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1996 Suburban Cummins 12V Conversion Build up with pics

321K views 279 replies 56 participants last post by  dixiepc 
#1 · (Edited)
We are almost done with a 12V Cummins into a K2500 Suburban 4x4.

The Suburban is a 1996 GMC and was a 454 Vortec truck when we started. We used the original transmission 4L80E with a controller. We ended up putting a 1" body lift on to make life easier although it wasn't required.

This entire swap was done without discharging the Air Conditioning.

Most all of the swap parts were from Autoworldmt.com - they were great during this entire swap. They supplied the motor mounts, trans controller, A/C mount, alternator mount, transmission adapter and tachometer drive.

Transmission was move back 3" to accommodate the longer Cummins engine. We moved the transmission coolers to underneath the truck, we used the factory cooler and a cooler from Derale with a fan on it.


Here is the engine, it is from a 1993 Dodge:



Another engine shot:



This shows what we had to cut from the core support to use a 1994-1998 Dodge Truck Intercooler, we did end up cutting more than what is shown but not much:




Here the engine is sitting on the mounts in the truck:



Another in truck shot:



Here is a clearance picture with the stock IFS and the Cummins Oil Pan. It doesn't touch but it's close. We have to countersink a few of the bolts:



Originally we tried to use the stock dodge manifold but ran into clearance issues since this Suburban has dual heat and A/C:






We ended up using a 2003 Dodge Manifold which is a lower mount and cleared everything:



 
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#52 ·
Exhaust Complete

We finished up the exhaust. It turned out really well. Directly on the turbo is a 3.5" pipe (the adapter is from Autoworld), the downpipe is 3.5" and then adapts to 4" pipe. It was all done with mandrel bends. Here are some pics:

Downpipe:




Here is just immediately after the downpipe, it comes up a bit to clear the crossmembers and adapts to 4" here:




4" V-band clamp is here. This is the perfect spot as it allows the exhaust to be removed completely if it is needed in the future:




We used a big Magnaflow muffler:




Over the axle:




Tailpipe:




I am very pleased with the sound, I didn't want it too loud since it is a Suburban, a pickup truck would get away with louder exhaust as they have the back of the cab and the bed to deaden the sound.

All of the exhaust work and fabrication that we were not capable of was done by Stainless Brain Fabrication (www.stainlessbrainfab.com), if you are in the Seattle / Tacoma area and need any sort of fabrication, this shop does phenomenal work!
 
#54 ·
Nope, we do get snow but not a bunch and from what I can see, I have only seen salt on the roads once. Whenever I do travel across the mountains or wherever, I always hose off the undercarriage to clean it off.

Our rigs our here in the PNW don't rust they mold.
 
#55 ·
Mounting Transmission Coolers

We had to move the transmission cooler and add an auxiliary cooler with a fan since they would no longer be in front of the radiator anymore (the intercooler pushed the A/C Condenser out which took all the remainder of the room between the grille and radiator).

Here is the stock transmission cooler, we built a bracket and mounted it by the rear axle:




We mounted the auxiliary cooler on the crossmember behind the torsion bar crossmember:




With the thickness of the crossmember, we were worried about creating a hot spot in the cooler so we used a hole saw and made some airflow for the cooler:




I just have to get the cooler wired and this part of the project is done!
 
#65 · (Edited)
Hood Latch

Since the condenser moved out the width of the intercooler, the safety catch for the hood would have dug itself directly into the condenser. We modified the catch so the hood was no longer facing front to back, it was now side to side.

Hood pic - you can see the stock insert that is not used. We used the other insert and the other, just drilled a hole and used a bolt:



Here is another shot of the latch:



Here is a shot of the striker we welded onto the factory piece, I just had to cut 1/4" slit out of the grille:



Here is just the striker:

 
#66 · (Edited)
Air Cleaner Mount

We used aluminum tubing for the air cleaner and our fabricator had a scrap piece of 1/4" plate. So we bent a 90 degree in it (he welded a bead on the inside of the bend to make it stronger), then we put a radius in it to match the tubing and tub welded it on there. Just drilled 2 holes for the factory mount in the inner fender and voila! The entire intake is 3.5"



We put that end of the filter in the cold air hole that the factory engine used. It is an Amsoil filter with the 'powercone' so it is getting air through that hole:

 
#67 ·
Ok, just a follow-up on this.

I have put ~1500 miles on it now and I am averaging 18 mpg. Most of my driving is in town, some freeway.

I believe the 4.10 gears (and stock-ish 32" tires) aren't helping down the freeway, I think I could eek a couple more MPG out of it with some 3.54 or 3.73 gears.

Also, on these 2 fill-ups we played quite a bit with the transmission controller and the lockup torque converter. I think we have them all perfect now -- on the 1st tank of diesel, the lockup wasn't coming on much at all, on the 2nd tank of diesel, it was coming on too much. Now we have it set just right.. or at least damn close.

