ZF 8-Speed Groaning Noise

[D4700]

Hello all,

I'm diagnosing a very faint "groan" when my ZF 8P75H (Full hybrid) is near the top of second gear, and immediately goes away as it switches to third. This is accompanied by an occasional rough switch to second gear, which I've been told is normal for these transmissions. The "groan" only seems to occur when I'm driving in electric mode - or perhaps I just can't hear it when the engine is running.

The car has ~75k miles on it. I did the first spill and fill as soon as I noticed the noise a couple of months ago by draining a gallon and putting a gallon back in, then rechecking the level (at the proper fluid temperature of 40C) after going for a long drive to open the thermostatic valve. Level was bang on, so that wasn't a problem.

I've now done two drain and fills and, although the gear shifts seem a bit smoother, the noise is exactly the same. It should be noted that I have not dropped the pan to change the filter. Has anyone experienced this in a transmission before? Any suggestions as to what this noise could be, and whether or not I should be seriously concerned?

Edit: I should also note that I do not experience any slip or other unusual shifting characteristics in any of the gears, aside from that occasional jerky 1-2 upshift. Although it's difficult to discern whether any of the gears are slipping in electric mode, I have not noticed anything that raises my eyebrows when watching the tach during gearshifts with the engine running.

 

[D60]

Honestly I've always felt my '19 JLUR does this, too. I'd call it less of a groan and more of a "GHACK!" and sometimes a "whirring grind", but the shifts are smooth.

Sorry no help -- if anything I'm happy to hear someone else might not think I'm crazy. Maybe we can find a church basement and start a support group.....?

 

[4WD]

Honestly I've always felt my '19 JLUR does this, too. I'd call it less of a groan and more of a "GHACK!" and sometimes a "whirring grind", but the shifts are smooth.

Sorry no help -- if anything I'm happy to hear someone else might not think I'm crazy. Maybe we can find a church basement and start a support group.....?

The 850RE in my JLU does it once in a while - but it’s not persistent …
I’m soon to do my 2nd spill and fill with Zeus juice …
(ZF LG8)

 

[D4700]

Honestly I've always felt my '19 JLUR does this, too. I'd call it less of a groan and more of a "GHACK!" and sometimes a "whirring grind", but the shifts are smooth.

Sorry no help -- if anything I'm happy to hear someone else might not think I'm crazy. Maybe we can find a church basement and start a support group.....?

Great idea. We'll call it "Vehicular Hypochondriacs Anonymous."

I genuinely conjured up this crackpot theory a while back to try and explain this noise from a psychological perspective: I'm extremely conditioned to listening and feeling for issues (owning a bunch of old German cars will do that to you). Now that I'm in a newer car that hasn't required a repair in a suspiciously long amount of time, my mind is so on edge that it's making up issues to calm itself down.

I'm glad someone else is hearing these noises - it must mean I'm not that far gone!

 

[D60]

Great idea. We'll call it "Vehicular Hypochondriacs Anonymous."

I genuinely conjured up this crackpot theory a while back to try and explain this noise from a psychological perspective: I'm extremely conditioned to listening and feeling for issues (owning a bunch of old German cars will do that to you). Now that I'm in a newer car that hasn't required a repair in a suspiciously long amount of time, my mind is so on edge that it's making up issues to calm itself down.

I'm glad someone else is hearing these noises - it must mean I'm not that far gone!

MANY years ago I brought it up on a JL forum and got no response except of course for "Jeep Cares" (a misnomer if I ever saw one) saying "please open a case, we'd love to help" (hilarious)

I can't even predictability recreate it so no way I'd expect a tech to find it. "CANNOT DUPLICATE" and all that....

Sometimes it also happens upshifting in low range, and that's perhaps when it's most noticeable because you're going slower. But it also happens in 1:1 ‐‐ it's not a t-case issue

I've got about 55k now so I guess it's not a big deal (shrug)

Again, no help but would love to see topic stay alive with ideas. You bring the coffee, I'll bring the cookies and I'll see you 7p Tue in the basement of St Mark's Unitarian Presbyterian First Calvary Chapel

 

[bhohn0]

I have a 24 JL 4xe and have not heard the noise you describe. Probably because that stupid pedestrian alert noise happens quite loudly in the conditions you are describing. I sorta wish there was a way to disable that stupid thing. I am at 8200 miles so far. Love the ZF transmission. Have an all wheel drive Challenger GT also.

