73-87chevytrucks.com

73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Transfer Cases and Front Drivelines => Topic started by: Godgunsrocknroller on April 29, 2006, 10:54:00 pm

Title: T-case problem and shift pattern
Post by: Godgunsrocknroller on April 29, 2006, 10:54:00 pm

I have a 76 k10 with an np-208 t-case. I have 3 questions.

1) What is the shift pattern for the t-case (the writing is rubbed off the knob)

2) When do I "lock" and "free" my hubs?

3) My t-case will only go to the forward most and second forward most positions, its stuck and refuses to go anywhere else, am I doing something wrong? And if i'm not, is there somthing wrong with my t-case?

This is a great site, thanks in advance for your guys help!  

Title: Re: T-case problem and shift pattern
Post by: 1976Scottsdale on April 29, 2006, 10:29:00 pm

Being a '76, are you sure that it is an NP-208 and not an NP-203?  The 203 is much larger than the 208 and is made mostly of iron, where the 208 is all aluminum.  Try putting the transmission in nuetral before shifting the T-case.

Title: Re: T-case problem and shift pattern
Post by: Blazin on April 30, 2006, 10:24:00 am

I agree it should be a 203 or 205. You mention locking and unlocking your hubs. It is most likely a 205, unless someone coverted a full time hub truck then it will be a 203 and most likely have the kit in the case as well. There should only be four positions for a 205 all the way back is 4 hi, next forward is 2 hi, next forward is nuetral, last is 4 low. Also a 208 does not have the shift pattern on the knob, it has an indicator like an auto trans has on the column. It is 2 hi all the way forward, 4 hi next back, nuetral, and all the way back is 4 low.
As far as hubs go if you want 4 wheel drive then thats when you need to lock them. When manuvering a trailer in a tight spot I use 4 lo with out the hubs locked for more control and less use on the clutch as in hi I would be engaging and disengaging it alot.

Edited by: Blazin at: 4/30/06 9:25 am

Title: Re: T-case problem and shift pattern
Post by: Godgunsrocknroller on May 01, 2006, 10:14:00 pm

The guy I bought it from told me it was a np-208, its sort of a frankenstein truck, lots of parts from different places. He could be wrong though. I hope he isn't though because I just filled up the transfercase with SAE 80W90. Is there any way I can tell which case it is?
Thanks!

Title: Re: T-case problem and shift pattern
Post by: Blazin on May 02, 2006, 07:34:00 am

A 208 is all aluminum, and has a slip yoke for the output. A 205 is all cast iron and has a fixed yoke ouput. 203s are cast iron and most times will have an aluminum tail shaft housing area.  

Title: Re: T-case problem and shift pattern
Post by: VileZambonie on May 02, 2006, 04:39:00 pm

Your transfer case does not take 80w90. If it's the 208 it takes ATF. If it's an old 203 it takes 10w30  

Title: Re: T-case problem and shift pattern
Post by: Blazin on May 02, 2006, 10:44:00 pm

I have 2 budies that rebuild transmisions / tranfer cases and they both recomend motor oil in a 208.  

Title: Re: T-case problem and shift pattern
Post by: VileZambonie on May 03, 2006, 05:09:00 am

Why?

Title: Re: T-case problem and shift pattern
Post by: Blazin on May 03, 2006, 07:11:00 am

One of them used to work at a Chevy dealer and that is what they used instead of ATF. The other told me it was recomended to him by Transtar, the company he gets his rebuild kits from.

Title: !!!!
Post by: Godgunsrocknroller on May 03, 2006, 11:50:00 am

Should I be worried that I put 80w90 in my t-case?!?!?!?!!??! This is not good......

Title: Re: !!!!
Post by: Blazin on May 03, 2006, 01:14:00 pm

If it is a 203 or 205 thats whats suposed to be in it. If its a 208 I would drain it and refill if it were mine with motor oil, or if keeping it original ATF.

Edited by: Blazin at: 5/3/06 12:15 pm

Title: .
Post by: Godgunsrocknroller on May 03, 2006, 05:41:00 pm

I looked at the case and stamped on there is:

C1
C-11890
6-74

and on the plate it says:

model: 20(either 3 or 8 its partially rubbed off)
ratio: 20

Im still not sure what case it is, guy who sold it to me told me it was a 208 but im not sure.

Title: Re: .
Post by: Blazin on May 04, 2006, 06:22:00 am

Is it cast iron or aluminum?  

Title: Re: .
Post by: VileZambonie on May 04, 2006, 04:50:00 pm

Blazin I worked at a chevy dealer for 4 years and there was never one class I took or TSB I ever saw that said to use motor oil instead of ATF.

Take a magnet and see if it sticks to the transfer case.

Title: Re: .
Post by: Godgunsrocknroller on May 04, 2006, 11:08:00 pm

Yep, its a 203. I drained the gear oil and put some 10w40 in it. I still don't understand how to shift the thing, it drove in all the positions, then it only drove all the way forward, and it grinds when I move the shifter to different positions, it goes ERRRRRRGGHHHHHH. It also goes CLANG CLANG CLANG when I try to shift it and to be honest it scares the crap out of me.... in fact I shut off the truck and lied in the fetal position crying for quite a while in the garage. Please show me the ways of the mighty transfer case!

Also I have the locking hubs where I have to get out and turn the thing from "free" to "lock". But it drives in "free" in the furthest forward position, which I beleive is 4low, which would mean the previous owner put a part-time conversion kit on it?

Thanks for putting up with all the questions, you guys are great!

