From Montana to PA... 1978 K10 Suburban

[RyanAK]

A few months ago I had decided to find a new home for ‘Earl’, my 1971 C10 Suburban. My young family spends a lot of time in the outdoors and Earl wasn’t really suited for trips in the state forest. We had been using my 2011 Z71 Tahoe, but that doesn’t have the feel of an outdoorsman’s truck. Too nice.

A few weeks back I finally found a nice 1978 4x4 in Montana. A few days after, Earl was sold to a nice local fella... so I get to see him from time to time. And last night, the ‘78 K10 Silverado Suburban finally made it’s way from Trego, Montana, to Mifflinburg, Pennsylvania. I think this truck is going to be a lot of fun for my family. My 4yo son has autism and he’s been exceptionally excited for “Silverado” to arrive from Montana from the moment I showed him a photo from the seller. He’s out of town visiting his grandparents at the moment, so the poor boy hasn’t even seen his new truck yet.



New GM crate 350, nice body, great interior. A/C doesn’t have a belt on the compressor, so need to get that sorted. Hopefully just a belt, R134 adaptors and a charge.... but nothing is ever that easy. Cruise isn’t working, and I don’t know where to even start on that... but I want it for my occasional 260-mile round-trip commutes to work. Those big towing mud flaps are gone now.



It will need tires soon. Thoughts? I’d like to go larger. These Toyos are 235/75R15. ~29”. Keeping the steelies. Will probably do shocks at the same time.

Not sure on the running boards yet. And trying to devise a strategy to deal with the minor rust scabs that won’t involve a full body/paint job.



This is a GM marketing photo from 1978. Pretty good inspiration, yeah?



Anyway, thanks for everyone that contributed to the “daily driving a square ‘burb” thread that got me here. I’ll use this topic to update

[cochino12]

Nice burb! a set of 285 BFG A/T's would look great on there.

[RyanAK]

Thanks, man!

I wanted to run 32x11.5R15 BFG All Terrains... I assumed 15x8 stock steel wheels but just looked at the door. 15x6?? Huh... What would that limit me to? These Toyos are on their last legs...

[68Timber]

Good looking truck!

[smokehouse]

converting over to 134a is not that easy someone did that to my burb before i bought it and locked the compressor up so now i'll have to redo the whole thing and buy a new compressor and lines. i hope to do that soon because it is so hot right now my wife really doesn't like riding in it without it to much.

[RyanAK]

Thanks, fellas. Appreciate the compliments. All I did was pull out the checkbook. Ha.

smokehouse - I did the conversion on my previous '71 C10 Suburban without issue and had it checked out by a local shop. No issues, they were approving of the work, and the big roof-mounted tunnel a/c on the '71 blew COLD. Squarebody '78 has a bit different set up, but the conversion looks straightforward enough. If I run into trouble, the local shop knows what they're doing on these older GM trucks. I do appreciate the words of caution, though!

Tires. 6" rims. Grumble.

R

[1976gmc20]

Congratulations!

I think I had those exact same running boards on my 1991. They are sitting in the junk pile now after I finally got disgusted enough with them to fight all those little rusted bolts to get them off. It looks more like a real 4x4 without them but I did keep the little flap on the front to protect the rocker and lower door area.

From the lack of front hubs I'd say you have the NP203 "full time" transfer case. You probably want to start working on a plan to convert to NP205 (or NP208?) part time, and add some hubs.

As far as tires and wheels, I would highly suggest spending the money for some new 16" steel wheels, so that you can run a load range E tire. These things are heavy and eat 15" tires if you get off of pavement. I searched all over for used 16" 6-hole wheels to fit and struck out. I finally ended up with some 15x8 rallies but still the same damn problem with tires. Just so you know, the 16" 6-hole GMT400 wheels Do Not Fit because of the backspace.

Anyway, these are just incredible vehicles. Your 1978 looks better than my 1991, but other than the color and grill they look almost alike.

[RyanAK]

I go back and forth on the running boards. They certainly do provide some protection.

Yes, “full time” 4wd. I’m not at all familiar with it. Why replace? I’m all ears.

I really would like to run stock steelies and caps. But practicality my win out. Grumble.

Thanks for the compliments and suggestions!

R

[1976gmc20]

Why replace?

Gas mileage. Wear and tear. Reliability.

Or so they say ...

Never had one but I worked for a Chevy dealer back when they were the new thing. I had a 73 part time and was not impressed.

