Rear end noise

Joined
Mar 12, 2020
Messages
7
Location
Kansas
Hey guys, new to this forum, long time on FJCruiserForum.
Getting concerned about the increasing noise from my rear end. Early build (purchased Nov 2006). Currently at 122k. Lite off-roading, and medium weight trailer towing. Mostly a hard surface road. The noise is increasing. Just left the stealership yesterday and they agree "unusual noise" but no option than a total replacement $2500-3500.
I'm in the KC area, any good off-road mechs that can look at third member, pinions, and bearings to tell me what I need to do?
 

BMThiker

I aim to misbehave
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Joined
Sep 19, 2006
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Find a local shop that can do differential work. You can buy a drop-in differential from Nitro Gear or East Coast Gear. They end up being significantly cheaper than the dealership parts, but you have to send them your old differential as a core return. The basic process is remove the wheels, brakes, then axle shafts. Then unbolt the driveshaft from the rear axle, remove the 3rd member (differential chunk) from the center of the axle. Bolt new 3rd member in it's place and replace everything. While the axle shafts are out, you should probably replace the bearings on them too. This is a fairly tedious project and one that should be done by experienced mechanics. Even with the drop-in 3rd member this is probably an all day job, so you're probably looking at $1000 in labor.
 
Joined
Mar 12, 2020
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Kansas
About what I thought, and I had seen the Nitro Gear but thought it was a complete rear end, axles, housings etc. Thanks for the info.
 
Joined
Oct 1, 2009
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Panhandle Floriduh
I think what he was saying was get the 3rd member out before it tears up a set of gears. To which you have to "eat" the cost of.

My thoughts are more diagnostic. See if you can identify where the noise is coming from. What does it sound like? Does it increase with speed?
What makes it change? Might not be the 3rd member. Wheel bearings? pinion bearing, brakes. Hell I even had a buzzing sound on my 06/06 build FJC.
In the end I found an oil deflector had come loose and was riding on the axle splines. Can you be more specific as to the noise?
 
Joined
Mar 12, 2020
Messages
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Location
Kansas
I think what he was saying was get the 3rd member out before it tears up a set of gears. To which you have to "eat" the cost of.

My thoughts are more diagnostic. See if you can identify where the noise is coming from. What does it sound like? Does it increase with speed?
What makes it change? Might not be the 3rd member. Wheel bearings? pinion bearing, brakes. Hell I even had a buzzing sound on my 06/06 build FJC.
In the end I found an oil deflector had come loose and was riding on the axle splines. Can you be more specific as to the noise?
OK, thanks for the explanation. Makes sense. Also the recommendation to do some more detective work. I think the first thing to do will be to check the temps of the pumpkin after a good drive at highway speeds.
For now, though, the sound is just a loud whining drone. Back in the day ('70s) driving M-151 Mutts in the Army, that same sound indicated insufficient lube in the rear diff. Intensity increases with speed, but levels out and stays consistent. I mean, the FJ has always been noisy, and worse with mudders, but the last few months seems to have gotten louder. It is not a screech, nor are there grinding noises, just a very intense drone.
 
Joined
Oct 1, 2009
Messages
214
Location
Panhandle Floriduh
Start simple and go up. Check the fluid levels first. Front to rear. Sounds can be hard to pinpoint. You say you tow, drone sounds could be transmission. ???
Is it std or auto? Check your drive shafts for play, grease your links etc... Easy enough to do, save money and is all needed maintenance anyway.
 
Joined
Aug 22, 2010
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Jersey, 07740
most likely it is one of the pinion bearings in the rear, check your gear oil level first but if it is a bearing it will only get worse and will need either just the bearing replaced or the whole third replaced
 
Joined
Mar 12, 2020
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Kansas
Thanks BirdManzFJ, and bigredmachine. Yeah, so after 30 years in the Infantry (Airborne, Light, Mech), hard to trust the ears. I'll break out the digital manual I downloaded years ago, and take the diagnostics from the easy to the ridiculous.
I'm sort of leaning toward bearing noise because of how constant it is, but hard to tell.
Appreciate your thoughts and experience. Know it will eventually cost some ducats, but love this FJ and want to keep it rolling. Wish I still had my Dad's FJ40 from 72 when I fell in luv.
 

abuck99

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Does it go away when you let off the gas? At what speed does it start to make noise? Is it a more of a gear whine or something different?
 
Joined
Mar 12, 2020
Messages
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Location
Kansas
Does it go away when you let off the gas? At what speed does it start to make noise? Is it a more of a gear whine or something different?
It doesn't go away, it just diminishes. It starts almost immediately on acceleration, perhaps at 10-15 mph, then increases to a certain pitch and stays there, until decelerating and then going down. I really think of gear whine more than bearings. I think that bearings would be more of a squealing sound? It has always been a bit noisy, but over the last few weeks seems to have gotten more intense. Thanks for any advice.
 
Joined
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I'm sort of leaning toward bearing noise because of how constant it is, but hard to tell.
if its a wheel bearing noise it will cancel when turning and driving at a constant speed, steady noise more likely to be in the rear. how do the tires look, cupped tires will sound similar to a bearing type noise.
 
Joined
Mar 12, 2020
Messages
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Kansas
if its a wheel bearing noise it will cancel when turning and driving at a constant speed, steady noise more likely to be in the rear. how do the tires look, cupped tires will sound similar to a bearing type noise.
OK, good info. Just did a tire rotation a week ago. Looking good, uniform wear and no unusual, or abnormalities. I'm going to be driving a bit today so I'll keep the radio off and listen closely to get more definitive. I really do think it is in the rear. Thanks again.
 
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