Author Topic: Transfercase  (Read 1584 times)

Offline Smitty31

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Transfercase
« on: August 26, 2018, 10:56:16 AM »
1979 gmc k10 350 400 turbo NP203 transfer case. Im switching from automatic hubs to lockouts for fuel economy. Do i have to do a conversion kit on my transfer case. I dont like the idea of having to loc it in once a week to oil the transfercase. Is the conversion kit necessary and if so why? Thanks.
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Offline Irish_Alley

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Re: Transfercase
« Reply #1 on: August 28, 2018, 04:09:53 PM »
if you dont have the conversion kit installed you will have to keep the 203 on hi Loc all the time. imo this is a waist as the only thing you wont have turning is nothing. everything will essentially still be turning the same except your hub wont be locked to the axle shaft. if you save any mpgs it will be very little and will negate the cost of the locking hubs.
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Offline Smitty31

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Re: Transfercase
« Reply #2 on: August 29, 2018, 05:40:44 AM »
Thankyou for the info. It appears the Np203 has two different kits. One with little wedges that you can install with the transfer case in truck. Or one where you pull the case and put a new shaft in. In that youtube video the guy saids it gives you a true 2wd when your in high. Which do you guys recommend? Just trying to gather all info and make the best descision
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Offline Irish_Alley

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Re: Transfercase
« Reply #3 on: August 29, 2018, 03:04:59 PM »
they both would do the same thing in the end. if youre worried about mpgs i would think you would want the cheapest one. i think the one you have to pull the t case would be cheapest but not sure. also see what available thought they stopped making one style. but yes your shift pattern would go from

Low Loc
Low
N
HI
Hi Loc

to

Lo Loc
Lo
N
2 HI
HI Loc
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Offline 75gmck25

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Re: Transfercase
« Reply #4 on: August 31, 2018, 07:04:53 AM »
The conversion kit with wedges and the one that replaces the shaft would work identically.   The shaft conversion is considerably stronger, but I haven't seen one in any catalog in the few years.  You might get lucky and find a vendor that has one NOS, but it will be hard to find.

The conversion kit with wedges is not expensive, and apparently not that hard to install.  However, in 2WD mode the internal pump no longer operates, which causes wear on the transfer case.  The directions recommend running it in 4WD mode at least once a month so that the pump lubricates the case, but of course many 2nd or 3rd owners never get the directions.  I believe an unconverted full-time case is more reliable than one with the kit, unless the owner understands the oiling issues and follows the monthly schedule.

Stock NP203s are very popular with snowplow drivers, since the standard AWD mode allows them to go between snow and pavement without the drivetrain binding.

Bruce

Offline blazer74

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Re: Transfercase
« Reply #5 on: August 31, 2018, 02:47:08 PM »
Left mine unconverted. Canít be bothered with the lubrication problem.
Been running mine for many years with just manual hubs.
Every thing still turns except you take the bind out while turning, etc
Matter of choice.

Offline Smitty31

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Re: Transfercase
« Reply #6 on: August 31, 2018, 03:36:50 PM »
Wow guys i really appreciate the info all good stuff. A few more questions i found the conversion kit with the wedges but have been unable to find a how to video. Do you guys know of one. And when you say lock it in for oil lubrication is that just putting it in high loc or does it require locking the hubs in also. I dont mind locking the tcase in once a week to oil t case but seems like more aggravation to have to do the hubs also. Also blazer you said you just loc your hubs out. Did your mpg improve ? Currently im getting 8.8 to 9 mpg.
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Offline blazer74

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Re: Transfercase
« Reply #7 on: August 31, 2018, 06:58:26 PM »
Sorry, canít really say.
Never really checked, I just put gas in when needed which is quite often. LOL

Offline Irish_Alley

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Re: Transfercase
« Reply #8 on: August 31, 2018, 08:50:40 PM »
yeah all you have to do is pull the t-case handle back to "hi loc" and youre re-lubing everything. some do it for one road trip lets say to work then will unlock it. you dont have to do the hubs, myself would actually ride with the passengers side hub locked (with my 205) so if i got stuck all i would have to do is lock the drivers side. but if you lock the t case you will be turning everything up to the hubs so theres no need to lock them or even ride with one locked like i would do.

i want to add also i generally drove my truck off road or around a farm.
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Offline Smitty31

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Re: Transfercase
« Reply #9 on: August 31, 2018, 10:33:12 PM »
Thanks guys very helpful. Does any one have pics or video of how to install these wedges in the T case
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Offline Irish_Alley

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Re: Transfercase
« Reply #10 on: August 31, 2018, 10:41:42 PM »
i want to say someone a couple years ago did a write up on here about doing theirs. but for some reason they pulled the t-case. but they took pictures. ill try to find it but use the search button cause time is limited right now
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Offline Irish_Alley

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« Last Edit: August 31, 2018, 10:46:01 PM by Irish_Alley »
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Smitty31

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Re: Transfercase
« Reply #12 on: August 31, 2018, 10:50:26 PM »
I had all ready seen that seemed confusing. Thanks irish alley. Here is my kit. This one can be done with t case in truck. Its when you change shafts you have to pull it.
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Online JohnnyPopper

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Re: Transfercase
« Reply #13 on: September 02, 2018, 07:19:28 PM »
That's the only kit available, tried to find the shaft version for my 203, no go.

Irish's link to the CK5 is the best I've found, and pretty thorough, just read it over a few times, especially about the internal roller bearings.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Smitty31

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Re: Transfercase
« Reply #14 on: September 04, 2018, 09:13:08 AM »
Thanks for the info guys ive never been in a transfer case before so its all new to me. Still cant find a video for dummys like me. I guess ill try and hire it out.
IF ITS WORTH DOING. THEN ITS WORTH DOING RIGHT.