The Story Of A Cummins Suburban (Lots Of Pics)

[83GMCK2500]

Originally Posted by mosesburb

Thank you!! Yeah, when you want a Cummins and don't care for Dodges, there is only one way to go I guess.



The wheels are stock GM 16 x 6.5" steel wheels that were available on a bazillion GM trucks troughout the 70's and 80's. The tires are somewhat strange though. They are 255 85 R16 BFG M/T KM's. The size is what drew me to them as I was able to use them on a 6.5" wheel. The dimensions come out to be about 33 x 10. This was perfect--tall and skinny, ready to go on my "old man" wheels. They went on, but even with the hubcaps, the truck lost the "old man" image. That image is gone, but I think it still looks cool, just in a different way.

HAHAHA! We think alike. 250,000+ mile motor in a 25,000- mile truck (Dodges). Yeah, I found that size tire a while ago, it is rather odd. Just about everything I've found in that size is a mud terrain, Toyo has a couple models (M-55 & Open Country MT) in it. I really like tall & skinny tires, I think they look good, perform better, and put less stress on the front end parts.

I am familiar with those wheels, I've got two sets + the original spare for my '83 (still has the original 215-85R16E tire on it too). Good choice on hubcaps too. I really like the Spicer hubs hanging off the D60, where did you find those?

[mosesburb]

Originally Posted by 83GMCK2500

HAHAHA! We think alike. 250,000+ mile motor in a 25,000- mile truck (Dodges).

Yeah, maybe not quite that bad but definitely not built to the caliber of the motor. It is very evident when you call around looking for a Cummins as most wrecking yards will have at least a couple compared to when you call around looking for a Powersmoke, you will call many that have none. Cummins outlast the Dodge they come in and Fords outlasts the powersmoke that comes in them.

Originally Posted by 83GMCK2500

Yeah, I found that size tire a while ago, it is rather odd. Just about everything I've found in that size is a mud terrain, Toyo has a couple models (M-55 & Open Country MT) in it. I really like tall & skinny tires, I think they look good, perform better, and put less stress on the front end parts.

I picked them because I could put them on my "old man" wheels--really. I have a set of aluminum wheels here that are wide--33x12.50s look right on them, but I have really grown to like the stock wheels and hubcaps.

Originally Posted by 83GMCK2500

I really like the Spicer hubs hanging off the D60, where did you find those?

Thanks. I bought them some time ago, but I do not remember where. Probably off of some internet site that has a classified section.

[Chevy-Art]

Wow, awesome build. I notice a lot of people using the Cummins diesel, why is that? Why not use the Duramax? I am diesel novice. Is the Cummins easier to get a hold of? More plentiful?

[mosesburb]

Originally Posted by Rush4x4

That is quite possibly THE COOLEST SUBURBAN ON THE FACE OF THE PLANET! I wanted to do the same thing, and now I want to even more. Still, I don't have the skills you do, yet. Awesome work!

By the way, if you just wanted to walk around, taking pictures from all angles: inside, outside, upside, and down; so guys like me could short circuit their laptops with drool, that'd be okay with me.

Really awesome truck!

Wow!! Thanks!! I don't think I can handle the responsibility of ruining laptops, but I'm sure more pics will be posted sometime.

Originally Posted by Chevy-Art

Wow, awesome build. I notice a lot of people using the Cummins diesel, why is that? Why not use the Duramax? I am diesel novice. Is the Cummins easier to get a hold of? More plentiful?

Well, I can't speak for others, but the reasons I chose the Cummins are:

Virtually bombproof--these motors have a 66,000lb GVW rating, durability of a mechanical diesel
Availablity--Most yards have a few
Simplicity--Depending on the setup, the only wires needed go to the starter
Coolness--Inline six sound, heavy underhood rattle

The Duramax is a sweet motor. It is almost hard to believe how well these motors run with little effort. They are a very complex motor that requires a good amount of knowledge in the electrical end of things to do a conversion with. I would imagine that they are quite pricey to purchase also. The Duramax will not run without electricity whereas once the Cummins is running no electricity is needed (provided the injection pump is not controlled by a solenoid).

