Procedure for engaging and disengaging 4WD?
 

I feel stupid for even having to ask but this is my first vehicle with 4WD and I wanted to make sure that I'm not gonna screw it up. I have a 1977 Blazer and just wondered what the proper procedure for putting the truck in 4WD......and taking it back out. I can't see the indications on the transfer case's shifter boot as they've warn off.If it matters, I have the 350 with a 3 speed auto on the columnand warn locking hubs. Anyway - I don't wanna thrash my truck 3 months in so any instruction would be appreciated.

Thanks in advance,
Wooten

RE: Procedure for engaging and disengaging 4WD?
 

If the transfer case is the same as what came standard, you have the NP203 which is a fulltime 4wd transfer case. Since you have locking hubs up front, then your transfer case has most likely been converted to part time operation (by swapping out the tail shaft, replacing the center differential in the transfer case).

The lever on the floor will have the following detents:
LO-lock
LO
Neutral
HI
HI-lock

With the part time conversion, you should put the transfer case into HI-lock at least once every week if you are driving it regularly. This is because the chain is what picks up the oil to lubricate the rear output bearings. Without the chain moving (which it does not do unless it is in one of the lock positions), the rear bearings will loose lubrication and prematurely fail.

With these transfer cases, you want to be going relatively slow to shift between modes (HI to HI-lock or LO to LO-lock and HI-lock to HI or LO-lock to LO). For any range shift, going through Neutral, you want to be stopped with the transmission either in park or neutral. I have done a range shift while slightly moving, but the transmission must be in neutral to do this. If it is not, you will grind like crazy trying to get back into gear.

RE: Procedure for engaging and disengaging 4WD?
 

I knew that boththe NP-205 and NP-203 came in the '73 - '79/'80's but other than Part-time/Gear Driven vs. Full-time/Chain Driven (respectively)what are the differences? Did the NP-205 not have locking hubs? Is there anyway to tell for sure (markings and such)? I was hoping for the NP-205 asa gear driven system seems like it would be much tougher than a chain driven one....but hey, at least they're both cast iron instead of aluminum.

As for the steps to lock in 4WD would this be correct:

1)Put transmission in park
2)Get out and lock the hubs
3)Put Transfer case in desired mode
4)Put Truck back into gear

Also, a few more questions - when I take it back out of 4WD do I need to reverse and, if so, how far? And, finally, what's the difference between LO and LO-Lock or HI and HI-Lock? I hate to sound so completely clueless....but I guess you gotta learn somewhere.

RE: Procedure for engaging and disengaging 4WD?
 

The NP203 transfer case is a strong case for sure. The chain that is used is a beast. Both cases are cast iron. The NP203 will have a round access plate off the back side of where the front output shaft is. The NP203 has a lower LO ratio at 2.01:1 than the NP205 at 1.96:1. CLICK HERE for a good writeup on making a doubler using the NP203 front section and the NP205 back section. I intend to do this with my truck once I track down a good NP205 transfer case. HERE is a better explanation of the differences between the NP203 and NP205.

This is what the back of the NP203 in my 74 looks like:
http://i11.photobucket.com/albums/a1...3_Speedo05.jpg

As far as the procedure goes, yeah, that works. You definitely want to lock in your hubs before you try crossing something you think you may not be able to get through. No one likes getting muddy because they forgot the front hubs!

*EDIT* - links did not come through properly.

RE: Procedure for engaging and disengaging 4WD?
 

I didn't know the NP203 had a lower ratio, so that's good.And not to harp onit butI still don't get thedifference between LO and LO-Lock (or HI and HI-Lock for that matter). Before this truck my only experience with 4WD was my Dad's 1998 1500 Cheyenne pickup.

The seletor read (from front to back):
2WD
Neutral
4WD Hi
4WD Lo

It was relatively easy to figure out as there was only one 2WD setting and the 2 different 4WD setting.What's throwing me ishaving4 to choose fromwith none clearly labeled as 2 or4WD. I meanIkeep the selector pushed all the way forward for day to day driving andif I'm reading you're chart correctly, all the way to the front would be Lo-Lock....is that 2WD Lo? I guess what I'm asking is whether 4 detents= aLO 2WD and LO 4WD and HI 2WD and HI 4WD....and which is which. I think it's clear at this point that I'm retarded so you don't know how much your help is appreciated...

RE: Procedure for engaging and disengaging 4WD?
 

That is because the NP203 transfer case is a full time 4wd transfer case as I stated in the first sentence of my initial reply. There is no true 2wd mode. With the part time conversion, it now does have a suedo 2wd mode. Whenever the front hubs are disconnected, it technically is in 2wd mode and it really does not matter what mode you are in when you drive. You will want to drive in HI range at all times though. LO really is not necessary on the road.

As your dads truck is a completely different transfer case and front axle engagement, nothing really transfers over to your truck.

I think you understand that LO range is LO range and HI range is HI range.

In the original full time configuration, the LO-Lock and HI-Lock positions (all the way forward or all the way back respectively) would lock the center differential in the transfer case which would push equal power to both axles. When in regular HI or LO, the differential would send power to the axle with the least amount of resistance.

Also, in the original configuration, there were only caps over the ends of the front axle. Locking hubs were added when the part time conversion was done in the transfer case. The addition of the locking hubs now gave a disconnect feature to the axles right at the front hubs. This increased fuel mileage by reducing rotational mass in the drivetrain. Now the front axle was stationary until you locked in the hubs.

I hope I have answered all of your questions. Your post bounces all over the place so I do not know if I have or not.

RE: Procedure for engaging and disengaging 4WD?
 

hi i am reading your reply to eggaging transfre case im a little confused i think i have a 203 case it is full time with a cap on the axels can i put locking hubs with out changing the transfer case to part time the truck is at this time my daily driver

RE: Procedure for engaging and disengaging 4WD?
 

I replied to the original thread you created. Please try to limit your questions to one thread. No need to PM anyone either (see sig for an explanation as to why).

RE: Procedure for engaging and disengaging 4WD?
 

Ah...I see where I was confused.I understood that the NP-203 was a full-time configuration but when you said it was converted I thought that what you meant was that it was converted to havededicated 2WD and 4WD....not that it simply worked by giving me the ability to unlock the front hubs. Totally my fault and, yes, it does clear everything up. Also sorry the post was so confusing; I tried to explain myself best I could but as I didn't understand the nature of the conversion I guess it made the questions I was asking the wrong ones. Bang up job explaining it though is there anything you don't know about Blazers?

RE: Procedure for engaging and disengaging 4WD?
 

If there is, just ask the question and I will try to find an answer! LOL Most of the time I succeed. It is not about knowing everything, just where to find it.

I just picked up the illustration manual and complete part # break down manual for 73-78 GM Trucks up to, but not including the commercial chassis vehicles. Man those diagrams are great!! Best part is that GM used a lot of the parts that my truck is lacking all the way up into the 80s so many of the parts are still available from GM!!