NP203 Conversion Kit question

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Hey guys!

So I'm kinda stumped. I've been doing my research and now I'm retiring the search bar and google so that I can pick some of your brains.

I just put in the Mile Marker 502 conversion kit into my NP203. The kit seems to be working correctly (t-case in what WAS 4hi with hubs unlocked, moves truck just fine). However, the front driveline is still turning. The hubs are unlocked and it's in 2wd. What the heck? If the conversion kit maintains power to the front driveline in 2wd what's the point of even having the kit?

Any way, I really would like to know if this is normal or not. I've looked all over and had about a 50/50 split on whether or not the front drive shaft should move. If it shouldn't move, what should I check first to remedy this issue?

Thanks in advance!
 

firebane

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This will be your new shift pattern and make sure your in "Hi" not Hi loc. Also you will always have the front drive shaft spinning as that is how a transfer case works it just depends on the power given to the front hubs of how much of the front axle is used..

Read here:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=27106.10;wap2

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Yeah, it's in 2wd (the old 4hi position). So whats the point in putting the kit in? If it's always spinning the front end just not the hubs unless they're locked...
Couldn't you just buy manual hubs and put them in instead of buying the conversion kit? Because essentially, that's whats happening and I still don't have 2wd (other than leaving the hubs unlocked).

Sorry, it just doesn't make sense to me. It's kinda frustrating that I can't truly have 2wd (no front shaft spinning) even after buying and installing the kit.
 

firebane

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Yeah, it's in 2wd (the old 4hi position). So whats the point in putting the kit in? If it's always spinning the front end just not the hubs unless they're locked...
Couldn't you just buy manual hubs and put them in instead of buying the conversion kit? Because essentially, that's whats happening and I still don't have 2wd (other than leaving the hubs unlocked).

Sorry, it just doesn't make sense to me. It's kinda frustrating that I can't truly have 2wd (no front shaft spinning) even after buying and installing the kit.

You own a 4wd. All 4wds have the front end doing exactly as you say. Its the amount of power than changes due to the gears in the transfer case that makes 4wd better.

Gear ratios change according to the lo/high mode you choose for 4wd. What you are experiencing is exactly what has happened with 4wd vehicles for ages.
 
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Not all 4x4's do though. If I'm not mistaken there's several transfer cases which DO NOT turn the front drive shaft.

So I guess the "part time" kit is a sham if it doesn't really do anything? Because even afterward the transfer case is doing the same as if it weren't converted. Basically all I did was put hubs in.

Thanks for your help firebane, I'm just frustrated that I apparently spent money on something that doesn't change anything.

If anyone has some light to shed on this I'd be more than happy to hear it!

Edit: all the websites that sell these kits say they should be used to "reduce wear and tear on your front drivetrain". That would indicate that it does not move post install of the kit. Hmmm... I'll figure this out eventually.
 
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Alright, I contacted Mile Marker and was able to get some clear answers. I'll clear this up for anyone in the future who may be searching for this.

Mile Marker no longer makes the kit to disengage the front end because of the availability of the transfer case chains. I believe they make chains for the 203 but apparently the previous model kit is no longer in production. This kit is the one piece shaft conversion kit which gives you TRUE 2wd. The 502 kit with the wedges does not.

The use of the 502 kit, is to allow you to be in 2wd (the old 4high position) with unlocked hubs. Previously the front end would just spin and you wouldn't go anywhere if you had manual hubs unlocked and no conversion kit in 4high. This allows you to leave the front driveshaft in and not have to put it in 4high lock to move.

Effectively, you now have 4low, "2"low, Neutral, "2"high, and 4high. While it will still turn the front end, you will be able to drive the truck without locking the front and rear ends together with your hubs unlocked.

Thanks again, firebane, for the help. You sparked some thinking that I needed to be able figure out what was going on.

I hope this helps someone in the future!
 

firebane

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Well I've owned 3 chevy 4x4s and all the driveshafts spin when in 2 hi. *shrug*
 

Johhny

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It might still be spinning after the conversion but not with the same force as normal (=less wear).

Up until recently I had hubs with a default np203. When the hubs were unlocked, any speed above 55mph would shake my tcase so badly I could barely drive normal. Now that I'm using the Mile Market kit I can easily speed up to 70mph without shacking.

Shift patterns change from:

low loc 4wd
low 4wd
neutral
hi 4wd
hi loc 4wd

To:

low loc 4wd
low 2wd
neutral
hi 2wd
hi loc 4wd
 

Green79Scottsdale

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edit: If you read my earlier comments, I do believe I was not thinking clearly when I posted. Oops.
 
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highdesertrange

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I worked for the company that invented and patented the 203 part time conversion back in the 70's. I have installed thousands of part time conversions. mile marker was one of the many companies that ripped off the design. the company I worked for eventually won in court but not after these rip offs with their inferior kits flooded the market. I have zero respect for mile marker and the others, they all knew what they were doing and did it anyway. my 2 cents. highdesertranger
 

Smith

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bringing thread back up. Can the conversion be done without removing the tcase from the frame? Looks like I should be able to but am unsure.
Thanks
 

highdesertrange

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smith short answer is yes you can do it without removing the t-case. you must remove the tail housing but not the whole t-case. highdesertranger
 

firebane

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Depending on the year of your NP203 you may need a extra part too. The 73-74 NP203 differ from the 75+ NP203.
 

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Depending on the year of your NP203 you may need a extra part too. The 73-74 NP203 differ from the 75+ NP203.

what extra part is this? Truck is an 84 but unsure on frame/drivetrain. Which year needs the extra parts?
 

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