Now, this comparison is Duramax (which all are electronic diesels) to a mechanical injection Cummins. Later model Cummins, 1998 and newer, are electronic, but I would not have done a conversion to one of those when the simplicity of a mechanical diesel is available.

[Chevy-Art]

What year are the preferred mechanical injection Cummins engines? Thanks for the info, Art...

[83GMCK2500]

Originally Posted by Chevy-Art

What year are the preferred mechanical injection Cummins engines? Thanks for the info, Art...

1st Gen: 1989-1993 Are a 12-valve engine mechanically injected via a Bosch VE rotary style injector pump.
2nd Gen: 1994-1998 Are a 12-valve engine mechanically injected via a Bosch P7100 inline injector pump. By far the 2nd gen's are the most sought after, they're the ones that have been used the longest to produce the big power pulling engines. Though you can convert the later 24-valve engines to the P7100 pump.

[justcuz]

Hey Mosesburb, what is your rear pinion angle set at? Do you think you may have a rear u-joint bind? Its hard to tell from the pictures but it looks kind of steep to me. Just a guess.

Love the completed pictures and the photos of the trip.

You running 4.10's?
You just went from about a 29 or 30 inch tire to about 33's right? I bet your mileage will improve some.
A .73 5th gear would give you 3.00's from the 4.10. It seems like you should be in the ballpark now. Plus the increase of tire diameter should net you a tick lower numerically.

[mosesburb]

Originally Posted by justcuz

Hey Mosesburb, what is your rear pinion angle set at? The u-joint angle is about 13.5deg. It is less than the fifteen practical maximum, but more than I would like. The front and rear u-joint angles are within one degree of each other. Do you think you may have a rear u-joint bind? No, not even close. Its hard to tell from the pictures but it looks kind of steep to me. It is. It is greater than the maximum manufacturer recommended angle, but less than the practical maximum.Just a guess.

Love the completed pictures and the photos of the trip. Thanks!!

You running 4.10's? Yes, still have 4.10s
You just went from about a 29 or 30 inch tire to about 33's right? I bet your mileage will improve some. Actually it was about 32" to a 33" tire, so not too much difference.
A .73 5th gear would give you 3.00's from the 4.10. It seems like you should be in the ballpark now. Plus the increase of tire diameter should net you a tick lower numerically.

...

[LOW DOUGH]

hmmm, is it a typo? You put a 16" tire on a 16.5" rim? The angles of the beads are different on a 16 and a 16.5 tire.

[LOW DOUGH]

Oh, The Burb looks great with it's new shoes.

[mosesburb]

Originally Posted by LOW DOUGH

hmmm, is it a typo? You put a 16" tire on a 16.5" rim? The angles of the beads are different on a 16 and a 16.5 tire.

I'm not sure where the 16.5 is coming from, but if I did state that then it is definitely a typo. The wheels are 16 x 6.5" wide and they have 16" tires on them.

Originally Posted by LOW DOUGH

Oh, The Burb looks great with it's new shoes.

Thanks!! I'm diggin the new look and the tires are finally getting broken in and calming down at speed so it is much easier to drive now (not as easy as the old man tires, but easier than it was when these were all squirmy).

[LOW DOUGH]

I just read it wrong. The Burb looks awesome. I like the pic with the caps off with the lugs and hubs hanging out.

[mosesburb]

I had a lingering doubt about the rear axle because I had never driven the truck that it came out of. I doubted that there was a problem in it, but for two reasons I purchased a complete 14FF assembly out of a you pull it yard. The first reason was I wanted to try a complete axle assembly--untouched--and see if anything changed with the vibration and second (more importantly) was I wanted to go with a higher gear ratio--3.73 as the 4.10's are just too much gear for a torque motor. They are fine for a small block, but running them with the Cummins was a chore as the motor wound up too quickly and spun too fast on the highway.