Edited by: Godgunsrocknroller at: 5/4/06 10:35 pm

Title: Re: .
Post by: Blazin on May 04, 2006, 11:42:00 pm

You are saying it will shift into all the positions when shut off and then start & it will drive? I have allways been able to shift any of my 203 or 205 cases in park or in gear in my auto trucks. You should be able to shift while moving at a slow speed from 2 hi to 4 hi, 4 lo you should be stoped.
Vile, all I know is that is what he said he was told to do with any 208 that came in with ATF in it. My other buddy that rebuilds transmisions, & tranfer cases told me he had heard the same thing. I don't know where he heard it.
I have been running 5W30 in every one of my 208s for about 12 years now and had no problems. I have bought several trucks with 208s and they already had motor oil in them.
Idono?

Edited by: Blazin at: 5/4/06 10:52 pm

Title: Re: .
Post by: Godgunsrocknroller on May 05, 2006, 11:27:00 pm

So the positions are

L-loc
Low
N
Hi
H-loc

so in which of those do I have to get out of my truck and lock the hubs?

Also is there a way I can tell if its been converted to part time? I thought I heard that if I have the hubs where I have to get out of my truck and turn them from "free" to "lock" by hand then it has been converted, but I wanted to confirm it.

Edited by: Godgunsrocknroller at: 5/5/06 10:45 pm

Title: when to shift and lock in
Post by: 1976Scottsdale on May 06, 2006, 07:36:00 am

You can lock in the hubs in any of the ranges if you want to.  However, first, unlock(Free) and put the case in HI, then see if it will drive around... almost forgot, to stop the grinding, put the transmission in N(Neutral) before shifting the case.  If the truck will drive in Hi with the hubs free, then it has been converted.  If it has not, the truck will not move in Hi unless the hubs are locked in.  Just always put the transmission in Neutral before shifting the transfer case.  Many people will just put hubs on the axle and run it in Hi-Loc with the hubs free if the case has not been converted.

Title: .
Post by: Godgunsrocknroller on May 06, 2006, 03:28:00 pm

It moves in forward and reverse in L-loc and H-loc, only moves forward in L, and doesn't move at all in Hi (all of this with the hubs unlocked) So I guess it hasn't been converted to part time.

How is that mile marker kit for the conversion w/o hubs for $45?  

Title: .
Post by: Godgunsrocknroller on May 09, 2006, 02:02:00 pm

I think I just figured it out, sorry for being a little slow. I have a full time case (203) that originally probably came without manual locking hubs, but someone put manual locking hubs sometime along the way, So thats why it only drives with hubs in free in Lloc and Hiloc, and only drives with locked hubs in low and hi, because the manual hubs connect and disconnect the tires from the front differential, so someone probably installed the manual hubs to save gas.

Is all this correct?

So is this the same as part time kind of? Or does this system still waste gas?

Should I put in the part time conversion where you replace the spider gears in the tcase with wedge gears?

Sorrry about all the questions, Thanks!

Title: Hubs
Post by: VileZambonie on May 11, 2006, 08:03:00 pm

Yeah sounds like you're driving around in HiLoc position. This works but locks the interaxle differential and usually causes it to prematurely fail. Convert it and use manual hubs or swap it out with a 208 transfercse.

The stock Xcase shift pattern is...

Low Lock
Low Full-time
Neutral
High Full-time
High Lock

If you convert it you will have...

4x4 Low
2x4 low
Neutral
2x4 High (Normal Street use)
4x4 High

Title: .
Post by: Godgunsrocknroller on May 11, 2006, 08:37:00 pm

Yup I'm buying that mile marker kit for like $40 to convert it to part time, I already have manual hubs so I don't need to buy the $130 mile marker kit with hubs. Thanks for the info!

Title: Re: .
Post by: VileZambonie on May 14, 2006, 09:34:00 pm

Well don't confuse the terminology now! LOL Part Time is now considered something you use when you are locked. You use it "Part Time". "Full Time" means you use it on any road surface. I know it sounds confusing and backwards but most manufacturers use the terminology as I just explained.

Title: .
Post by: Godgunsrocknroller on May 18, 2006, 01:58:00 pm

I still don't understand the point of locking the hubs. If its four wheel drive all the time why dont they just have the hubs be always locked?

Title: Re: .
Post by: 1976Scottsdale on May 18, 2006, 03:21:00 pm

Well, originally, without the hubs, your truck was considered full-time 4x4 because the wheels were were bolted directly to the front axle shafts(sort of) and they had no hub or locker or anything, it was all a nut and bolt solid piece.  The transfer case acted just like a rear axle, the power went to the front or rear, dependant upon which one needed it at any given time.
Now, your's has locking hubs, which as you siad, disconnect the wheels from the front differential.  This gives you two wheel drive.  The hubs are locked in by you whenever you feel like getting out and locking them in.  This re-connects the wheels to the front differential.  Once you install the Transfer case kit, you will no longer have the differential in the transfer case and you will have 4x2 in HI or LO and 4x4 in HI-LOC or LO-LOC.

The original point of the NP203 case was for driver convenience or work use where 4x4 is often needed.  This made it easier to have a truck that was always locked into 4 wheel drive of some kind.

Also, once you convert the transfer case, lock in the hubs for about 10 out of every 200 mils and shift into hi-loc.  This will cirulate the fluid in the case since a 203 uses the chain to sling oil into a container that lubricates the case.  Once converted, you won't have that in Hi or LO any more.  

Title: .
Post by: Godgunsrocknroller on May 20, 2006, 10:40:00 pm

Thanks man, I really appreciate the info! I think I understand how it works now