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Discussion Starter #1
How much noise should a NP205 make? and is there a way to make it quieter? It starts for the time I step on the gas and gets noisier the faster I go.....
 

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What kind of noise is it making?? If it is just whining it may need more gear oil. If it is making grinding/rattling noises you probably need bearings.
 

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205's are normally pretty damn quiet, maybe you're driving around in 4 hi?!
drain the fluid. that'll tell ya if you got bad bearings or other internal problems. see how contaminated the fluid is and if you can see a bunch of metal swirls when you look at the old fluid in the sun light.
rear end noise maybe?! how are the u-joints?
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Originally posted by frisbee:
<STRONG>How much noise should a NP205 make? and is there a way to make it quieter? It starts for the time I step on the gas and gets noisier the faster I go.....</STRONG>
Check your body mounts and your case mounts. I was pulling some heavy loads with my truck with a 203 and stated getting all sorts of noise that sounded just like the case eating itself. Well it turned out that the bolts for my skid plate had got up against the mounts that were ruined by ATF leak. The crossmember was acting like a speaker and transmitting the normal noise at many times louder than it would be if the mounts were isolating it like they are supose to. Pulled the bolts out that were touching the mount and quiet as can be unless under heavy load. Then the top of the case touches the floor pan. <IMG SRC="smilies/smile.gif" border="0"> My cab mounts are pretty hashed also hehe. Ordering new this week.
Also check your motor mounts. If the newer design (clam shell) fails the motor drops onto the metal cross pin and transmits noise to the frame.
 

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205 should be real quiet in 2HI. 4HI a little louder, and they do whine in 4LO.
 

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DUH!!!!! <IMG SRC="smilies/rolleyes.gif" border="0"> I should have put more info in the orginal posting..... The noise is gear whinning...It's so loud that anyone next to me in highway traffic rolls up their windows!!!!! This whine has been there since I bought the truck.. At first I thought it was the tranny (SM456)...now that I have the TH400........well keep reading... I have put in fresh gear oil I believe its called "hypoid" or something like that... is there any gear oils out there that can help with the whine? or is there a recommended gear oil if I'm using the wrong oil now! the T-case is isolated from the cross member using rubber mounts.... should I isolate the crossmember from the frame?.... I have left it in 4hi before and the performance drops off.... I have checked that twice.... 4hi all the way back... 2hi then netural... then 4lo right? also when I frist drained the gear oil it was full of water!!! and I'm not sure how long the water was in there ..... I had the truck about 2months and only drove it 5 miles before I drained the T-case... The rear end is fine I had that checked about 5k miles ago... u-joints are brand new.... This is really annoying as a last resort what would be a replacement..... I'm not doing any hard-core wheeling...mostly used when it snows or around the lake and property when muddy <IMG SRC="smilies/biggrin.gif" border="0">
 

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If it had water in it, I would take it apart and inspect, gears are more than likely rusted. Plus when you run a NP205 with a auto tranny, the xfer case will have the same oil as the tranny. You need to run auto tranny fluid in your 205! <IMG SRC="smilies/skull.gif" border="0">
 

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Discussion Starter #8
Run auto tranny fluid? Why is that? I have been running gear oil with the automatic for about 1500 miles I hope that didn't hurt anything.....
 

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The 205 uses gear oil no matter what tranny is in front of it. Their is a seal in the adapter that keeps the two from mixing . With the additional information of their having been water in the oil I would have to say the gears as well as the bearings most likely have rusted. A new set of bearings should quieten it down when in 2hi however in 4wd it will still whine.
 

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all cast iron transfer cases use gear oil. if you find atf in a 205 it's either because somebody mistakenly filled it with atf or the seals in the adapter are bad and the trans fluid is "bleeding" into the t-case. running atf in a 205 will not do any harm, but you should run 90wt anyways. much thicker; likes to stick to all the parts better.
if your t-case had a bunch of water in it, it's probably going to need at least bearings, maybe more. let me know if you need parts, i can get overhaul kits for a decent price and i have 5 205's sitting in my garage. pm me.
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Lots of people in the snow belt with long zero or below temps will run ATF in cases instead of gear oil in the winter months. When it's that cold it's like turning molases in the case.
 

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The 205 uses gear oil no matter what tranny is in front of it.
No it doesn't. The 205 was used in ALL 1980 GM trucks. All the ones behind the autos came with ATF in them. That was the year they also had that shity slip-yoke set up. Very easy to change over though.
 

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I know this is an old thread. I had a chain rattle like noise, thought it was the transfer case. I removed the shift panel so I can watch the front drive shaft while driving. I noticed that the splines on the shaft were stripped and the drive shaft worn out splines were rattling against each other. I was in 2 wheel drive but residual torque was making the front shaft spin a little, but enough to cause the stripped shaft to rattle.
 
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