I finally got fed up one day and went shopping. One yard--nothing, second yard had one that could have been something, but the SPID label was gone and I did not feel like pulling a diff cover in a mud puddle, so I passed. The third yard had what ended up being the cat's ass. I found a super-clean '97 G3500 passenger van. I checked the SPID label and found the GT4 code indicating the desired 3.73 ratio. I pulled it out and loaded it onto one of the wagons tha they provide and dragged it about 1/8-1/4 mile to the cashier. I left it outside as it had completely kicked my ass dragging it across the yard on two flat tires and it not being light to begin with. The cashier made me bring it inside. I stated that it is what it looks like and it looks the same out there as it would in here, but she still made me drag it inside (thank you nice lady). I paid my money, loaded it in the truck and headed home and unloaded it.

As a side note, I had looked at the van that this came from and I wondered why a truck this clean was in the wrecking yard. It had no insurance company information on it, but then I found the "c4c" on it. Ahhhh, the wonderful Cash For Clunkers program. Well, I cut the SPID label off of it and when I got home I ran the vin on the state website to see how many miles it had on it when it was last emission tested--and also how bad it was polluting. I found that it had 157,000 on it and it ran so clean it practically made air. Yeah, great truck to take off the road guys.

So, I wanted to put this diff in without touching anything. I only had one problem and that was the parking brake cables were the later design that I had initially wanted, but couldn't find. Now I had them, but I had already set the truck up to use the older bolt-in style. Now, I could redo the truck and use the newer cables, but I did not feel like doing all of that to swap out a diff. I happened to have a set of one ton (13x3.5") backing plates that use the bolt in parking brake cables. I swapped those on with all of the late model brake components that came on the axle. One sweet bonus of this swap is I get slide-off brake drums!!! Woo-hoo!! I did have to pull the hubs to swap the backing plates though, but when I did I checked out the bearings and they look great. The gear oil smelled good. I got a unit that is in great shape.

I cut the perches off and welded them in the correct place. Before I swapped the new axle in I took my 2.5 deg angle milled Zero Rates and turned them around thus raising the existing pinion five degrees. That made no change at all. I got home and pulled the diff and swapped in the new one. While I was taking it apart one nut on one of the new u-bolts galled. Nobody in town stocks them and spring shops are closed, but a couple phone calls later to some fellow gear heads had a replacement located and the project back in motion.

I got the new diff in and bled the brakes and went for a drive. The first thing I noticed is how nice the truck drives with the higher gears. I can drive around without having to use fifth gear. Prior to the swap, my maximum speed in fourth gear (1:1) was 55mph. I had to be in fifth to merge onto the freeway. Now, my top speed in fourth is about 65mph. It doesn't seem like much, but it make a huge difference in drivability. It spins slower on the freeway such that it quiets the motor down significantly. The motor lays down above 90mph now instead of 82mph. All in all it wa worth every bit of effort to install. I can not convey how much nicer this thing is to drive now that the motor spins slower. The fatigue factor of a roadtrip will be lessened significantly.

It has the cool, ribbed-for-her-pleasure housing:




So, it drives soooo nice now, the vibration...


















oh yeah.....





























remains alive and well!! No difference whatsoever!!

Argh. I guess I knew it going in, but I really hoped it would take care of it.

[mosesburb]

Soooo, what to do now. I decided to compose a couple emails and send them to people who have more experience in this arena than I do. I wrote a couple emails that looked like novels and sent one to Dan at quad4x4. I have had great luck with everything that I have purchased from him but more importantly, I have never been able to stump him with any question I have asked of him. He responded back with some quality information and helpful suggestions. I checked a few of the things out and while I was doing that I got a response from my second email that I had sent to Jess at High Angle Driveline.

