79 1/2 ton 4X4, full time four wheel drive?

[57NAPCO]

I have a long trip question,
This is a bone stock 4X4 1/2 ton, 400/350, 1979 shortbed truck, it has no lockout hubs....are the front axels, drive shaft spinning whilst driving down the road even if it is in two wheel drive?
Thanks

[BigRed76]

Yes, If it does not have lockout hubs then the front drivetrain spins anytime the truck is moving.
I don't know a lot about the full time 4wd trucks but do they even have a 2wd range?

[57NAPCO]

Thanks.
I'm traveling and finally had time to sit at a computer and research it. It looks like a #502 conversion kit from mile marker is the way to go. This will convert from full time 4X4 to conventional part time 4X4 with the installation of the kit and lock out hubs.
The question is, has anyone done it and how tough of a job was it?

[bilfman]

The conversion kit just let's you unlock the diff from the t case. A 203 case which you have is designed with an oil pump which needs to be spun in order to lube the rear of the case. So a common problem with these conversions is peeps burning up the t case because it is not being spun and getting oil. An easy fix to this is about five bucks, on the oil fill 1/2 inch bung on the np203 take a short nipple, a 90 degree elbow, a 2 inch long 1/2 inch nipple and 1/2 inch cap. With these items you make you oil fill 2 inches higher then the case fill hole. You then can fill the entire case with 2 inches more of oil and this will then keep the rear case lubed when not being spun because of the part time kit. Remember a 203 Does not use gear oil!!! It uses a light weight oil, I recommend 10-40 .

[franken]

Might want to troll for an NP205.
Ok, or a 241
Save the 203 for a doubler, but that's going away.

[57NAPCO]

Originally Posted by bilfman

The conversion kit just let's you unlock the diff from the t case. A 203 case which you have is designed with an oil pump which needs to be spun in order to lube the rear of the case. So a common problem with these conversions is peeps burning up the t case because it is not being spun and getting oil. An easy fix to this is about five bucks, on the oil fill 1/2 inch bung on the np203 take a short nipple, a 90 degree elbow, a 2 inch long 1/2 inch nipple and 1/2 inch cap. With these items you make you oil fill 2 inches higher then the case fill hole. You then can fill the entire case with 2 inches more of oil and this will then keep the rear case lubed when not being spun because of the part time kit. Remember a 203 Does not use gear oil!!! It uses a light weight oil, I recommend 10-40 .

Great info, thank you!

I'm out here in Gold Beach,Oregon getting ready for the long drive home. I flew out to Sacramento on the 11th of July and bought this truck in Clearlake, CA. I drove it 550 miles up to Oregon to visit a buddy and now I'm getting ready to head out....problem is, I can't help but think about that front end spinning for the 2300 mile drive home, so yesterday I went over to Medford and bought a 1991 ford f600 diesel flatbed truck....yep, gonna drive the 79 on the back of it and make my way home, what a life

[57NAPCO]

Originally Posted by franken

Might want to troll for an NP205.
Ok, or a 241
Save the 203 for a doubler, but that's going away.

Getting home is first

[1tuff71]

I put one of those Mile Marker kits on my 78 Blazer years ago and it was fairly simple. Can't remember the details but if I recall it took about 2 hrs with simple tools. Well worth the trouble cause my mpg went up and saves a bit of wear on the drivetrain. Goodluck

[57NAPCO]

Originally Posted by 1tuff71

I put one of those Mile Marker kits on my 78 Blazer years ago and it was fairly simple. Can't remember the details but if I recall it took about 2 hrs with simple tools. Well worth the trouble cause my mpg went up and saves a bit of wear on the drivetrain. Goodluck

I was thinking about ordering the parts and doing it on my buddy's garage floor until the truck idea came up. I'll sell the F600 as soon as I get back.
I have a lift at home so I'll wait and do the conversion when I return.
Thanks

[special-K]

The conversions were a great upgrade back when these trucks were fairly new. Now,30+ years later,I'd try to find a good 208 or 205 transfer case and swap. I understand you were looking at the 2,300 miles ahead,but once you're home it's a different story. It's my personal opinion that 203s were a big mistake GM got away from. But,there's no need for concern driving that far with the factory full-time,that's what it was designed to do. The axle isn't locked,it just spins,and the biggest concern is fuel economy.

Sounds like a great adventure. I'm jealois

[Redcap]

The 203 is a garbage case. Pull the reduction section and scrap the rest once you get it home.

[burnin oil]

My dads blazer had the conversion done and it picked up maybe one tenth of a MPG. It was a 305/th350/203 with 3.07 gears. When I got my 76 blazer it had a 400/th350/203 with 3.07 gears. She got 6 MPG on the interstate and 8 in town. I averaged 14 MPG after swapping in a 465 4spd manual. I ran it with both the 203 and 205 transfer cases without a big difference in milage. I actually would swap the 203 case in for the winter. It was nice having full time 4wd running country ridge roads with black ice. Then in summer the 205 went back in as it will take alot more abuse. I wore out several 203 drive chains. Thats just my experience.

