Questions about '74 All Time 4wd, HELP

[Memaloose]

This is awesome information! I guess I haven't looked deeply here, I don't really know how to use stuff yet. Strick, So the K20 pickups and suburban's are the same underneath? is there anything different to lookout for on the 'burbs? This one is a 350 automatic, don't know much else. fairly rust-free.

In looking to purchase something like this, is there anything extra I should watch for or give special attention to? To make sure its decent?

Memaloose, thanks too, this is all stuff I was wondering. Is yours a pickup? so I assume it would get better mileage than a 'burb? Sorry about your learned experience! ha ha

Yes, mine is a 3/4 ton pickup.

 

[dvdswan]

I'm not following some of the technical aspects of what your saying, but I understand the concept, totally new to me.

I have not been on the big blue ball for very long, I only got my drivers' license last year!

There are 2 types of differentials; "open" and "with traction device". An "open" differential will power only one wheel, if that tire looses traction, then you are not going anywhere. i.e. if you lift the tire off the ground offroading then you have no power to any wheels on that axle. A differential "with traction device" would have a LSD, air or electric locker, or spool.

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[Turbo4whl]

Another question, Does the K20 hop and jerk around corners on pavement in 4 HI like a regular 4wd? I would guess not since its safe to drive on pavement?

No, not if the you are in 4wd. If you are in 4wd loc on dry pavement you will have issues. This is true with any engaged 4wd systems with the front hubs locked.

Because the front axle is always engaged, you will notice some power steer. This is the same effect felt in a front drive car. Since today's front drive cars are smaller and lighter with smaller engines, not as noticable. With a well dressed small block in a pickup you can feel this power steer more. You will get used to it right away.

When you make a turn the rear wheels have less distance to travel. Since the Full Time system is always driving all wheels, the rear axle wheels move slower when turing. The differential in the transfer case forces the front axle faster.

What this all means, when you hold the power going into the turn or increase the power into the turn, you will feel the truck pull into the turn.

Like I said, you will get accustomed to this, and I embrace the drive!

 

[DrvnDrvr]

Copy and pasted from snowplowforums.com:

The NP203 is a full time case, which always turns the front driveshaft. Most didn't even have hubs as they were not needed. It does have an internal differential system. It works the same as an open rearend and splits the power between the front and rear. It prevents driveline binding when turning hard by allowing the driveshafts to turn at different speeds. You can lock this out by using the HI or LO LOC positions for better traction.

The shift pattern should be

4 LO-LOC
4 LO
N
4 HI
4 HI-LOC

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The converted NP203 will still have 5 positions, but instead of 4HI it will become 2HI. 4LO becomes 2LO.So it will shift like this even though it won't say that on the knob.

If you put the truck in 4HI (according to the knob),and the hubs unlocked it will move forward if it has been converted as you will now have 2WD.If it's stock it may or may not move depending if the internal differential kicks in or not.

4LO
2LO
N
2HI
4HI
The kit basically eliminates the internal differential and does not allow front to rear speed differences. If it does have the kit either convert it back to stock or make sure it's overfull and use 4 HI or LO every 30-40 miles or you will cook it.

Converted NP203s do not lube the back half of the case properly. If you have a part time kit in the 203 don't forget to overfill it by at least 1 inch and you should use synthetic or it won't last. Running it in 4 HI or 4 LO once a week helps too.

The full time NP203 case is the best for plowing as you can run 4WD all the time but it's easier on the drive train as there is no binding when turning hard. It is so much easier to maneuver in tight spaces without throwing it in 2WD when the ground isn't real slippery. If you do get stuck, just LOC the case and drive out.

Don't forget to drain the fluid first. I'd refill with synthetic afterwards. The NP203 uses 10W30 (Mobil 1 works well) .

It would not make a very good long distance towing vehicle due to the lack of OD and very low gear ratios. I have a friend with a similar setup, and what he does is swap trannies in the summer for towing his mowers. He uses a TH400\NP205 in the winter for plowing and then swaps in a TH700R4 (2WD version) without the transfer case for the summer. The lower 1st gear and the OD are a big plus for towing. You should be able to find a used 700R4 and the correct drive shaft at a wrecker so it is a bolt in affair.

This was cut from several different posts and helped me understand how a np203 conversion works. My problem was it wasn't shifting onto 4LO Common problem with this shifter. Adjusting the shifter is a B to get to short of removing the transfer case. Doing the cheap and easy thing first, I hosed the shifter down with WD40 and PB Blaster and got it to shift into 4LO and quite a bit easier through the whole range.

 

[Turbo4whl]

My problem was it wasn't shifting onto 4LO Common problem with this shifter. Adjusting the shifter is a B to get to short of removing the transfer case. Doing the cheap and easy thing first, I hosed the shifter down with WD40 and PB Blaster and got it to shift into 4LO and quite a bit easier through the whole range.

I believe @Snoots had the fun of servicing a NP203 shifter and had written a "how to."

 

[Snoots]

I believe @Snoots had the fun of servicing a NP203 shifter and had written a "how to."

Did that some time back. It's a LOT easier to remove and disassemble the shifter, clean everything then grease and re-install it. Done and done.

 

[DrvnDrvr]

@ Snoots, Did you remove the transfer case from the truck?

 

[Snoots]

No. Not a need to. The file is too large to post. I'll try to cut it up.

 

[DrvnDrvr]

No. Not a need to. The file is too large to post. I'll try to cut it up.

Did you go through the hump hole or come up from the bottom?

To remove the shifter

 

[Snoots]

I didn't have any trouble coming up from the bottom.
The article I used was from :
http://forum.73-87chevytrucks.com/smforum/index.php?topic=27288.0

No pix there anymore but his instructions were spot on!

 

[DrvnDrvr]

Yup, read that thread when researching my 203. Even copied in my K20 word file. Pretty well done. Good example of why pics are encouraged.

 

[GTX63]

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You mentioned in post #6 that the truck purrs like a kitten. You might have a little closer look and down below.

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[74Blaze]

If you have locking hubs, make sure they're unlocked.
If it still hops you may have a locker in the rear end.

If you have a stock NP203 and you have Locking Hubs and they are Unlocked the truck will not move.

 

[idahovette]

^^^^^^^^this is true. Fulltime 4WD is a misnomer....if it is NOT in lock position power will go to the 1 wheel that does NOT have traction unless one differential has a locker of some type in it.

 

[mcarlo86]

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When you said this suburban is from Minnesota, make sure you go around with a magnet or something and double-check for bondo. It appears to have had some body work done at some point. (the grill looks like a '77, and the hood looks like it has been repainted along with what appears to be '80's body molding and Ford mirrors on the doors) Crawl under it and look at the inner rockers, the body mounts, floor boards, etc. Just want to "double-check" that it is a low rust as it appears from first glance. Most '74 models from MN were rusted out by the mid '80's due to all the road salt they use there. If the body checks out as solid as it looks from the picture, then you definitely have a good foundation. There has been a lot of good info already on this thread about the 203 t-case. My two cents are just rock it as is if it is in good running order. I doubt you would gain much fuel economy by trying to convert it to part-time.