which mechanical parts the pressure is sent at any point. Within that, the hydraulic pressure activates the shift points, shift aggressiveness, torque converter lock-up, and so on. Any loss of pressure across the mechatronics unit will cause some noticeable faults, like what happened with this Land Rover LR3.
Causes of ZF 6HP Faults
Failed sealing plate
Clogged/damaged shift solenoids
Worn valve body bores
External fluid leaks
Owner Mike Roselli was experiencing some funky behavior in the form of hesitation and slippage under load, tipping him off to a transmission issue - the question is, which side would the issue be on (mechanical or hydraulic)? ZF's 6HP automatic has a few wear points, including the valve body sealing plate and the valve body pistons. Worn valve body piston bores are a common cause as the metal-on-metal contact will cause wear with significant mileage. The same goes for the sealing plate, as its rubber/silicone seals can dry and shrink. Replacing the pistons or sealing plate means draining the transmission and removing the valve body for disassembly. It's a fairly straightforward procedure but one that does require caution, patience, and a bit of dexterity.
In the end, addressing all of the seals and possible wear points in the hydraulic side of the transmission proved to address all of the symptoms the LR3 was exhibiting, avoiding costly (and more labor-intensive) mechanical repairs.
Watch along as FCP Euro's BMW Expert, Gareth Foley dives into the 6HP with a bunch of parts to give it a long-overdue service and solve the Land Rover LR3's slipping transmission.
Expert Tip For those with a 6HP looking to start this repair on their own, start first by identifying the specific transmission you have by locating the number plate on the driver's rear of the transmission. From there, you can order parts and have everything ready to complete the repair.
Also, pay special attention to which separator plate to order, as there are several options available.
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This definitely fixed the issue with my x5 E70. 163k miles and the transmission was gradually starting to slip in 1st and second gear. I took to two mechanics who only read codes and wanted to just swap the transmission instead of trying this. I replaced the bridge seal and the 4 other valves seals plus the pan. Put new fluid in it and magic. Works like brand new. The sleeve at the end was a pain in the ass a little but I took breaks and let my frustration subside.
Hey guys that is one of the best DIY videos that I have ever watched. Very thourough and descriptive. Blessings!!
Great video!
I have a 1999 540i with A5S440Z. It had an issue which would cause it to jolt sometimes when coming to a stop. A transmission specialist said it was the Tq converter and rebuilt it and at the same time did the clutch packs. The car was new to me at the time and had done 160,000km (100,000 miles).
After several visits back and then a ZF specialist (replaced some solenoids), the problem remained.
I worked out it was related to the TCC Solenoid in that it would happen when coming to a stop after the Lock Up TC had been engaged - it was slow to disengage, the engine would al.ost stall, the ECU would step in to prevent this and a jolt would occur with the sudden incease of rpm and the TCC would then let go.
Eventually, I noticed the ATF, when scanned, seemed to be quite high so I compared it with an infra-red on the pan and changed the harness with the temp sensor on the end and this fixed the problem.
My engine had to be replaced (timing chain failed) and since I got the car back, I have the same issue only it doesn't seem that ut needs to be above a certain temperature this time or necessarily be after a speed where the TCC has locked up. I did an oil change (in case they used the wrong oil to refill after the engine swap) - it seemed to improve it a bit. I also replaced the speed sensors and the harness (again).
Any ideas on what might be happening and how to fix it?
Other than this issue, the transmission works really well with no slip, it puts down the power really well and shifts smoothly.
A very good video. Plenty of pointers for things to look out for.
Glad you think so!
I’d love to see FCP euro send some ATF samples to blackstone labs. See what’s normal for MB trans. Both healthy and slipping.
We are always happy to send samples out to Blacksone for testing - we did that recently on an X5 video. We can look to do so on an MB.
I don't know much about transmissions, but the best company that I could only recommend for guidance is Level 10 Transmissions out of Hamburg NJ.
Replacing the solenoid valves and seals fixed the same issues on my 2006 BMW 530i. I didn't open up the valve body or use a Zip Kit. I used Mercon SP transmission fluid since it is chemically identical (do some searching) to the Lifeguard 6 and costs less than 1/2 the price.
would love to see a video like this for Volvo AW 50/51
💙
I believe if the vehicle has a transmission fluid cooler with a thermostatic valve you need to get it up to operating temperature by driving, then let it cool below 30degC to do a final top off. At least that's the rumor I heard. I would reset the adaptions right from the get go and do the recommended drive cycle.
We need to see this for the Mercedes 722.9.
I have a 1990 240 that needs to warm up for a while before it shifts from lower gear up. It is a AW70 transmission, got any ideas.
I feel like I'm having this issue on my w204 c350. I thought it was the engine, but I'm getting this same surging at low rpm during cruising.
my insulation strip is in pieces, can i get by without or what to use or can i buy only that part
Bushing wear is also a common failure point on the 6HP.
I think I have a programming issue on mine. A fluid and adaptation reset was done, and that's when the "issue" started. It's a 4f8d code. I
I have 0 issues if the car is driven in sport or + mode. It only lights up the cog if I drive in regular D mode. So, I've resorted to driving in sport for the las year and no problems. The only time I can throw it into D mode is on the highway as long as I stay above 60mph. I can take long highway trips no prob. All my shifts are smooth and strong, no slippage is detected...milage is 25.3k. Anyone with advice?
Hello , I have a F30 335D 2013 with the ZF8 speed ... It has 32k miles, I had to gearbox serviced by a local garage with "sp matic ATF" and not sure what pan filter they used... ever since it's been done the shifts are horrendous (was completely fine before this oil drain and pan) , feels like slipping especially under any heavy acceleration. I tried to press throttle 80% for kickdown and the car just jolts and the revs go up then it jolts back into gear. felt like a stall. Normal light driving is mostly ok once warmed up but you still cant floor it or it'll slip hard. they mentioned there was a "fair bit of metal shavings" in the pan. Any idea what I could try to try solve this?
Daca au făcut resetarea cutiei va dura ceva până va schimba ca prima dată
@sorinspiru8597 driven about 500 miles no change 😞
always go to specialist for these kinds of jobs... the local garage across the gas station is not to be trusted on delicate matters...
you can solve it by never taking a Euro car to a local garage
Du-te la alt service auto pentru a verifica nivelul uleiului
damn wish they would do this for the 8 HP
We can do more on the 8hp - one of our favorites 😁
"Brick the entire brain" - G
Clutch burning up
¿Qué opinan de usar aditivos como Lubegard Platinum o ATF Additive de Liqui Moly como parte de los servicios preventivos a las cajas ZF?
Saludos!