79'gmc

BAD2500HD · January 18, 2008

I just bought a 79' GMC K25 with 62,600 miles on it , it's in great shape the cab corners are just starting to let go and have a few very small holes at the end of the bed , i have been trying to find out what the trans. is and the transfer case along with what gears i have in it , it has the 350 motor and is automatic which is a 3spd i want to change all the fluids etc. in it and give it a good grease job it has sat for the most part of a year , any help would be great , thanks

Cadha13 · January 18, 2008

I say the trans is a turbo 350 and a NP 203 full time 4WD transfer case and most likely it has 4:10 gears. They put THM 400's in the 1 tons before the 80's.

BAD2500HD · January 18, 2008

Thanks ! i thought i might be the TH350 but another guy i know said it would likely be the 400 i thought that the 400 was more for the 1tons, now for the transfer is that a good one ? at least for strengh etc.? also would this have come with the auto hubs ? it has manuel now but they could have been replaced , the transfer case i had forgotn to say has the 4HI-4LK 2HI and 2 LK i beleive is what it said on it, thanks again .

nhproxr · January 21, 2008

Yep its got a th350 in it. The th400 was only used with 400 small blocks and 454s in K20s. Also you do have a np203 case, the 205 was only used with the 4-spds. As far as gears its either 3.73s or 4.10s, but most I've seen seem to be 4.10s.

Welcome to the club! I have a '77 K20 and love it, mine's got a 4-bolt 355, 4.10s in a full floating 14 rear and dana 44 front, np205, and a sm465 4-spd. These trucks are beasts, they don't make them like this anymore.

BAD2500HD · January 23, 2008

Yep its got a th350 in it. The th400 was only used with 400 small blocks and 454s in K20s. Also you do have a np203 case, the 205 was only used with the 4-spds. As far as gears its either 3.73s or 4.10s, but most I've seen seem to be 4.10s.

Welcome to the club! I have a '77 K20 and love it, mine's got a 4-bolt 355, 4.10s in a full floating 14 rear and dana 44 front, np205, and a sm465 4-spd. These trucks are beasts, they don't make them like this anymore.

This truck is in really nice shape for a truck up here in VT the salt really eats them up and this one has been lucky ! i just need to replace both cab corners (getting tender) and the left corner of the tailgate is rusty other then that is great , my first truck was a 75'K10 with the 350 auto good truck had a lot off fun in it , my son is really eyeing this truck pretty heavy he wants to put a lift ( 3" or 4") and little bigger tires told him we will see he's 19 and wants this truck bad . anyhow thanks for the help...on other thing have you or do you know what might be wrong with the gas running out of the carb ? or thats what i think it's doing , after it sits for a little time it needs to have some gas dumped into the carb to get it to start the fuel pump looks new but it has set aolt so ?? thanks for any info !

nhproxr · January 23, 2008

This truck is in really nice shape for a truck up here in VT the salt really eats them up and this one has been lucky ! i just need to replace both cab corners (getting tender) and the left corner of the tailgate is rusty other then that is great , my first truck was a 75'K10 with the 350 auto good truck had a lot off fun in it , my son is really eyeing this truck pretty heavy he wants to put a lift ( 3" or 4") and little bigger tires told him we will see he's 19 and wants this truck bad . anyhow thanks for the help...on other thing have you or do you know what might be wrong with the gas running out of the carb ? or thats what i think it's doing , after it sits for a little time it needs to have some gas dumped into the carb to get it to start the fuel pump looks new but it has set aolt so ?? thanks for any info !

I'm your neighbor to the east, my truck is either a true NH survivor as well or maybe a southern truck cause its in fantastic shape as well.

My first truck was a '79 K10 shorty that I restored (a couple times) and swapped on a stepside bed. I drove the wheels off that thing for 8 years and loved it. Wasn't really looking for an old truck when I saw my '77 last year at a dealership, but I had to have it.

As far as needing to add gas to get it started, its likely not the pump or it wouldn't run once it was going. I'm assuming it has the factory quadrajet? There really is nowhere for the fuel to go as there is typically no gaskets lower then the bowls. I bet it just is getting tired and in need of a rebuild, especially if it has been sitting a lot without being driven. Write the numbers down off the carb (there are hundreds of quadrajet combinations!) and go down to a Napa for a rebuild kit.

I've switched my truck over to a 600 cfm edelbrock that came off my '71 Nova (got a newer carb for that) and its in dire need of a rebuild. Truck is real tough to start anytime its lower then 20 degrees (usually dies at least one time even in temps above that) and performance just isn't what it should be.

88k2500 · January 27, 2008

Yep its got a th350 in it. The th400 was only used with 400 small blocks and 454s in K20s. Also you do have a np203 case, the 205 was only used with the 4-spds. As far as gears its either 3.73s or 4.10s, but most I've seen seem to be 4.10s.

Welcome to the club! I have a '77 K20 and love it, mine's got a 4-bolt 355, 4.10s in a full floating 14 rear and dana 44 front, np205, and a sm465 4-spd. These trucks are beasts, they don't make them like this anymore.

This truck is in really nice shape for a truck up here in VT the salt really eats them up and this one has been lucky ! i just need to replace both cab corners (getting tender) and the left corner of the tailgate is rusty other then that is great , my first truck was a 75'K10 with the 350 auto good truck had a lot off fun in it , my son is really eyeing this truck pretty heavy he wants to put a lift ( 3" or 4") and little bigger tires told him we will see he's 19 and wants this truck bad . anyhow thanks for the help...on other thing have you or do you know what might be wrong with the gas running out of the carb ? or thats what i think it's doing , after it sits for a little time it needs to have some gas dumped into the carb to get it to start the fuel pump looks new but it has set aolt so ?? thanks for any info !

your carb needs a rebuild, what kind of carb is it? i have an edelbrock 650 and she sat for about 2 years cleaned her out re gasket it and no problems.

BAD2500HD · January 29, 2008

I'll try and take a look this week at the carb to see what it is i'm sure that is the problem , it sat for two weeks and i had to prime the carb again just doesn't stay in it , anybody know what is a good allround carb for street and off-roading ?

Cadha13 · January 29, 2008

A properly built Quadrajet like a M4ME electric choke, I have not seen a better truck carb than a Quadrajet. Parts are everywhere, a snap to overhaul and quite simple and reliable. Also quadrajets are variable cfm carbs, they can by used on anything, from a tiny 231 V6 to a 502 rat engine. Keep the heated air cleaner to prevent throttle icing and to have faster warm-ups Not those open element types, they suck hot air that is right above the engine when running, while the old factory one takes air off from the side away from the radiator taking in cool air. Also Edlebrocks suck from personal experience and are based off of old Carter AFM designs from the early 60's. And in the end, it seemed like everyone but Ford was using quadrajets and other GM designs till the end of the 1980's. The Quadrajet, the carb that beat CARB standards for over 20 years 1965-1989.

nhproxr · February 2, 2008

I might agree the quadrajet might be a good choice. I just can't seem to get this eddy 600 electric choke carb dialed in right and its driving me crazy. On my Nova I found one of those edelbrock quadrajets they made for bit a while back and I can't believe how good it goes. The nice small primaries get decent milege at cruise plus give nice crisp throttle response, but when you kick in those huge secondaries hang on it pulls like a freight train. The eddy 600 was on the Nova before this and went good, but I can't believe how much better the quadrajet is.