Auto To Locking Hubs Swap?

[77K10Silverado]

Guys I'm considering doing this and wanted to know if this can be done and or what I can expect. Has anyone done this, do I need anything else besides the hub kit, any links out there? Any feedback would be appreciated! Oh yeah it's for a 77 K10 with a 10 bolt up front.

Best,
Mike

[andrewmp6]

Which t case do you have the np203 or np205?

[95 S_Trucker]

Do you have auto locking hubs now? Or do you have a full time front axle in your truck now?

Auto locking hubs weren't popular until the 80s. They get removed and you can install a regular locking hub in its place.

The same is true for the full time front axle. There is a solid "slug" that gets removed, and you can install a regular locking hub in its place.

I installed a np205 and locking hubs on a 78 full time truck. I have also replaced the auto locking hubs on my 85 with regular locking hubs.

[95 S_Trucker]

Also, has somene swapped the front axle in your truck? It should have a Dana 44.

[enaberif]

For a NP203 you'll need a part time kit to make locking hubs useful at all.
For a NP205 would just be a hub kit.

76/77 was when they switched from Dana44 to 10 bolt. So make sure to 100% double check your front diff.

[77K10Silverado]

It's a full time setup with a 10 bolt from the factory. They used 10bolts and 44s in 77. The case is a np203. I'll eventually swap the 203 for a 205 but for now I'll do the manual hubs. I do know the deal with the 203 and having to run it in high lock if you unlock them. Also you have to make sure you run the tcase in other positions every once in a while to oil everything. Do you have any pics or vids of the swap 95_S_Trucker??

[enaberif]

Originally Posted by 77K10Silverado

It's a full time setup with a 10 bolt from the factory. They used 10bolts and 44s in 77. The case is a np203. I'll eventually swap the 203 for a 205 but for now I'll do the manual hubs. I do know the deal with the 203 and having to run it in high lock if you unlock them. Also you have to make sure you run the tcase in other positions every once in a while to oil everything. Do you have any pics or vids of the swap 95_S_Trucker??

NP203 to NP205 isn't a staight swap and will require new axles.

[77K10Silverado]

Axles or driveshaft due to lengths?

[JIMs70GMC]

I would say driveshafts. You should be able to get a kit from Milemarker to make the 203 part time and it comes with manual hubs for up front.

[enaberif]

Originally Posted by JIMs70GMC

I would say driveshafts. You should be able to get a kit from Milemarker to make the 203 part time and it comes with manual hubs for up front.

Driveshaft for sure. If you can find the front NP205 shaft it may work I'm not 100% on this.

Milemarker kit is +$100 for hubs and part time kit. Yes you do need to run in high loc at times but I've heard you can add a pipe nipple and elbow and overfill it and it will be ok as well.

[bmchevy1979]

Also with part-time kit if you don't run it in Loc you fill fry range box making it a pain in the ass to shift into low from high my truck when I got it was so bad that you had to roll and it would grind until it finally caught the gear you could stand on shifter and bump in gear on trans and it wouldn't shift you had to roll and it took a good 50ft to finally go in

[77K10Silverado]

So what the heck is the best route here? I'm golden with doing some swapping.. driveshafts and all. I'm looking for gas mileage not trail strength. I'll start another thread for tcase tranny combo. I just wanted to go ahead with the lockers first because the hubs need rebuilding asap!

[cadillac_al]

Another 203 gets castrated. They don't hurt mileage that bad. I always got 10 mpg with my K20 and usually 11 mpg in my K10. I can smoke Camaros and Mustangs out of a stop light on rainy days lol. That live front axle AWD is actually pretty handy on wet roads and I never have to slow down when I leave the pavement. mileage shmileage.

[77K10Silverado]

Yeah I know Al but smokin Mustangs an Camaros isn't important to me. I want a clean efficient truck that I can get on the hwy from time to time. My tires are starting to get chewed up too... :/

[rich weyand]

My 78 K10 had the part-time kit and cheap manual hubs when I got it. I replaced the cheap manual hubs with Warn hubs.

I do run in HI LOC for the first two miles or so I drive it on any given day to fill the oil reservoir on the rear output shaft bearing. Also, when traveling, every time I leave a gas station or rest area. Then I just pop it out of HI LOC while moving.

I think this setup is good for trucks that are mostly paved road use with just snow and some muddy roads once in a while. We have county roads around here with no bridges -- you just ford the stream.

