Question about tow weights

[rtphillips370]

Hello, Im new to the forum, i browsed around to see if I could find a thread to answer my question however, I was not all that successful.

I am a proud owner of a 1999 C3500 Chevrolet Silverado. Its a crew cab pickup with a long bed and its two wheel drive. Its equipped with the 6.5L diesel and the 4L80E 4-speed auto w/ 4.10 rear end and duel wheels. The truck is stock with the exception the cadilac converter is replaced with a pipe and i run a K&N airfilter. It has 143k in miles and I have been pulling a 6800 pound, 27ft fifth wheel for the past few years with no problem although the truck feels bogged down abit. Until this week, I was always under the impression that the truck is rated to tow up to 10k pounds.

This week, I recently began to shop around to trade in my old trailer for a newer one when I found out that the truck is in fact only rated to tow 8000 pounds, which shocks me as the door panel states 10,000 GVRW

Anyhow down to my question. I am looking at fifth wheels in the 8000-9000 pound range empty, is there anything I can do to increase my tow capacity the extra 1000-2000 pounds? figuring that empty plus packed weight and wind resistance, I would probably need to be able to move approx 10,500 in all.

I am looking at adding a GEAR VENDERS over/under auxillary transmission that splits gears giving the truck 8 gears verses the 4 it has now. Their salesman swears by it and claims it would help but I am skeptical especially when the price is in the 4 digit range. Am i looking in the right direction? I hate to purchase a trailer to find out the truck cant move it, and i prefer to do some after market mods as it is cheaper than a new truck, IF it will work.

thank you ahead of time for any help someone can give me.

[Craig M]

The Gear Vendors gear splitting helps a little on hill climbing with heavy trailers. While you technically will have 8 gears, some of them will be so close to each other that they are useless. You will have a double overdrive (the 4L80E is already an overdrive transmission) with the Gear Vendors. If you like to go 75/85 mph on the open road then the lower rpm's with the double overdrive will be nice, but you will only get this speed with a bare truck, not towing any significant weight. You might be better off spending your dollars on power enhansements for the truck rather than the Gear Vendors.

[rtphillips370]

If a aux tranny isnt all that great, what would be the best course of action to increase the tow capacity from the 8000 to approximately 10,000 ish?

[AndyL]

If a aux tranny isnt all that great, what would be the best course of action to increase the tow capacity from the 8000 to approximately 10,000 ish?\

Instead of the 4k on the aux tranny, call up Kennedy Diesel, order an ECM reflash and an intercooler. It will be the best towing money you have ever spent and cost 1/2 of the aux tranny.

[The Lurch]

Not only will you want to add those power modifications, you must do some cooling modifications. Order a 180 degree thermostat and a modified fan clutch. If I had my choice between adding power or adding cooling upgradfes to the 6.5, I would do the cooling upgrades first. Both of these items can be bought through Kennedy Diesel and they are worth every penny

[kenisret]

My dually and 33ft 5th whl are 17800 lbs.I'm not sure what the truck alone weighs but I guess 6500 or so.I guess I am over the trucks limit somewhat but I haven't any problem,s so far except on grades you know you are pulling something.On really steep grades the temps will start to rise.I have just added the cooling sys mod but haven't towed as of yet but I suspect it should be ok

[rtphillips370]

This spring I had an issue where the truck would run for a bit and then die out. The GM dealer told me it was a plugged catylitic converter and wanted 1500+$ to replace the whole exhaust system (which still shined and had nothing wrong with it). So i went to a local shop and they removed the converter and put in a test bypass pipe and since then the truck is a whole new animal, so that is the only mod I have done with it since I have owned it, the alleged plugged converter later turned out to be a bad lift pump, so much for 80+$ an hour for a trained manufacturer mechanic.

I pull a 27ft, 6800 pound (empty) fifth wheel now and it runs about 200 deg (according to the stock temp guage) on level ground with A/C on and the cruise set at 70 mph. when I hit a couple of hills in norhten michigan on the way to the Sault Ste marie, I would see it coughing about a considerable amount of black smoke and then slow down to about 55-60MPH with the engine floored due to the grade it was climbing. Then the SERVICE ENGINE SOON lamp came on and stayed on for the rest of the day, it went off the next morning when driving normally and the engine never ran differently with or without the lamp, the engine temp did reach near 210 on the stock guage. Interestingly enough I was able to get a 9.998 miles per gallon at those speeds.

