MAX. TOWING CAPACITY - Suburban 2500; 4x4, 6.5L Turbo Diesel [Archive]

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Jochen Woern

09-16-2007, 12:46

Would anyone out there know the MAX. Towing Capacity of my 1996 Suburban, 2500, 4x4, 6.5L Turbo Diesel?????

When towing my 9,000 lbs Travel Trailer up a hill, the truck slows down to about 30 mpH and there does not seem to be any "juice" left in her? The truck has the 4.10 Gear ratio.

Am I towing too much? What can be done in order to improve the power?

I just recently installed a aFe stage 2 Performance Air Intake Kit which helps a lot already in regards to power, I will install a 4" Exhaust system next. Will that help or does anyone have any suggestions how I can improve the power while towing any further?

Thanks in advance.

AndyL

09-16-2007, 15:10

Gauges first, what was your Boost/Exhaust Temp/Engine Temp at the top of the hill? Does your 96 have dual thermostats?

If so:

1. Clean the radiator. All kinds of junk will be stuck between it and the AC condenser.
2. Exhaust, bigger the better, loose the soot trap if they don't inspect in your area.
3. Intercooler. Apparently Peninsular has a front mount almost ready. Kennedy and others have one that mounts under the front skid plate.
4. Reflash your ECM, this can add ~50HP.

If you don't have dual thermos add that between 1 and 2. Performance injectors are completely worthless IMO.

Jochen Woern

09-16-2007, 17:32

Thanks Andy.

Could you be a bit more specifc regarding Item 4, flashing the ECM Module? (I assume ECM stands for Engine Control Module?) What needs to be done, what is the cost?

In regards to the radiator, do you mean flush it or disassemble it and clean the outside?

Do you think my truck should easily tow my trailer or am I pushing it????

Thanks.

a5150nut

09-16-2007, 19:48

Thanks Andy.

Could you be a bit more specifc regarding Item 4, flashing the ECM Module? (I assume ECM stands for Engine Control Module?) What needs to be done, what is the cost?

Yes that would be a reflash or an exchange

In regards to the radiator, do you mean flush it or disassemble it and clean the outside?

Inside and out would be better, outside at minimum

Do you think my truck should easily tow my trailer or am I pushing it????

Thanks.

It should.

diesel65

09-16-2007, 20:00

According to GM's 1996 trailering data in the GMC Yukon/Suburban sales brochure, you are overweight for the diesel package.
2500 series with the 6.5 diesel and 3.73 gears and 4wd has a max trailering weight of 6000 lbs and tongue weight of 750 lbs.
With 4.10 gears and 4wd the max trailering weight is 7500 lbs and 900 lbs tongue weight.

If you had the 7.4 gas motor with 4wd and 3.73, the max trailering weight would be 8000 lbs and 900 lbs tongue weight, with 4.10 gears the max trailering weight is 10,000 lbs with a tongue weight of 1000 lbs.

Jochen Woern

09-16-2007, 21:36

Ok Guys, now help me out here: I see some of you guys with 6.5, 1 ton Dually's all over this website and you guys are pulling way more trailer than I ever will. I would assume that the 6.5 engine is identical regardless if in a 1 ton dually or a two door Tahoe? YES??? NO???

I think what some of you guys are pulling out there by looking at some of the pics must be in the range of 10,000 - 12,000 lbs dry weight at least?

Are you saying I must purchase a 7.4L Gas engine in order to pull my trailer? I do not like gas engines and unfortunately can not afford a new Duramax. AND, I really do not want want to have to go and buy an Excursion with a 7.3Powerstroke.

Any help here would be greatly appreciated.

AndyL

09-17-2007, 04:17

First we need to confirm your truck is performaning the way it should stock. Clean area in-front of the radiator, fuel/air filters and sustained boost?

You didn't say what the grade was when you were pulling, but 9000lbs on a stock 6.5 is pushing it if say it was 7% for a mile heading through West Virginia!

A properly equiped 6.5 will handle 9000lbs no problem.

Jochen Woern

09-17-2007, 06:07

Robyn

09-17-2007, 06:18

As has already been mentioned, Gauges, cooling, exhaust and a ECM upgrade. (Lower temp fan clutch) get that fan on as soon as you can.

The issue with the weight is also related to the Burb being able to tow ownly off a rear hitch.
The weight of the trailer in this situation should not exceed the tow vehicle weight. (To be safe) Now I will tell you straight out that these rigs will do far more but the safety issue should be foremost on ones mind.
The DaHoooley's are mostly reefin on 5th wheels and the weight issue is a whole different story then.