Some people don't like manual hubs. "You have to get out in the snow and mud to lock hubs." No I don't. That's why the garage has a window in it. So you can look out and see if you want to lock hubs in the nice dry garage before you leave home.

If you have the hubs in without the part-time conversion, you are correct, you will have to be in HI LOC when the hubs are unlocked. That will give you 2WD. With the hubs locked, you will have 4WD with open differential in the transfer case or locked transfer case, just like you have now. With the part-time kit, you will have 2WD and 4WD when locked, and when unlocked will have 2WD only, but the front hardware won't spin.

So, without the part-time kit, you have one extra mode: 4WD with open differentials all around, which gives you a 4WD you can use on dry pavement, which you cannot ever do with the part-time kit installed.

With the part-time kit, you have one extra mode: 2WD without the front hardware spinning. Which should give better gas mileage. And which gives you a tighter turning radius because the U-joints on the front will rotate to where the front wheels will go over harder. At least that's my experience.

[cadillac_al]

Are you getting any better mileage Rich?

[hatzie]

The difference on my Dodge Power Wagon when I went back to full time 4WD after smoking the kitted NP203 was .5mpg
Not remotely worth it.

[77K10Silverado]

Rich, thanks for all that info in your post. Key info right there.

[enaberif]

Originally Posted by rich weyand

And which gives you a tighter turning radius because the U-joints on the front will rotate to where the front wheels will go over harder. At least that's my experience.

This here is alone one of the biggest reasons why the NP203 is best as a part time unit. Swapping ujoints sucks and the turning radius of these trucks is horrid at best lol.

[motornut]

My 78K5 came with some kind of kit for 2wd with the 203.
I also have manual hubs.
I run hubs loose and 4X locked in for lube
I'm was thinking the 205 swap and bigger axles would be the way to go.
cause with this 203 jimmy setup in the snow,It gets loose fast.
I'd bet a real 203 would help with it fish tailing.


I was told a set of "auto hubs" i had "unlocked" when I reversed,So i bought manuals,not sure if they all do.

[rich weyand]

Originally Posted by cadillac_al

Are you getting any better mileage Rich?

It had manual hubs when I got it, they were just cheap POSs, and I threw a hub at one point. So I put Warn hubs on it. But it already had manual hubs, so it didn't change anything.

Hard to compare gas mileage, these trucks are all so different and there are so many factors. I have a newish 350 base crate engine with a marine cam, carbed with an Edelbrock 1406 that has been tuned with an A/FR meter, TH350, NP203 with part-time kit, 3.73:1 ratio, and BFG All Terrain TAs in 31x10.5R15 on 15x8 rims that I run 32 psi front and 28 psi rear. The different inflations are to get the same rolling radius, given the weight distribution. That's a little soft for those tires in order to get a better ride, and those tires aren't good for gas mileage in the first place.

With hubs FREE and xfer case in HI, around town and on the interstate at 75mph, I get 10 mpg, and on the state roads at 55 I get 12. Because I have both cold- and warm-air induction, that mileage is pretty much the same all year round.

In the winter with snow on the side roads, I often run around town with hubs in LOCK, and I lose somewhere between a half-mile and one mile per gallon.

[cadillac_al]

I don't get the turning radius myth. Of course if it's locked in 4loc it not going to turn just like any 4x4, but when it's unlocked it turns like any other truck and seems to park at Walmart easy enough. Just sayin' it's a lot of money and time spent for no savings in fuel. It was just good ol' American marketing to sell a product

[rich weyand]

My truck turns much tighter with the hubs FREE and the xfer case unlocked -- that is, with the front axles and u-joints not spinning -- than it does if either end of the front drivetrain is locked.

[enaberif]

Originally Posted by cadillac_al

I don't get the turning radius myth. Of course if it's locked in 4loc it not going to turn just like any 4x4, but when it's unlocked it turns like any other truck and seems to park at Walmart easy enough. Just sayin' it's a lot of money and time spent for no savings in fuel. It was just good ol' American marketing to sell a product

ANY modern 4x4 has a reduced turning radius when 4x4 is engaged compared to 2wd.

[rich weyand]

Originally Posted by enaberif

ANY modern 4x4 has a reduced turning radius when 4x4 is engaged compared to 2wd.

But it has a reduced turning radius whenever the front half axles are turning, whether they are being driven by the xfer case being in 4WD or by the hubs being locked or solid, even if the transfer case is not engaged.