ZF8 Trans low speed sequential downshifting
10-23-2018, 11:40 AM
#1
AudiWorld Member
Thread Starter
ZF8 Trans low speed sequential downshifting
'13 A8 4.0T
I know the topic of low speed shudders and jerks has been beat to death, but is this trans really suppose to be downshifting this often? No matter what mode I'm in, it will downshift 3-2-1 every single time I come to a stop. What is the reason for this? Why not just decouple and stay decoupled when coming to a stop. Is it possibly to reduce brake rotor/pad wear (it is a big girl after all...)? Also, out of curiosity, does an APR tune address this issue at all?
I know the topic of low speed shudders and jerks has been beat to death, but is this trans really suppose to be downshifting this often? No matter what mode I'm in, it will downshift 3-2-1 every single time I come to a stop. What is the reason for this? Why not just decouple and stay decoupled when coming to a stop. Is it possibly to reduce brake rotor/pad wear (it is a big girl after all...)? Also, out of curiosity, does an APR tune address this issue at all?
10-23-2018, 04:50 PM
#2
AudiWorld Super User
A-T's in general shift down. By regulation they were not allowed to freewheel--back to the olden days when a drum brake car going down a grade could overheat its brakes. That rule is being changed for fuel economy and electric car reasons apparently, but only currently.
FWIW, if I pay super close attention on my 2015 S8 I can pick it up, but it is smooth in general. Often to really know a gear change is happening, I have to look at display, which I have enabled w/ VCDS to show current gear.
Sometimes when shifting is more obvious or a bit rough, it is a sign of a possible fluid level issue/leak.
FWIW, if I pay super close attention on my 2015 S8 I can pick it up, but it is smooth in general. Often to really know a gear change is happening, I have to look at display, which I have enabled w/ VCDS to show current gear.
Sometimes when shifting is more obvious or a bit rough, it is a sign of a possible fluid level issue/leak.
10-23-2018, 05:10 PM
#3
AudiWorld Member
Thread Starter
A-T's in general shift down. By regulation they were not allowed to freewheel--back to the olden days when a drum brake car going down a grade could overheat its brakes. That rule is being changed for fuel economy and electric car reasons apparently, but only currently.
FWIW, if I pay super close attention on my 2015 S8 I can pick it up, but it is smooth in general. Often to really know a gear change is happening, I have to look at display, which I have enabled w/ VCDS to show current gear.
Sometimes when shifting is more obvious or a bit rough, it is a sign of a possible fluid level issue/leak.
FWIW, if I pay super close attention on my 2015 S8 I can pick it up, but it is smooth in general. Often to really know a gear change is happening, I have to look at display, which I have enabled w/ VCDS to show current gear.
Sometimes when shifting is more obvious or a bit rough, it is a sign of a possible fluid level issue/leak.
10-23-2018, 06:03 PM
#4
AudiWorld Super User
I'm sure 124k miles retracts slightly from the smoothness as well, haha. Transmission fluid flush isn't apart of the normal maintenance, and I havent noticed any leaks in that area so I've avoided doing it. If I'm going to do it I might as well pay to get it fully flushed as opposed to just changing the fluid myself? Dealer quoted ~$600 for that job.
ZF says kinda sorta, maybe, but basically recommends for "aggressive driving" what translates into miles (instead of km) as 60-100K.
No such thing on most Audis as a flush. That is, you can't tap into something like a fluid line going to/from radiator to do the flush type procedure. Thus, you have to do it by sequential drains, and around ⅓ stays behind in torque converter area. Nets to at least two sequential drains to do it reasonably thoroughly when you do the math; 3x by the book Audi.
ZF rebuilts through an indy shop were about four grand 7 or 8 years ago on the piece o crap 5 speeds in D2's, discounted. Maybe $1500 R&R...assuming nothing among the 100 or so things disconnected gets messed up. Fortunately the 6 and then 8 speeds in D3 and now D4 got quite reliable in general.
Last edited by MP4.2+6.0; 10-23-2018 at 06:13 PM.