Jess' response was basically one sentance stating that he knew what my problem was and that I needed his patented drive flange and a double cardan shaft. He guaranteed that this would solve my problem and while I have no reason to doubt the master, I still wondered why. I gave him a call and he spent a fair bit of time on the phone with me explaining the situation. He said that the problem I am having is called gear rattle. It occurs when the joints operate over eight degress and they create a oscillation in the shaft and the shaft will push the oscillation out into the transfer case or into the ring and pinion. I had not told anybody that the vibration under decel sounded like the ring and pinion was coming apart, but he told me that it was--I was very impressed.

Anyways, I ordered up a 1350 series double cardan shaft assembly and a a week or so later a box showed up. Inside the box was one of these:







I had to change the pinion angle that I had just installed, so out came the new diff. I decided to get new perches so I wouldn't have to cut these off again and re-re-weld them on. I got the new perches tacked on and the axle temporarily re-installed. I installed the output flange on the transfer case and installed the driveshaft. I finalized the pinion angle two degrees down from the driveshaft and welded the perches on and installed new u-bolts. I got the shocks re-installed and hooked the brake lines back up. It was time to go to work and I knew there was no way I was going to be able to get work done efficiently thinking about this thing sitting at home in the driveway, so I decided to take it on a test drive to work--all or nothing.

So I did a quick transfer of all my rain gear from my S10 back into the Suburban (it wasn't needed, but if I didn't have it, it would have poured), grabbed my lunch and jumped in. Now, from the get-go, the biggest pain of the vibration has been that it occurs at 60mph and higher. That means that no matter what I try I have to drive it atleast 60mph. Now, the only place nearby to drive that fast is the freeway and there is no getting on slowly or taking your time getting up to speed. With that in mind, I get on the freeway as gingerly as possible. I get up to speed and merge on and all seems well. I play around in the range that I think it should be in (at this point I have not gotten my speedometer recalibrated for the 3.73's) and all seems well. I get to work and am fairly pleased and I believe the vibration is gone, but I want to be sure so I reserve judgement until the ride home.

I get out of work and and quite anxious to drive the truck for some reason. I get on the freeway and all seems well. I roll into and out of the throttle and it seems good. I run it way past where the vibration should have been and all is good. Then I run it way up and let off abruptly and it coasts down smoooothly and quietly--all is good--life is good!!

Yessir, all it took was a gold-plated driveshaft to fix the problem. Now, there is nothing wrong with my previous driveshaft--nothing at all. It just happens that he length, diameter, angle and any other variable added up against me to create an issue. I have seen drivelines with much more angle run smooth as can be--why did I have a problem?? Basically it came down to bad luck. An identical truck might not have ever had an issue while mine did. One Blazer with a driveline that practically hangs straight down has no isssues while the same setup in an identical Blazer vibrates like all get out--luck of the draw.

So me and my boy head out for an extended test drive. We head about fifty miles east to an antique tractor show and the whole drive is absolutely wonderful. Worth every penny of driveline and 3.73s. It is so nice to drive now.

So the vibration is gone and all is well right?? Well, sort of. I developed a new vibration. Are you getting tired of vibrations?? I sure am.

Near the end of our journey back (on our way to our second destination of the day--still on a freeway) I picked up a horrible grinding type very deep vibration. WTH now?!? I tried a few things to see if it affected the situation at all. I tried accelereation, braking, swerve right, swerve left and nothing affects it. The wierd thing about this vibration is it is intermittent--yes it comes and goes. After driving for a couple miles while trying to get on the other side of a mountain to where a good friend lives, the vibration stops--smooth sailing. Huh?? Gone?? Yup, gone. How, why, what...?? I hit a bump--an expansion joint at the leading edge of a bridge--and it is back in full force. Huh?? How?? Then I hit the expansion joint at the far side of the bridge and it is gone--just like that--GONE!! Huh?? How?? It basically repeats this scenario over every bridge/overpass. No worries as there are no mile long bridges or anything, but the problem comes in a single bump that has no partner. The bump kicks in the vibration, but there is no second bump to "turn it off".