 

[D4700]

I have a 24 JL 4xe and have not heard the noise you describe. Probably because that stupid pedestrian alert noise happens quite loudly in the conditions you are describing. I sorta wish there was a way to disable that stupid thing. I am at 8200 miles so far. Love the ZF transmission. Have an all wheel drive Challenger GT also.

I think I only started to notice the transmission groan when I changed the sound generator to something more subtle (sorry, not sure how to do this on the Jeeps). It's a pretty mild noise. Perhaps just some resonance with the chassis and whatnot, but I may change the pan to see if it helps. I have noticed a slight improvement since switching to Valvoline fluid.

 

[OVERKILL]

I think I only started to notice the transmission groan when I changed the sound generator to something more subtle (sorry, not sure how to do this on the Jeeps). It's a pretty mild noise. Perhaps just some resonance with the chassis and whatnot, but I may change the pan to see if it helps. I have noticed a slight improvement since switching to Valvoline fluid.

What vehicle is this on, an X5?

 

[D4700]

What vehicle is this on, an X5?

A 2021 530e. My old man's got a 21 X5 45e and I have not noticed any noises when I've driven it. He's at the same mileage.

 

[OVERKILL]

A 2021 530e. My old man's got a 21 X5 45e and I have not noticed any noises when I've driven it. He's at the same mileage.

Figured it was a bimmer, from your previous posts. I really liked the X5 45e when I test drove it. Interestingly, the only ZF 8HP I ever had a semi-concern with was in a 2015, it was a goofy shift behind the V6 in a Durango, which liked to do a firm shift into 2nd the first shift of the day. We've owned 6x ZF 8HP equipped vehicles now, so I'm intrigued by this issue of yours.

Does it have any sort of harmonic sound to it, like a resonance?

 

[D4700]

Figured it was a bimmer, from your previous posts. I really liked the X5 45e when I test drove it. Interestingly, the only ZF 8HP I ever had a semi-concern with was in a 2015, it was a goofy shift behind the V6 in a Durango, which liked to do a firm shift into 2nd the first shift of the day. We've owned 6x ZF 8HP equipped vehicles now, so I'm intrigued by this issue of yours.

Does it have any sort of harmonic sound to it, like a resonance?

They are really compelling cars. Nice driving dynamics and we both hardly use gas anymore. I've been thrilled with it other than this dang noise! The 8hp is excellent.

It does seem to resonate throughout the chassis. I've been thinking about fixing a camera to the service tray underneath the transmission. Will update if I do.

 

[D4700]

An interesting update. I'm home for the holidays, so I got the chance to drive Dad's X5 45e again. Now that I know what to listen for, I hear the EXACT same transmission noise - albeit slightly quieter (potentially due to more isolation in the X5) - accompanied by some very minor vibrations throughout the chassis.

I have a trans pan/filter on order (Hengst, $110+$16 shipping on RockAuto) and will pump in some more Valvoline EP ATF when I get back to Arizona. Will update the thread if I notice any improvements, but I'm starting to think that this might be some normal vibration due to the lack of a torque converter/spinning engine to smooth things out.

 

[D4700]

Update - changed the pan/filter assembly last night. Here's some pics of an original ~80k mile ZF full hybrid trans pan.

A bit different from the typical 8HP pan. There's this little reservoir with a flapper door on it.

Another pic of the flapper.

The magnets... Not sure how much is normal on here. Definitely has a solid metallic coating.

The bad news is that I haven't noticed much of a difference after replacing the pan and replenishing the fluid (~6qt). The groaning noise is still present, and the rough 1-2 shift is still there, especially when the fluid is cold. But, I'm happy I got this out of the way. It was a pretty easy job and it's one less thing that I have to worry about now! For $130 shipped to my door, not a bad deal on the pan.