Yet to be named... ‘78 K10 Suburban

[RyanAK]

Brought the truck out of town for work the last two weeks for a little shake down... and because I'm bored to tears in the hotel after work and thought I'd do some small projects in the parking lot.

Other than the vibrations I'm chasing at 45-55 and 65-70 mph, the truck is pretty darn comfortable and seems reliable.

I have an oil leak that's wetting down the starter pretty good... and since this is a GM crate 350 I suspect that the passenger side dip stick hole is open and the cause of the leak. Ya think I'd be able to see the hole to verify and make a plan to plug it. Nope. More effort needed.

Last week I decided on a quick little project one night - replacing the bushings on the door strikers. Well a 10 minute project turned into a 12 hour overnight ordeal. There should be a warning label letting every fool like me know that the nut holding the striker bolt is loose and will fall into the B-pillar and you'll need to remove trim and the access hole is too small for human hands and you'll end up replacing all the trim so you can drive the truck to work in the morning in the pouring rain holding the door closed and then you can beg a magnet off of a co worker and pull all the trim again and fish the nut out and replace the striker....

Yeah.

This week my little project was to replace the one-piece speedo cable (which was working perfectly...) to the two-part so I could run through the cruise transducer. 160 miles of interstate each way would be so much nicer with cruise, and everything seems as if it's in place and hooked up. Wires, vacuum lines, etc. I assumed the guy that dropped in the crate motor just bypassed the transducer because it takes a little effort to figure out which cables are needed. I found the cables and install should be easy-peasy. 15 mins and I had the new cables from the transfer case to the transducer and from the transducer in to the speedo. After 5 feet of test drive... BOING! Cable snapped at the transfer case. Apparently the transducer is seized or almost seized up. The speedo DID move for the 3 seconds before I pretzled the lower cable. Anyone know if these Speed Master transducers can be freed up? I'm finding it tough to source a reman'd unit.

This afternoon I'll put the old cable back for the drive home.

Good grief. Old trucks.

[Big Chip]

I believe O'Reilly has them, you just need to know which one you need. Now that you say that about your transducer being seized I think I may have diagnosed my speedometer/cruise control issue.

[RyanAK]

Out of stock at O’Reilly and all other places I’ve looked. They seem to be hen’s teeth at the moment. Glad you might have gotten a clue for your cruise/speedo issue!

And because we’re now on page 3... we need a photo or two.

[RyanAK]

Cheap, but new, U.S.-made 16x8 Cragar wagons with spendy General Grabber A/TX 265/75R16 rubber. Tires ride great! Better than expected. Very quiet. Wheels look good but were hell to balance.

[Originalthor]

Looks good man. I just replace my factory's with some rims that look just like that.

[Originalthor]

Did the new tires fix your vibrations? Mine new tires fixed 90 percent of them but still got a small one at 90 km/h but I think that's my loud welded chamber muffler.

[bhc41051]

I remember when the full time 4x4 trucks were only a few years old the constant velocity joint in the front driveshaft causing vibrations. You might
remove the driveshaft, put the transfer case in Hi Lock and see if helps.

[RyanAK]

Vibration... ugh.

Wheels and tires greatly lessened but didn’t eliminate the vibration at 45-55mph. It moved appropriately with the change in tire size and now seems to modulate a bit. The new tires are quieter, so now I’m hearing some sounds I hadn’t heard before. I think the exhaust is certainly a component. The vibration is now more sound than feel. Haven’t had it up to interstate speeds yet, so don’t know if the rumble at 65-70mph is any different.

The front driveshaft double-cardan CV joint is high on my list of suspects... along with both driveshafts’ balance. I replaced all the other driveshaft U-joints. This is my first experience with the full-time NP203, so what is “normal” is still a bit of a mystery. There seems to be a little bit of a whine at low speeds. Maybe the transfer case and the differentials need a look... Dropping the front shaft is probably a good idea.

(Somewhere in my mind I’m still contemplating a part-time conversion or swap, but I’m hoping to stay stock NP203.)

Other things running through my head: Can rear suspension sag change the pinion angle enough to be an issue? Wheel bearings? (Never had a bad one, so not sure how to diagnose...) Brake drums or rotors? Torque converter? Fan? Exhaust resonance? Worn out suspension bushings? Front axle u-joints? Alignment? (Front axle actually appears as if it isn’t perfectly centered under the body/fame, though the truck handles fine...)

I’m 85% of the way to having this rig running down the highway almost as smoothly as my 2011 Z71 Tahoe. I’ll get it eventually... just hope I solve the remaining niggles before I end up completely rebuilding the drivetrain and suspension! I’m super happy with this truck.

Appreciate the interest, suggestions and encouragement, fellas.

[Originalthor]

It probably wouldn't be a bad idea removing the front drive shaft and checking out the Cardan joint. I remember working on a friends dodge trying to find a vibration in 4x4 and horrible noise at hwy speeds. There was tons of play in is chain in the transfer case so he ordered up a new one and we put it in. Got rid the noise but vibration was still there so he took the front drive shaft in and it was slightly out of balance making it vibrate bad at the joint.