10-23-2018, 06:16 PM
#5
AudiWorld Member
Thread Starter
Yea I don't buy the "lifetime" crap either. Mercedes said the same thing and it was complete bull****. I guess I'll ask the dealer what their "flush" process is. If it's just sequential drains I'll probably skip the labor charge and do it myself.
10-25-2018, 10:45 AM
#6
AudiWorld Member
Thread Starter
@MP4.2+6.0 Couple things:
I've noticed that when the car transitions from acceleration to deacceleration (Im assuming this is the torque converter decoupling) theres quite a noticeable shudder, extremely noticeable in lower gears. Is this also related to low/old fluid?
I saw the other post about changing trans fluid. At 124k miles do you think it prudent to pull the pan and replace the filter, or is a couple drains going to be sufficient? Reason I ask is on my car there is a subframe cross brace covering the pan, and I'm a little nervous about removing that (drain/fill holes are still accessible though).
I've noticed that when the car transitions from acceleration to deacceleration (Im assuming this is the torque converter decoupling) theres quite a noticeable shudder, extremely noticeable in lower gears. Is this also related to low/old fluid?
I saw the other post about changing trans fluid. At 124k miles do you think it prudent to pull the pan and replace the filter, or is a couple drains going to be sufficient? Reason I ask is on my car there is a subframe cross brace covering the pan, and I'm a little nervous about removing that (drain/fill holes are still accessible though).
10-25-2018, 11:50 AM
#7
AudiWorld Super User
@MP4.2+6.0 Couple things:
I've noticed that when the car transitions from acceleration to deacceleration (Im assuming this is the torque converter decoupling) theres quite a noticeable shudder, extremely noticeable in lower gears. Is this also related to low/old fluid?
I saw the other post about changing trans fluid. At 124k miles do you think it prudent to pull the pan and replace the filter, or is a couple drains going to be sufficient? Reason I ask is on my car there is a subframe cross brace covering the pan, and I'm a little nervous about removing that (drain/fill holes are still accessible though).
I've noticed that when the car transitions from acceleration to deacceleration (Im assuming this is the torque converter decoupling) theres quite a noticeable shudder, extremely noticeable in lower gears. Is this also related to low/old fluid?
I saw the other post about changing trans fluid. At 124k miles do you think it prudent to pull the pan and replace the filter, or is a couple drains going to be sufficient? Reason I ask is on my car there is a subframe cross brace covering the pan, and I'm a little nervous about removing that (drain/fill holes are still accessible though).
But, back up even a step first. Fluid doesn't evaporate or get used up. If it is low, there must be a leak. Thus, if it were mine, likewise I would be under it looking for any telltale leak signs first, before deciding my next step. If signs of a leak, go in more confident the fluid top up (and likely change, + fixing leak) will address it. If no leak, less so, though many with D3's found fluid change cured a lot of ills. Realize there are casual lots of posts around the web saying fluid changes late on cause transmission failures. A lot of them seem like old wive's tales and 5th hand they heard it somewhere while chewing on something kind of posts. I personally don't believe those except in rare corner case scenarios and/or that involve mechanics' errors. But know those questions are always out there. My own belief is statistically someone is more likely to have trans. issues when they do the fluid change, and it may not work. Thus, if you have heart disease and need a transfusion for some other issue, the transfusion didn't cause the heart attack a week later. Or, if the doc gives you statins on day one for your clogged arteries and all, and on day 5 or 50 or 500 you have the heart attack anyway, the statins didn't cause that either. But in both cases, the patient had an issue going in.
Yes, I have see the problematic brace on mine too. BTW, look into the trans filter on a D4. I think it may be integrated into pan now, so you end up replacing that too in classic Audi "vee know besser" style. Yes, you may just go for the fluid change as a result. You can for example try one drain cycle, and if you like the results, go on to #2. If not, maybe stop or reassess. See this link for when I did my D3 W12 at 100K. Honestly, if you look carefully at the filter media in the pics from when I cut it open, there wasn't much there. Pan was cleaner than I expected too. I think that is likely because lead is now banned in transmission manufacture in Europe, which used to be used on bearing surfaces. Now it is basically steel to steel. Puts a premium on fluid, but less of the old metallic shedding probably from softer metals. https://www.audiworld.com/forums/a8-...rance-2861255/
Also, look into how to do a transmission recalibration/adaptation for D4's. I know it on D3s, but not D4's. You could trigger it via VCDS on D3, and then it forgets all its accumulated learning (including bad habits) and starts over. Can get more effect perhaps if coupled w/ fluid change.
