1991 Cummins Suburban

Spur

Adventurer
A new project has begun:

This:
1991suburban.jpg


Is getting the engine from this:

92%20Dodge%20%201.JPG



I’ve been researching for a while now, what kind of expedition vehicle I want to build. I've considered an FJ-80, Dodge diesel with a camper top, or using my 2004 Tahoe Z71 I also have a 1992 Dodge 250 12v Cummins sitting in my driveway. It's a great truck. It only has 100k miles, but it's 2wd and the tranny is shot. Thinking about selling my Dodge pickup, it seemed a shame. It has such a great engine. So, I started thinking about a swap. Reading up on the forums, a lot of people are putting the 12v into 80s body style GM trucks. There are even some companies that make the adapter mounts, etc. I began a national search for a ¾ ton 2500 Suburban with 4wd. Not many out there. I only found about 3 in the whole country, but one was in Round Rock. I drove up there today and paid $2,000 cash and drove it home. The drive-train is pretty worn out and so is the suspension, but the body is straight and relatively rust-free. There is a little surface rust on the roof, but that will get repainted.

Most of the mechanical work that needs to be done is over my head. I'm only good for maintenance and light repairs. Luckily, Austin has one of the best custom fab shops in the state. Krawltex. www.krawltex.com Young smart guys who have a lot of experience. Their fab work is beautiful. I’ve had several meetings with them and they’re really excited about the project. I’m hoping they will start tearing it apart next week.

In the end, the goal is to have a large, self-contained vehicle that can take me to S. America and back. It should be reliable and have readily available spare parts. It's large enough that I don't need a RTT or trailer. Plus, it's a freakin' Cummins Suburban!

Update (as of May 3rd, 2010): Truck is drivable. Here is a pic of the truck with all the major mechanical work done. It's a beast!

12V_Finale_002_zps293f1246.jpg


Below is an updated (Nov 7, 2010) list of everything that has been done and planned projects:

Done:
1. Gut the entire interior, gut the engine compartment
2. 4” Tuff Country suspension lift, repair any broken suspension pieces, weld on and bolt on steering brace, PSC power steering pump
3. Boyce Dana 60 front axle with ARB locker
4. Rebuilt 14 bolt full float rear axle with Detroit locker
5. Undercarriage coated in por 15, paint engine
6. new brake lines, upgraded master cylinder from 1-ton
7. New nv4500 manual transmission
8. Overhaul diesel engine, replace any worn pieces, repair KPD, smaller turbo housing for quicker spooling
9. New Die Hard Platinum battery
10. Replacement 40 gal fuel tank, new fuel lines, new sending unit
11. Rear bumper, swingout tire carrier, and sliders
12. 12,000 lb Warn Winch with synthetic line from Viking
13. Replace all gauges with Autometer, add boost, EGT
14. On-board Air, Viair 450C continuous duty - 2.5 gal tank, outlet at front bumper
15. Custom Kenworth 200 amp alternator
16. New starter
17. New AC system, delete rear AC
18. Boxed frame to support extra weight of Cummins
19. Custom driveshaft
20. 4" exhaust
21. King 2.5" remote reservoir racing shocks on all 4 corners
22. new aluminum radiator
23. Custom switch panel where factory stereo was
24. Lightforce lights on front bumper (two driving lights, two fog lights)
25. Paint exterior
26. BFG AT 37" tires with 17" Mickey Thompson Classic II wheels (6 total, 2 spares)
27. Bilstein Steering Stabilizer
28. Repair driver's seat
29. Refinish grill and headlight bezel
30. Rebuild rear swingout (upgrade to 4x4labs spindles)
31. Repair dash
32. National front springs
33. New Injection Pump, HX35 Turbo, Bosch 190 Injectors
34. Sound deadener and new vinyl flooring
35. Tuffy Center Console
36. New Headliner

To be done:
1. Custom drawer system over entire cargo area
2. expand electrical system - 2nd battery, national luna kit, blue sea fuse panel, new circuit for fridge, etc
3. Water System, Pump, filter, 18 gal tank
4. 12v 60L refrigerator on slider
5. Led lighting
6. Fantastic vent/fan with remote and rain sensor
7. Install stereo (ipod Alpine head unit, 4 speakers, 10" sub)
8. Install mount for MSI Wind netbook
9. Replace upholstery
10. Door panels and trim
 
Last edited:

UHAULER

Explorer
Looking forward to the build pics/report. It sounds like it is going to be a well buillt and clean rig.
 