But I now have a Jeep with the full time option and it works great.

[68Timber]

You could add some Warn hubs now. The front driveshaft will still turn but you'll save some wear and tear on your tires. And possibly better mpg. About $100 and half an hour to install. You'll need the hubs later anyway if you convert to 205 or 208. The 208 will be easier to find and MUCH cheaper. You won't need more for family excursions. 16" x 8" steelies will open up better tire choices and you'll still be able to run factory dog dish caps.

[RyanAK]

Wow, thanks guys.

The transfer case wasn't really on my radar. Not going to be a near-term project, but I'll definitely consider it when I get some other things sorted out. I see that there's a conversion kit to convert an NP203 to part-time... anyone have an opinion there? Plus hubs.

Just as a point of reference, this truck will see something like 5,000-7,500 miles a year. Good mix of around town and up on the state forest roads in all weather. Nothing too extreme... our mountain roads are pretty well maintained hardpack. Rougher, looser road leading to our camp. Snow. And the occasional commute with interstate travel.

You know... everyday truck.

Does anyone make an OEM-style 16" steelie? Proper backspacing when going to 16x8"? I was really hoping to get decent tires and go drive, but the 15x6 sorta threw me for a loop. But that's half the fun with these old trucks.

Thanks for all the suggestions. This stuff is fun.

R

[68Timber]

A set of front hubs is really all you need. I would never waste money converting a 203. You could buy a 208 for less.

[1976gmc20]

If you're not doing a lot of highway commuting, then maybe you will get along with the 203 just fine. My complaint is that even in "full time" with the center differential, the front end tends to jerk and scrub a bit on tight turns. But I had to jockey these things around in a tight service garage

I just didn't see the advantage of full time 4wd, compared to just locking in your hubs beforehand if you thought there was even the slightest possibility of needing 4wd. But the low range full time setting could be nice. I've actually used low range with hubs unlocked for Big loads on very steep hills.

Our old jeep actually works very well in full time. You can hardly tell even on a sharp corner and it just seems to go where ever you point it regardless of the conditions.

I think there are some aftermarket 16" 6 hole steel wheels available, that I discovered after I gave up and bought the 15x8 rallies. Not cheap, but probably not more expensive than buying the wrong wheels first like I did I had to do something because one of my factory alloy wheels cracked. Stay away from those no matter how cheap you find them.

[RyanAK]

Hey, great input on the 4wd. Thanks for that. Gives me something to think about for sure.

Dad suggested wagon wheels might be easier to source in 16x8 until I can track down steelies to run with hubcaps. Or put 235/75/R15s on it to get it on the road until I get larger wheels/tires sorted. Hmmm.

Off for an A/C belt and retrofit ports...

R

[1976gmc20]

put 235/75/R15s on it to get it on the road until I get larger wheels/tires sorted

I've run those tires on Suburbans since 1990. Just make sure you get LT Load Range C and not passenger car tires. We live off on a horrible gravel/dirt road and our Suburban has yet to wear out a set before ruining one or two or three. But you might do fine if you're mostly on pavement. Heck, millions of people have probably driven Suburbans billions of miles on 235/75R15 tires!

I just suggest going to straight to a 16" wheel (if you can find them) if you're going to spend money on wheels. All the half ton pickups/suburbans after 1988/1992 have 16" wheels (or bigger). It makes a big difference riding on Real Truck Tires in such a heavy vehicle.

[RyanAK]

Roger-roger on LT and Load Range C. Thanks! IF I have to stay with these 15x6 wheels. I'll get it sorted. Not having much luck finding 6-hole 16x8s that will take the dog dish caps.

Front hubs went to the top of the list - right after tires and A/C. Lots of scrubbing in the gas station parking lot and a bit of chatter turning street corners in town. Will consider swapping to part-time down the road. But thanks so much for the knowledge and suggestion to throw on hubs now. What a simple, cheap upgrade that I hadn't even considered!

This board really is pretty great, ain't it?
R

[RyanAK]

A/C retrofitted and charged. 52* out the vents... pretty good considering it was 97* and 100% humidity (Raining. Ugh.) Blowing 45* once things cooled down to 84* when the sun went down. Cooled the cabin pretty well for front-only air.

