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73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Topic started by: Payton1979Silverado350 on July 01, 2017, 12:17:42 AM

Title: All time 4 wheel drive transfer case problems?
Post by: Payton1979Silverado350 on July 01, 2017, 12:17:42 AM

I have a 1979 Chevy Silverado 3/4 ton four-wheel-drive 350 with a 400 Turbo transmission and it was built in Michigan with all time four wheel drive. I heard from my fathers Mechanic that having it as an all time four wheel drive will tear up the transfer case. I wanted to ask this community about it and if this true?(https://uploads.tapatalk-cdn.com/20170701/6cb4063060c2c9c934bd6e96d880d2e2.jpg)


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Title: Re: All time 4 wheel drive transfer case problems?
Post by: FlatBlack77 on July 01, 2017, 06:12:08 AM

Welcome to the forum!

If it was built with an np203 transfer case then the transfer case will not get damaged from functioning the way it was built to

Title: Re: All time 4 wheel drive transfer case problems?
Post by: Irish_Alley on July 01, 2017, 09:09:23 AM

it wont damage it but will cause front end parts to wear and hurt mgps a little. essentially youre turning the front end parts when they dont have to. the 203 is also like an open differential. if you have it in "open" and your front tires are in mud they will have less resistance and will receive all the power.
shift patter
4 lo loc
4 lo
n
4 hi
4 hi loc

there is a part time kit you can install that will change the shift pattern
will be
4 lo loc
4 lo
N
2 hi
4 hi loc

in the loc position it will lock the differential and split the power 50/50.

without the part time kit
you cant run manual hubs in the unlock position unless youre in a loc position

so will just install manual hubs and run the truck in 4 hi loc. but this really doesnt save MPGs and is kind of a waist of money IMO

Title: Re: All time 4 wheel drive transfer case problems?
Post by: 75gmck25 on July 01, 2017, 06:17:33 PM

Its interesting that your "mechanic" thinks full time 4WD will destroy the transfer case on a  truck that is already 38 years old.  Somehow I think it would have already happened by now if it was a real problem.

I have a '75 K25 with 350/TH350/NP203, and it was one of the most common transfer cases for GM, Ford and Dodge during the 70's.  Many were converted to part-time 4WD with a milemarker kit, but I would not recommend making that change.  It works fine overall, but you must be very careful to periodically run it in 4WD (about once a week) because in the 2WD position it does not properly circulate oil in the T-case. Very few folks understand that, and many of them have ignore the maintenance and have significant problems after being converted to part time.

An unconverted NP203 may get a little noisy if the chain stretches, and the shifter linkage can get out of adjustment, but there are no major issues with them.

Bruce

Title: Re: All time 4 wheel drive transfer case problems?
Post by: Payton1979Silverado350 on July 16, 2017, 11:28:11 PM

Thank you all so much


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