Metcalf

Expedition Leader
This sounds like a REALLY cool project!

I found this project while looking for inspiration for my dodge project....

http://www.chaosfab.com/projects/blazer/blazer.html

blazer07.jpg


My advise....

Solid Axle front?

Ditch the 4" suspension lift idea. I would get a custom made set of springs made for the FINAL travel weight of the vehicle. This sounds like it is going to be fairly steady with the configuration you listed. The overall weight isn't going to change much so the springs will be able to perform that much better. With the Cummins you really NEED a set of custom springs....other springs will not hold up in the long term. If you going to get them

Find a way to fit the tire size you want without adding lift. On my project I ended up sectioning the fenders to make them longer. It ended up working sweet. With all the aftermarket support for GM product you should be able to find a great set of front glass to run that will allow you to run a larger tire without much lift at all....37s would be nice on a 'burb with no lift.

Invest in GREAT springs and shocks. For a big 'burb I would think about a 2.5" body shock min. A 3" body and large reservoir would be much better if you have the funds.....especially with that big heavy diesel over the front end.

What are your plans for the front axle? I don't know if a D44 is going to stand up to the Cummins in the long run. Perhaps see if you can find a GM D60 front...should be a bolt it.

Since your adding the Cummins keep the front end light....no big bumpers with big winches. Its tempting....but that stuff adds up FAST! If your unaided and traveling alone most of the time I would think about mounting the winch in the rear. I am contemplating it on my dodge for sure....

Post lots of pictures...

Nothing wrong with a Cummins in a 'Burb!

Good luck!
 

KEENO

Adventurer
Another Cummins 12v!

Awesome Spur! Welcome to ExPo!

What transfer case are you planning to put behind the Cummins? NP205 or are you looking for a better Low Range? LoMax would be a great way to fly if you're starting fresh. (either "kit" or complete) http://www.jbconversions.com/pages/products/lomax205/completetcase.html

When looking for a NVG4500, be aware that a "HD" version was made to be placed behind the mighty Cummins. NVG4500HD is the ticket!

If it's 3/4 ton 1991 Suburban, it should have a D60 in the front.

Looking forward to the build!

KEENO:)
 
Last edited:

Metcalf

Expedition Leader
Keeno has a point. The LowMax would be a GREAT transfer case behind the Cummins. I asked the manufacturer if they could get me a blank input gear so I could have the 29 spline version cut for my Dodge. They didn't have any, so you are stuck with either a 10,27,32 GM input spline. I wonder what you can get for an output on the 4500? I know the Dodge ones are 29 spline but I wonder if you could do a hybrid?

Edit: Most GM versions of the nv4500 had a 32 spline output. This would be ideal for the LoMax. The front input should be able to be changed to a dodge input to make the clutch stuff easier?
 
Last edited:

ntsqd

Heretic Car Camper
3/4t Sub's do not have a D60 front. They were all 10 bolts until you go back far enough to run into D44's. Last couple of years got 30 spline inner axles instead of the older 27 splined axles.
This is a 1/2t '91 that I converted to 8 lug using the outer bits from my '79 3/4t Suburban.
http://www.expeditionportal.com/forum/showthread.php?t=15439
Too bad that you didn't find it in your search because I had a use for it's power-train. I've since traded off another vehicle for a TPI donor.

For that kind of use, and it is one that I considered intimately, look at using the F-250 TTB with custom radius arms and coil springs. The crawler guys all hate TTB's, but for going at any reasonable clip over the rough they will flat out ride better than any Live Axle.
 
