78 k20 np203 and concerns about noises

[Bthomas78k20]

So, im a newbie that bought a 78 k20.
Knowing little about the 4x4, i bought it and drove it an hour home as is. (55-60 mph on freeway) it ran fine and i didnt have concerns, but after reading, it was in L the whole way and read i should be driving in H. So when i took it over to a shop for the lift install, i made sure it was in H. (It was obvously not in N and was not in H lock bc the light wasnt on on the dash)

My concern is that it drove like what sounded like a desiel or loud tapping that faded out as i excelerated but got loud when going into 2nd then faded out again.

Its an automatic

Im concerned about damage, the trans, the front driveshaft or if something else needs attention??

When i get it back what can i check or do to trouble shoot the issue??
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[landy]

Hmm, driving in low range at those speeds would result in the engine reving very high for an extended time period. Perhaps the tapping sound you're hearing is a knocking connecting rod in the engine, i.e., engine damage.

You should try and id where the tapping sound is coming from, and then report back as to what you found.

[El Dorado Jim]

not sure what your noise is, but if you are planning on keeping the truck for a long time, you should replace the 203 with a 205 t case....find one from a truck or blazer that had an automatic, you will need the 205 adapter also....the 205's are gear drive and bulletproof....

[cadillac_al]

I have been running np203's down the highway for 30 years. I also won many mud bog competitions with the 203. It's the best transfer ever made. If I need to pull down a dirt road or up a steep driveway I don't have to do anything, just drive.. Those part timers need to get out and lock the hubs whenever they need 4wd and then unlock them again on hard pack. I suppose city folks only need 4x4 occasionally while us country boys are going back and forth from muddy roads to tar roads. I can put the wife in the truck and tell her to just put it in drive and never worry about the 4 wheel drive.

Now if you have a noise it needs further investigation. If your truck is high mileage (200k) it could just be worn out. I don't know how you can drive 50 in low unless you hearing is impaired. I think you got a very good truck if it isn't too worn out. Front driveshaft failures are fairly common in trucks that don't get any maintenance. That would be my first guess for noise. My K10 is approaching 180k on the original drivetrain. It feels like it is ready for another 100k.

[Bthomas78k20]

Fwiw it has 70,000 miles, which is a bug reason i bought it.
It was a farm truck that got driven a couple times a yr to plow driveway.


More pics and details later...
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[El Dorado Jim]

203's are crap,I have owned both 203's and 205's..... I live where there is lot's of four wheeling,I live near the Rubicon trail guys use part of the 203 to double it up to a 205 so they can get extra low gears....any hard core 4 wheeler will tell you a 205 is the way to go, bulletproof...gear drive not chain drive...I will leave my hubs locked in all winter then only have to put the trans case in and out of 4 wheel drive...not a big deal to lock and unlock hubs anyway, my wife does it also..."country boys" prefer locking hubs and the 205 trans cases.full time chain drive is for wimps!! Nice truck you have, just letting you know how to make it better with stock parts

[cadillac_al]

If you ever try to drive a 205 in 2wd with the hubs locked on ice or snow you are going to find out how nice they are.(crap) I agree they are probably better for rockcrawling. I have never broke a chain in all my hard driving but I hear it happens. In any case used ones are very cheap too. I would never downgrade to a part timer unless the 203 was already broken. Bthomas should have many miles left in that truck.