2002 montero limited rear end rumble/vibration over 50mph

[spacecowboy7777]

Drove about 30 minutes on the highway after an errand. Parked the truck on a level surface, put it in nuetral with parking brake on, kept the engine running. Tranny fluid was at just past the top of the "hot" mark. Slight oily smell, but super faint, and only if I put the stick or towel right up to my nose. Definitely doesn't have any hint that burnt atf smell. Appeared clear in color on the dipstick, but has a faint pink color on the paper towel.

Also, the truck came with a single liter of Mitsubishi branded SPIII atf among the extras, so I believe the PO to have the correct fluid.

I think my tranny fluid is perfect both in level and condition. I'll still do a full service in the future, but I don't think this is a priority.

I'll get under there and take a look at the rear diff bushings and engine mounts today at some point.

 

[Michael Brown]

Are the wheels and tires balanced?

 

[plh]

I wouldn't recommend the "dilution method" if you have never done a complete flush with OEM fluid. If a previous owner did not use OEM fluid, that could be the reason for the vibrations/shuddering. Complete flush takes about 12 quarts. These transmissions are bullet proof if care for properly.

Cheers

Good point about not knowing if the P.O. had previously changed the fluid.

 

[spacecowboy7777]

Are the wheels and tires balanced?

Tires are new H/T tires from Falken. Installed at Discount tire. I've had unbalanced tires before, and this does not feel like that.

 

[spacecowboy7777]

Motor mounts are difficult to inspect, but look pretty good:



Rear diff bushings look suspect. But the front rear diff bushings are really tough to get a good look. I think this may be my issue:

 

[spacecowboy7777]

I've also got the center diff light blinking sometimes. Going to replace the 4x4 freewheel solenoid and see if there is any change. Another thread suggested the 4x4 solenoid malfunctioning could cause the 4x4 to engage when it shouldn't which could cause some driveline noise/vibes.

 

[Michael Brown]

I've also got the center diff light blinking sometimes. Going to replace the 4x4 freewheel solenoid and see if there is any change. Another thread suggested the 4x4 solenoid malfunctioning could cause the 4x4 to engage when it shouldn't which could cause some driveline noise/vibes.

This is possible, but it would be a noticeable noise from the front axle when it engages. There used to be a good diagnosis page, but it seems to have a broken/404 error now.

If you haven't already, grab an FSM from the link in my signature. There should be a diagnosis section for the C-diff light.
This is a vacuum powered system, so it can atrophy without use. Things get stuck and need exercise. If all the vacuum lines are good, just keep regularly moving it into 4H and the system can free up on its own.

It could also be dirty connections on the transfer case plugs. Since the Limited 5-speed uses fully electronic shifting, these can get some corrosion and cause slow or poor function.

 

[Michael Brown]

For more troubleshooting, put the car into 4H and see if you get the same vibration. This should move some of the output load to the front axle.

Also for reference:
2Hi - Standard RWD
4Hi - AWD with open center diff
4HLc - 4WD Hi with locked center diff
4LLc - 4WD Lo with locked center diff

 

[spacecowboy7777]

For more troubleshooting, put the car into 4H and see if you get the same vibration. This should move some of the output load to the front axle.

Also for reference:
2Hi - Standard RWD
4Hi - AWD with open center diff
4HLc - 4WD Hi with locked center diff
4LLc - 4WD Lo with locked center diff

Thanks for the FSM links. Had some rain yesterday and put it in AWD for a grocery store run, and noticed absolutely no difference. I did not take it on the highway though. I'll take it on the highway in AWD and see what happens

 

[MontySquareo]

 

[spacecowboy7777]

tested it out in AWD yesterday on dry streets and I think it drives smoother. Still some ruble from the rear end under load, buuuut, I think it's smoother. Based on this info, I'm going to try and swap out the rear diff bushings.

For the center diff light blinking, it only happens after a little while of driving around. I've got a cheap free-wheel solenoid coming to test out. That Diagnostic Info Super Sheet is a life saver for troubleshooting.

 

[Inyo_man]

Swapping out the rear diff. bushings can be done without the rig on a lift, but it's certainly harder.