Last edited by MP4.2+6.0; 10-25-2018 at 11:54 AM.
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10-25-2018, 12:07 PM
#8
AudiWorld Member
Thread Starter
Trannies are obviously complicated and somewhat black box, but yes the shudder can also be related to fluid issues. The typical approach would be to try a fluid change before escalating to next steps, which are likely the valve body/Mechatronics and definitely require pan pull, more $$$ and some experience to be comfortable doing that kind of more advanced work--very few owners ever go there. Net, given your descriptions, I personally would be doing fluid.
But, back up even a step first. Fluid doesn't evaporate or get used up. If it is low, there must be a leak. Thus, if it were mine, likewise I would be under it looking for any telltale leak signs first, before deciding my next step. If signs of a leak, go in more confident the fluid top up (and likely change, + fixing leak) will address it. If no leak, less so, though many with D3's found fluid change cured a lot of ills. Realize there are casual lots of posts around the web saying fluid changes late on cause transmission failures. A lot of them seem like old wive's tales and 5th hand they heard it somewhere while chewing on something kind of posts. I personally don't believe those except in rare corner case scenarios and/or that involve mechanics' errors. But know those questions are always out there. My own belief is statistically someone is more likely to have trans. issues when they do the fluid change, and it may not work. Thus, if you have heart disease and need a transfusion for some other issue, the transfusion didn't cause the heart attack a week later. Or, if the doc gives you statins on day one for your clogged arteries and all, and on day 5 or 50 or 500 you have the heart attack anyway, the statins didn't cause that either. But in both cases, the patient had an issue going in.
Yes, I have see the problematic brace on mine too. BTW, look into the trans filter on a D4. I think it may be integrated into pan now, so you end up replacing that too in classic Audi "vee know besser" style. Yes, you may just go for the fluid change as a result. You can for example try one drain cycle, and if you like the results, go on to #2. If not, maybe stop or reassess. See this link for when I did my D3 W12 at 100K. Honestly, if you look carefully at the filter media in the pics from when I cut it open, there wasn't much there. Pan was cleaner than I expected too. I think that is likely because lead is now banned in transmission manufacture in Europe, which used to be used on bearing surfaces. Now it is basically steel to steel. Puts a premium on fluid, but less of the old metallic shedding probably from softer metals. https://www.audiworld.com/forums/a8-...rance-2861255/
Also, look into how to do a transmission recalibration/adaptation for D4's. I know it on D3s, but not D4's. You could trigger it via VCDS on D3, and then it forgets all its accumulated learning (including bad habits) and starts over. Can get more effect perhaps if coupled w/ fluid change.
But, back up even a step first. Fluid doesn't evaporate or get used up. If it is low, there must be a leak. Thus, if it were mine, likewise I would be under it looking for any telltale leak signs first, before deciding my next step. If signs of a leak, go in more confident the fluid top up (and likely change, + fixing leak) will address it. If no leak, less so, though many with D3's found fluid change cured a lot of ills. Realize there are casual lots of posts around the web saying fluid changes late on cause transmission failures. A lot of them seem like old wive's tales and 5th hand they heard it somewhere while chewing on something kind of posts. I personally don't believe those except in rare corner case scenarios and/or that involve mechanics' errors. But know those questions are always out there. My own belief is statistically someone is more likely to have trans. issues when they do the fluid change, and it may not work. Thus, if you have heart disease and need a transfusion for some other issue, the transfusion didn't cause the heart attack a week later. Or, if the doc gives you statins on day one for your clogged arteries and all, and on day 5 or 50 or 500 you have the heart attack anyway, the statins didn't cause that either. But in both cases, the patient had an issue going in.
