2002 montero limited rear end rumble/vibration over 50mph

[steevo_102]

I'm wondering if the rear CVs are either worn, or at too high of an angle, or are aftermarket

I've seen it discussed in a forum before and I cant find the thread that talked about it in detail, but the forum link I sent you in my previous post, one member mentions that same thread mentioning aftermarket axles not doing well with excessive angle and causing vibrations since aftermarket axles for the Montero/ Pajero are 3 bearing and stock is 6. So if it's lifted, it can contribute to the issue. My google search also shows several other cars going with aftermarket axles and experiencing vibrations, so I safely assume this can also be the case, especially if they look recently replaced.

You can see this aftermarket one is a 3 bearing


vs the Monteros looking something like this


Not saying this is the source of your issue but could be worth looking into. Start with the simple issues first (wheel balancing, alignment, hubcentric rings, cupped tires) then work towards the bigger/ harder ones (wheel bearings, axles, differential, etc.).

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

So...how much for those stock CV axles? 👀

 

[Vector78]

Try adding your diff and trans dampeners back in. This sounds resonance related...

 

[spacecowboy7777]

Try adding your diff and trans dampeners back in. This sounds resonance related...

I tried adding both back in, separately and together. The trans damper definitely added a different, rpm related vibe back. The rear axle damper might have reduced the consistency of this speed related rumble/vibe. Right now, running the truck with the rear axle damper installed but no trans damper.

 

[spacecowboy7777]

I've seen it discussed in a forum before and I cant find the thread that talked about it in detail, but the forum link I sent you in my previous post, one member mentions that same thread mentioning aftermarket axles not doing well with excessive angle and causing vibrations since aftermarket axles for the Montero/ Pajero are 3 bearing and stock is 6. So if it's lifted, it can contribute to the issue. My google search also shows several other cars going with aftermarket axles and experiencing vibrations, so I safely assume this can also be the case, especially if they look recently replaced.

You can see this aftermarket one is a 3 bearing
View attachment 820366

vs the Monteros looking something like this
View attachment 820367

Not saying this is the source of your issue but could be worth looking into. Start with the simple issues first (wheel balancing, alignment, hubcentric rings, cupped tires) then work towards the bigger/ harder ones (wheel bearings, axles, differential, etc.).



So...how much for those stock CV axles? 👀

I think you’re on to something here. The rear axles appear original, but I want to take the rear end apart and check each cv axle condition. I found an aftermarket cv axle that sounds like they use the rezepa style joint. I also see used axles on eBay for $120 each.

Additionally, I thought I heard a squeak or slight metal sliding sound coming from the rear end at slow speeds. Very faint. Sounded like wheel bearing, but could also be brakes dragging, or nothing at all.

Bottom line is, I need to jack up the rear end and dig in to see if I can find anything. These could be related or separate issues. It will take me a few weeks to get to this. Thank you all for your input

 

[EpicPlanet]

@spacecowboy7777 Still having the issues? What have you found out?

 

[spacecowboy7777]

When cold, the truck is smooth as silk. After driving 10-15 minutes on the highway, the rumble comes back. Only under acceleration, and only above 50-60 mph. I took the truck to a mechanic who told me all the wheel bearings are good, and there is slight play in the main drive shaft. The entire internet says the main drive shafts don't go bad, so I'm hesitant to spend $800-$1000 for nothing to change.

I've got oem cv axles on the way and I'll give them a try. I might also try removing the rear spring spacers, see if that helps.

However, it's such a minor rumble, it's only noticeable when the pavement is perfectly smooth. For now, I've been living with it. Just did 1300 miles out to Utah and back and didn't notice it until I remembered to listen for it.

I was also thinking, maybe when the diff fluid warms up and becomes less viscus, the maybe it's starting to vibrate more?

I'll keep looking, just not too worried for now.

 

[MontySquareo]

Wait have you checked the torque converter?

On my scanner I can see the slip RPM for my torque converter. I don't know what it's supposed to be though, because I've never watched it while driving

 

[Michael Brown]

When cold, the truck is smooth as silk. After driving 10-15 minutes on the highway, the rumble comes back. Only under acceleration, and only above 50-60 mph. I took the truck to a mechanic who told me all the wheel bearings are good, and there is slight play in the main drive shaft. The entire internet says the main drive shafts don't go bad, so I'm hesitant to spend $800-$1000 for nothing to change.

I've got oem cv axles on the way and I'll give them a try. I might also try removing the rear spring spacers, see if that helps.

However, it's such a minor rumble, it's only noticeable when the pavement is perfectly smooth. For now, I've been living with it. Just did 1300 miles out to Utah and back and didn't notice it until I remembered to listen for it.

