loud pop/snapping when reversing up a steep hill

[Clint Beastwood]

The driveway of the house I rent as a big "home office" is very steep - when backing up i get a loud pop/snap from the transmission as soon as I hit the steepest part. It doesn't sound great, but I have noticed no deleterious effects. Does this happen for anyone else? Car's a 2017 with ~13k miles on it, cobb RMM if that matters. Gearbox is otherwise well behaved, just this *very* loud snap, once, when backing up on steep hills. I did try to search and found references to mechanical noise or clunking but this was more of a sharper metal striking metal sound, like if you banged a hammer against the transmission housing.

 

[TyphoonFiST]

The driveway of the house I rent as a big "home office" is very steep - when backing up i get a loud pop/snap from the transmission as soon as I hit the steepest part. It doesn't sound great, but I have noticed no deleterious effects. Does this happen for anyone else? Car's a 2017 with ~13k miles on it, cobb RMM if that matters. Gearbox is otherwise well behaved, just this *very* loud snap, once, when backing up on steep hills. I did try to search and found references to mechanical noise or clunking but this was more of a sharper metal striking metal sound, like if you banged a hammer against the transmission housing.

I think it was the vehicle utilizing the hill start assist and making the clacking noise from the brake engaging and disengaging.....IMO.

 

[Clint Beastwood]

I think it was the vehicle utilizing the hill start assist and making the clacking noise from the brake engaging and disengaging.....IMO.

Wouldn't it always make that sound when the hill assist thingy engages/disengages? Hm. Is there a way to disable the hill start shenanigans to validate? It's plausible, I'd like to mythbuster it and see if thats it or not

 

[TyphoonFiST]

Wouldn't it always make that sound when the hill assist thingy engages/disengages? Hm. Is there a way to disable the hill start shenanigans to validate? It's plausible, I'd like to mythbuster it and see if thats it or not

Why yes...yes you can in the Touch screen on the dash in vehicle settings I do believe.

 

[Clint Beastwood]

Wouldn't it always make that sound when the hill assist thingy engages/disengages? Hm. Is there a way to disable the hill start shenanigans to validate? It's plausible, I'd like to mythbuster it and see if thats it or not

Ah found it, all I found the first pass around was for non-sync cars. I'll disable it and try when I head home ~4am

 

[Intuit]

... driveway ... is very steep - when backing up i get a loud pop/snap from the transmission as soon as I hit the steepest part. ...... *very* loud snap, once, when backing up on steep hills. ..............

Okay so the drivetrain load changes as you hit the steeper part... any clutch or/and throttle application changes? Preliminary suspicion lies with an engine mount. Probably an engine mount. E-brake applied, can you play with the clutch and throttle a little bit to try and twist the engine? Just a little bit... don't abuse or stall it.

 

[Clint Beastwood]

It was still doing it after disabling hill start assist (my lord the car is much easier with that garbage turned off! I can feel the friction point!) - I pulled the cobb mount and lubed up every metal/poly interface with shin-etsu honda silicone grease. Reassembled, torqued to 53 ft lbs (I found 50 and 55 recommended so... split the difference). So far, no popping or clanging. It was in there pretty tight still but while under the car I rocked the engine by hand with the bolts loosened and the sound was similar to what I initially reported.

 

[Clint Beastwood]

Service manual calls for all RMM fasteners to be torqued to 70nm which is 51.63 ft-lb, so you're very close. Congrats on the fix.

Note that this doesn't apply to the nuts for the bracket that the downpipe mounts to, as they are to be torqued to only 24nm (17.07 ft-lb).

Hm I think I set those to ~15 ft lbs, I'll check tonight. Thanks!