Driving full time 4wd with front drive shaft removed

[Ricko1966]

It is a 203.

I was asking/quoting 77dmax because I think his Dad's 77 would have been av205 not a 203. I keep seeing a lot of my friend did etc. But not knowing which transfer case.

 

[77Dmax]

Was that a 203? Or a 205?

It was the full time 4wd case, i have no idea what the model was. It all started when the front shaft needed a u-joint badly. The old man is cheap and slow to finish any project. He pulled it out and took forever to repair and replace. My mother was the primary driver of it. They sold it in 99 or so for 500 bucks with a bad trans.

 

[Fat 454]

NP203 Transfer Case

The full-time four-wheel-drive NP203 transfer case is one of the most standard items found in 70s fullsize 4x4s. Big, heavy, and relatively strong despite its chaindrive, this box can be converted

www.motortrend.com

My understanding is that you should NOT run an NP203 ( or other "continuous transfer case ) in LOC, as it will eventually grenade the case. I'm not sure on the NP205 gear type cases.
I have been looking for the conversion kit to make the 203 a part time, however the Mile Marker kit ( which was a re-issue of the older Doug Nash kit ) is no longer available. Re-build / conversion article on the Mile Marker / Nash kits are available on line, and the conversion looks good.
Does anyone know of an alternative ?

 

[chevdude]

If you really want good results, put some lockouts on your front axle and remove the front drive shaft.
Unlock the hubs and put the tcase in 4hi.
This will totally disconnect the front axles and gearset from turning.
Your steering will feel better on slow, tight turns.
They make conversion kits to disable the full time 4wd function of the np203.
I've never used one but I'd like to hear from someone that has.

 

[telecat89]

My understanding is that you should NOT run an NP203 ( or other "continuous transfer case ) in LOC, as it will eventually grenade the case. I'm not sure on the NP205 gear type cases.
I have been looking for the conversion kit to make the 203 a part time, however the Mile Marker kit ( which was a re-issue of the older Doug Nash kit ) is no longer available. Re-build / conversion article on the Mile Marker / Nash kits are available on line, and the conversion looks good.
Does anyone know of an alternative ?

I saw a conversation kit in my LMC catalog

 

[chevdude]

Never really heard of bad things happening by doing this.
I have a conversion kit. Never got around to installing it.
The kit instructions say that, after installing the kit you should run the case in 4 hi occasionally to lubricate something inside there.

 

[Old Guy Bill]

I didn't even consider keeping the original 203 my truck came with.
They're not worth anything in my area.
I put in a 208 and adapter plate. Required driveshaft changes but the truck badly needed them anyway.

 

[Fat 454]

@telecat89 that set up is just the clutches, and is not the full conversion. If you look up the Mile Marker or Doug Nash conversion, it was a full shaft and bearing replacement. Apart from finding a used case that someone has converted in the past I have not found anyone selling the "full" conversion.

@chevdude - Running the transfer case constant 2wd means the chain and 4wd mechanism never sees any splash oil lubrication. This can lead to bearing failure over time, which is why there is a recommendation to engage and run the 4 lo from time to time - like many things I guess - use it or lose it !!..

 

[Robert Davis]

Does anyone know if I should or should not drive my 79 K20 with NP 203 transfer case with the front drive shaft removed? I was thinking I could remove it in the spring then drive the truck daily then when the snow started to fall I would put it back on then put my plow on it? What do yall think?

I have a service manual for a 1975 Chevrolet K5 Cheyenne model. There is a warning against driving the NP-203 withtout the front drive shaft. The warning alleges that the 203 will wear out due to "Stress", but it does not explain how or where this "stress" occurs. You will have to drive it in HI Lock or Low Lock to move as the NP-203 has a "Differential" action and if it is not in Lock, the front output shaft stub will just spin (Like all unlocked differentials). You can modify the NP-203 with a "Part Time" kit that has been around for many years. This would probably be a better modification (Of course you will also have to install locking hubs on the front). Many others have done this as a more preferred solution.

 

[telecat89]

@telecat89 that set up is just the clutches, and is not the full conversion. If you look up the Mile Marker or Doug Nash conversion, it was a full shaft and bearing replacement. Apart from finding a used case that someone has converted in the past I have not found anyone selling the "full" conversion.

@chevdude - Running the transfer case constant 2wd means the chain and 4wd mechanism never sees any splash oil lubrication. This can lead to bearing failure over time, which is why there is a recommendation to engage and run the 4 lo from time to time - like many things I guess - use it or lose it !!..

Good to know thanks

 

[telecat89]

I have a service manual for a 1975 Chevrolet K5 Cheyenne model. There is a warning against driving the NP-203 withtout the front drive shaft. The warning alleges that the 203 will wear out due to "Stress", but it does not explain how or where this "stress" occurs. You will have to drive it in HI Lock or Low Lock to move as the NP-203 has a "Differential" action and if it is not in Lock, the front output shaft stub will just spin (Like all unlocked differentials). You can modify the NP-203 with a "Part Time" kit that has been around for many years. This would probably be a better modification (Of course you will also have to install locking hubs on the front). Many others have done this as a more preferred solution.