You should be able to handle your trailer fairly well after the upgrades, just make sure of the brakes on the trailer and keep safety in mind.

Robyn

AndyL

09-17-2007, 06:29

Any noticable black smoke from the tail pipe at full throttle? If the condition of the fuel filter is unknown replace it anyhow, then every 10K miles.

It is very easy to hit defueling on a 6.5. You could have only been makeing 100HP by 1/2 way up the hill! Increasing boost with either a ECM reflash or a mechanical spring, adding an Intercooler will allow you to maintain power pretty much indenfiantly!

ECM reflash = more boost and more fuel, $500

Intercooler = $1500 for a prepackaged kit, or 1/3 of that for a ebay DIY.

Adding both and you'd likely maintain 60+ MPH up that same grade.

Jochen Woern

09-17-2007, 09:27

Thanks Robyn.

Should I keep my confidence in my rig based on your comments? Braking is no issue at all, trailer is brand new with excellent brakes. The only issue is power going up hill.

OK Andy, back to you (and forgive me please, maybe some of my questions seem a bit odd to you but I am trying to gain my knowledge here as I go):

- My truck does not smoke at all, not when cold, not when hot, not at idle not at full throttle, there is no difference if I tow or if I am running empty.

- Can I replace the fuel filter myself or is it fairly difficult? Where exactly is it located? Do you know what the cost of the filter is and what the GM Dealer would charge for the exchange?

- What is considered "defueling"? Not enough diesel flowing through the engine due to a clogged filter???

- Could you describe the ECM flash in detail? What do I need to do, where can this be done? Or do I buy a part (Chip) to replace the ECM with? Where is the ECM located?

- What will the Intercooler do for me, how does it work?

Again, MANY THANKS for your help, I greatly appreciate it.

I just do not really want to sell my rig, the truck looks awesome, (Two tone white and gold, with the nice rims and the BF Goodrich All-Terrains, Chrome Nerf/Step Bars) other then towing runs awseome and the interior is in top shape, not even the drivers seat is worn out/split like on so many other trucks of this year.

daustin

09-17-2007, 09:32

Hello again Andy.

As far as I can tell, area in front of the radiator is very clean, air filter is a brand new aFe Stage 2 Air Intake Performance Kit, not sure about the fuel filter though.
Not sure how to measure the boost, I have no gauges that would possibly tell me this.

I was going up a pretty steep grade and definitely for more than a mile. However, not sure how many % of a grade. The truck at that point got pretty hot, it has the bigger waterpump with dual thermostats as well.

So, if I read between the lines, it seems that everyone out there is telling me that my Burb will not pull all this unless I modify it extensively?

If you didn't take the top portion of the shroud off and look in between the A/C and radiator i'd bet there's junk in there. That's where the leaves..etc accumulate and block the air flow. The enhanced clutch/fan combo with the duramax blades will help as well. A 3" downpipe in place of the factory crushed one should be looked into also. My radiator looked clean, but when i took it out it wasn't and had about 3" of leaves..crud at the bottom between it and the A/C area. Several vendors also sell 180 deg thermostats, the above stuff and a good flush helped my heat situation out a lot.
Good luck.
Don

AndyL

09-17-2007, 09:49

No problem on the questions.

The fuel filter is super easy to change, it will also give you a chance to check the lift pump. Do a search here, you'll find the info needed to complete it.

Defueling means the computer is pulling back fuel to try and save the engine from a melt down. With no intercooler these engines can reach intake temps of almost 300 degrees in a very short time. The computer pulls fuel when the coolant or intake temps get to high.

I'm with daustin, I found all kinds of crap jammed in the bottom of mine I couldn't see before I took it apart.

Is pulling the main purpose for your Burb? How many miles on the engine?

Jochen Woern

09-17-2007, 09:58

Thanks Andy.

- What about the ECM Flash?

- I guess I will have to take that radiator shroud apart this weekend and see what's going on in there.

Pulling is definitely NOT the main purpose for the BURB, it is used as a daily driver and family rig. However, when pulling with the family on a camp trip, it is somewhat nerve recking when the darn thing is getting hot and it does not want to go up the hill as fast as I think it possibly should.

The engine has not quite 166,000 (165,8_ _) on it.

AndyL

09-17-2007, 10:14

The reflash will add 15-20mm3 of fuel, probably ~40HP, but also cause you to hit defueling just that much faster!