Cruise... everything seemed to be there and in working order, which made me scratch my head. All wires, vacuum good everywhere, no leak at the solenoid. Was thinking maybe transducer or the dreaded switch in the turn signal lever. Then I saw it... when the crate motor was swapped in they installed a new speedo cable right from the transmission to the speedometer, skipping the transducer! I guess they couldn’t get the 2-piece speedo cable in Trego, Montana. So hopefully that will be a straightforward fix, once I motivate myself to dig into it. How’d I miss that? Anyone have part numbers for the speedo cables?

Definitely doing front hubs. Again, thanks so much for the point in that direction!

Wheels/Tires are still giving me heartburn. Ugh. No luck finding 16x7 or 16x8 6-lug steelies. WV has 6-lug OE-style 15x8s for $97 each. Shipping is probably gonna kill me, and I can’t get an E rated tire. Still, 15x8s with 32x11.50-15 BFG T/As would be a pretty big improvement. Big money, though. I could put 235/75R15 MUSA Goodyear Wrangler Trailrunners on these rims for ~$450 installed....

While I’m stewing over that... tonight I noticed a deep rumble/vibration at 45-50mph. It doesn’t happen at lower speeds and by 55mph+ it’s smoothed out again. Still does it in neutral, coasting at those speeds. There’s also a pretty good clunk when I accelerate after coasting, like the drivetrain is taking up slack when I apply power. U-joints? Been a while since I had a truck with these symptoms and I think that’s what it ended up being. Thoughts?

Again, thanks for the help. These trucks are fun, eh?

R

[1976gmc20]

Wheels/Tires are still giving me heartburn. Ugh. No luck finding 16x7 or 16x8 6-lug steelies. WV has 6-lug OE-style 15x8s for $97 each. Shipping is probably gonna kill me, and I can’t get an E rated tire. Still, 15x8s with 32x11.50-15 BFG T/As would be a pretty big improvement. Big money, though. I could put 235/75R15 MUSA Goodyear Wrangler Trailrunners on these rims for ~$450 installed....

I think I remember that some time after my disaster with the junkyard GMT400 wheels, that I found an online source for 16" 6-hole wheels to fit the solid axle pickups. But they were $100++ each so it would have been $600 to $800 just for a set of five, plus the new tires. By that time I had already bought four 15x8 steel rally wheels from a ranch junkyard for $200, and I bought a new set of 235/75's for those. That guy actually suggested that I just get a couple of 3/4 ton axles and swap them instead but I wasn't quite that ambitious. Those projects always just grow and grow and grow ...

You will probably do fine with a new set of LT235/75R15(C) tires. You might think about spending a little more for a road hazard warranty so that if you ruin a tire or have a non-repairable flat, then they give you four brand new tires

[RyanAK]

I hear ya. I’m still searching. I think there’s some sort of Ford van rim that is 6-bolt 16” and takes our dog dish caps. These Toyos might pass inspection so maybe I have some time. I really would rather a taller tire for a little more clearance and to get the rpms a bit lower on the highway. Plus, ya know, make it look more like a truck.

Good tip on road hazard warranty!

On to wringing my hands about this vibration and hoping it’s just U-joints. Or an unbalanced tire.

Ahhhh. Old trucks!

R

[1976gmc20]

make it look more like a truck

Getting rid of the running boards will help with that

[RyanAK]

Well since you mentioned it...

Before...


17 minutes later...




More better? The area on the driver’s side where the running board attached needs some paint. Passenger side is good. I actually fell getting out of the truck when I ran for gas right after taking them off! Ha!

Wheels still look small... Not as “grandpa grocery getter” as before, (and I actually enjoy that look...)... but a taller tire is my preference. Still, a set of 235/75R15s is probably the practical answer until I can go to a 16” wheel.

[1976gmc20]

I actually like your stock factory wheels

I think those are the same as my spare wheel.

I had a set of Toyos. They were supposed to be such a great tire (and expensive!) but they were about the worst I've ever had. Two got ruined by rocks in short order and the other two wore out quickly. They're sitting out by the garage right now on the factory alloy rims that I don't trust because one of them split radially at the bead and started leaking.

[RyanAK]

Thanks, man. I like the stock wheels too... just wish I could run a larger tire. But they have the look, eh?

Hubs... is this really as easy as pulling off the drive hubs for the full-time fwd and replacing with a set of Warn or Mile Marker lockers? I know when changing automatic hubs there are a few other parts needed. And no issues with the axels still turning? Seems so straightforward... just don’t want to get jammed up because I missed or misunderstood something.

R

[RyanAK]

More discussion over on the projects board if anyone wants to take a peek.

http://67-72chevytrucks.com/vboard/s...d.php?t=790519