Front wheel drive Four wheel drive? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

brothers69c-10 · 01-10-2009, 10:04 PM

Justbought this 78 3/4ton 4x4 3 weeks ago. Put a motor in it and have slowly been fixing little things on it. Long story short, i put lockouts in it two days ago. When i went to pull it out of the garage i could feel it shift into gear, but it wouldn"t move. This is while i have it in 2high. So i thought maybe it was just cold so i lock the front hubs in, get in it and backs right out no problem. So i turn the front hubs to the free position and try to move it again and it wouldn't. It acted like it wanted but it just wouldn't move. After screwing around with it the only way i can get the rear axle to engage is to have it in 4 high. After some thought, since it is still a full time transfer case, it seems to me as if its treating the front axle as if it were the rear, and the rear as if it were the front. So i guess my question is,
Is it possible to put something in backwards in the transfer case?
or do i just have the worlds only front wheel drive 4x4.

Thanks in advance for all your input.

Mathew

Cyclone · 01-10-2009, 10:17 PM

some good NP203 info here and here and a little more

Mike C · 01-11-2009, 12:31 AM

Read the links above. The 203 is a FULL-TIME t-case, and lockouts alone don't get it done.

Pyrotechnic · 01-11-2009, 03:11 AM

The NP203 has a differential in it. You know that with an open differential axle, the wheel with least traction will get the most power. That is what is happening here. With your front hubs unlocked, the center differential sends all to the power to the front axle because it has the least resistance.

When you put it in 4 Lock, you locked the center differential and this is why you were able to move. From what I understand, it is hard on the transfer case to leave it in 4 Lock with the front hubs unlocked.

brothers69c-10 · 01-11-2009, 09:58 PM

Thanks guys for the info.
Its still wierd though, my other 78 is a full time and it has lockouts, but has no problems. Whats wierder yet is that i drove it a little today and put in two high with the lockouts turned to the free position and it drove fine for about a block and then it quit again. Somebody told me it could be the clutch thats inside?

Prong · 01-11-2009, 10:31 PM

Your other one was converted to part time--which is why it works with the hubs unlocked. You'll need a conversion kit to make your new one behave the same way.

01-10-2009, 10:04 PM	#1
brothers69c-10 Suburban Hick Join Date: Aug 2008 Location: Altoona, IA Posts: 810	Front wheel drive Four wheel drive? Justbought this 78 3/4ton 4x4 3 weeks ago. Put a motor in it and have slowly been fixing little things on it. Long story short, i put lockouts in it two days ago. When i went to pull it out of the garage i could feel it shift into gear, but it wouldn"t move. This is while i have it in 2high. So i thought maybe it was just cold so i lock the front hubs in, get in it and backs right out no problem. So i turn the front hubs to the free position and try to move it again and it wouldn't. It acted like it wanted but it just wouldn't move. After screwing around with it the only way i can get the rear axle to engage is to have it in 4 high. After some thought, since it is still a full time transfer case, it seems to me as if its treating the front axle as if it were the rear, and the rear as if it were the front. So i guess my question is, Is it possible to put something in backwards in the transfer case? or do i just have the worlds only front wheel drive 4x4. Thanks in advance for all your input. Mathew __________________ Mathew 1947 Chevy 3600 1951 GMC 100 1969 Chevy C-10 396/500hp TH400 lowered 4" 1968 Imapla Custom 396/325hp TH400 "Grandmas Car" 1976 Crew Cab 4x4 diesel http://67-72chevytrucks.com/vboard/s...d.php?t=488505 1978 Chevy K-10 454 1983 S10 4x4 "Bumblb" (Grandpa's truck) 1993 Chevy S10 V8 conversion 1990 Ford Probe Gt 1992 Dodge W-150 "Old Man's Truck" 1992 Pontiac Grand Prix SE 1992 Mercury Grand Marquis-Mercruiser 2000 Ford F150 (Currently my mother drives this) 1946 Farmall H with Stan Hoist loader 1965 John Deere 110 1961 Wheel Horse " Rat Tractor"

01-10-2009, 10:17 PM	#2
Cyclone Registered User Join Date: Oct 2004 Location: Sonoma, CA Posts: 319	Re: Front wheel drive Four wheel drive? some good NP203 info here and here and a little more Last edited by Cyclone; 01-10-2009 at 10:21 PM.

01-11-2009, 12:31 AM	#3
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,727	Re: Front wheel drive Four wheel drive? Read the links above. The 203 is a FULL-TIME t-case, and lockouts alone don't get it done. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

01-11-2009, 03:11 AM	#4
Pyrotechnic Registered User Join Date: Feb 2007 Location: Austin, TX Posts: 3,930	Re: Front wheel drive Four wheel drive? The NP203 has a differential in it. You know that with an open differential axle, the wheel with least traction will get the most power. That is what is happening here. With your front hubs unlocked, the center differential sends all to the power to the front axle because it has the least resistance. When you put it in 4 Lock, you locked the center differential and this is why you were able to move. From what I understand, it is hard on the transfer case to leave it in 4 Lock with the front hubs unlocked. __________________ 1977 GMC Sierra Grande

01-11-2009, 09:58 PM	#5
brothers69c-10 Suburban Hick Join Date: Aug 2008 Location: Altoona, IA Posts: 810	Re: Front wheel drive Four wheel drive? Thanks guys for the info. Its still wierd though, my other 78 is a full time and it has lockouts, but has no problems. Whats wierder yet is that i drove it a little today and put in two high with the lockouts turned to the free position and it drove fine for about a block and then it quit again. Somebody told me it could be the clutch thats inside? __________________ Mathew 1947 Chevy 3600 1951 GMC 100 1969 Chevy C-10 396/500hp TH400 lowered 4" 1968 Imapla Custom 396/325hp TH400 "Grandmas Car" 1976 Crew Cab 4x4 diesel http://67-72chevytrucks.com/vboard/s...d.php?t=488505 1978 Chevy K-10 454 1983 S10 4x4 "Bumblb" (Grandpa's truck) 1993 Chevy S10 V8 conversion 1990 Ford Probe Gt 1992 Dodge W-150 "Old Man's Truck" 1992 Pontiac Grand Prix SE 1992 Mercury Grand Marquis-Mercruiser 2000 Ford F150 (Currently my mother drives this) 1946 Farmall H with Stan Hoist loader 1965 John Deere 110 1961 Wheel Horse " Rat Tractor"

01-11-2009, 10:31 PM	#6
Prong Registered User Join Date: May 2007 Location: CO Posts: 475	Re: Front wheel drive Four wheel drive? Your other one was converted to part time--which is why it works with the hubs unlocked. You'll need a conversion kit to make your new one behave the same way.



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