'02 Mitsubishi Montero Diagnosis Help Sought

"Rusty Vandura - www.tinyurl.com/keepoppo" (rustyvandura) 07/10/2017 at 13:36 • Filed to: None

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Our friend has an ‘02 Montero with a bad rumble in the front on the driver’s side. 182k miles on the drivetrain. Some shop told her it needed a prop shaft and maybe a front bearing. Personally , I’m afraid it’s the front differential. I have the car in the air on jackstands, and clearly, the sound only happens when the front half of the driveline is happening; no news there. But the way the sound is transmitted into the cab of the truck, it sounds like it’s coming from the diff. I drained a little bit of gear oil, which is probably original to the vehicle, into a clean bucket. The black crumbs are likely from crud around the drain plug. I have a Harbor Freight stethoscope, but I can’t confidence that way either. If it were my own vehicle, I’d start by draining the diff and filling it with Red Line or Amsoil synthetic gear oil.

What are your thoughts or recommendations?

Die-Trying > Rusty Vandura - www.tinyurl.com/keepoppo 07/10/2017 at 13:48

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if you were to have the thing in neutral, and turn the front driveshaft, back and forth, how much “play does it have before it hits from one tooth to the other? can you lift and shake the pinion by the yolk? is there play there? how do the u-joints at the outer front shafts look when you wiggle the slack out of the driveline?.......... just stuff to look at while youre relaxing under the montero, trying to catch a nap......

benjrblant > Rusty Vandura - www.tinyurl.com/keepoppo 07/10/2017 at 13:52

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It clearly needs new differential oil anyway. I’d start there. Any signs of chunks or excessive metal fragments in the differential oil? The drain plug might be magnetic so it could be holding onto those bits. Might not see unless you fully remove the plug.

With the vehicle in neutral, on the ground, and wheels chocked, you should be able to grab the drive shaft and check the u-joints for play.

With the front axle on jack stands, you should be able to wiggle the wheels axially (up/down, left/right) to check for wheel bearing play. 

Could also be CV joints- at 182k miles and questionably original differential oil, I’d start checking everything I could get my hands on.

Rusty Vandura - www.tinyurl.com/keepoppo > Die-Trying 07/10/2017 at 13:56

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So you’re talking about slop at the input to the differential?

By u-joints, do you mean the CV joints at the ends of the half-shafts outboard?

Rusty Vandura - www.tinyurl.com/keepoppo > benjrblant 07/10/2017 at 13:58

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Yeah. I’m nearly ready to punt this project back to my friend... I’m on the rebound from changing an engine and the transmission is not happy and I will be very disappointed if the engine/trans has to come back out of that car...

Rusty Vandura - www.tinyurl.com/keepoppo > benjrblant 07/10/2017 at 13:58

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But I can change the diff fluid for her...

Future next gen S2000 owner > Rusty Vandura - www.tinyurl.com/keepoppo 07/10/2017 at 14:08

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Swap the fluids. All of them. It probably needs it anyway and recheck. Fluids are relatively cheap.

benjrblant > Rusty Vandura - www.tinyurl.com/keepoppo 07/10/2017 at 14:11

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Nothing wrong with doing what you can and suggesting it be taken to a mechanic.

Rusty Vandura - www.tinyurl.com/keepoppo > benjrblant 07/10/2017 at 14:15

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http://oppositelock.kinja.com/this-looks-like-what-i-think-im-hearing-1796780616?rev=1499710479651

RPM esq. > Rusty Vandura - www.tinyurl.com/keepoppo 07/10/2017 at 14:39

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I’m not sure if you’re describing a “rumble” of a grinding type or more of a vibration type, but if the latter, are you certain about the location? Driveline rumble/vibration noise is really common on these due to either the crossmember bushings or the vibration damper... in fact, I’ve read that the official, service bulletin fix for driveline vibrations is removing the damper.

Rusty Vandura - www.tinyurl.com/keepoppo > RPM esq. 07/10/2017 at 15:02

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I don’t know. It’s not my car and I fear getting in over my head. I think I am going to punt.

Die-Trying > Rusty Vandura - www.tinyurl.com/keepoppo 07/10/2017 at 18:39

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yes, and yes....... twist the driveshaft back and forth to also see if there is excessive slop between the gears......

also see if you can shake the output driveshaft from the transfercase leaving.... see if there is slop there.....

Rusty Vandura - www.tinyurl.com/keepoppo > Die-Trying 07/10/2017 at 21:02

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Looks like it’s the wheel bearing. But I messed up the prop shaft getting it out, so we’ll be replacing that too. Fresh synthetic gear lube in the diff. No pinion wiggle that I could discern.

You’re the man. Some day, I hope we can meet up for real.