Aside from that, we modified the pump a little and put a fuel pin and 3200 RPM spring in it. The spring was the most noticeable increase in power since it doesn't start to de-fuel at about 2100 rpm.
 
#70 ·
Hey Crummins, NICE JOB!

I have a 94 6.5L K2500 Sub and am thinking about doing the same thing you did!

Bought it new in Tacoma and now have 190,000 on it. I think a 12V is the BEST engine for a Suburban. I'd like to know how your mileage is doing so far....I have a 3.73 axle ratio and 265-75R-16 tires. and have considered a 3.42:1 ratio which was available in 94.

The slower you turn a Cummins(or any diesel), the better the mileage.

I currently get 18 on the highway, cruise control, empty......16 driving back and forth to SEATAC and around town........... (The best I ever got was 19 between Puyallup and Sacramento.... 635 miles and about 34 gallons but I had to keep it below 70!......EVERYBODY WAS PASSING ME!!!:eek:)

Last year I towed a 5000lb 21ft boat to Sacramento area and back and got 14 going and 13 coming back. (60-65 each way....except going through the Siskiyous )

Any additional info to report on your excellent conversion?


Thanks,

Rick
Buckley, wa
 
#72 ·
Hey Crummins, NICE JOB!

I have a 94 6.5L K2500 Sub and am thinking about doing the same thing you did!

Bought it new in Tacoma and now have 190,000 on it. I think a 12V is the BEST engine for a Suburban. I'd like to know how your mileage is doing so far....I have a 3.73 axle ratio and 265-75R-16 tires. and have considered a 3.42:1 ratio which was available in 94.

The slower you turn a Cummins(or any diesel), the better the mileage.

I currently get 18 on the highway, cruise control, empty......16 driving back and forth to SEATAC and around town........... (The best I ever got was 19 between Puyallup and Sacramento.... 635 miles and about 34 gallons but I had to keep it below 70!......EVERYBODY WAS PASSING ME!!!:eek:)

Last year I towed a 5000lb 21ft boat to Sacramento area and back and got 14 going and 13 coming back. (60-65 each way....except going through the Siskiyous )

Any additional info to report on your excellent conversion?
It gets 18 MPG w/ no load on winter diesel. It gets driven about 50/50 hwy and town. I have the 4.11 gears so I did some calculations and 3.73 would be a good ratio and 3.42 might be better.

I am extremely happy with how the conversion turned out and everyone should do it!!
 
#71 ·
i'm gathering parts to do my 99 gmc.i to am getting rid of my 454. were you able to use your 454 ecm to run your speedo and anti-lock cruise ect. i'm go'in with a 24 valve. hopefully with a p-pump conversion and a 6- speed also converting to 4x4. can't buy the truck i want so figured i'd buld it
 
#73 ·
That is exactly what I did. People keep asking me why didn't you buy a Dodge truck? Well, I don't really like Dodge trucks and I don't want a truck, I want a Suburban-type vehicle and I HATE how the Excursions drive (not to mention the diesels are still pricey around here) so this was my best option.
 
#79 ·
Yes, stock converter. The 454 and the 6.5 diesel used the same converter so we saw no need to replace it. It seems to stall until 1600-1700 which is right when the turbo spools up so it is about perfect.

Yes, we tow a 10k travel trailer and it does great. The only gripe is the 4.10 gears. When I am above 50-55mph, I don't have a passing gear. At 65 mph it is about 2200 rpm. I would like to see that down a bit so some 3.73 gears may be in the future.
 
#83 ·
Crummins, could you get a measurement for me? I'm swapping a 12 valve into my 97 burb and need to know if your engine is centered up in the frame, or is it set tot the pass. side? If it's not centered can you measure off each framerail and tell me the measurements? Also, where is the front edge of the oil pan relative to the frt. crossmember?
Thanks for your help, and I wanted to say that seeing your swap was the one of the main influences that made me want to do mine.
 
#87 ·
I'll see what I can do on measurements, it probably will be a couple of weeks. I haven't had to work on it since it was done and I am quite enjoying not having to crawl under the hood of it!

I can tell you that it is not centered, it is kicked off to the passenger side by a bit.

I will visually look at where the oil pan sits.

I just bought the motor mounts from Auto World MT, they bolted right onto the stock frame mounts with some drilling and removing of material and I had to countersink the bolts for the differential (the oil pan is that close) and it worked perfectly.
 
#85 · (Edited)
Cummins my hats off to you bro that looks great!! Ive been planning my swap for about 8 months now and this is going to make it that much easier for me! I also plan to post my progress to contribute to the thread and get some more folks out there to do the swap!

