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1978 w150 318 727
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Discussion Starter · #1 ·
I have a 1978 w150 with full time four wheel drive. We did a complete conversion on the axles to part time. I used a 1985 front axle to get the knuckles, spindles and hubs. That all went well. However now it is time to convert the transfer case. The two choices are keep the 203 and rebuild it and install the mile marker part time conversion kit or buy a new transfer case adapter for an 80's tf727 and install a 208. Keeping the 203 would mean having to put in four wheel every once in a while to lube the rear bearings and would cost about $700 or more all said and done. The 208 would cost about $700 for the transfer case adapter part number 4130675 along with the 208 case and lengthening the rear drive shaft. What would be the best route to go. The 208 is much lighter but weaker. The 208 is geared lower i believe and it wont be four wheeled too hard its more of a daily driver hobby truck. I have seen it done on a 77 and thought that would be nice. What are your thoughts and what would you do, keep the 203 or go to the lighter already part time 208?
 

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There may be some info on my thread you might find useful.

https://ramchargercentral.com/vehicle-help/trailduster-engine-choice/

I was basically in the same boat, but I had also changed the motor and transmission, so the NP203 wouldn't have bolted up. I am also thinking that the 208 might not bolt up to your earlier 727 transmission.

Do you have the stock motor/trans and is it a big block or small block?
 

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1978 w150 318 727
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Discussion Starter · #3 ·
I have the original 1978 318 and tf727. I know it won't bolt up. I would have to change the adapter which I found. The adapter being changed would allow the 208 to be mated to the tf727. Seen it done on another truck at a truck show. Looked easy enough. Found lots on other site also. Main thing is would it be any advantage or not especially since it would be the same cost roughly.
 

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I think I remembered wrong. My last set up was a 203 and adapter for a 440. I must have confused it for a small block adapter.  I don’t think you could really go wrong getting rid of the 203. I also have an adapter from an 85 RC that was bolted to a 208, along with both front and rear driveshafts if you needed.
 

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1978 w150 318 727
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Discussion Starter · #5 ·
I think the part number on the adapter is 4130675. This should be the part number that connects the tf 727 to the 208. I don't know what the drive shaft number would be but all I know is mine will be too short as the 203 is much thicker than the 208. Let me know if that part number matches and we will see what we can do. Thanks
 

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You will also need to change the tailshaft of the 727 in order to bolt up a NP05, NP208 or NP241.  The shaft length is different as well as the adaptor bolt pattern.  To change the tailshaft will require you to completely disassemble the transmission as it's one of the last parts to be removed out the front.

There is nothing wrong with a NP203, it is certainly stronger than a NP208 or NP241.  If you do the part time conversion you will have to shift it into 4WD periodically to lube the rest of the transfer case.  Or you could lock the CAD and just leave it full time 4WD, which is also not a bad thing.  If you do swap to part time, I would look for a NP241 over the NP208, though if you have the 208 on hand it may be worth using.
 

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Keep the 203 range box and bolt it to a 205
 

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1978 w150 318 727
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Discussion Starter · #8 ·
If I have to replace the tail shaft on the tranny than that pretty much answers my question. Not going to that extent for sure. Especially when I was thinking of changing to a518 on the future. Guess I'll wait.
 

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In your shoes, I would be looking for the a518 and NP241.... or any 4-5 speed manual w/part-time case.



 

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I love the NP203 case, but it is my opinion that it shouldn't be swapped into or out of a vehicle unless you are doing the entire drivetrain including axles. The difficulty (or lack) of interchangeability means it's best to just leave it alone.

Bucky
 

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Discussion Starter · #11 ·
Dually noted, I will be sticking with the 203 case and installing the mile Marker part time kit. I would just leave the hubs unlocked but after the lift the driveline angle on the front Driveshaft left us with a pretty good vibration at high speeds. Short of cutting the knuckles and turning them I see no other option to just make the t case part time to eliminate the vibration at high speed.
 

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With the NP203 in stock form, you wouldn't be able to leave the hubs unlocked.  The NP203 needs both axles engaged to work correctly due to the open differential in the transfer case.  You can run it in the Loc mode, but it will eventually wear out the locking pins in the differential.  So the part time kit will probably be the best way to go.
 

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Discussion Starter · #13 ·
Exactly. Also as long as I remember to put it in 4x4 once a week to keep it lubed. I was hoping to kinda avoid that but it is what it is. 203 has to stay till I do the a518.
 

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You would want a A518, also known in later years as a 46RH.  They were used from '90 to '96.  The NP203 will not mount to an overdrive transmission without a custom adaptor so you will most likely be stuck with a NP205, NP208 or NP241.  Note that the overdrive transmissions are longer, so new/modified driveshafts will also be required.
 

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Discussion Starter · #16 ·
So I am going to have to keep the 203 and do the part time kit from mile Marker. We are doing the knuckle out swap to a part time on the axle. Since that will be done to accommodate the larger tires we will need to do the part time on the t case.
I looked back at multiple postings on this subject and have done a ton of research and realize how the t case works and what needs to be done.
However looking at all the past posts I couldn't find anyone or anything on doing this conversion yourself. I have asked wuite a few tranny shops and can't find anyone that wants to do it let alone a rebuild on the case.
Has anyone done the mile Marker kit on their own, how hard was it and do you have pics or advise?
Please let me know if anyone has done this.
 

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daryl78powerwagon said:
So I am going to have to keep the 203 and do the part time kit from mile Marker. We are doing the knuckle out swap to a part time on the axle. Since that will be done to accommodate the larger tires we will need to do the part time on the t case.
Why? a 203 is fine with any size wheels. I agree with the axle conversion, or better yet, get a D60F.

With either axle, stick with the drive gear instead of locking hubs. For the 44, get a CAD axle, and swap all the parts from the ball joints outward, and you will be good.
 

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Discussion Starter · #18 ·
I meant the with the bigger tires I would be doing the knuckle out swap. I did get an 86 axle donor already to use from the ball joints out.
Since I can't afford to do the entire a518 swap and transfer case upgrade to a 241 i will be just keeping the 203 but need to do the part time mile Marker conversion to the transfer case so I can drive the truck with out keeping the front hubs locked. That being will also need to put it in 4 hi weekly to lube the case or even if I just do it every day down my street until I get going.
That's pretty much what I have found people doing. At least until I get the a518 thing, but for right now it's going to have to be the 203.
 

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But, why convert the 203?
 

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Discussion Starter · #20 ·
The truck has a 4 inch lift, leaving me with a bad front driveline angle. Pretty severe front drive shaft vibration. Took it out and it drives fine, put it back in and it's so bad it ruined the yoke on the axle. Tried some 2 degree shims and that helps a alot however left me with really squirly steering. So to get the caster back as well as get the better front bearings we decided to convert the front axle as well as the case. This will keep the front drive shaft from spinning until we are off road. The drive shaft isn't too bad up to 25mph but past that forget it. Can't afford to cut and turn the axles so just doing what every one else is doing for that matter. Before I bought it I was convinced I could convert it pretty easily, had I known all this I would have held out for a later model truck that already had overdrive and a part time system. Since it will be a daily and will only see dirt every other weekend. This seems to be my best option.
 
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