I would have all the drive axles inspected F/R. You probably can't eyeball them to see if they're good or not. Driving a hybrid on the road, you're never going to know exactly when the rear wheels get engine torque since it can come on and off many times per second.

 

maybe a rear wheel bearing, worth a check

 

Just spitballing here really but if the problem only occurs while under load I'm wondering if you don't have a bad torque converter. :shrug:

 

Good call scaped-1, if it goes away when taken out of overdrive you'll have a good idea.

 

Good call scaped-1, if it goes away when taken out of overdrive you'll have a good idea.

Except hybrids like the OPs have e-CVTs with no torque converters, overdrives, or gears like a conventional automatic transmission.

 

Good call scaped-1, if it goes away when taken out of overdrive you'll have a good idea.

Except hybrids like the OPs have e-CVTs with no torque converters, overdrives, or gears like a conventional automatic transmission.

Ahh crap! Thwarted by my old nemesis: CVT! :rant:
I'm still thinking that it is a torque induced drive line issue which leads me to think that it is one of the driveshaft u-joints. Or, and I hope I'm wrong, and that used PTO that you had installed has failed.

 

Sorry for the delay but here is the latest update...

I marked and pulled the entire driveshaft and drove the vehicle for 2 weeks with it out. No codes and no vibrations! Installed new U-Joints and replaced the center support bearing and put the driveshaft back in (indexed correctly of course) and all noise and vibrations are back. So to summarize:

No driveshaft - no issues.
New driveshaft - All issues return. Speed sensitive humming noise all the time, and a harsh vibration while accelerating at 50-55 and above. Foot off the gas and vibration is instantly gone.

I did note that there is quite a bit of backlash in the rear diff pinion. Is there a spec on this? Could I have a bad pinion bearing? Bad rear axles? Bad rear wheel bearings? Only thing that makes sense to me is the pinion/ring gear interaction.

Thoughts?!?

Thanks!

 

I posted in another thread yesterday...the Bosch MTS 4100 NVH/harmonic analyzer is the tool you probably need to figure out what's going on.

 

Quick follow-up:

Jacked the "monster" up at all 4 corners and jerked around on everything...

-The rear CV/axles look good and seem tight.
-Rear wheel bearings seem tight.
-Front wheel bearings seem tight as well and all spins smoothly.
-There is still more backlash than I would like in the rear diff but it seems ok.

I pulled the level inspection plug from the rear diff and checked out the fluid. All looked at the right level, very clean and in good shape.

I pulled the level inspection plug from the PTU and checked out the fluid. First off the truck was sitting higher in the rear than in the front and the plug is toward the rear of the unit so I expected the fluid to be slightly below the threads but it immediately started trickling out, There was alot of metal in the fluid in the form of very small flakes; also a good amount stuck to the plug. I cleaned the plug and closed it up.

I grabbed the driveshaft and spun it back and forth 90° or so and the only noise I got was from the PTU. More noise than I would like. The rear diff seems quiet.

So my question: Could the symptoms I've described be the PTU? Hard vibration at 50-55mph while accelerating? Silence when foot is off the gas. No symptoms at all with the shaft out?

Thanks!
Brad

 

Hi, Brad -- way back in 2014, you had a vibration when accelerating problem with your 07 Mariner. Sounds like the prob I currently have. Can you remember what you did to solve it? I'm guessing engine mounts, but I am a non-mechanic.
Thank you, Dan Asheville

 

Not Vrad, but given the symptoms, and the description of the PTO unit, I expect that he replaced the PTO with a used unit. When the lube fails, it has been cooked and turns to a tar-like substance, providing less-than-ideal lubrication properties. The bearings inside could be damaged, causing runout and binding of the output shaft, or other components. Essentially, when the drive shaft was removed, the load on the PTO went to zero. Without a load, the PTO could not cause vibrations. FWIW, as I understand, the PTO is a bolt-on component that can be unbolted from the side of the transaxle and a replacement bolted on with little difficulty.
Engine mounts would not, I think, be affected by removing the drive shaft. If they were failing, and allowing the assembley to rock forward and backward as the load is applied/removed, it could change the angel of the output shaft to the drive shaft, but it should not really be a large difference, unless you had total failure of the torque handling mounts.(and a BIG rocking motion)
tom

 

you seeing excessive amount of metal flakes point you to where the problem is, The play in the rear differential yoke is also suspect… It sounds like someone may have done neutral drops… or got stuck and tried to reverse neutral their way out
lol
just teasing you… Go with what is obvious though.

get a strong magnet, and stick it to the check bolt head(ducktape it in place to be sure you don't lose it), and then recheck for shavings again after a few days, or a hundred miles.