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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8538
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I hope all is well with you - here again - I have a 2002

Customer Question

Hi Doug I hope all is well with you - Don here again - I have a 2002 Montero Limited (125000 miles) with a slight grinding noise coming from the front axle I think. I can best describe the situation as follows: 1) In 2WD after 20-60 minutes of driving
I hear a slight (mild) grinding noise when coming to a stop. 2) If I shift to 4WD the noise disappears immediately and everything is normal. 3) If I shift back from 4WD to 2WD I will get another 20-60 minutes of smooth driving. 4) I had a similar problem about
2 years ago but the grinding was considerably more pronounced. In this case I changed a vacuum solenoid device on the inner fender wall under the air filter and the problem immediately stopped. 5) Earlier in the summer I was driving on the highway in 2WD and
the 4WD-2WD indicator group started to blink. After I stopped and started the engine the system returned to normal and I have had no further problems. I doubt this is related but figured I might as well mention it. Any troubleshooting or other suggestions?
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.

Hi Don,

This is very common behavior and is nearly always related to either a bad free wheel clutch solenoid pack or a vacuum hose issue like you are familiar with.

You are going to want to approach this similar to you did before when the solenoid failed.... first make sure ALL of your vacuum lines are intact, none damaged or disconnected etc and that includes down on the front axle and around the engine intake etc.
If all look good, I would take a hand vacuum pump and apply it to the off side of the actuator on the front axle and draw the actuator out to fully engage 2WD. Make sure it is secure (zip tie it up etc) and confirm the grind is gone. If the grind is still present there is likely damage to the actuator or fork etc in the differential. More than likely the grind will be gone.
At that point we know there is a vacuum supply issue to the actuator preventing it from fully engaging 2WD.
From there you would want to pull the solenoid pack again, test resistance on both coils, and check with a hand vacuum pump for vacuum retention on both solenoids... if either solenoid holds vacuum regardless of voltage being applied/removed or leaks vacuum (even a tiny bit) regardless of voltage being applied/removed, you will be in for another free wheel solenoid pack.
I know it was just replaced 2 years ago, but if the vacuum lines are all intact it is still the most likely culprit... I've seen them fail earlier than 2 years old as well. Do the checks though and it will get you to your issue.

Customer: replied 1 year ago.
Thanks Doug - I thought there might be other reasons like the diaphragm actuator on the axle itself or something. I also thought if there was vacuum leaking it would give me a service code light. Regarding the solenoid, it was a cheapo deal from china for like 25$ so perhaps it is not as good as the original although it looked identical. Anyway I will double check as you suggest. When applying vacuum to the actuator should I apply to the port on the passenger side? Is that the "off" side? Have you seen the actuator on the axle fail, is this a possibility too? When you say "tie it up" do you mena pull the rubber boot back and prevent the shaft from moving somehow?
Expert:  Doug replied 1 year ago.

Yes, the passenger side should draw away from the differential and the driver side toward it.
I've seen one actuator fail. Ever. The solenoids are usually it.
When I say tie it up, I mean secure the vacuum pump while it is holding vacuum so you can test drive it.

Customer: replied 1 year ago.
duh - I get it. I will get back yo you in a day or so when I have had a chance to try it. thanks
Expert:  Doug replied 1 year ago.

No problem.