Your suburban sits pretty level for factory springs in it. I had to put 2 1/2 inch blocks in mine to bring it to level, but I got a pile of tools in the back.

Wheel bearings are easy enough to check but with the big tires best to have a friend move the tire back and forth and you watch to see if theres any movement in wheel bearing and upper and lower ball joints at the same time.

One other thing to check now that I was thinking of wheel bearings check your front axle shaft needle bearing play. They have crappy seals and if grease drys up in them is don't take long to wear out. I blew both of mine in one 4x4 adventure cause both seals were shot and dirt got in there.

Hopefully that gives you some more ideas to get it to that last 15 percent.

[RyanAK]

Thanks for the suggestions. When I did the tires and wheels over the weekend, there wasn't any noticeable play, but we weren't specifically looking at the bearings and ball joints. Front axle u-joints are a contender, but there hasn't been anything to move them up the list.

I think dropping the front shaft is a good play. I'm leaning more and more towards driveshaft imbalance or the Double Cardan. I was looking through the service manual and the Cardan joint replacement/service looks like a sonuva*****. And there isn't really a reputable driveshaft place even somewhat local... If I drop the front shaft and that seems to solve the vibration, I wonder how cost effective it would be to replace the whole shaft/Cardan compared to labor and parts to rebuild/re-balance...

There's a guy in the Poconos that has stockpiled Squarebody parts and I think he has shafts available for something like $50. Maybe buy a front and rear and drop them off at a shop to rebuild?

In other news... the A/C compressor seized up and smoked the belt at the end of my 160 mile commute last night. At least that can wait until the spring!

[bhc41051]

If you do decide to convert your NP203 to part time I think you'll be pleased. A lot less moving parts and better fuel mileage.

[RyanAK]

The conversion looses the differential action of the 'H' position on the NP203, yeah? So 'H' becomes 2WD, and 'H-LOC' is 4WD with the front and rear axles locked... i.e. they spin together at the same speed.

I think I have that right...

I'm considering it. Just trying to determine what's most practical for my use. I'd prefer to get things to the point where it's running smooth at all speeds with the NP203 in stock configuration, but if that ain't gonna happen, I'd consider a conversion.

[AJC]

Have you changed the fluid in the NP203 yet? If you remove the driveshaft you need to run it in HI/LO Lock. Since the NP203 has an open diff in it, HI/LO will send power to the shaft with the least amount of resistance. So it won't move in HI/LO without the front drive shaft. The part time kit just locks up the open diff in the transfer case and stops the front driveshaft from spinning in HI/LO. Sadly the best part time kit that replaces the diff with a new shaft vs wedges that lock it, has been discontinued.

[RyanAK]

When I had the truck inspected and the oil changed I asked them to change the transfer case fluid. They said 'yeah, sure', but I just looked on my bill and it doesn't look like they did it... I'll have to find time to do that or take it in some evening while I'm on the road for work.

Roger-roger on not moving in HI or LO with front shaft removed. This would just be to help diagnose the vibration. I think the Cardan CV on the front shaft is a good suspect.

I'm not sure which way I'll go with the 203... I'm not sure I'd like being limited to the LOC-only version of 4WD, but having 2WD and fewer rotating parts during 'normal' driving is pretty appealing.

The more I drive it, the more I'm pretty darn pleased with how this rig is riding up to about 65. I think the new wheels and tires made a bigger difference in how the truck rides that I first thought. That mid-range vibration at 45-55mph isn't hardly worth mentioning any more. 65mph and up it starts to vibrate again... which has me back to thinking about tire balance. It was hell to get the new wheels and tires to balance and two of the set never did balance perfect on the machine. They went on the rear as 'close enough'. This was on a pretty modern machine, but not a road force balancer.

Now these aren't the biggest tires (31.6"x10.5"), but they're a pretty beefy high profile tire compared to what most modern trucks are running. And I'm not even entirely sure the Cragar wheels are perfectly round and true. Like I said, we had a hell of a time getting them to balance and one or two took a bunch of weight. These are guys that started with bubble balancers in the '60s. Family friends. They spent more time on this than they would have for anyone else, and they still aren't 'prefect'. So...

Would a 'close but not perfect' balance job more-or-less eliminate the vibrations at 45-55mph but allow the vibration at 65+ to remain? Should I consider finding a shop with a road force balancer? How about balance beads? There's a thing called something like a 'maintenance level' dose of beads to help get the last few percent of balance on tires already balanced with weights.

Anyway... was just thinking about tire balance again. Still gonna chase the front driveshaft CV and consider driveshaft balance. Just couldn't help think about the new wheels and tires.

This stuff is fun, ain't it?

R

[Originalthor]

I ran balance beads once for about a week. Hated them. You would be cruzing down the hwy and sometimes it would be good some time not. And you would have to slow down to reset them. Horrifying.

That's some good info on the 203 kinda wondered how that worked. Mine in 4x4 jumps all around when turning tight corners. I see the 241s alot on the buy and sell where I'm from for 100 bucks all the time. Maybe it might be worth doing especially if your on the hwy alot and don't need 4x4 unless needed. It would be alot less parts moving.

