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Thread: 90's Suburban Duramax Conversion

  1. #1
    Join Date
    Feb 2000
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    Montana
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    11,382

    Arrow 90's Suburban Duramax Conversion

    Member Gordon Marks has been hip deep into converting his late 90's 2WD Suburban to Duramax/Allison these past few months. He's getting real close to finishing it, and has already run the engine. We thought you might like to see a couple photos.




  2. #2
    Join Date
    Jun 2006
    Location
    St. Albans, WV
    Posts
    368

    Default

    That's interesting!
    I'd like to see more about that!
    96 Suburban K2500 6.5L TD. High miles and daily driven (for now). Remote mount FSD with cooler, Turbo Master/Boost fooler, 4" Jardine turbo back exhaust, 2.5" cross-over pipe, Boost, EGT, & Tranny temp gauges, working on more.

  3. #3
    Join Date
    Sep 2001
    Location
    Lubbock TX, USA
    Posts
    4,194

    Default thumbs up!

    Very cool, now I have someone to shoot questions back and forward to this winter on mine.

    Looks like on the blinker signals to clear the intercooler in this install cutting the back side of the lenses and only using one bulb will work, because both bulbs are wired the same.

    J
    1982 C10 SCSWB 6.5TD, mods too extensive to list. (13.69 1/4 mile @94.6 MPH) RACE TRUCK
    1982 C10 SCSWB 6.2NA, 2.73 700
    1986 C10 SCLWB 6.2TD 3.73 700
    1989 V20 SUB 6.2NA, 3.73 400
    1994 G20 VAN 6.5NA, 3.42 60E
    1994 K20LD ECSWB 6.5TD, 3.42 80E
    1995 K20 SUB 6.5TD, Wrecked, ran into by stupid teen.
    1995 C3500HD DRW 6.5TD, 12' Flatbed 5.13 80E
    1995 C3500HD DRW 6.5TD, 18' Rollback Wrecker 4.63 80E
    1994 C20HD ECLWB 6.5TD 3.73 80E Wifes Truck.
    1995 C20LD ECSWB 6.5TD 3.73 80E
    1995 K20LD SCLWB 6.5TD 3.73 80E
    1996 K30 DRW 6.5TD 4.10 80E
    1997 C10 Tahoe 2Door 2WD 5.7L to 6.5 Conversion Underway

  4. #4
    Join Date
    Nov 2006
    Location
    pa
    Posts
    132

    Default

    Any updates on this?
    95 suburban 2500 4x4
    6bt
    47 re
    373
    under construction

    6.5 parts for sale
    http://home.dejazzd.com/jkauto/6.5%20PARTS%20PAGE.htm

    MY SUBURBAN INFO HERE

  5. #5
    Join Date
    Nov 2000
    Location
    Valrico, Fl, USA
    Posts
    6

    Default G's conversion

    No updates other than I'm in the middle of the A/C season in FL-fortunately a HOT summer FINALLY!
    It does run & drive, I'm in the laborous(?) process of IDing all of the 99 inside harness connectors then "breeding" them to the correct wire in the 01 harness--so when the a/c fuse blows(01 panel)it's actually the a/c that blew it!, etc., etc.
    Oh, we didn't mention.....I had a donor truck-01 K2500HD; I'm using all of the harnesses.....mine is a 99 L65 C2500 Sub.
    No, there are NO clearence issues...actually, it is about as tight as the 6.5L was.
    I'm not a big forum user(cause between this & the 409 stuff I wouldn't get anything done on the truck if I was), so if you have ?'s, post & I'll try to be better about reading. If you're in a hurry, email me @ gordon@marksair.com.
    This is NOT a conversion for the "lighthearted"!
    G
    99 Sub L65<BR>IC,3.5\" Kennedy Exh.& boost cont.,TT PCM, FSD cooler(didn\'t help),rr bar,Isspro gages,B&M trans control
    Gordon Marks

  6. #6
    Join Date
    Nov 2000
    Location
    Valrico, Fl, USA
    Posts
    6

    Default G's conversion

    Oh, John;
    You are correct about the IC/park/ts.....if you'd like some pics of what I did, email me.
    Gordon
    99 Sub L65<BR>IC,3.5\" Kennedy Exh.& boost cont.,TT PCM, FSD cooler(didn\'t help),rr bar,Isspro gages,B&M trans control
    Gordon Marks

  7. #7
    Join Date
    Jan 2008
    Location
    Valrico, FL(TAMPA)
    Posts
    21

    Default

    I've been driving the Sub for about 3 weeks now. So far, So good. There ARE a very few minor issues; some related to the conversion, some just to the fact that the enging had not run much for about 3 years.

