203np or 205

[speedd67]

I have a 78 gmc w/203np that I bought. Someone put manual locking hubs in and when i engage the four-wheel drive it makes really bad noises. checked hubs,u joints,and gears in front and all are fine. I believe that they changed it over to one ton cause when i needed rear break parts for e-brake that was what i had to use cause the 3/4 was different. I think it may be the chain in the transfercase. But i was wondering if i should go with the 205 part time or another 203 or change it to a 208 because that is for one ton. I need help because i don't know enough about four wheel drive to know the difference and not enough shops around to help me . Please help if some knows the difference.

[orionwy2002]

First off, I think in 78 3/4 and 1 ton both came with the14 bolt full floater rearend. The way to tell is if you can take the brake drums off the back w/o taking out the axle, then it is a 12 bolt. Most 3/4 and 1 ton have 8 lug nuts while 1/2 ton has 6.
But to answer your question, the 205 is the strongest of the three.If you can find one of these it would be your best choice but you might have to change the output on your trans.
The 203 has a chain that can stretch and cause problems, but they are good transfer cases that can be converted to part time. I am not sure how hard it is to rebuild a 203, but if you do a search you will probably find something about it.
The 208 was not offered until 81 and is chain driven like the 203. They are lightweight and have the lowest geared low range but some people don't think they hold up well.
All three transfercases were offered all GVW trucks.

I am not an expert, this is just what I know about these transfer cases. Hope I was of some help.

[speedd67]

yes the axles have to be taking out to do the brakes. I have the book on the truck and that is what it said about the axle same as you said. The not so smart people around here didn't know so said it was a one ton. I have looked all over and I can not find the tags to tell what they are. oh well. So the 203 and the 205 bolt up different? I can get a new one of each for around 800-900 dollars what do you think. Thanks for your info

[Blazer1970]

3/4 ton 14 bolt axles came with 11 inch brakes, and 1 tons came with 13 inch brakes. I would just pull apart your 203 and see what is wrong with it. It has probably been converted to part time operation with one of the aftermarket kits, since lockout hubs were added to the truck. Otherwise, 203s are a dime a dozen in the junkyards if you just want to take a chance on another one. Conversion to a 205 would require driveshaft changes, and you would need the adapter to adapt the 205 to your transmission. I would not recommend a 208.

[mkmiller1]

I'd have to agree with blazer 70. Since you're kinda new to 4wd I would just fix the 203 or buy another(dime a dozen & cheap). My guess on the 203 is this: With a part-time kit in it you have to engage the 4wd every 200-250 miles(for a couple of miles)to get oil to the pump in the rear part of the case. I'm guessing this was not done and the pump ran dry, in turn leading to bearings not getting oil. This is only my guess about the grinding noise.
I've had a 203 with the part-time kit and just got used to putting it in 4wd everytime I filled up with gas. If you have any other questions just email me and I'll try to help as much as I can.

Matthew
mkmiller@magnolia-net.com

[red450ih]

I have 76, 79, and 83 K20 trucks that all have the 13 inch brakes in the rear and the 83 has a semi floater. I have a 73 GMC C2500 and a 74 C20 (2WD) and they have the 11 inch brakes. None of these axles have been changed, all of them are farm trucks bone stock. Just thought I would trow that out there.

Keith

[speedd67]

Thanks for all the info guys. I am going to see what i can get done around here and if anyone has anything. Thanks again.