NP203 whats the deal with axel swap? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dmartin1 · 07-11-2011, 03:48 AM

so i have a 1978 k20 with an NP203 transfercase..it was factory fulltime 4x4 or whatever that deal is.

so i swapped out front and rearend out of a 1979 k20 suburban with a different transfercase.

the front has wolverine manual locking hubs.

in unlocked,2wd mode the truck doesnt go anywhere much and makes a grinding sound.
when there locked in,the truck drives perfect like it regularly did before(all with the transfercase in 2wd)

What makes it do this?like,with the transfercase in 2wd and the front hubs unlocked,shouldnt it still move? i dont get it.

mcmlxix · 07-11-2011, 04:57 AM

Are you sure the axles you swapped into the truck have the same gear ratio?

6T8 · 07-11-2011, 06:04 AM

You will need to put in part time kit in your 203 transfer case.........Rick

Redcap · 07-11-2011, 10:38 AM

Quote:

Originally Posted by 6T8

You will need to put in part time kit in your 203 transfer case.........Rick

Or chuck the 203 and get a far-superior 205.

snj8198 · 07-11-2011, 02:05 PM

Yup, what those guys said. Now that you have a new front end with unlocked hubs, power is taking the path of least resistance and the motor's torque is being sent to the front. You need to either install a part time kit into your existing 203 or swap the full timer out for a part time TC.

martindc1 · 07-11-2011, 09:22 PM

Basically your transfer case has a differential in it, so when you unlock the front hubs it is only turning your front driveshaft. Its the same thing that happens when you have a 2wd drive and one tire goes into a mud puddle and you get stuck because that tire just sits there and spins while the other one sits still. When you put your T-case into "4-Hi Loc" it locks that differential.

So as the others have said you can either put in a part time kit, put in a np205 or just drive around with your front hubs locked.

cabcorner · 07-13-2011, 07:43 PM

Daja Vu. Should i make the obligatory boat anchor comment?Do a search on the 203 there's a lot of information out there and a lot of posts like this one.

tomtuna1978 · 07-17-2011, 01:36 PM

where did u get the front and rear diffs? it sounds like your rear diff is toasted ! is the grinding noise coming from the rear diff or t-case ? my 79 truck tossed the rear drive shaft and so i just locked the front hubs and drove home in front wheel drive (rear d-shaft removed ofcorse)... the 203 t-case is full time 4x4 and you can do that ! check if the noise is coming from the t-case or the rear diff ! and look at the rear d-shaft and see if it is spinning when its grinding ! good luck !!!

cabcorner · 07-18-2011, 07:02 AM

The 203 is not meant to have locking hubs , unless the transfer case is converted to part time . Unlocking the hubs and driving in high lock will eventually damage the case. I would , like an earlier reply suggested keep the hubs locked and drive in the High position .I suspect the grinding is coming from trying to shift the case without putting the transmission neutral .

07-11-2011, 03:48 AM	#1
dmartin1 Registered User Join Date: Aug 2008 Location: mohave valley,arizona Posts: 1,088	NP203 whats the deal with axel swap? so i have a 1978 k20 with an NP203 transfercase..it was factory fulltime 4x4 or whatever that deal is. so i swapped out front and rearend out of a 1979 k20 suburban with a different transfercase. the front has wolverine manual locking hubs. in unlocked,2wd mode the truck doesnt go anywhere much and makes a grinding sound. when there locked in,the truck drives perfect like it regularly did before(all with the transfercase in 2wd) What makes it do this?like,with the transfercase in 2wd and the front hubs unlocked,shouldnt it still move? i dont get it. __________________ 1969 Shortbed in progress 1982 short step, few suspension and motor upgrades.getting a 468 1978 Shortbed fleet side bonanza fully loaded 1978 k20 Silverado loaded.currently engine-less 1989 k10 suburban 9" lift 65 nova And more

07-11-2011, 04:57 AM	#2
mcmlxix Collector of Projects Join Date: Apr 2003 Location: Las Vegas Posts: 3,106	Re: NP203 whats the deal with axel swap? Are you sure the axles you swapped into the truck have the same gear ratio? __________________ Rich 1972 K5 Blazer CST Click HERE D60 BIG BRAKE UPGRADE Click HERE

07-11-2011, 06:04 AM	#3
6T8 Active Member Join Date: Dec 2004 Location: Tucson, AZ Posts: 233	Re: NP203 whats the deal with axel swap? You will need to put in part time kit in your 203 transfer case.........Rick

07-11-2011, 02:05 PM	#5
snj8198 Registered User Join Date: Feb 2007 Location: Star Valley, WY Posts: 2,038	Re: NP203 whats the deal with axel swap? Yup, what those guys said. Now that you have a new front end with unlocked hubs, power is taking the path of least resistance and the motor's torque is being sent to the front. You need to either install a part time kit into your existing 203 or swap the full timer out for a part time TC. __________________ Steve 1971 GMC Longbox. Full Roller Stroker 489 w/ FiTech EFI, Chris Straub Cam/NV4500/205/D60/14B w. Grizzly Locker and 4.11's. 2" Lift on 33's

07-11-2011, 09:22 PM	#6
martindc1 Registered User Join Date: Jul 2009 Location: La Crosse, WI Posts: 218	Re: NP203 whats the deal with axel swap? Basically your transfer case has a differential in it, so when you unlock the front hubs it is only turning your front driveshaft. Its the same thing that happens when you have a 2wd drive and one tire goes into a mud puddle and you get stuck because that tire just sits there and spins while the other one sits still. When you put your T-case into "4-Hi Loc" it locks that differential. So as the others have said you can either put in a part time kit, put in a np205 or just drive around with your front hubs locked. __________________ Currently truckless, previous trucks: 67 K20, 87 K10 aka V10 & 72 C10

07-13-2011, 07:43 PM	#7
cabcorner Registered User Join Date: May 2011 Location: Rochester NY Posts: 14	Re: NP203 whats the deal with axel swap? Daja Vu. Should i make the obligatory boat anchor comment?Do a search on the 203 there's a lot of information out there and a lot of posts like this one.

07-17-2011, 01:36 PM	#8
tomtuna1978 Registered User Join Date: Apr 2009 Location: Bend,Oregon Posts: 225	Re: NP203 whats the deal with axel swap? where did u get the front and rear diffs? it sounds like your rear diff is toasted ! is the grinding noise coming from the rear diff or t-case ? my 79 truck tossed the rear drive shaft and so i just locked the front hubs and drove home in front wheel drive (rear d-shaft removed ofcorse)... the 203 t-case is full time 4x4 and you can do that ! check if the noise is coming from the t-case or the rear diff ! and look at the rear d-shaft and see if it is spinning when its grinding ! good luck !!!

07-18-2011, 07:02 AM	#9
cabcorner Registered User Join Date: May 2011 Location: Rochester NY Posts: 14	Re: NP203 whats the deal with axel swap? The 203 is not meant to have locking hubs , unless the transfer case is converted to part time . Unlocking the hubs and driving in high lock will eventually damage the case. I would , like an earlier reply suggested keep the hubs locked and drive in the High position .I suspect the grinding is coming from trying to shift the case without putting the transmission neutral .



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