  8. #8
    Join Date
    Nov 2005
    Location
    Bismarck, ND
    Posts
    19

    Default Diesel vs. Gas Rear Heat Valve

    We're in the process of converting a 1999 true half ton suburban gas to 6.5L diesel. So when we go to the parts book, we say we have a '99 1500 4wd Suburban with a 6.5L. We know that they may be looking at a rig with 8 bolt wheels, but we should be ok for what we need. To make a long story short, our gas Sub had a wire driven, vacumm valve that appears to either control hot water flow (or simply on/off flow) to the rear heater. When we ask the gm parts guys how the diesel works, they say there is no valve. They also tell us that the rear hvac box does not have a flow control valve. Can you, or anyone help us out as this doesn't make sense to me. Thanks!!
    1995 GMC Sierra 6.5L K1500 Ext Cab Short Box, 316,000 miles, Kennedy Heart Beat @ 233k miles (21:1), GM Dual Thermostats - Housing - High Flow Water Pump, 9-Blade Steel Fan, Kennedy Diesel Special Calibration Fan Clutch, Kennedy Diesel Exhaust - 3" Downpipe - 3.5" Pipe - See Thru Muffler, DSG Cam Phazer, Kennedy Remote FSD Behind Drivers Side Headlight, A-Team Turbo, Kennedy Diesel Fuel Economy Programming, A-Pillar EGT, Boost & Tranny Temp, GU6 3.42 & 245-75-16 Rubber, Stock GM Flat Air Filter & Box, Zero to 60 mph in 9.5 seconds on Wintermaster.

  9. #9
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,382

    Default

    The HVAC won't change once you install a 6.5 - whether or not there is a difference between the gas & diesel versions.

    I recommend using a mechanical fuel injection system in your conversion. It'll be a whole lot easier and less problematic. However, you will need a diesel torque converter for the transmission and possibly a separate transmission control module (TCM).

    Jim

  10. #10
    Join Date
    Nov 2005
    Location
    Bismarck, ND
    Posts
    19

    Default Interesting

    We bought a '96 3/4 6.5L pickup with relatively low miles that caught a falling tree. Thus, a great donor. So we have most of the diesel goods needed. The only thing better would have been a diesel Suburban donor. As it is, we ended up buying a couple expensive harnesses to avoid the rewire time. As if changing out the under dash and under hood harness wasn't tough enough. I've found that the '96 and '97 ecm is the same, very good news. As for the electronic pump, I've had good luck if you flush the engine fuel system and buy a new pump. I've also had bad luck, repeatedly, when you don't flush. Hmmm, I guess that may have been the difference between warranty and my dime, eh? At any rate, we'll see if the new diesel harness mates up to the electric over vacumm valve. I'm still uncertain why goodwrench can't see that in the parts book? Is the rear heater a full flow system like the front? If so, do you suppose the gas rig has a shutoff for warmup or emissions reasons? Perhaps one item to note, the rig we are putting together will actually be a heavy half ton six bolt wheel. But the engine and wire harness set up would be like the legendary 1/2 ton Subs with the 8-bolt wheels, which did not have egr. In summary, I'm even more curious about the rear heater flow thing. Thanks!!
    1995 GMC Sierra 6.5L K1500 Ext Cab Short Box, 316,000 miles, Kennedy Heart Beat @ 233k miles (21:1), GM Dual Thermostats - Housing - High Flow Water Pump, 9-Blade Steel Fan, Kennedy Diesel Special Calibration Fan Clutch, Kennedy Diesel Exhaust - 3" Downpipe - 3.5" Pipe - See Thru Muffler, DSG Cam Phazer, Kennedy Remote FSD Behind Drivers Side Headlight, A-Team Turbo, Kennedy Diesel Fuel Economy Programming, A-Pillar EGT, Boost & Tranny Temp, GU6 3.42 & 245-75-16 Rubber, Stock GM Flat Air Filter & Box, Zero to 60 mph in 9.5 seconds on Wintermaster.