[RyanAK]

I was honestly surprised how nicely the full-time 4WD (AWD?) on the NP203 actually works. With the open diff in the case, I only get tire scrub on the sharpest of turns in parking lots. Otherwise, you don't even know it's working. Super nice and will be great for those slushy situations on local roads where a locked-up 4WD is gonna be sketchy jumping around on tight corners and when you grab a dry piece of road. I really like the concept and want to get everything smoothed out on the truck before I decide on a conversion or swap of the t-case.

Thanks for the feedback on your experience with balance beads. Reading around on the interwebs, it seems like one of those really polarizing topics like Q-jets and religion. Ha.

[RyanAK]

I thought I noticed this before, but with the new wider wheels/tires it's more apparent...

The front axle isn't centered under the truck.

The passenger side tire projects from the wheel well by 1-1/4" to 1-1/2". Driver side is tucked in. Truck tracks down the road pretty well... but could this be contributing to the vibration at 65mph+? I'd assume that this would keep the front driveshaft from being in proper alignment between the transfer case and the front diff...

[AJC]

Check if your front leaf-spring shackles are bent. Also check the leaf spring bushings.

[RyanAK]

I don’t know how this could even be... I’ll need to spend some time underneath and inspect/measure everything... but on first glance nothing seems bent and the passenger side inside u-bolt mounts around the axle AND front diff pumpkin... so how could it all slide in relation to the leaf springs? It definitely seems like drivetrain-to-frame rather than body-to-frame...

Curious...

[RyanAK]

Friday after Thanksgiving means heading to the family cabin in Sullivan County for the start of antlered rifle deer season in PA. Took some time to mount (but not wire) the KC Daylighters that my parents gifted to me for my birthday. Kids love the “smiley face” lights. I had thought to use these as auxiliary driving lights but apparently they aren’t street legal here. Maybe with a 55W bulb?

Anyway, I think they look good. Happy Thanksgiving and good luck (an be safe!) to those that will be in the woods this season.

[wixthedog]

Those wheels look great on there, a very classic look. Good luck on your vibration search!

[AJC]

I dig the lights.

Here are the PA laws concerning lights. Vehicle Equipment And Inspection Regulations - PennDOT -The lighting section start page 29.

(l)Auxiliary Driving Lamps and Fog Lamps- Auxiliary driving lamps and fog lamps may be installed on a passenger vehicle or light truck if the lamps comply with the following:

(1)Auxiliary driving lamps may not be substituted for headlamps. Auxiliary driving lamps may only be used with high headlamp beams.

(2)Fog lamps may not be substituted for headlamps.

(3)Auxiliary driving lamps and fog lamps shall be mounted on the front,spaced at least 20 inches apart from center to center and at height not more than 42 inches above level surface upon which the vehicle stands nor lower than the lowest chassis part. Rear fog lamps, if originally installed or offered as optional equipment, are acceptable.

(4)Auxiliary driving lamps and fog lamps shall be aimed when the vehicle and lamp assembly are in the straight ahead position with the beam not above horizontal center line of lamp at 25 feet.

(5)A vehicle specified under this sub chapter may have only one pair of approved auxiliary driving lamps and fog lamps.

(6)Auxiliary driving lamps and fog lamps may not be placed in front of a required lamp.

Whats going to get you is the approved part. SAE J581 is the compliance needed for auxiliary driving lamps and SAE J583 is for fog lamps. Even with a 55w bulb the lights still are not SAE J581 compliant. But if mounted and aimed right you might be fine, unless they are really looking. Now KC dose make a led version of those in a driving beam pattern, that are SAE J581 compliant. For if you like the look and want to be 100% legal.

Also here in MN the light don't need covers unless above the maximum mounting height, but your not "suppose" to turn them on unless they are approved or you're off road. I did not find anything to whether that is true in PA.

[ShortHaul]

What's new? Been cruising the burb lately or has the PA weather got ya laying low?

[RyanAK]

Hey, man. Been driving the Suburban pretty much every day. I think I have about 25,000 on it since I bought it. Other than a few hiccups, it's been great. Winter salt and working in a coal-fired powerhouse have made the small rust scabs larger rust scabs, but I still enjoy daily driving a truck that's as old as I am.

Need to dig into the front end soon... There's a clicking and a squeak that are related to wheel rotation at slow speeds. And I'm pretty sure I have the cause of my vibration located... also in the front end. Other than that, just chugging along. Also enjoying a '63 Olds Cutlass that I picked up for short money as a summer car. Helps keep the miles off of the Suburban.

I'm a family man with two vehicles. One 43 years old, the other 58. The lovely Samantha remains sane with a late model Subaru. Ha.

The pandemic and a horrible work load have kept me away from major car projects and checking in here, but I hope to do better. The Olds is super fun and can be made funner. The Suburban really suits me and once I work through the front end and get the small amount of rust dealt with, will be with me for a long time. Then there's that Model A Gow Job I've been meaning to build... never ends, eh?

Good to see Sweet Pea and Bourbon in fine shape. I'll try to comment over there soon.

Cheers!