A few years back I had a blinking center diff. light. I disconnected each electrical connection, one at a time, from the transfer case and checked for corrosion. I ended up cleaning them and reconnecting with dielectric grease. Problem solved.

Cheers

 

[steevo_102]

I'm suspecting the remaining high speed rumble has to do with the CV axles

I've been away from the forum for a couple months but came back and saw this thread and wanted to chime in.

I currently have this issue in my gen 3 as you described, but for the front axle. I noticed this happened to me as soon as I switched to aftermarket axles, they were clicking while turning or articulation. The clicking stopped once I put new aftermarket units in, but after driving it for some time, I put it in 2Hi and it rumbles only on acceleration at freeway speeds. Once I let off, the rumbling stops.

I misdiagnosed thinking the issues were elsewhere since I didn't immediately drive in 2Hi after swapping out the axles but according to this thread, the issue was the axles. Post #30 the OP mentions the resolve. I have yet to try this but I'm confident this is the issue since the issues was non-existent before changing them (for me at least).

Montero shudder/vibration in 4HI Only - Mitsubishi Forum - Mitsubishi Enthusiast Forums

Mitsubishi Montero & Montero Sport - Montero shudder/vibration in 4HI Only - Hey guys I recently started using 4hi and 4WD on my Gen 3 Montero and I found a vibration so I am hoping you all might be able to help me track it down. Here's the issue, I get a shuddering vibration when I accelerate...

mitsubishiforum.com

Our issues aren't directly related but it's something you can look into. Did this issue start randomly, overtime, or after servicing your gen 3?

 

[spacecowboy7777]

Still working on this issue ya'll, just been busy with work and family.

I've been away from the forum for a couple months but came back and saw this thread and wanted to chime in.

I currently have this issue in my gen 3 as you described, but for the front axle. I noticed this happened to me as soon as I switched to aftermarket axles, they were clicking while turning or articulation. The clicking stopped once I put new aftermarket units in, but after driving it for some time, I put it in 2Hi and it rumbles only on acceleration at freeway speeds. Once I let off, the rumbling stops.

I misdiagnosed thinking the issues were elsewhere since I didn't immediately drive in 2Hi after swapping out the axles but according to this thread, the issue was the axles. Post #30 the OP mentions the resolve. I have yet to try this but I'm confident this is the issue since the issues was non-existent before changing them (for me at least).

Montero shudder/vibration in 4HI Only - Mitsubishi Forum - Mitsubishi Enthusiast Forums

Mitsubishi Montero & Montero Sport - Montero shudder/vibration in 4HI Only - Hey guys I recently started using 4hi and 4WD on my Gen 3 Montero and I found a vibration so I am hoping you all might be able to help me track it down. Here's the issue, I get a shuddering vibration when I accelerate...

mitsubishiforum.com

Our issues aren't directly related but it's something you can look into. Did this issue start randomly, overtime, or after servicing your gen 3?

Thanks for the info, this is definitely something I'm thinking may be an issue. Since the rear is raised via a spacer, I'm wondering if the rear CVs are either worn, or at too high of an angle, or are aftermarket. I recently replaced the front CVs with aftermarket because the stock ones had torn boots and the joints were stiff. The new aftermarket solved some steering wheel shimmy, but the front is stock height, so I don't think aftermarket CVs will be a problem. As a side note, the front CVs were super easy to replace. Easier than the Gen 2 I used to have.

This rear rumble issue has been present since I got the vehicle. It did not change at all when I changed the front CVs. Also , I feel and hear the rumble from the rear of the truck, which could be an illusion, but it still makes me think it's the rear diff or rear CVs making the noise. I'll try the frequency measurement on my phone to see if it gives any insight.

Got the rear diff bushings delivered. Hoping to get them installed this weekend.

Thanks again for everyone's help. Pictures of the front CVs for good luck:

 

[spacecowboy7777]

Hung ~290 lbs way off the back and the vibration is way lower maybe gone. So, either the lower ride height changes geometry enough to take the vibes away OR the bike acted as a big damper on the monocoque chasis