Yes, I have see the problematic brace on mine too. BTW, look into the trans filter on a D4. I think it may be integrated into pan now, so you end up replacing that too in classic Audi "vee know besser" style. Yes, you may just go for the fluid change as a result. You can for example try one drain cycle, and if you like the results, go on to #2. If not, maybe stop or reassess. See this link for when I did my D3 W12 at 100K. Honestly, if you look carefully at the filter media in the pics from when I cut it open, there wasn't much there. Pan was cleaner than I expected too. I think that is likely because lead is now banned in transmission manufacture in Europe, which used to be used on bearing surfaces. Now it is basically steel to steel. Puts a premium on fluid, but less of the old metallic shedding probably from softer metals. https://www.audiworld.com/forums/a8-...rance-2861255/
Also, look into how to do a transmission recalibration/adaptation for D4's. I know it on D3s, but not D4's. You could trigger it via VCDS on D3, and then it forgets all its accumulated learning (including bad habits) and starts over. Can get more effect perhaps if coupled w/ fluid change.
The fluid change kit on blauparts for 11-18 8speed has a stand alone filter. Also, alldata manual pages show the filter as a separate piece. But, sounds like a drain and refill is in order first. Alldata calls for the cross brace bolts to be replaced if removed, not sure if this is because of anti corrosion or stretch characteristics. My main concern is if I remove the brace, even with the car on 4 jack stands...am I going to be able to put it back on lol. I.e., is the frame going to flex with the brace off to the point where I can't get it back on (alldata vehemently emphasizes to not put the car down with the brace off). All speculation, but if true would cause a serious problem.
I'll check for any leaks when I do rotors this weekend and try the trans adaption reset if I can find out how to do it. I'll update when I have more info.
10-25-2018, 12:52 PM
#9
AudiWorld Super User
I understand it is a closed system but I would think over time the fluid would get saturated with worn off particles and possibly cause the fluid to lose "performance", just guessing though.
The fluid change kit on blauparts for 11-18 8speed has a stand alone filter. Also, alldata manual pages show the filter as a separate piece. But, sounds like a drain and refill is in order first. Alldata calls for the cross brace bolts to be replaced if removed, not sure if this is because of anti corrosion or stretch characteristics. My main concern is if I remove the brace, even with the car on 4 jack stands...am I going to be able to put it back on lol. I.e., is the frame going to flex with the brace off to the point where I can't get it back on (alldata vehemently emphasizes to not put the car down with the brace off). All speculation, but if true would cause a serious problem.
I'll check for any leaks when I do rotors this weekend and try the trans adaption reset if I can find out how to do it. I'll update when I have more info.
The fluid change kit on blauparts for 11-18 8speed has a stand alone filter. Also, alldata manual pages show the filter as a separate piece. But, sounds like a drain and refill is in order first. Alldata calls for the cross brace bolts to be replaced if removed, not sure if this is because of anti corrosion or stretch characteristics. My main concern is if I remove the brace, even with the car on 4 jack stands...am I going to be able to put it back on lol. I.e., is the frame going to flex with the brace off to the point where I can't get it back on (alldata vehemently emphasizes to not put the car down with the brace off). All speculation, but if true would cause a serious problem.
I'll check for any leaks when I do rotors this weekend and try the trans adaption reset if I can find out how to do it. I'll update when I have more info.
Issues w older fluid are probably a combo of some very fine particles beyond filter's ability to capture, and degradation of additives from years/heat/pressures. Among additives are friction enhancers and modifiers specific to the application/fluid spec, and then among the reasons the various flavors of fluids. The friction modifier concerns can be among causes of shutter type symptoms you are noting.
Last edited by MP4.2+6.0; 10-25-2018 at 12:55 PM.
10-25-2018, 01:29 PM
#10
AudiWorld Member
Thread Starter
Oh the other thing I wanted to look into is tcm software version. I've read tsb's about software updates fixing problems and wondered where to start with that. Can I do any verification with VCDS or do I have to take it to the stealership?
Last edited by sushistrip; 10-25-2018 at 01:33 PM.