[Redcap]

Originally Posted by burnin oil

My dads blazer had the conversion done and it picked up maybe one tenth of a MPG. It was a 305/th350/203 with 3.07 gears. When I got my 76 blazer it had a 400/th350/203 with 3.07 gears. She got 6 MPG on the interstate and 8 in town. I averaged 14 MPG after swapping in a 465 4spd manual. I ran it with both the 203 and 205 transfer cases without a big difference in milage. I actually would swap the 203 case in for the winter. It was nice having full time 4wd running country ridge roads with black ice. Then in summer the 205 went back in as it will take alot more abuse. I wore out several 203 drive chains. Thats just my experience.

Makes no sense. Just run the hubs locked with the 205 during winter. Same thing, tougher setup.

[special-K]

When GM came out with full-time the guys up home didn't take long to hate it. They claim they'd be driving along,hit some slick on a curve,front wheels engaged,and steered them straight off the curve. They either traded them in or did the conversion.It's best for the driver to be in full control and not let the truck decide what you need.

I could never understand how trucks got such bad mileage back then. I figured they were choking. My '72 K2500 with 4.10s was getting 12.5 mpg consistently till the carb started acting up. I have a vacuum gauge on the dash and the way the carb is now it idles in the "power" range and when you rev it it goes to "idle" range. It's way rich,you can smell it. I'm sure the mileage sucks,so I checked it the other day. Yep! it sure is worse. I'm only getting 11.3 mpg now. How the heck did new trucks get that much worse mileage than a 42 year old truck with a crapped out carb?

[RPBurris]

Originally Posted by bilfman

The conversion kit just let's you unlock the diff from the t case. A 203 case which you have is designed with an oil pump which needs to be spun in order to lube the rear of the case. So a common problem with these conversions is peeps burning up the t case because it is not being spun and getting oil. An easy fix to this is about five bucks, on the oil fill 1/2 inch bung on the np203 take a short nipple, a 90 degree elbow, a 2 inch long 1/2 inch nipple and 1/2 inch cap. With these items you make you oil fill 2 inches higher then the case fill hole. You then can fill the entire case with 2 inches more of oil and this will then keep the rear case lubed when not being spun because of the part time kit. Remember a 203 Does not use gear oil!!! It uses a light weight oil, I recommend 10-40 .

Always proving that you can learn something everyday on this site! I am only a few days away from filling my np203 tcase and already bought gear oil! Looks like 10-40 will be the way to go. Thanks!

[57NAPCO]

Just pulled into Kingman AZ. Drove about 55 hours straight, no food (3 red bulls and a 5 hour energy) just gas and rest stops. It was 110 damn degrees going across Mohave desert today and no A/C.

[57NAPCO]

Excuse me, 27 hours ....I was rather tired when I posted from the hotel.

[special-K]

Better check. Maybe it was 55 I hope you at. I bet you slept good and that shower never felt so good. I guess your OTR right now,or did you make it home yet?

[57NAPCO]

Just pulled into the 66 casino hotel outside Albuquerque, gonna throw some dice

[BigRed76]

How's the '91 F600 holding up?

[57NAPCO]

Doing great, has the 6 cylinder Brazilian ford diesel in it, getting between 9-10 mpg. It got a bit hot pulling the hills but I had my foot in it so I backed off and all has been well.

[special-K]

Sounds like a great time

[57NAPCO]

Originally Posted by special-K

Sounds like a great time

I'll be out your way on another adventure august 6th. I bought a 2001 blue bird flat nose short bus. One owner, 56,000 miles, cummins 24 valve handicap bus. The bus is in Joppa MD. Not sure what I'm gonna do with it yet, it has a great handicap lift for loading motorcycles

Gave em 9400 bucks for it.
http://cgi.ebay.ca/ebaymotors/2001-B...e#ht_500wt_922

[special-K]

What a great deal! No miles on that motor at all. Bus is clean and a great size for a conversion. I think you'll be rolling right past Mt. Airy on I-70,just before Baltimore. I know you have a lot of road to put under your butt,but if you can't stop by,let me at least buy you a coffee in town for a short break

[burnin oil]

Originally Posted by Redcap

Makes no sense. Just run the hubs locked with the 205 during winter. Same thing, tougher setup.

Did that also. Running in 4wd on a 205 would bind when you hit dry pavement and do not have slip. Snow covered roads are no problem. Plowed with black ice is when I really liked the 203 case. It all depends on apllication. I run around for days at a time with the 205 case and the hubs locked just to kick oil around.