One thing I do notice, when it gets warm the fan kicks in and the power really drops off making the truck feel real bogged down, so that is whay I want to make sure the added 2000 or so pounds would hurt or not and/or what mods to look at. Ive been told that there were no real mods for the 6.5 due to a alleged weak crank / crank journals, but i see they appear to be wrong after cruising through the forum.

This is the first diesel ive owned so all of the "gas engine" knowledge I have seems sort of useless, heck I havent even been able to find a book on the engine in any local stores such as a chiltens etc.

[moondoggie]

Good Day!

The only safe modifications to make on a 6.5TD are to get the air in & out, or modify the intake like JK suggests on his website (don't know if this is necessary on a 99, sure was on my 95's), & a replacement exhaust system. You'll never of course get full agreement, but consensus seems to be that 3" might be too small, 3 1/2" is just right, & 4" is cool but maybe not necessary.

Then, GAUGES!!!!! At least EGT & boost. Without these, you have no idea what's going on that could grenade your engine. (See ronniejoe's three articles about his Suburban.)

Then, play to your heart's content.

(There may be other safe mods before gauges; I'll count on our experts chiming in & correcting me, for all our benefit.)

Blessings!

[ronniejoe]

If you want to tow heavy, make sure you read the articles in my signature...

[autocrosser]

I just brought my 8500lb boat back from the coast last weekend. With the tripple axel trailer I'm sure It's at least 10k. I have a computer reflash, Kennedy exhaust and the boost is set for 12lbs. No intercooler. The fan clutch has been tweeked to come on full at 200deg. It only came on a few times during the 300mi trip. I will say that I was pretty well tapped out on power on small hills on the interstate. Other than that It pulled great. The boat is only about a foot shorter than a tractor trailer rig and has a lot more resistance than my 28' travel trailer.

[rtphillips370]

Thanks for the input, Im saving my pennies to join up. I plan on doing alot of reading up so I can pre-plan what tweaks I can do to the ole truck...

Right now from what I have been reading, I am planning on the guages, fan clutch, chip/programmer, intercooler, and eventually the aux tranny from gear vendors. Looking at my truck now it appears to have fairly decent oil and trans coolers... Are factory installed equipment adequate or should I look at replacing / adding to those too?

On the pyro guages I see there are two versions, one i believe they call pre heat and one for post, I think they are referring to where the probe is located, which one is better? off hand seems the post heat would be the easiest to install...

I have looking for intercoolers and dont see to much in the variety section as the only one I have found is the one size fits all for 6.5 on the kennedy site. I also notice the lack of choices for chip/programmers to so far...

Tax refund season, she goes to the shop for restoration, as the 143k miles in MI is taking its toll in the form of salt rust on the tail gate, back door and duel wheel fairings, and then on to buying the add on gadgets one at a time... The truck serves me well and the tweaks with the restoration will be alot cheaper than the 50K price tag of a new one.

[ronniejoe]

Install your pyro pre-turbo. You want to know temperature as close to the engine as possible.

Kennedy's intercooler is the biggest and I think best laid out kit for the 6.5. The plumbing is routed neatly and stays inside the engine compartment unlike others that route a tube out through the wheel well.

There are only a few real choices on chips or reflashes for the 6.5. Kennedy, Heath and Westers. I prefer Kennedy's electronics because he doesn't make a bunch of bogus HP claims like Heath and SSDiesel. Wester's also claims to have made big power in a 98 with just a reflash...highly dubious.

I've been on a long journey to 6.5 power land and have been over the rough road of overheating, high egt and engine failure. After setting a new record at the Pull-Off last weekend for 6.5 powered trucks, I think I'm getting close.

[rtphillips370]

Well, I took your advice and finally was able to scrape up the money for the Kennedy guage kit (pre turbo EGT and Boost). Although during the wait for my make-shift saving plan, my injector pump module took a dump and had to be replaced. Long story short, he replaced it with a OEM in the OEM location, I did inquire with having it externally mounted but the mechanic stated it was to costly as he refused to look at the vendors I recommended and he had me over the barrel as I am not comfortable enough to work on the 6.5 at that level yet.

After the module was replaced, I did experience some slight lag in pulling power with the ole fifth wheel, accompanied with a bluish haze that was more noticable if you look long in the rear view mirror rather than at the bumper, the SES did come on. I took it and had it plugged into a OBDII and found some minor error codes in a turbo sensor, one point of interest, we ascertained through the OBDII that my injector pump is at 10 deg of advance, he states it should be around 3 deg... Is this healthy? he reset the codes and advised to run diesel service through it every other tank as he believes my injectors may be getting worn out. The SES will come on and stay on for a day when the truck hits a hill at 55+ and the pedal goes to the floor, which is usually accompanied by a considerable amount of black smoke, but once the hill is topped the smoke goes away and the guage goes off by the next day...

