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99 Suburban 6.5 to 5.9 Cummins Swap

usanumber1

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Got it started this weekend. Core support, crossover pipe, lower bellhousing, flex plate bolts, exhaust, harnesses, oil cooler, trans, etc taken care of.

E22ED1CF-A876-4720-BF0A-B90DBD66267F.jpeg

Gonna pull the 6.5 this weekend, have one big question: where are the lift points? I think this loop on the front by the AC compressor is one, but I don’t see anything in the back.

57880

57881
 

usanumber1

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Now is about the time when I need to make a decision on the cooling systems.

What is the best all around option for the radiator/intercooler? I have seen people use 1st gen Cummins rads, Powerstroke intercoolers, 6.5 rads, Duramax intercoolers, 2nd gen etc etc. I personally was thinking the a LB7 intercooler might be a good choice in front of a 6.5L rad. Thoughts?

Trans cooler: Under the truck with an electric fan seems like the obvious answer for packaging, however I'm concerned about rocks and mud clogging the fins when I go offroad. It should be noted that I'm no hillbilly mud pit guy, but there are water crossings in the desert from time to time.
 

FellowTraveler

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I went w/2nd gen Cummins radiator and CAC simply because it lines up with the 2nd gen CAC pipes with little modification.
However, you will need to get a GMC or CHEVY sealed beam grill to clear the CAC or modify your existing turn signals.
You will have to remove the windshield washer fluid container and find something else to use in a different location.
Both battery tray brackets will need to modified so the CAC pipes clear.
 

FellowTraveler

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Trans coolers need to be big and placed where they will get some airflow otherwise its fans that will not hold up well constantly running. My combined coolers are 60k btu rejecting however; I've seen 147 deg f a few times in slow to stopped traffic.
Running a high stall will create more heat so BIGGER the coolers the better.
I did not run a fluid to fluid heat exchanger which are generally used to cool down fluid as it exits torque converter because I'm running a low stall and because of the risk of unit failure that would in-turn destroy the transmission by coolant intrusion if it fails.
 

Will L.

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Hummers with 6.5td have overheating issues worse than pickups. When the guys do cummins swaps they dont have the issues near as bad. 6.5 simply puts more btu into the radiator. This is comparing only lightly modded cummins to gm7 turbos with wicked wheels and tunes with 4” exhaust. So unless you are really turned up, expect similar or less cooling requirements.

So since you currently have stock radiator: I would fab up the cummins inner cooler, iirc there is a thread or two here showing how. Then keep the trans cooler through radiator, add external trans cooler up where it belongs.

Once it is all fabbed up, pull he cac and external trans cooler and ship to Chris for coatings, and get the new aluminum coated radiator he offers.
 

FellowTraveler

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Unless you buy a new unpainted CAC expect to strip it before any coating.....I had stripped mine which came powder coated in the Ram tha powder coating chipped cracked making the outside look like s___ I then an aviation coating on the aluminum to prevent chalking and corrosion.......
 

Will L.

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That chalking that occurs on aluminum- it is aluminum oxide. Steel oxide is known as rust, aluminum oxide luckily forms a barrier and once it has 100% surrounded the aluminum, it slows the process of more oxidation.

So thats ok if it something like a fuel tank, or tool box. The problem is on something like a radiator that is designed to shed heat- aluminum oxide is an insulator of thermal conductivity- means one day one it gets rid of heat great, on year 3 you are not doing so well.

The thermal dispersants as coating is obviously best, but if not doing that you are better to put a light coat of flat black paint on it than leave it bare. Powder coating is also an insulator and should not be used on radiator, cac, etc., but most consumers dont do their homework and when 50% of the people ask for powdercoat instead of paint- manufacturers will make what sells. Yes i want to loose weight so a diet soda, extra large please.

Talk to Chris about if you should do any stripping or leave that to him, I know he has to etch the thing before coating.
 

usanumber1

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All awesome information. Thanks.