What did you do as far as wiring codes and how did they tie in on the chevy?
Im running a Stock 1996 2500 silverado with the 6.5TD and 4L80E 4x4. Thats all coming out and being replaced with a 98 12 valve 6bt with a nv4500 trans. So wiring for the automatic is getting taken out along with the chevy motor wiring as well. I have the 6bt computer and theres one big white plug where it tied into the vehical harness on the dodge. Im cutting that off and just dont know where I need to start tieing it in on the chevy

P.S. I looked at the intercooler pics and no S**T went and bought a stock dodge 94 intercooler off a guy here locally about 10 mins later. Thanks for that!! :)
 
#89 ·
In 1998 I am not sure what the computer would do for the engine (maybe it is the transmission computer?), I thought that they weren't computer controlled until they went 24 valve in 98.5. I thought there was a solenoid that would allow the engine to run and kill the engine and that was it as far as getting the engine to run.

On my 1993, it is 1-wire. You supply key on power to that wire and it will start, you pull power from that wire and it shuts off.

For the stock wiring, I painstakingly removed all of the factory wiring for sensors and controllers that went out with the 454. I pulled each wire out from the harness all the way to the computer. I pulled 36 pins out of the factory GM computer and about 200 feet of wire.

I also removed most all of the transmission wiring since I had to run a standalone computer. I kept the speed sensor wire so my speedo would work.

You will also need the 94 Dodge Radiator since it is clearanced for the intercooler.
 
#90 ·
Man I just sold the radiator off the parts truck I had. Oh well I guess ill have to find another :/ Anyways yeah Im not sure what the computer is for but it looks like it ties into everything on the engine. I havnt gotten to deep into the wireing just yet though. The motor Im useing is the 98 12 valve before they went to 24 valve. Its got the P7100 fuel pump on it. And the transmission it had was a auto with a kick down cable and nothing from the engine harness really tied to it. Ill do alittle digging and see if somehow it tied in through the body harness to the tranny and that being what it was used for. 1 wire to run sounds like my kind of motor so Im hopeing is going to be easier than I thought.
 
#91 ·
Just a quick search, it looks like all you have to wire is the solenoid, I found this blurb on another site:

If its a p-pump, the solenoid has 3 wires. ground, hold and pull coils. cant recall off the top of my head the color coding, but you want ONLY the hold coil to have constant keyed power. The pull coil can only be energized momentairily (usually energized with the starter) as it draws high current and produces alot of heat.
 
#94 ·
Crummins,

I am doing this exact swap just with a 1995 K2500 that had the non vortec 454. I read that you pulled 36 pins from the computer, but what did you leave it in for? What is it left controlling? Just trying to get a better handle on this as I am starting all the wiring and I don't want to pull something I shouldn't at the same time I want to pull everything I can. Or if you can point me to where you were able to find the info on the computer that rocks too.

I still have all the features, dual A/C, power everything and want to keep all that. I especially want to leave things like cruise control, which I think is controlled via its own little computer, but I haven't researched it completely yet.

Any help you can provide on this (or anything you want to offer) is greatly appreciated. You certainly did a bang up job on your conversion. I also am using autoworld partially because of your recommendation/experience and a lot because of how they so professionally and politely responded to my questions etc. They seem like top notch people.

TIA,
Mark.
 
#95 ·
Oh, you are bringing back a lot of bad memories for me. Wiring was the most time consuming part. It wasn't bad just a little tedious.

Yours is going to be OBDI which should be a lot easier to convert as it is less complicated than the OBDII rigs.

Basically what I did is I left all of the wires off of the 454 and marked them. Once the Cummins was in, I wired up the water temp sending unit, the oil pressure sending unit, the key on power for the VE pump, tach, etc. (there might be a few more that I am missing but you get the point). I also had to keep the speed sensor wiring for the computer as well.

Then I methodically pulled each and every wire that was unused all the way back to the computer. I only made 2 mistakes. One was I pulled the tach wire from the computer (the tach on the dash still worked but the computer needs to see engine RPM for the A/C to work on my year - it may not need to see this on OBDI), the other was my daytime running lights don't work anymore.. the warning light doesn't tell me they aren't working either. I am not sure how I did it but I am happy, I didn't care much for them anyway.

Autoworld helped me a lot through this as well.

If I think of anything else, I'll post later. It's late and I might think of other tips in the morning.
 
#96 ·
Lol, bad memories, uh oh.

Yea I kinda figured since I have the OBDI it might be easier, but I like the method you used. I really appreciate you taking time to respond.

So you were able to use all the gauges in the dash than, with just the cummins sending units? Or did I misunderstand?

Again, thanks so much.
 
#101 ·
That's a neat setup! And boy are they proud of it! Lol. So the GM tach does take a 4 pulse signal. I couldn't find any info that said 100% for sure that it did. I think ill try and do the same but home brew it to save some bucks.

Sent from my Droid using Tapatalk
 
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