Back to the guages, I installed them based on the tech tips at Kennedy, and took it around the block empty and loaded with the fifth wheel. At 55 MPH w/rv I got an average 6-9 psi of boost and a EGT of 700-900F (outside air temp is 55 deg F on level ground). When I kicked it up to 70MPH and engaged the ole A/C she rode the 1200 F mark on the EGT so it appears no 70MPH anymore.

Also noted that w/ the RV I floored it from a dead stop, i got 12-13PSI boost and watched the EGT touch the red line between 1250-1300 F. Im impressed with the very quick response of both guages when driving.

Anyways, I have not purchased any new "tweaks" yet or any manuals yet (im saving for them) so forgive me on the questions, Is the truck running within acceptable parameters? or should I be aware of certain conditions to look for wen reading the guages other than the obvious that running in the RED is bad.

Also, i think the next add on would be a intercooler, I base this on my reading here, that the cooler will affect the EGT in the long run... Well I look forward to everyone's input.

[Shikaroka]

I am no expert on pump timing, but it sounds like they did not get it timed quite right after putting the new module on.
Also, have you every replaced the injectors? Most people recommend replacing them around 100k. I recently replaced mine and it made a big difference.

[JohnC]

How much boost are you seeing when the black smoke is blowing and the SES light is on? From your description, it sounds like you have a boost problem. Something may have been distrubed during the PMD transplant.

[KTM Mike]

rtphillips

I am in a similar boat as you - same state even...Northern Michigan. (my wife says I am actually in the State of Confusion though) My 96 K2500 does OK towing a 8,000 lb (empty) trailer we recently bought - deals with hills OK, though some do drag it down. When we bought the trailer, I to had the impression my truck was rated at 10,000 lbs - but like yours, it is only 8,000 lbs. If I cross a line somewhere between 8,000 and 10,500 lbs - totally different ball game. Absolutely does not like hills - even the stuff we have here in Michigan. My truck is not showing any issues like black smoke, hard starting etc. so it seems I am OK in that regard at least.

I to have been listening in here for a while and learning - my conclusions so far - these guys really do seem to know their stuff! (waaay more than I do!)

My planned on mods are 1) Exhaust 2) Gauges 3) Reflashed ECM. 4) cooling mods - Intercooler not on the list due to cost. I do need to get doing on injectors though with the mileage as it is on the truck. With that done, I am hoping towing loaded will be much better. (it should be)

To this point, I have not done anything yet as towing season is quickly drawing to an end. Fact is, I really do need a crew cab so dont want to dump in to much money then end up selling it to get a crew cab. So I need to get by cheap. Keep us posted on how it goes - I hope to learn from your experience!

[ak46champ]

I bought JK's Exhaust boost controller and set Injection pump per JK's reccomendation. I have a
1Ton CC SRW. I left PA GCVW of 19000lbs including a trailer weight of 9500lbs 32' V nose enclosed snowmachine trailer (Weighed at scales). I had absolutly no problems pulling it. I was able to climb hills in cruise control and maintain 65-70, Even in the hills in the Yukon Territory headed back to Alaska I was able to maintain 65mph. I still had plenty of power, I limited myself to 855 egt, sensor is installed in the downpipe. I got as high as 18psi boost. My average milage was 9mpg. Its been almost a year since the trip and the truck runs great. I let a ford friend barrow it to haul wood and he was very impressed. He he towed a 10K lb trailer full of wood. I installed a X-monitor Piller mount with tranny gauge. I highly!!! reccomend JK's products and support. My next upgrade is his intercooler.

[rtphillips370]

As mentioned, the day after I picked the truck up from having the module replaced, I hooked my RV to it and took it for a run and that's when I noticed the slight blue haze in the far distance and a slight to mild loss on power under load.

The SES lamp came on when I accelerated from a dead stop under load. When I took it back to the mechanic that replaced the pump module about this problem, he found that the error code was due to a sensor in the turbo system, I cant recall the name of the sensor, but he described it as the equivelent of a MAP sensor that is associated with the turbocharger and is a relatively cheap to replace and all he did at the time was reset the lamp.