Wiring, I got as many wiring diagrams as i could off alldatadiy and vatozone's website. Is there anything else I should have in my arsenal before ripping into the engine harness? Things I would like to keep/add in the harness are the the glow plug signal to the grid heater relay, and add cruise control.

Thanks again.
 

razur65

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All awesome information. Thanks.

Wiring, I got as many wiring diagrams as i could off alldatadiy and vatozone's website. Is there anything else I should have in my arsenal before ripping into the engine harness? Things I would like to keep/add in the harness are the the glow plug signal to the grid heater relay, and add cruise control.

Thanks again.
Awesome looking Burb, can't wait to see this put together, more inspiration for my back-burnered conversion project... I use a set of factory service manuals to keep mine together and working, especially when it comes to wiring diagrams. Really useful when tracing out wiring behind dash or in the engine bay.
 

usanumber1

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Thanks for the compliments. I really should invest in a factory service manual to have on hand. They really have all of the important detailed stuff.

Made a little progress this evening. Removed drive lines, disconnected PS without making a big mess, Dropped the tank, replaced the FSU, removed all factory lines and replaced with rubber lines. Hope to have the trans disconnected and 6.5 posted to craigslist tomorrow.

Modified the FSU with hardline-to-AN adapters to make any future servicing easier.

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Will L.

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That rubber line you have is transmission fluid line. While great rating for abrasion, I don’t think it is rated for the ethonal/methonal that is mixed into all or diesel fuel now days.

Sae30r9 is rated for it, had the highest abrasion rating of any fuel line, and is rated to 180psi and 300 degrees so it can live a long safe life not too far from exhaust or touching the engine. So it is my goto recommendation.

Sae30r6 or sae30r7 is rated up to 50 psi, but has lower temp and abrasion rating (cant remember what right now) but it is not way more flexible or easier to work with and cost is a few pennies a foot less so not worth the minor savings imo.

What happens when the hose material is not rated for the alcohols in the fuel is you don’t experience a leak. It just slowly deteriorates the inside of the hose with it damaging the lift pumps and plugging filters. The return hose obviously contaminates the tank. Some fine particles make it through filters and gets to play games with injectors and injection pump.
 

FellowTraveler

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Goddamnit. Dude sold it to me as fuel line. I’m really not looking forward to dropping the tank aloneagain.
Counter personnel a auto parts outlets know little or nothing about hose in general and you get screwed having to buy the right one and installing it but lucky for you Will L caught it before something bad happened.........
 

Will L.

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Dont drop and change it yet.
Need to do some research, maybe calling mfr and find out if it is rated for it. It might be. Maybe call the store and talk to manager about specifications or get their contact number/ email of that manufacturer so you can chase it.

Most places would refund your cost of hose, but won’t do much more. But it may be worth it to see if they will issue you store credit for your lost labor and cost of hose if it is wrong. Remember tendency is to yell, but calm and understanding conversation brings better results with store managers of large corporation supply houses.
 

usanumber1

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Unfortunately I had already gotten to NAPA, tank dropped, and gotten new line installed before I saw the replies. Thanks for putting forth the effort though.

Not much really accomplished this week. But some work is some work. Was able to get to local Pick Your Part this weekend because they had a pre-facelift Suburban with a tailgate. Scored a two-pickup washer reservoir that sits above the wheelwell as opposed to in front.

If someone is looking to do this quick mod to an existing 6.5, here’s a quick run down, for the sake of Cummins swap information, I’ll post it up. Gas wagons are likely different because there is a big computer on top of the wheelwell. Also, barn door trucks are easier to source reservoirs.

Remove the old reservoir, the connectors are different for front/rear pumps, use the sheet metal thread adapters from the donor burb, there are holes for the under the engine bay insulation, place it in, there is a third point, I had to drill a hole, use sheet metal thread adapter from old reservoir, insert pumps, modify lines as needed.

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