Anyways, I get to where I am going and on the way home on surface streets I get no vibration at all. Is all well?? No. On my way home from work (not to work, but from work) just before I get to my exit, just after hitting a bump it is back in full force. Swell. Same thing the next day, but it came back about a mile sooner, but not enough to diagnose it. Hit one bump and it is on, hit another bump and it is gone. Now I am to the point I do not want ot drive this thing on the freeway or any distance far from home for fear of this thing going crazy, but I have to drive it 10-12 miles to get the vibration to occur.

So, here I am. Everything works fantastic--except whatever is causing the current vibration. I checked my mileage for about 175mi of driving--some highway and some city with a corrected speedometer and netted 19.55mpg without trying--just driving normal. So, with that, I am pleased. I hope to pass twenty soon, but we'll see.

Any guesses on the latest and greatest vibration?? The winner will get a cool prize!!

[justcuz]

Wow! I would start at the front and work your way back tightening all the driveline mounting bolts and look and see if there is an obvious rub somewhere. It seems weird that it changes with a bump. I'm going out on a limb here but do you think the previous harmonic may have loosened the 5th gear bolt in the transmission? Maybe a u-joint needs more grease. Maybe the adapter housing from the trans to t-case came loose or adapter to t-case. The last thing would be the throwout bearing maybe? It is hard to think of stuff. (I am trying to visualize in my mind your running gear). Is it directly related to vehicle speed or powertrain speed. If it happens again and you can safely do it, I would depress the clutch and throw it in neutral and see if it is isolated to the driveline or the engine. I had a input bearing crap out on a transmission once because the bell housing was not perfectly centered. The bell housing had been on a truck for years with no wear to the trans, but when I put the same engine and bellhousing in a passenger car with a Saginaw 4 speed the input bearing crapped out. I did remove the bell housing to clean it and reinstalled it, not checking the runout. My point is I ended up with a little rumble I could not figure out untill the transmission started shifting hard. Then I figured the bearings were getting loose. I have no idea what is happening but I hope you find it. This must be driving you nuts by now.

[jbclassix]

Here is how I figured out what was vibrating in my Yukon. I drove it. And drove it, and drove it, and drove it... and then the problem shot through the diff cover. Hey! I found it!

Probably not the best troubleshooting method.

on a serious note... bring the truck up to operating temperature and check the exhaust for contact or miss-aligned hagers when expanded.

just one suggestion for now

[northburb]

Just found this thread. what a nice build... there must be something with some of these old burbs, I have been fighting a vibration ( or gremlin as I like to call it ) as well and can't seem to make it go away, However, after reading that yours was gone for a short time after replacing the driveline, I guess thats the only logical next step for me. keep posting, I'm definately keeping tuned in to see how this turns out.

here's mine from December
http://67-72chevytrucks.com/vboard/s...d.php?t=375291

[LOW DOUGH]

[justcuz]

I used to see that on a lot of early F-250's. The front driveshaft would be slowly rotating driving down the road...at a speed that was not directly related to wheel speed. There is only one guess I have on this happening and that is the circulation of oil in the transfer case has a parasitic effect on the front output gear and spins it slowly. The oil is the wind and the front output gear is the blade of the windmill. If you had a clunk hitting bumps I would have guessed slip yoke right away. I found out about greasing output splines on slip yoke when I had that clunking on the Blazer. Transmission shop guy clued me in to it.

I am slowly learning a little about diesels, when you leave the black signature when you accelerate does that mean you can up you turbo boost pressure a little, or is the black just momentary? The Cummins from my research seems to be the most cost effective diesel from a reliability and ease of modification standpoint for light duty trucks. Seems like you made a good engine choice.

Its amazing how just a roughly 10% reduction in engine speed can make such a difference in the way the truck runs. Basically if you ran 35 inch tires the 4.10 would have been fine then. Reason I ask is I am thinking of building a diesel off roader in the future and plan on roughly 35 inch tires with a 4" lift and some fender trimming. Its gonna be a square body Suburban or longbed pickup with a shell.