  11. #11
    Join Date
    Feb 2009
    Location
    Ridgefield, Wa
    Posts
    1

    Default

    any updates on this? is it finished yet? i'm extremely interested in how difficult the swap was, or what the hardest part was.

  12. #12
    Join Date
    Oct 2009
    Location
    Southern MD
    Posts
    9

    Smile

    Updates?
    2005 GMC Sierra 2500hd Duramax
    1986 GMC C2500 6.2 banks turbocharged

  13. #13
    Join Date
    Jan 2008
    Location
    Valrico, FL(TAMPA)
    Posts
    21

    Default 99 C2500 Conversion

    Sorry that I haven't been on lately. The Sub has about 12K on the conversion now including 1 trip to Auburn-about 1K roundtrip.
    No problems other than my stupidity. It pulls my 10K race car trailer great!!(26" PACE).
    Feel free to call me with any questions 800-521-9854x0 & ask for me-If I'm not there, tell them what you want-I'll call you back when I get in. Otherwise; gordon@marksair.com
    Gordon Marks
    Tampa, FL (Valrico, FL actually)
    99 Suburban C2500 W/LB7
    55 Series 1 3600
    33 Chevy 4dr street Rod
    64 Biscayne 409 NSS
    "10.81@124.65"]10.81@124.65 3920lbs.
    gordon@marksair.com

  14. #14
    Join Date
    Jan 2008
    Location
    Valrico, FL(TAMPA)
    Posts
    21

    Default

    More:
    If you attempt this, you need a GM(HELM) manual for the wiring at least(there are 6 books for the 01) AND Jim's book. The Conversion book has the mounts and a wealth of other info. I had a donor truck, I can't imagine trying this without one like Jim did!
    I think the IC clearence is even tighter(is that a word?....motighter?)in the later ones. I cheated, I had been looking at using a full face IC on my 6.5, so I had a bit of a headstart.
    Gordon Marks
    Tampa, FL (Valrico, FL actually)
    99 Suburban C2500 W/LB7
    55 Series 1 3600
    33 Chevy 4dr street Rod
    64 Biscayne 409 NSS
    "10.81@124.65"]10.81@124.65 3920lbs.
    gordon@marksair.com

  15. #15
    Join Date
    Nov 2014
    Location
    Denton, TX
    Posts
    2

    Default Cover me, I'm going in.

    I have a '96 suburban, and just acquired a LML with the allison, transfer case (mine has been beefed up for off-road), controllers, etc. to do this swap. I ran across this thread while researching whether it was feasible, or even possible.

    If the original poster is still watching this thread, I'd love a "things I wish I knew when I started" list when you get a chance.

    It seems from what you posted that you mated the existing instruments and wiring to the new harnesses. I was thinking I'd just take my dash wiring out and install an instrument cluster and wiring from a duramax truck. Is that naive on my part?

  16. #16
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,382

    Arrow

    Quote Originally Posted by bhastings View Post
    I have a '96 suburban, and just acquired a LML with the allison, transfer case (mine has been beefed up for off-road), controllers, etc. to do this swap. I ran across this thread while researching whether it was feasible, or even possible.

    If the original poster is still watching this thread, I'd love a "things I wish I knew when I started" list when you get a chance.

    It seems from what you posted that you mated the existing instruments and wiring to the new harnesses. I was thinking I'd just take my dash wiring out and install an instrument cluster and wiring from a duramax truck. Is that naive on my part?
    "Things I wish I knew when I started"... My truck was the first 90s era body style converted by anyone in the country - other than maybe at GM. There were many-many questions in the beginning - like "is it even possible?". Now, there is an information resource and the knowledge that it is indeed possible.

    I procrastinated for about 18 months in the beginning because I couldn't decide how to proceed with the electrical systems. The mechanicals were easy by comparison.Took grit to strip the electrical systems out of a nice truck - cuz there's no going back. My breakthrough came when I committed to stripping the existing electrical systems and replacing them with systems sourced for my model year engine/trans. Then, it became much easier. Jim

  17. #17
    Join Date
    Nov 2014
    Location
    Denton, TX
    Posts
    2

    Default

    My breakthrough came when I committed to stripping the existing electrical systems and replacing them with systems sourced for my model year engine/trans. Then, it became much easier. Jim
    I appreciate the tip. I bought a book that I found online that covers doing the conversion, and I've got the shop manuals coming for both my truck and the '11 silverado that the engine came from. Hopefully that's enough to get me started.

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