Oh yea, 9000lbs travel trailer? What is that a 32'er!?

Don't give up on your Burb, you'll have a hard time finding a nicer vehicle IMO.

With 166K i'd probably start with this:

1. Serious radiator cleaning
2. Change out both thermostats, most install the 180s. Get these from kennedydiesel.com to make sure your getting the correct ones.
3. New fuel filter.
4. Gauges! Gauges! and more Gauges! You need to confirm your vacuum actuated wastegate is working, this is what controls your turbo boost.
5. Exhaust.
6. Reflash/Intercooler.

And if that doesn't work, sell it to me cheap! :D

Jochen Woern

09-17-2007, 10:34

Thanks Andy.

Well, the travel trailer is only a 26' er but it has a super slide on it. The dry weight on it is 6,165 lbs, add 45 gallons of water (8.33 lbs/gallon = 374.85 lbs) and you are now looking at 6,540 lbs.

Add all the things you load in a trailer, all the stuff you take for the kids PLUS all the Beer, I am thinking I should be close to 9K lbs.

OK, so:
- I have the air intake kit on it already
- will change the exhaust system to a 4" JARADINE soon.
- the raditor will get cleaned with no problem, thanks for the input.
- fuel filter changed

- Wll the thermostats make a big difference and why? Are the original factory ones a problem? What is the cost at Kennedy?

However, the gauges will cause me some problems since I have no clue how to install this. How else can you confirm the wastegate is working???

Looks like I have a lot of work ahead of me,................

And HOW CHEAP is cheap??????????

AndyL

09-17-2007, 10:47

Good call, I'd forgotten about the required stash of beer!

166K is about the usefull life for a set of thermostats. IIRC they are like $12 each from Kennedy.

If your not a big wrencher, drive down to the local cruise strip, find the guy blowing the most black smoke out of his tail pipe, and pay him $75 to install your gauges!!! A good set will run you about $220, Kennedy has a pile of these as well.

With a fresh fuel filter (assuming your lift pump is working) you should not be blowing hardly any black smoke. If your not, your probably making the factory boost numbers.

ECM reflash, about $500, intercooler about $1500.

Jochen Woern

09-17-2007, 10:54

Thanks for all your help Andy!

AndyL

09-17-2007, 10:57

No problem, keep us posted as to your progress..

autocrosser

09-17-2007, 13:02

jochen,

I had about the same results you have when I first bought my 96 extended cab new. I first chaged out the very restrictive exhaust system and put a turbo boost and Exhaust temp gauge on it. I then bought a Manual Turbo master waste gate control from Heath diesel. I later got his reflas of the ECM done. It's a whole different truck now. I would have installed a intercooler but I have what they call a light duty 2500 (6 lug wheels) and the frame is a little narrower so I can't install the normal intercooler that most install.\

I do have the dual thermopstat crossover (late 96) and 3.73 gears that were stock on the truck.

I also did a minor adjustment to the spring on the radiator fan clutch to make it come in at 200 deg instead of 220.

I pull a 7200lb (dry) bumper hitch type camper up some pretty steep mountains here in NC with no problem. It will get a little warm if I try to run them at 65 so I back it off a little. I origanally could only get about 25 going up Black mountain near Ashville.

I also pull a 8500lb boat which runs out to around 11k with the tripple axle trailer and don't have any problems on the interstates here in NC. I don't climb mountains though.

GMC Hauler

09-17-2007, 17:38

rustyk

09-17-2007, 21:14

For comparison, my motorhome (with the AMG 230 HP engine) can generally pull, at 16K lbs., a 6% grade at 40-45 mph (3200-3500 RPM), and is EGT-limited. I think my diffy is 4.73. That's more weight than you're pushing, but OTOH, mine is all mechanical (for a reason...)

moondoggie

09-18-2007, 11:19

Good Day!

You mentioned no smoke at any time, so your boost must be working - you only get smoke if air is short or fuel is too much.

There's no way you can see the radiator debris that's been described until you get stuff out of the way. My brother's a mechanic - his theory is that the oil & tranny coolers slow down the bugs & stuff, & they then stick to the front of the A/C condensor or radiator. Both my 95s had what appeared to be perfectly clean A/C condensors until I pulled off the grill & moved the coolers out of the way - the condensor was completely plugged behind both of them, & there was no way to see this until I did this work.

