6.7 Cummins Suburban Build

[Blackbeard44]

First and foremost badass build you put together!!.

Dana 60 front diffs came in k30's either dual rear wheel or single rear wheel trucks, the duallys have a different spacing on the rear perch pads, not sure about the front spacing.

the front diff from a dually has a wider wheel hub that makes it about 4-5 inches wider, so its best to find one from a single rear wheel truck.

the big benefit in my mind (why i found one for my truck) is the kingpins, they are alot stronger than a balljoint, and with the weight of that cummins on top of them, I bet your balljoints would be screaming at you if they could talk.

bigger tires and more power is going to require a bigger axle at some point, maybe wait and find a pair and change everything to 8 lug at once.

 

[Big Ray]

They beat me to it. The 10 bolt is o.k. for a stocker, but with the torque that motor puts out you need to upgrade. If you like to push it hard off road I'd get a stronger driveshaft too.

 

[grampsbutler]

Here are some more of the interior progress. I still need to do the carpet in the back.

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[grampsbutler]

Dead Pedal not quite gone: I was driving home on Thursday evening last week, and I lost my accelerator pedal while stopped at a red light. Same symptoms as before, I shut the truck off and restart, and the problem goes away. Last time around I polished all my ground connections, and that definitely made a difference.....I thought I'd cured it, but since than Thursday evening, I had the same issue.

Next steps: I suspect a voltage drop might be the culprit. I have quite a bit of current draw on the switched ignition, so my next step is to install a relay box to eliminate a low voltage fault. I don't have any evidence for this, just eliminating possible causes.

Also up this weekend is the stereo install and carpets in the back....I'll get after it, and post some pictures when I'm done.

 

[grampsbutler]

First and foremost badass build you put together!!.

Dana 60 front diffs came in k30's either dual rear wheel or single rear wheel trucks, the duallys have a different spacing on the rear perch pads, not sure about the front spacing.

the front diff from a dually has a wider wheel hub that makes it about 4-5 inches wider, so its best to find one from a single rear wheel truck.

the big benefit in my mind (why i found one for my truck) is the kingpins, they are alot stronger than a balljoint, and with the weight of that cummins on top of them, I bet your balljoints would be screaming at you if they could talk.

bigger tires and more power is going to require a bigger axle at some point, maybe wait and find a pair and change everything to 8 lug at once.

Hey Blackbeard44..... I am on the same page as you and others. A donor K30 seems to be the way to go. They are a little hard to come by. I've seen a lot of k10 and k20s, but not a single non-dually K30. I am not in a hurry so I'll watch the market. I'd like to get the axles done in the spring so that I can be confident taking it off road next summer.

Rear axles seem to be easy to find, but fronts are a rare commodity, and expensive.

 

[Blackbeard44]

the front 60's are definatley getting harder to find, they pop up on Craigslist ocassionally for $2k, I had to drive 600 miles round trip to buy one for $1600 a few years ago, the dodge 12 valve trucks have them as well, just have to cut and re weld the spring pads to fit the chevy, the chevy has a 1310 u joint that is the same as the corporate 10 bolt and im pretty sure the dana 440, im not sure about the dodge versions though

 

[bucket]

Do you plan to tow with it? If not, is it desirable to stick with 6 lugs? For keeping with 6 lugs but increasing braking power and rear axle strength, you could swap in a 6-lug 14 bolt 9.5 from an '88-'98 truck. For the front, there was a company that offered a kit to run modern Hummer H3 brakes on a 10 bolt. I don't remember if it's still in production, but there may be used pieces available. @nvrenuf or @77k20 may know what I'm thinking of.

For ultimate beef, of course there's the D60 front and 14FF rear. Or the 11.5 AAM which was used in newer GM trucks too.

 

[grampsbutler]

Thanks for all the pointers on the axles.

Bucket: I don't plan to tow anything very heavy.......but I do want the truck to be strong enough not to leave me stranded off road.....so I see the D60 as a good investment for the front. The rear is way easier to solve for, I could do a 14FF or an 11.5 AAM. I realize that I'll probably have to move the spring perches (not a big deal) but the rear axles are a lot more plentiful, and way cheaper. I'll keep prowling on fleabay and craigslist, either for a K30 donor or a D60 front.

The weekend yielded some good progress: DEAD PEDAL is solved! It was a low voltage condition, too much current draw on the key on circuit. I hotwired a direct line from my battery to my engine fuse panel, and took a ~250 mile drive on Sunday....dead pedal was gone. I removed the hotwire today, and took it for a ~30 mile spin, and my pedal died twice. I have ordered a master relay, and a sub relay box to hopeful cure the problem for good.

I got the Retro Sound system installed and wired in (much to the delight of my son who spent the drive today singing along to Mathilda the musical sound track). I ordered all the parts from Crutchfield, and I can highly recommend them. The install was very easy....they provided all the right connectors to connect into the GM speaker harness and OEM radio connector. No upside down soldering required. It was the easiest under dash wiring experience I can conceive.....and it all worked first time! The only downside was that they sold me an under seat speaker, which is all bass and no treble, its not my taste, but it seems to make my son happy.

I also got the carpet, jute and seats into the back with new seatbelts.

The real test: I am planning to take the truck to Utah for some skiing over Christmas. My parents are visiting, so it will be 5 of us and all the paraphernalia that goes along with that. This will be the first major outing, with about ~1400 mile in a week including winter conditions and mountain driving. I am rushing to get the functional details ironed out before the departure date.

I have chains for the 37s (they are HEAVY). I'll do the first oil change on the motor next weekend, and refresh the oil in my rear 10 bolt (right after i have knocked on wood and said a prayer to the differential gods).