Last edited:

Rot Box

Explorer
Sounds like an awesome build! :lurk:

The Suburbans IFS, D44 or 10bolt (depending on year) won't hold for long under that weigh. For a swap I would find a 78-79 or 85.5-91 Ford dana 60 as it will have king pins and a high pinion differential. You could find an NV4500 out of a 94 and newer Dodge and also use the t-case behind it as it will place the drive shaft on the drivers side to match the Ford axle :elkgrin:

Can't wait to see some progress :wings:
 

Spur

Adventurer
This sounds like a REALLY cool project!

I found this project while looking for inspiration for my dodge project....

http://www.chaosfab.com/projects/blazer/blazer.html

blazer07.jpg


My advise....

Solid Axle front?

Ditch the 4" suspension lift idea. I would get a custom made set of springs made for the FINAL travel weight of the vehicle. This sounds like it is going to be fairly steady with the configuration you listed. The overall weight isn't going to change much so the springs will be able to perform that much better. With the Cummins you really NEED a set of custom springs....other springs will not hold up in the long term. If you going to get them

Find a way to fit the tire size you want without adding lift. On my project I ended up sectioning the fenders to make them longer. It ended up working sweet. With all the aftermarket support for GM product you should be able to find a great set of front glass to run that will allow you to run a larger tire without much lift at all....37s would be nice on a 'burb with no lift.

Invest in GREAT springs and shocks. For a big 'burb I would think about a 2.5" body shock min. A 3" body and large reservoir would be much better if you have the funds.....especially with that big heavy diesel over the front end.

What are your plans for the front axle? I don't know if a D44 is going to stand up to the Cummins in the long run. Perhaps see if you can find a GM D60 front...should be a bolt it.

Since your adding the Cummins keep the front end light....no big bumpers with big winches. Its tempting....but that stuff adds up FAST! If your unaided and traveling alone most of the time I would think about mounting the winch in the rear. I am contemplating it on my dodge for sure....

Post lots of pictures...

Nothing wrong with a Cummins in a 'Burb!

Good luck!


Good advice. I'll keep it in mind.

The 4" inch lift is to allow for the extra height of the 12v Cummins. There are some newer custom crossmembers that would allow for less lift, but it's still the easiest to lift it at least 4".
 

Spur

Adventurer
Awesome Spur! Welcome to ExPo!

What transfer case are you planning to put behind the Cummins? NP205 or are you looking for a better Low Range? LoMax would be a great way to fly if you're starting fresh. (either "kit" or complete) http://www.jbconversions.com/pages/products/lomax205/completetcase.html

When looking for a NVG4500, be aware that a "HD" version was made to be placed behind the mighty Cummins. NVG4500HD is the ticket!

If it's 3/4 ton 1991 Suburban, it should have a D60 in the front.

Looking forward to the build!

KEENO:)

NP205 is probably what I'll go with. Thanks for the advice on the LoMax and the HD. I'll check it out.
 

Spur

Adventurer
Thanks for all the advice on axles.

My thought has been that it's ok stock for now with the 10 bolt front and 14 bolt SF rear.

It would be on my list of upgrades down the road, but not something I want to spend money on straight away.
 

RADAR12

New member
sub

Good luck on the build . I wish I would have had the extra coin to do the cummins swap but I am pretty pleased with the 6.2 swap in my 90 suburban. I hope to do the 3/4 ton drive line conversion along with all the other interior mods soon. i found my 90 locally here in georgia but the truck spent 95 % of it/s life in california. Extremely solid body and interior with only light surface rust on the top from the wonderful gm paint peel. I tried to find a diesel 4wd suburban for a long time and they were either junk or 2wd so I decided to make one. i knew the exspense was going to be higher but I believe it was worth it. Looking forward to your pics for some good ideas.
 

Metcalf

Expedition Leader
Oh yeah...

What are you doing with the 2wd once you pull the engine? I would be interested in it when you get to that stage.....
 

Czechsix

Watching you from a ridge
I'll second the advice on spring packs, and doing it custom. I've gone with National Springs on mine, front axle load is 3890 by itself. The old off the shelf lift springs were very compliant, but sagged on the DS, plus didn't have a high enough rate for my tastes. Getting them custom made made all the difference.
 

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