[mosesburb]

Originally Posted by LOW DOUGH

Originally Posted by justcuz

I used to see that on a lot of early F-250's. The front driveshaft would be slowly rotating driving down the road...at a speed that was not directly related to wheel speed. Yeah, the old High-Boys with the six foot long front shaft. There is only one guess I have on this happening and that is the circulation of oil in the transfer case has a parasitic effect on the front output gear and spins it slowly. The oil is the wind and the front output gear is the blade of the windmill. If you had a clunk hitting bumps I would have guessed slip yoke right away. Nope, no noise whatsoever I found out about greasing output splines on slip yoke when I had that clunking on the Blazer. Transmission shop guy clued me in to it. The High Angle Driveline that I got was completely packed with grease, but the front shaft I had lengthened by my driveline guy was returned dry. I thought filling the zerk would do it--wrong (obviously). I wish I would have known that it wouldn't work prior as it took a bazillion pumps to fill the void in the end of the yoke.

I am slowly learning a little about diesels, when you leave the black signature when you accelerate does that mean you can up you turbo boost pressure a little, or is the black just momentary? Yeah, boost can be added. What the smoke is is too much fuel. Mine is not bad. It pumps a bit out under heavy acceleration at low speed, but is almost non-existent on the freeway under heavy throttle. Excessive fuel in a diesel nets high exhaust gas temperatures (EGT) which will kill a motor quick if allowed to get out of hand. The Cummins from my research seems to be the most cost effective diesel from a reliability and ease of modification standpoint for light duty trucks. They are plentiful because they came in Dodges and the motor will typically outlast several Dodge bodies, so they are plentiful in classifieds and wrecking yards. They also have tremendous aftermarket support which makes modifications simple. Their factory parts availability is good also as these motors came in damn near everything--big trucks (Freightliner, Peterbilt, International), farm equipment (Ford, Case IH, etc), Indutrial equipment (the "B" series Cummins was developed for Case equipment). All of this makes parts readily available at many different locations. Seems like you made a good engine choice. I hope so as I really don't want to re-do it.

Its amazing how just a roughly 10% reduction in engine speed can make such a difference in the way the truck runs. Basically if you ran 35 inch tires the 4.10 would have been fine then. Reason I ask is I am thinking of building a diesel off roader in the future and plan on roughly 35 inch tires with a 4" lift and some fender trimming. Its gonna be a square body Suburban or longbed pickup with a shell.

If you would have told me about the difference I would experience from a slight gear change I probably would not have believed it.

[BLACK AND BLUE 67-72]

Awesome job!!!

[MrBeast]

Man every time I look at that thing, its just well, cool. If gm built what you have today, well they wouldnt be going broke, cause I know id buy one.

[mosesburb]

Originally Posted by BLACK AND BLUE 67-72

Awesome job!!!

Thank you!!

Originally Posted by MrBeast

Man every time I look at that thing, its just well, cool.

Thanks!!

Originally Posted by MrBeast

If gm built what you have today, well they wouldnt be going broke, cause I know id buy one.

Yeah, if nothing else, they would have gone down swinging.

Well, I passed 6000mi on the way home from work today. The only notable issues so far have been the injection pump seal that failed, the radiator situation and the rear driveline vibration. Other than those, it has been smooth sailing considering all that was done to it.
Oh, it is still fun to drive.

[MrBeast]

I am glad to see, you are enjoying it, In a couple weeks once I have got my new garage door cut into the new shop the 85 will be going in to start on its conversion.

I was going to ask, did you rebuild the NV4500 yourself?

[MrBeast]

I have a good question for you, I have heard that the stock GM master cylinder is not sufficiant to push the dodge slave on the cummins, I am looking at a wilwood that has a 1" bore and 1" stroke, do you think that would be sufficiant?