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Discussion Starter #1
Ok, I have an 86 samurai that is making a grinding noise in 4wd. Everything is fine in 2wd, no noise. I can accelerate in 4 High with no noise but as soon as I coast it makes a very noticeable metal on metal/grinding noise that is relative to the speed. Clutch in or out, same noise. Trans in gear or neutral, same noise. If I step on the brakes I can get it to change or go away for a second. So far I've gotten under the truck and checked all driveshafts and U joints for play and all are seem tight and in good condition. I swapped transfer cases with a used one with no change. Changed fluid in trans, t-case and front and rear diffs. All looked good, no milky fluids or metal shavings. I am under the assumption that there is something bad in the front axles, differential, wheel bearings, birfield joints, or hubs? I am not familiar with working on solid axles at all and am not sure how to proceed at this point. If anyone has any ideas I would surely appreciate it!
 

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Check the (t-case) front output shaft for movement. A trashed front output housing and snapped output shaft can duplicate almost any break (noise) in the front of the drivetrain. It is hard to diagnose without seeing actual cracks or pulling the front off. Here are a few shots of my last output break:



The front housing can be removed without pulling the t-case out of the truck. Just drop the front drive shaft, drain it and then pull the shifter up into the cab and remove the 7 bolts. It takes 30 minutes, but it will save you many hours of yanking everything else apart if it truly is the culprit.
:cool:
 

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Discussion Starter #3
Is it a pretty common issue Bill? I already swapped my T-case for another one with the same result but I guess it beats tearing the front end apart if I don't have to. Thanks for the reply, I really appreciate it.
 

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Is it a pretty common issue Bill? I already swapped my T-case for another one with the same result but I guess it beats tearing the front end apart if I don't have to. Thanks for the reply, I really appreciate it.
The only noise problem that is more common is a worn out U-joint. Sometimes they feel tight until you actually remove the shaft from the vehicle. But the last few 'phantom noises' I have diagnosed turned out to be the output shaft. You can get a beefed up replacement (if that is what the problem is) from Low Range Offroad, Trail Tough or PetroWorks.
 

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Discussion Starter #6
Excellent. Thanks for the pictures. I'll tear into it and report my findings. I do have grease fittings on my Ujoints so I'm going to grease them and see if it makes any difference in the noise. I played with them both on and off the truck and they pivot nicely and have no apparent slop.
 

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Check you're front pinion bearing for slack.
Had a rear pinion do the very same thing recently.
I agree. Not recently, but I've had the same. Quiet on pull, horrible racket on coast. Nut backed off and let the gear drift when not loaded. Somebody replaced the pinion seal, without using a new crush sleeve, when they put it back together (Dana 60, I think).
 

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Discussion Starter #9
Ok, I tore into the wheel bearings and kingpin bearings and they are looking good. I packed the snot out of them with grease and back together for a test drive. I also found a grease fitting on the slip joint? on the front driveshaft and shot a ton of grease into that figuring if I regrease everything heavily the noise would at least change if the offending part was involved. No change. Myself and my passenger hung our heads out the window to try to isolate the sound then switched seats and it does sound like from the front center. So, is it worth it to go ahead and replace the ujoints on the front driveshaft even though they feel fine? No grease fittings on the actual ujoints on the front shaft but they are tight and they move freely with the driveshaft bolted in and while removed. I am going to check the output shaft in the transfer case this afternoon. I am leaning toward front diff noise, how do you get at the pinion bearing? Will I have to pull the axles out of the front and get the diff out of the housing? Please excuse my ignorance, I have never done any of this before so I'm learning as I go.
 

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To pull the pumpkin out of the axle housing, yes, you have to pull the axle shafts first. But before you go through all that, take a look at the nut and drive shaft flange.



After removing the drive shaft, pull on the flange and twist it around. If you feel a lot of movement before the teeth engage, and/or you feel that the nut is not on tight and the whole pinion moves in and out, then you have a problem. Sometimes the nut doesn't get 'staked' after the person tightens it and it then vibrates loose...
 

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If you have a little time and want to page through some tech articles, there are a few on my personal site that show the inner workings of some of the drive components. The link is in my signature as ZookTech.
 

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Discussion Starter #14
Thanks guys. I have a spare front and rear diff from a parts truck sitting on the shelf. Is there an easy way to tell if they are good? Maybe just swap it out with my spare or is the pinion bearing easily fixed once the diff is out? From what I'm reading it looks like they are not very user serviceable, more for a specialized shop? Is the pinion bearing included in this assumption? I live on an island in Alaska so anything that needs to get rebuilt needs to be shipped to the interior. My goal is to get this buttoned up and reliable for the winter and not have to tear it down again if at all possible. I will be pulling the driveshaft and yanking on the pinion shaft in a few hours as well as looking at the output shaft on the t-case.
 

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The quick answer is to yank on it, spin the flange and visually check the teeth for wear, chips or cracks.

Given your location, I would download the service manual, get a set of feeler gauges and a good dial indicator. Then after you put the best diffs into the rig for the winter, sit down with the old ones and play with them until you get the process down. It took me only 2 R&P swaps to get pretty good at it. Now I can almost do it in my sleep. I built a table that I bolt the flange to so the diff will stand up and not fall over. You can do almost the same with a rear drum brake.


Use a nut and bolt to secure it to the drum.
 

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Discussion Starter #17
Are front and rears interchangeable? I read something about different spline counts, am I counting axle splines?
 

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Discussion Starter #20
I feel fortunate to have experienced people as a resource! Kids dance recital kept me from under the truck yesterday evening so I'll be back at it today. I dug out my spare front diff from the parts shelf and I spun, pulled, and wiggled it in every direction and it seems to be as good as it gets. Teeth look perfect. My confidence level is rising.
 
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