 

[grampsbutler]

Updated Snag List (in order of priority)

I have done many of the items on my last snag list, but have discovered some new ones. Here is the new list:

Key-on relay install
Install inner left fender
Engine bay AC plumbing for Vintage Air
Dual Battery install and wiring
Door hinge pins
Dakota Digital Instrument Cluster Install
Refresh body wiring harness
1T Rear Axle (including drive shaft modification)
1T Front Axle (including drive shaft modification)
Roof rack and spare tire carrier

Reflections: As the year draws to a close I am taking a minute to reflect. I started the project back in June (interrupted by a 2 month trip overseas) with the goal of getting it done by the end of the year......In some senses it IS done. It drives, has more creature comforts than it ever did, and is about to take my family on a winter road trip. It has also been a LOT of work. I have spent every weekend on it since mid-August, which on top of my day job has been exhausting. I am really looking forward to taking a week off, to drive the truck and enjoy some time with my family and not working or wrenching.

What has it cost so far? I obviously don't count my time.....I enjoy doing this stuff. However, it has taken time from other things that I enjoy, including family and other hobbies. It is a good thing that I have a very tolerant wife.

I keep careful track of all the parts and expenses. So far I am in it for approximately $16K. This includes the motor, transmission, transfer case, drive shafts and all the other parts (including dakota digital instrument cluster which is back ordered). It does not include the cost of the truck ($2900 5 years ago). All the small parts add up surprisingly quickly. It's my forever truck, so I have privileged doing it correctly, and not cutting corners, and I have no regrets about that. I fully expect the truck to outlast me.

Looking forward I am budgeting an additional ~$7k to get it over the finish line. Major components I still need to source include 1T axles, most of the additional items can be fabricated, sourced or I already have parts just need to put the work in. All in, I expect the build will have cost ~26K including the cost of the truck. I'll post the full build list when I'm done, to see how close my guess is.

How long until it is done? I am going to take a breather over the Christmas break, and get back at it in January. My goal is to have it completely finished by June 2024. I want it to be completely done, so that I can spend my time enjoying the truck rather than building it. I'm planning an extended family camping trip this summer, to keep me motivated to get it done.

 

[Blackbeard44]

Car-Part.com - Used Auto Parts Market

www.car-part.com

search here for a dana 60 front, maybe you can find some parts along your journey, when I travel somewhere one of the first things I do is look for parts on here or Craigslist. good luck and hope you have a good time taking the family out.

 

[grampsbutler]

Key Learning Point: When people say don't run a 10 bolt......listen!

I had a catastrophic rear end failure today. It drove great for about 400 miles.....then I got an ugly pop sound in stop and go traffic, on a shift from 2nd to 3rd. I kept on going and it took me to my destination, but something was up with the drive line. I suspected the dual mass flywheel, but the noise followed the speed of the vehicle and not RPM.

I narrowed it down to the rear diff, and decided I needed to take it to lower elevation so that I could work on it. It was running "okay" under power, but it sounded horrible on the overrun/engine brake. When I popped the cover I discovered that the 10 bolt carrier was broken, and there was a mess of smashed gears, and bearings.....

So lesson learned....the Cummins puts out too much torque for the 10 bolt... You will break it. Even if you baby it. Here is a picture of the carnage.

 

[grampsbutler]

Back in action: The truck is back in action. The rear diff grenade'ed the day before Christmas eve.....I had it towed to a shop in Cedar City (Matts Auto and RV), and found a great salvage yard in Paragonah UT, with a ton of squares. I bought a 14 bolt FF with the 3.73 ratio (same as my old 10 bolt axle). They salvage guy overcharged me slightly, but I was in a corner.

Matt and his team were amazing, they fitted the new axle. They went through it, inspected bearings, brakes, replaced the seals and got me back on the road by the 28th. Their charges were very reasonable.

A couple of points to note on this. The breaks on the 1 ton axle are huge and work amazingly well. I am running 17" wheels, and I would be worried about them fitting in a 15" or smaller. The driveshaft did not need to be shortened. The yoke on the bigger axle is further forward, but the difference ~1" was taken up by the splines in the drive shaft. The parking brake is not compatible, and will need to be fixed later.

i am now on the hunt for a Dana 60 for the front, because I no longer trust the 10 bolts, and I want to go to 8 lug wheels all round.

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[grampsbutler]

AC plumbing: I spent some time plumbing the air conditioning. I made up stainless steel hard lines and flex hose to the compressor. Making the stainless lines was way easier than I expected, with the stainless being more malleable than I had feared. I got all the connections and fittings from Vintage Air, and used stiff wire to make a pattern for the lines.

I still need to crimp the soft line (I'll take it to a local place to get it done), and I need to wire up the trinary switch. I also seem to have a small coolant leak that I need to track down.....I noticed a little dampness on the carpet....this is still to do.

After plumbing I need to put some time into cleaning up the wiring......it is a real mess.

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[grampsbutler]

Rear Brake Lock up: Since getting the 1 ton rear axle, I have noticed that I am tending to lock up my rear wheels under hard braking. I did a little off pavement driving in the wet today, which at times was really problematic due to rear wheel lock up.

Does anyone have a fix for this? I assume I need a different proportioning valve?

 

[HighTechRedneck]

Rear Brake Lock up: Since getting the 1 ton rear axle, I have noticed that I am tending to lock up my rear wheels under hard braking. I did a little off pavement driving in the wet today, which at times was really problematic due to rear wheel lock up.

Does anyone have a fix for this? I assume I need a different proportioning valve?

Do you still have the "Load Sensing" rear brake valve? The one that applies more rear brake pressure when the truck squats more, and less with normal suspension height. It has a linkage from the axle up to the valve underneath the body. I'd check the adjustment on that first.

Also, double check the adjustment on the brake shoes. Assuming you kept the brake shoes, and did not convert it to rear discs.