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73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Transfer Cases and Front Drivelines => Topic started by: 81GMCBILL on November 20, 2011, 06:31:12 pm

Title: NP 205
Post by: 81GMCBILL on November 20, 2011, 06:31:12 pm

Hi... newby here. 

1981 GMC k3500    TH400/NP 205

What does it take to rebuild the NP 205 ? Any special tools?
Ive got a leak coming out of the front of the transfer case where the front(4x4)
driveshaft comes out,  the shifter is way loose (horizontally) and there is some vibration
at around 50-55 mph.
Would I remove the transmission and transfer case together ?
Also, where is the balance point located when I lower the TH400 & NP205 down,
like maybe the adapter area ?

thanks for your help ...

Title: Re: NP 205
Post by: bake74 on November 20, 2011, 06:49:28 pm

     There a couple of special tools you will need, or make up your own.  If I was doing it, I would drop only the transfer case and rebuild it.  I would support the trans with block and jack, and use another jack to get the 205 free and let it down.
     Do a search on the internet if you do not have a haynes or such book for tools needed, it will show and explain the tools needed.

Title: Re: NP 205
Post by: snibook7537 on November 23, 2011, 10:11:46 pm

yeah I don't know how much a TH400 weighs but i imagine it ain't light and the 205 on it's own is heavy.  When I did the clutch in my truck( K30 sm465 and 205) I just dropped each individually. I'll tell you if you can lift a sm465 and a 205 together then you sir are a man.  LOL

Title: Re: NP 205
Post by: 81GMCBILL on November 24, 2011, 12:02:34 am

well ive done this before when i had a 76 gmc   with the np 203/th350 and dropped it together, so i was just wondering about doing the same thing with the np 205. But im going with what you say and just drop the 205 alone.
As for the rebuild , Im going to attempt rebuilding this with a kit....
Q- anyone have an idea about where to get this kit? my budget is $200.

thanks for all the comments.

Title: Re: NP 205
Post by: Engineer on November 24, 2011, 10:55:13 pm

eBay has a ton of 205 rebuild parts. Make sure if you are replacing all of the bearings that you get the right input bearing. The SM465, and TH350 use one input bearing, the TH400 uses an entirely different, and considerably larger input bearing.

I have rebuilt my 205 a couple of times. The only special tools that I know that you need are a monster set of snap ring pliers. The snap rings that hold the thrust washers for the low range gears are pretty stout.

There are no tricks to rebuilding a 205. Just take out the old parts, and put in the new.

One tip though, on a street truck the preload on the tapered roller bearings on the idler shaft should be set at zero "0". By this I mean no end play, and no preload. There will probably be some play from normal wear, this is bad, and could in extreme 4-low situations cause the idler shaft to walk the rear output shaft right through the rear bearing retainer.

In an application like my sled puller you will want some preload (drag) on the bearings. I do not plan to drive my truck on the street, so preload (even slightly excessive) is preferred. On a street truck heat expansion will load these bearings, too much preload will burn them up. Under no circumstances do you want end play on these bearings.

If you deceide to replace the idler shaft bearings you will need some preload in all applications, as the bearings will loosen slightly as they run in.

Title: Re: NP 205
Post by: 81GMCBILL on November 24, 2011, 11:55:11 pm

great advice, thanks a million !

Title: Re: NP 205
Post by: pedigo78 on January 07, 2012, 01:55:01 pm

You can check out Northwest Fab, they have good products for the transfer case.

Title: Re: NP 205
Post by: 81GMCBILL on January 07, 2012, 11:05:36 pm

thanks pedigo78! i'll look them up right now.

Title: Re: NP 205
Post by: pedigo78 on January 08, 2012, 01:08:16 pm

no problem

Title: Re: NP 205
Post by: heavychevy91 on January 10, 2012, 06:01:52 pm

How is all of this going for you? I NEED to do the same on my truck soon. What tranny do you have BTW? just wondering how the parts search went. I have the 465 in mine.

Title: Re: NP 205
Post by: pedigo78 on January 10, 2012, 10:20:59 pm

I have a TH350. I just rebuilt my np205 but i am going to do it again cause it is still leaking.

Title: Re: NP 205
Post by: beastie_3 on January 11, 2012, 02:28:58 pm

Pedigo,

If you could make a detailed how to post with pics on rebuilding the 205, that would be awesome. Post it in the Tech section.

Title: Re: NP 205
Post by: pedigo78 on January 11, 2012, 06:03:21 pm

I am sorry, but I actually dont have time. I am getting ready to head to 29 palms for a month of training. then predeployment leave, then im off. so i am pack.

but it is pretty, ez. just like going a front hub. just pull everything out and line it up as they come out. Also becarefull with removing the actual drive shafts. cause they have alot of needle bearings. just make sure you have alot of grease in order to put thebearings back on the shafts.

Title: Re: NP 205
Post by: 81GMCBILL on January 11, 2012, 11:39:05 pm

beastie_3  : 

I while I was searching I found this site >>    www.okcnetworks.com/bronco/205/np1.htm
it has  a detailed instruction and pics.

pedigo78 > good luck on training.

Title: Re: NP 205
Post by: beastie_3 on January 13, 2012, 02:26:44 pm

Yay for 29! EMV???

Title: Re: NP 205
Post by: 454k30 on February 06, 2012, 10:36:56 pm

I rebuilt my 205 several years ago.  Except for snap ring pliers I don't recall any special tools that I needed.  The sm465 was a whole 'nother story!