After doing the reading here, I did inquire about the vacum, and I was advised that it is very good and not a factor. I then asked about the pump timing based on items I have read here, and that is when the mechanic noticed when using his computer, found that the injector pump had been set to approximately 10 deg of advance and that the only way that could be, is somone physically moving it as there is no way to do so via a computer, and that he did not move the pump position when he serviced the module. The mechanic states that it should be around 3-3.5 deg of advance. I dont know either way as I do not have the books or experience with diesels yet. I can only guess that advance on the pump is similar to that of a distributor on a gas engine, Some advance is good but to much is bad, is this true?

The mechanic did state that at the 149k+ miles that most likely the loss in power may be the need for new injectors. Initially when the truck died, he was suspecting it to be the injector pump itself based on that a sensor within the pump goes bad over time and the only way to fix it is to replace the pump however, after nearly a week of diagnosis, he determined most likely it to be the pump module which was replaced.

As mentioned I suggested the external mount variant however, the shop i had to take it to, only purchases parts from specific locations and would not look at any of the locations I recommended and with the truck out of commission and 30 miles away from home (in the town where it broke down) i had no choice but go with economics and have it repaired there.

However, if it was the pump itself, it was planned to have the injectors replaced at the same time and that was quoted with labor to be in the neighborhood of $3300-$3500 out the door and they would have used OEM parts.

To date, the truck appears to runs ok, but at times I swear I can feel it skip a beat once in a great while, I dont know if im paranoid or a lingering problem. I did add "diesel service' to the fuel that is suppose to be very good at cleaning injectors and once in a while when it is idling, hear it surge once in a while for a moment, I figure that it is the cleaner doing its magic.

Other than the loss of the converter and the addition of KD guages, the truck is stock with 149K miles. So far when driving without a load, the boost only registers when accelerating, once at a cruise speed, there is barely any boost, and EGT is running an avg of 600F. When empty and floor it from a dead stop, she will hit 12 PSI boost and drops as the truck accelerates then once it changes gears goes back up till rpm comes up, the EGT will hit high, around 900-1100F, with mild trace of dark smoke.

Now with the below listed RV, in 55deg F outside temp, w/o air condition on, it runs approx 6-9 PSI boost and 600-900F EGT on level ground at 55 MPH. when I kicked it up to 70MPH with the A/C turned on the EGT held level near 1200F EGT and the boost on the upper end of 9-10 PSI. The one time i have towed the RV with the guages, I stompped on it once, and got some dark smoke and no SES light and when doing so, the EGT hit near 1200+F EGT and 12 or so PSI boost until it got up to cruise and then it settled down. This week, ill take it out again with the trailer and subject it to a series of scnerios and record the egt and psi and let you all know.

One question, I see that OBDII scanners are becoming more affordable, is it possible to use them to adjust computer settings? what im getting at, is using one myself so I can replace the injector pump myself etc without having to pay a garage the big dollars, seems the biggest hurtle to working on this myself aside from getting the manuals, is not having the computer tools.

[rtphillips370]

As mentioned I took the ole girl for a ride with the rv on the back this morning. To preferace the numbers, the weather was clear and sunny at approximately 70 deg F. Readings are from the KD guage kit for pre turbo EGT.


Regular acceleration (approx 2000rpm) to 55 MPH:
with A/C on: 6PSI boost / 1100 deg F EGT
w/o A/C on: 6PSI / 900 deg F

Highway Cruise:

@60 MPH (level ground):

w/ A/C: 6 PSI / 1000deg F
w/o A/C: 4PSI / 850deg F

@ 70 MPH (level ground):

with A/C: 4-6 PSI / 1250deg F
w/o A/C: did not test

Then Last test is from dead stop floored max power accel to 55 MPH:
with A/C: 8-12 PSI / 1250-1300+ deg F
w/o A/C: approx the same result...

both instances averaged a sustained rpm of 2500 to 2900 rpm. So its apparent that ill have to work on the down pipe, intercooler aspects for modification and quite possibly replace the injectors, as they are to my knowledge original equipment from 1999. During this round of tests the SES did not come on nor did i witness any unusual smoke.

Are these numbers about average for the 6.5? I am kind of shocked at the difference of 10 MPH on the highway and the A/C turned and am glad that I have not driven it at this load settings on a regular basis.

So I think my next stage of mods would be new injectors due to age, new down pipe, intercooler... I have been looking at injectors at various websites presented at this website and am curious about the difference between the OEM style injectors and those labeled for marine use... are the marine version usable on the street? any input and advice will be appreciated.