73 and 80 4x4 comparison info needed - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**kidatheart** · 12-25-2018, 08:09 PM

I have been looking for and '80 k10 automatic running gear because of the 205 transfer case. I have come across a '73 GMC 1/2 ton that has a 205 from the factory, as far as I can tell. Is this pretty much the same running gear as an 80? Did they change the transfer case much between those years? If I remember the right, the '80s might have had a 400 trans. That really doesn't matter to me. Any information is appreciated!

sweetk30 · 12-25-2018, 08:26 PM

205 is a 205 for the most part . in the early 80's tho they did have a kind of mutt that was syncro'd for the front engagment on the auto hub dana 60 trucks . only a problem if you wish to go 32 spline upgrade on the front haft as you will need the front guts from another NON syncro 205 to make it work . also the early units with a yoke for the front output got a small 10 spline shaft over the bigger 30 spline shaft from the flat flange style front output units . easy to swap over tho is you wish to have the 30 and only got the 10 spline . just a shaft and flange for the swap over .

otherwise pick the case you need and run it . also 85-up went round adaptor pattern over the orignal fig 8 style .

**kidatheart** · 12-25-2018, 08:46 PM

Thank you for the fast and great information. I am building a truck that will mostly be just a driver and will not be used very hard very often. I want dependability and simple. I am not real fond of the 203. I understood everything that you said, except for the adapter part. Is that between the transmission and transfer case? Thank you.

sweetk30 · 12-26-2018, 01:17 PM

yep the np205 went to the round 6 bolt pattern in 1985 for the normal stuff . some military trucks still did weird stuff tho .

**kidatheart** · 12-27-2018, 10:34 PM

Thanks for the info!

GonicGM · 12-28-2018, 10:54 AM

76 and older NP205 has formal u-joint saddle for connection to front driveshaft, driveshaft likewise. 77 and later have flat flange front output, likewise mating round ring flange on shaft as well. Rather certain front yokes cannot be swapped as with the change in the styles also came course versus fine front output splines.

80 K10 slip yoke tailshaft, 79 back all fixed yoke.

12-25-2018, 08:09 PM	#1
kidatheart Senior Member Join Date: May 2012 Location: Assaria, Ks Posts: 465	73 and 80 4x4 comparison info needed I have been looking for and '80 k10 automatic running gear because of the 205 transfer case. I have come across a '73 GMC 1/2 ton that has a 205 from the factory, as far as I can tell. Is this pretty much the same running gear as an 80? Did they change the transfer case much between those years? If I remember the right, the '80s might have had a 400 trans. That really doesn't matter to me. Any information is appreciated!

12-25-2018, 08:26 PM	#2
sweetk30 Registered User Join Date: May 2012 Location: horseheads,ny rust belt Posts: 2,794	Re: 73 and 80 4x4 comparison info needed 205 is a 205 for the most part . in the early 80's tho they did have a kind of mutt that was syncro'd for the front engagment on the auto hub dana 60 trucks . only a problem if you wish to go 32 spline upgrade on the front haft as you will need the front guts from another NON syncro 205 to make it work . also the early units with a yoke for the front output got a small 10 spline shaft over the bigger 30 spline shaft from the flat flange style front output units . easy to swap over tho is you wish to have the 30 and only got the 10 spline . just a shaft and flange for the swap over . otherwise pick the case you need and run it . also 85-up went round adaptor pattern over the orignal fig 8 style . __________________ 77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great.

12-25-2018, 08:46 PM	#3
kidatheart Senior Member Join Date: May 2012 Location: Assaria, Ks Posts: 465	Re: 73 and 80 4x4 comparison info needed Thank you for the fast and great information. I am building a truck that will mostly be just a driver and will not be used very hard very often. I want dependability and simple. I am not real fond of the 203. I understood everything that you said, except for the adapter part. Is that between the transmission and transfer case? Thank you.

12-26-2018, 01:17 PM	#4
sweetk30 Registered User Join Date: May 2012 Location: horseheads,ny rust belt Posts: 2,794	Re: 73 and 80 4x4 comparison info needed yep the np205 went to the round 6 bolt pattern in 1985 for the normal stuff . some military trucks still did weird stuff tho . __________________ 77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great.

12-27-2018, 10:34 PM	#5
kidatheart Senior Member Join Date: May 2012 Location: Assaria, Ks Posts: 465	Re: 73 and 80 4x4 comparison info needed Thanks for the info!

12-28-2018, 10:54 AM	#6
GonicGM Registered User Join Date: Mar 2014 Location: Rochester, NH Posts: 168	Re: 73 and 80 4x4 comparison info needed 76 and older NP205 has formal u-joint saddle for connection to front driveshaft, driveshaft likewise. 77 and later have flat flange front output, likewise mating round ring flange on shaft as well. Rather certain front yokes cannot be swapped as with the change in the styles also came course versus fine front output splines. 80 K10 slip yoke tailshaft, 79 back all fixed yoke. __________________ 83 K30 SRW 350 TH400 NP205 4.10 9' Fisher 85 K30 SRW 350 TH400 NP205 4.10 87 V3500 Dually 454 TBI SM465 NP205 4.10 9' Fisher 83 K2500 350 TH700R4 8600GVW Dual Tank 4.10 1973 Cheyenne Super 30 DRW Std Cab Z83 4.10 1976 Silverado C30 Std Cab 4.10 DRW (4 sale)



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