Thank you . I believe I will just leave it be for now and maybe look for a conversion kit.

 

[xm20k]

Had to limp my Scout home once on the front driveshaft but it wasn't on purpose. Never had to or tried to run a 4x with the front shaft removed maybe in and out the garage while working on one of them but don't recall. Haven't owned a 4x in over 20 years.

 

[Fat 454]

OK - here is me nerding out on this ( as I have been looking to convert my 203 for some time ). There is an excellent ( old ) article by @Grim reaper on the .ck5 board, that describes the transfer case mechanism, conversion parts and real world driveability that you should read. A google search will bring it up.
Basically the "full time" 4x4 worked using a chain driving a differential. The pic below shows the OEM differential at the bottom.
The doug Nash / mile marker ( MM ) conversions either replaced the spider gears in the diff ( the #501 kit ) or replaced the entire diff altogether with a shaft ( #503 kit - shown at the top of the pic ). By replacing the diff meant that drive can now be positively engaged / disengaged to the front axle assembly, which in the full time ( factory / oem ) setup it cannot.
Np203 cases are extremely durable, despite having a chain, rather than gears. The issue is that they are often not cycled through 4wd Loc enough, and therefore dry out causing chain and bearing wear. Disconnecting the front shaft therefore will also promote wear and eventual failure.

You must be registered for see images attach

The MM #503 ( shaft ) kit is much stronger than the #501, and therfore better for hard core off road / bigger tyres etc. because it eliminates more parts. The #501 kit ( below ) is still available however. There is one advertised on Ebay right now, - again if you google search they can be found much cheaper.
If you want part time, read the CK5 post, and install at least the #501 kit. Ensure seals are replaced and fluid is clean and topped up, then regularly cycle the transfer case through all 4wd options ( high / low etc. ) eg. weekly for a minute or so, and the case will last forever and 2 wheel driving will be possible for the bulk of the time if that is what you are looking for - without dropping the front shaft. The #501 kit is shown below. Post pics when you install, as that will be helpful to others.

You must be registered for see images attach

 

[Fat 454]

A part time transfer case ( NP205 etc. ) operates the same way as the converted MM kit, ie the front drive can be positively engaged / disengaged.
The "full time" np203 set up was introduced as a "modern convenience" at the time, claiming to be less "rustic" as your better half did not need to exit the vehicle to lock / unlock hubs in the mud and dirt.....

 

[telecat89]

OK - here is me nerding out on this ( as I have been looking to convert my 203 for some time ). There is an excellent ( old ) article by @Grim reaper on the .ck5 board, that describes the transfer case mechanism, conversion parts and real world driveability that you should read. A google search will bring it up.
Basically the "full time" 4x4 worked using a chain driving a differential. The pic below shows the OEM differential at the bottom.
The doug Nash / mile marker ( MM ) conversions either replaced the spider gears in the diff ( the #501 kit ) or replaced the entire diff altogether with a shaft ( #503 kit - shown at the top of the pic ). By replacing the diff meant that drive can now be positively engaged / disengaged to the front axle assembly, which in the full time ( factory / oem ) setup it cannot.
Np203 cases are extremely durable, despite having a chain, rather than gears. The issue is that they are often not cycled through 4wd Loc enough, and therefore dry out causing chain and bearing wear. Disconnecting the front shaft therefore will also promote wear and eventual failure.

You must be registered for see images attach

The MM #503 ( shaft ) kit is much stronger than the #501, and therfore better for hard core off road / bigger tyres etc. because it eliminates more parts. The #501 kit ( below ) is still available however. There is one advertised on Ebay right now, - again if you google search they can be found much cheaper.
If you want part time, read the CK5 post, and install at least the #501 kit. Ensure seals are replaced and fluid is clean and topped up, then regularly cycle the transfer case through all 4wd options ( high / low etc. ) eg. weekly for a minute or so, and the case will last forever and 2 wheel driving will be possible for the bulk of the time if that is what you are looking for - without dropping the front shaft. The #501 kit is shown below. Post pics when you install, as that will be helpful to others.

You must be registered for see images attach

Wow! That is terrific information! Thanks so much. I bought the truck last week and this is my first full time 4x4 experience. I have only driven it about 40 miles since last week and yesterday discovered that it was in Hi loc which caused the front wheels to hop when turning at low speeds. So i deduced that this was normal for the full time 4x4 and was looking for a solution short of doing the conversion. With the issue resolved I will leave it alone and thanks to all the information from everyone here I will periodically run the t case through all the selections. Thanks again yall!!