Bigger exhaust - about the only power mod you dare do to a 6.5 without gauges. The most important thing is getting an aftermarket 3" downpipe to replace the stock one, which looks exactly like it fell off & got run over, several times. For the rest of the exhaust system, 3 1/2" is more than adequate; 4" is overkill, but if the price is right, who cares?

Gauges - EGT & boost, minimum. With a properly-mounted EGT gauge, you can be quite sure of not melting down. You'll likely find yourself pulling hills with your eye glued to the EGT gauge, especially if you later re-flash your 'puter. (Re-flash is so named because the 'puter's program memory is flash memory. It doesn't go away when power is removed, so disconnecting the batteries has no effect on it - the program's still there.)

Now you can start to play.

Inter-After-Whatever cooler - I think Jim mentioned elsewhere that there's an article in the works that describes a ~ $400 intercooler. If this is so, it's probably the single most effective thing you can do to dramatically increase the safety margin of adding more fuel (re-flash). This will almost eliminate the 'puter defueling due to too hot intake air temps.

Foolers - you can buy a boost fooler that tells the 'puter that the boost is lower than actual, which will disallow it from defueling & dropping boost. You can buy a MAP fooler that tells the 'puter you're at high altitude when you're not, so boost comes up quicker & higher. You can (I think) get a reflash that will take care of both, although I can't name vendors - ask our advertisers, eh?

Fan - JK sells a fan clutch that comes in at a lower temp, & is calibrated, so all of them he sells reliably come in at the same lower temp. Do some searching - there's been lots written about different fans that can be used, although JK's clutch on a stock fan might at least be a good place to start. Actually, if you get your radiator, condensor, etc cleaned up & 180° 'stats in place, maybe that's enough for awhile, eh?

Keep searching, buy the old article reprints & read them (best investment I've made, other than joining the Page).

Keep us posted & Blessings!

Jochen Woern

09-18-2007, 12:56

Thank you very much moondoogie.

sparkylisle

09-18-2007, 15:35

Would anyone out there know the MAX. Towing Capacity of my 1996 Suburban, 2500, 4x4, 6.5L Turbo Diesel?????

When towing my 9,000 lbs Travel Trailer up a hill, the truck slows down to about 30 mpH and there does not seem to be any "juice" left in her? The truck has the 4.10 Gear ratio.

Thanks in advance.

I'm planning on changing the diff gears in my 1999 k2500 Suburban and I was told by the shop foreman at Truck Parts Specialists that the 14 bolt rear axle in 2500 Suburban is the 9 1/2 inch version not the 10 1/2 inch version found in trucks. If that's true, thats why our Burbs have less towing capacity than trucks.

Jochen Woern

09-18-2007, 16:08

One more question moondoggie:

You stated: "Bigger exhaust - about the only power mod you dare do to a 6.5without gauges."

Well, I also have installed a "afe Stage 2 Performance Air Intake Kit", will this cause a problem without the Gauges, I hope not.

In regards to the Exhaust System, is a system "turbo back" sufficient, or do I also need to change the cross over pipe?

Thanks in advance.

moondoggie

09-18-2007, 17:08

Good Day!

"Well, I also have installed a "afe Stage 2 Performance Air Intake Kit", will this cause a problem without the Gauges, I hope not." Oops - in a hurry. If it provides more air to the engine (which I'm sure is why you did it), it can only serve to drop EGTs, although likely only a little.

"In regards to the Exhaust System, is a system 'turbo back' sufficient, or do I also need to change the cross over pipe?" I'll defer to actual experts. Almost everything I write is parrotting others who obviously know what they're talking about that I've read here on the Page over the years. I count on positive constructive feedback when I'm wrong, & generally get it, which is good for all. :D

Some folks get a ceramic-coated crossover pipe, to keep more heat in the pipe; some (I suspect lots) don't. Searching might help you find the answer you want / need.

Blessings!
(signature in previous post)

AndyL

09-19-2007, 08:56

With the factory crossover wrapped with fiberglass heat tape I noticed no difference in spool up or EGT. When my factory crossover blew off the truck I installed a nice mandrel bent stainless piece, i again saw no difference that I could measure!

JSSBurban

12-23-2018, 18:49

Jochen - I see this post was a LONG time ago but I was hoping you could provide some insight. I just bought a 1999 Suburban 6.5 Turbo Diesel that has been garage kept, looks brand new inside & out and is completely stock with 73,000 miles. I'm hoping to tow a 30' travel trailer (just under 9,000lbs fully loaded) with my family of 5 and saw your post. Did you ever get your Suburban to tow your travel trailer better than what you had indicated in your original post?