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73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Transfer Cases and Front Drivelines => Topic started by: JohnnyPopper on January 14, 2019, 03:18:19 PM

Title: Part Time Kit for NP203
Post by: JohnnyPopper on January 14, 2019, 03:18:19 PM
I bought a used Mile Marker 501 kit from a Truck recycling here in town, good guys, finally had them install it.

Started making loud racking noise in the transfer case, back into it.

Seems the kit came with the lockers for the differential but also has a radial roller thrust bearing spacer  that keeps the front axle from engaging while in 2x4.

The tech had never seen anything like that, so didn't think to install them, thus the racking noise under load.

 'CK5.COM has a write up where they illustrate the install and sure enough, they are needed.

Found some that fit, and she is running really good, It feels like I shed 500 pounds of steel!

Also found a former mechanic who had MM Supreme Locking hubs online, so she's styling.

He advised running it in 4x4 at periodic times to circulate oil into the rear tail stock. I'll do that by shifting into 4x, but not locking the hubs.

Only wish I had don't this sooner...  ;)



Title: Re: Part Time Kit for NP203
Post by: ehjorten on January 06, 2023, 09:11:47 AM
Anybody know if the Mile Marker Shaft Conversion is still available for these NP203s? My 203 in my '77 is making a lot of harsh vibration noises. I don't believe it is the chain, but it could be. I had my transmission rebuilt a while back and when they were doing that, they rebuilt the transfer case as well. It was already converted to part time, but I worry that they did something wrong. It is still under warranty, so I need to get it back to their shop. I just know that the crown gears in the 501 kit wear down and cause a lot of slop in the system. Mile Marker had a shaft kit that totally got rid of the differential in the back of the transfer case and it really tightens things up.
Title: Re: Part Time Kit for NP203
Post by: VileZambonie on January 07, 2023, 04:42:35 PM
I don't think so. Have you tried shifting it to see if it only does it in a particular range?
Title: Re: Part Time Kit for NP203
Post by: ehjorten on January 09, 2023, 09:07:36 AM
It is all the time Vile. Being in 4wd (AKA Chain Spinning) doesn't make a difference. There is a certain RPM band where it is most harsh and you can hear it pinging from the rotational slop when you load and unload the drivetrain. The rear gears are in great shape and it is not coming from there. U-joint appear in good working order.
Title: Re: Part Time Kit for NP203
Post by: VileZambonie on January 09, 2023, 03:17:07 PM
I actually picked up another unit and was going to rebuild it, then take mine out and rebuild that one as well. It's such an unpopular unit, there isn't a lot of aftermarket support left.
Title: Re: Part Time Kit for NP203
Post by: ehjorten on January 09, 2023, 03:43:04 PM
Vile...I have been eyeing a NP205 and a 4L80e as a replacement option. I have that stock in my crew cab and love the overdrive! My '77 could use a little more leg with the 4.10:1 gears.
Title: Re: Part Time Kit for NP203
Post by: VileZambonie on January 09, 2023, 03:50:02 PM
My only reservation on these ones is keeping it original otherwise I'd probably do something more modern as well.