Front Lock Out Question

[72 Cheyenne K20]

I’m looking at a 1976 GMC k25 350 / automatic that he says is all original. So assuming it has the Dana 44 from differential but have never seen this style of cap where a lock out would be. Anybody ever seen these before ?

Thanks Scott

[kwmech]

Yep all the time back in the day. With that is going to be a 203 transfer case which gives you a Full time 4wd truck. Can be converted to standard 4wd with a set of locking hubs and a full time 203 t-case delete kit.


https://www.milemarker.com/collectio...s/products/503

[russgt]

I thought they were usually round, like a cap?

[57taskforce]

Those are called drive flanges or drive slugs. At least in the 67-72 days lock outs were optional. Not sure if this was the case in the square body days but for sure those would have been on a full time 4x4 truck, but maybe could have come on an NP205 equipped truck if the lock outs were still optional in the early square body stuff.

[MJN]

In 1976 the only transfer case you could get with an automatic transmission was the NP203 making it full time four wheel drive, so thats why it has drive flanges instead of locking hubs.

[russgt]

Originally Posted by russgt

I thought they were usually round, like a cap?

Hammer on cap is what the half tons had.

[kennyw]

Originally Posted by russgt

I thought they were usually round, like a cap?

The 1/2 ton Dana 44 would have had the round cap with internal drive flange in 1976 but the 3/4 ton Dana 44 had the bolt on, external drive flange with the small wheel bearing hub for 1973-76.

In 77+ with the change to the large wheel bearing hub, the 3/4 ton Dana 44 and corp 10 bolt both changed to a round dust cap with internal drive flange and would use the same lockout hubs as the 1/2 ton if you convert to part-time.

[franken]

The full time 4x4 trucks liked to eat driveshafts and drink gas like mad.

[cadillac_al]

Originally Posted by franken

The full time 4x4 trucks liked to eat driveshafts and drink gas like mad.

I have been driving them for 35 years and never had any abnormal driveshaft issues. I love being in four wheel drive all the time. I can pull off the road at any time and never think twice about it. This need for part time must be a city thing.

[57NAPCO]

74 K20

[4793]

In 1978 my dad bought a '74 K20 with full-time 4wd and a 350. I remember him talking about what a gas hog it was. He did a propane conversion, which if I recall correctly was even worse MPG but cheaper fuel. It got body rot *fast*, but that's how it was in those days, especially with the stock rack hauling hogs and cattle to town.

The full-time 4wd sucked on the pavement, always fighting you on turns.

[THI]

In the 1980's you could buy the full-time 4WD trucks cheap, they got what was perceived as poor mileage and yes they rusted fast back then! Had several 1976 K5's for winter beaters. I would drop the stock single exhaust in favor of a manifold back dual set with turbo mufflers and I would rebuild the quadrajet that came on them. Left the full-time 4WD and would get 16 mpg on the highway (55 national speed limit)! Considering they all had 350/th350 combo with 3.08 gears I thought 16 mpg was pretty good!

When I traded my Lieutenant bars for Captain bars, I quit driving the beaters and bought a new K20 decked out Silverado trim truck for my winter driving. That is when I suffered the mpg loss, but I did look good!

[MJN]

My 74 K20 was full time from the factory, odd ball SM465/NP203. I never noticed any mileage issues but I wasn't really concerned either. The only thing that was a pain was turning, it would hop and surge as the front would bind up but otherwise it drove the same as it does now with it switched to a NP205 and lockouts.