M56x Clunks From 3rd to 2nd to 1st When Approaching Lights

[Ilya]

Any thoughts on what I'd check to see why my M56x 'clunks' from 3rd to 2nd to 1st when approaching a light? I don't think it's as much transmission related as it's something with maybe bushings or mounts? How do I diagnose this? Doesn't clunk when shifting from 3rd to 2nd in actual driving situations like corners when RPMs are higher.

Reminder: I filled the rear subframe bushing with epoxy and it's rock solid (did it a couple of weeks ago).

I'm considering taking it to the dealer and doing a suspension inspection and have them tell me what all is close to or needing changing (and hopefully do most of the work myself).

[VStar650CL]

Most likely culprit is one of the u-joints. Check those first.

[Ilya]

Most likely culprit is one of the u-joints. Check those first.

They don't seem terribly expensive or hard to fix based on the ChrisFix video I just watched - this car has two right? One on each end of the driveshaft? Might just replace both and call it a day. Off to find the part numbers but may try to get under the car to do an inspection before ordering.

EDIT: On InfinitIPartsDeal and InfinitiPartsUSA, I'm only seemingly seeing u-joints for the steering column? Any idea what the search term is for the driveshaft ones? Or is aftermarket the only option for this part?

[VStar650CL]

On a 4WD M you actually have 5, three on the rear driveshaft (one in the middle behind the carrier bearing), two on the front driveshaft. I'd put a prybar on them and check them before throwing parts at it. They're the prime culprit for downshift clunks, but they aren't the only possibility.

It does look like aftermarket is the only option for joints, Infiniti only lists the whole driveshafts.

[Ilya]

On a 4WD M you actually have 5, three on the rear driveshaft (one in the middle behind the carrier bearing), two on the front driveshaft. I'd put a prybar on them and check them before throwing parts at it. They're the prime culprit for downshift clunks, but they aren't the only possibility.

It does look like aftermarket is the only option for joints, Infiniti only lists the whole driveshafts.

Will do in the next few days and will report back. Thank you!

[Ilya]

Finally got around to check the u-joint. Here's a picture and a video of the one I could see. To me it seems like natural play? Nothing special?

The others I either was too blind or were hidden behind a ton of stuff that I didn't have time to get off today...will have to post pone till late October when I'm back from caring for my rental out of state.

[Elchotogrande]

I'm kinda noticing this on my M35h. Doesn't happen always, just sometimes when I'm slowing down and the light turns green I accelerate again, it hesitates and I feel a clunk noise/feeling type. Mine being a hybrid, idk if it has something to do with the regenerating from the wheels and then asking the electric engine to kick again, but it's just in certain situations like that, slowing but having to accelerate few seconds later. I gotta change the rotors and pads soon, so I'll ask them to cheek the u-joints just in case.

[Ilya]

Honestly, mine has been doing it for like 80kmi lol...I'm just finally getting around to fixing all of the little things on my cars and this is one of them. Seems fine otherwise.

[mikedamageinc]

My guess is front diff bushings. I just replaced them on my Yukon, different vehicle of course but exact same issue. Clunk on each downshift, now its nice and quiet.

[emm3seven]

If you are still running the original “rear motor” mount (really transmission mount) it’s another candidate as well. My 2011 M37 with ~83k had a mount that was collapsed almost an inch. It’s a pretty easy job to replace.

[Ilya]

If you are still running the original “rear motor” mount (really transmission mount) it’s another candidate as well. My 2011 M37 with ~83k had a mount that was collapsed almost an inch. It’s a pretty easy job to replace.

Yeah that's definitely still original. Any pointers on where it is or the part number?

[emm3seven]

Yeah that's definitely still original. Any pointers on where it is or the part number?

It's not too bad. Here's some info on my 3.7 / AWD, yours is a bit different.



I replaced the rear transmission mount (11320 in diagram) and bought some new bolts just in case the rust monster got uppity.

The rough job, from memory, was:

• Raise front on ramps / jack stands
• Remove nuts (08918-3401A in diagram) holding bottom of mount to crossmember (11340 in diagram)
• Support the back end of the transmission with a jack and/or jackstand
• Remove bolts holding crossmember to frame (11520AA in diagram), drop crossmember
• Unbolt/remove/replace mount
• Reinstall crossmember (follow the torque sequence in the FSM)
• Replace nuts holding mount to crossmember
• Done

On a whim I looked up your 2011 M56x and it looks a little bit more complex:



The part number for your rear mount looks like 11320-1CA0A but obviously double check that.

Looks like a few more dampers (not shown in that diagram but in a couple of others), beefier crossmember, and different mount attachment method, but I don't see anything that would make it terribly more difficult than the 3.7.

I will say that the rear mount on the 5.6 AWD looks quite a bit beefier than the one from my 3.7 AWD, so my experience of a collapsed mount may not apply to you. If nothing else it's easy to pull a few bolts and check for evidence of the transmission hitting the crossmember or something similar.

[Ilya]

Good stuff! Will have to add this to the list or just continue living with it if I get under there and it seems to much effort hah. Been dealing with it for nearly a decade hah.