I was also thinking, maybe when the diff fluid warms up and becomes less viscus, the maybe it's starting to vibrate more?

I'll keep looking, just not too worried for now.

If it only happens or is noticeable on smooth pavement, I'd say it is likely the tires. Not imbalanced, but their normal road noise.
The Gen 3 monocoque design tends to amplify road and tire noise more than other similar vehicles. It is more rigid than body on frame or unibody so it transmits easily. Mud tires are known to be very loud, but normal AT tires can make noise as well.
My Toyo AT2 and AT3 tires both had noticeable noise on freshly paved or smooth roads. If it is not shaking the car, I'd suspect this is the noise you hear.

 

[spacecowboy7777]

Wait have you checked the torque converter?

On my scanner I can see the slip RPM for my torque converter. I don't know what it's supposed to be though, because I've never watched it while driving

I think you were on to something here. I never checked torque converter slip, but I did 2 transmission drain and fills in the past few weeks. Just drained the pan and refilled with about 4 quarts to get back to correct level. The shifting got smoother both times. I didn't think the transmission was vibrate-y, but sure enough, it is noticeably smoother now. Also, the rumble is mostly gone now. I still think it could be better, but I'll try another drain and fill in a few thousand miles. I'm using sp3 from Luso Overland.

 

[Inyo_man]

I think you were on to something here. I never checked torque converter slip, but I did 2 transmission drain and fills in the past few weeks. Just drained the pan and refilled with about 4 quarts to get back to correct level. The shifting got smoother both times. I didn't think the transmission was vibrate-y, but sure enough, it is noticeably smoother now. Also, the rumble is mostly gone now. I still think it could be better, but I'll try another drain and fill in a few thousand miles. I'm using sp3 from Luso Overland.

As posted earlier in this thread, your best bet when changing the transmission fluid is to do a complete flush.
It is truly not that difficult.
Pull the trans. fluid hose off the cooler and place it in a bucket.
Crank/start the rig for a brief time then shut off, watching old fluid come out.
Replace the approximate amount of fluid with new through the dip-stick (long funnel).
Continue this process until the fluid is coming out looking new.

Cheers

 

[Michael Brown]

Also agree with the torque converter being possible and needing a flush helps.
Some also do the filter, but not always necessary. If I can find the video or thread with instructions, I'll post here.

You will be draining ~2qts at a time from the cooler line and refilling through the dipstick.
You MUST use only SP-III fluid. It can be Aisin, Mitsubishi Diaqueen, KIA, Hyundai, or Denso brand.
eBay sells cases of OEM branded fluid. You need at least 8 qts if I remember correctly. Other fluids will make the problem worse and behave badly with the valves and bushing materials.

I do not have any information on whether the SP4 fluid is compatible, but I would say no as a gut feeling.

 

[spacecowboy7777]

Ok, I've made a bunch of improvements. Some helped a tiny amount and others helped a ton. I'm stoked to say that my vibrations are GONE. This truck is smooth as SILK. MAGIC CARPET

Thank you all for your input and suggestions. Here's what we did:

Removed the 50mm strut spacers from the front. This put the ride height back to stock with the front cv axles almost horizontal. This helped vibration a little bit.

Replaced front cv axles: mine had every boot torn. Literally both axles had both boots completely torn and the joints were totally dry and totally sloppy. I replaced with aftermarket. Yes, oem are better, but I believe my oem were beyond serviceable. With the truck now at stock height, aftermarket axles should be sufficient. The new axles noticeably reduced vibration felt through the steering wheel.

Removed the damper from the transmission and from the rear axle. I tested multiple configurations thoroughly, and removing both is the smoothest option. This made a big difference in felt cabin vibration.

Replaced the bushings on the transmission crossmember. This made a big difference.

Did a few transmission drain and fills with Mitsu spIII. This effectively replaces 4 - 5 quarts of fluid at a time. This made a good difference, but not as drastic as the bushings and damper removal. I think I got lucky and my trans fluid was in pretty good shape. But doing 3 drain and fills still definitely helped.

After all of that, my truck drove great, but I'd still get a little hum above 50 mph.

Finally, I got new shocks and while in there, decided to try removing the 50mm spacers from the rear spring perch. And what do you know, the hum is completely gone. I guess 50mm spacer on the spring is enough to overwhelm the angle of even the oem cv axles. At stock height on all four corners, my truck is so freakin smooth and buttery, even all the way up to 90mph. (I haven't tried faster). I still want a little more height in the rear, so I'm going to try a 20mm spacer. I expect a small lift to be smooth. We will see.