1st Tow - Not Sure

[Tudge]

Just got back yesterday from my first camping trip - I wasnt sure what to expect since this is my first diesel and first fifth wheel.
Using tow haul mode - I was able to maintain 80mph with 11,000lb fifth wheel on flat ground (approx. 2400 RPM) but whenever heading up any type of incline it would downshift and hold at (3100-3200 RPM) and take a long time to shift back into 5th (and if the fan clutch would engage during these times in 4th gear it was very loud and a noticable decrease in power was observed)
I guess what I am asking is this normal??? Eventually I took it out of tow/haul mode once I was in fifth gear - it still downshifted on the hills but was much quicker to upshift back to fifth.
My wife said the problem was that I was driving way too fast - but I dont buy that. Anyhow any suggestions or ideas would be appreciated.

[tmg115]

your wife is right. when you hit a hill going that fast the tranny sinces that you are loosing speed fast and shifts down. this is normal. it is worse if you are on cruise thow. and tow haul mode will make it shift down even faster.

[ 05-28-2002: Message edited by: tmg115 ]</p>

[TLA]

I have made a number of trips at about 23,000# (incluiding to/from Parker over the weekend), and my results are the same as yours. One thing I have noticed is that if I am in cruise, see a hill, and mash the accel pedal to anticipate it, I get no response, and the EGT does not increase. I have to wonder if the MAF sensor sees no airflow increase, and prevents the addition of additional fuel - no fuel, no heat, no boost. Once you get the downshift, everythings is OK. I just received my Juice from John Kennedy, and I think it will make a real difference. I wonder if those of us who operate at high altitude have more of this.
Anyway, I think it at least typical, if not normal.

[Kennedy]

TLA hit the nail on the head! Those who have read my performance primer have seen my statements that the FIRST key in diesel performance (especially MAF sensor equipped trucks is air flow!

The ECM will only give so much fuel as a "power enrichment" which follows a preset curve. Now add a power box (preferrably pulse width type in this case) and the amount of additional fuel is increased. This is immediately evidenced by the puff of black that the Juice/Amp emit during the brief instance of turbo lag.

[LarryM]

Help me out with this air flow concept.

I punched lotsa holes in my air box and put a Amsoil filter in. Saw no difference in downshift performance or MPG.

I have been watching the exhaust mod threads and have not noticed any one commenting about reduced downshifting and/or significant MPG gains. Did I miss sometthing?

Assuming air box and exhaust mods actually do improve air flow, should you not see an improvement in MPG and power (as evidenced by less downshifting) even in a stock engine?

[midwestdmax29]

I've got a 4" exhaust on my truck and it definitely has more punch on the low end with my 5th wheel (@13,000 lbs) than stock. I'm not sure if it has any advantage in the hammer lane, but it sure sounds cool when you blow by someone. I too have seen the downshift issue, but I've found that when bucking a headwind, or on a steep grade, just drive a bit slower and it'll be fine. I've run 65 bucking a 40 mph headwind and it just wanted to stay in 4th gear. In situations like this, I just try to run around 2200-2400 rpm, and it seems happy even if it won't hold 5th gear. I have yet to see anything stock that will keep up this truck at or above full gross, so I don't complain.

[Kennedy]

Punching lotsa holes in the airbox can go the wrong way too, by letting you breath hot, underhood air. The only additional cutting I did was a forward facing triangle below the filter. Any other holes were small drain holes in the floor.

[LarryM]

I have a few small holes in the bottom for water. All the rest are in the forward side. I saw no difference in performance between 100

[GBurton]

Tudge

"I wasnt sure what to expect since this is my first diesel and first fifth wheel."

"My wife said the problem was that I was driving way too fast "

"I was able to maintain 80mph with 11,000lb fifth wheel on flat ground."

You are very lucky, 80mph with your first 5th wheel trailer. I suggest that you listen to your wife before you kill yourself and who knows how many other people. Do you have any idea how long it will take to stop a 6 or 7k pound truck and 11,000 pound trailer?

George

[bora]

I towed for the first time tonight. I picked up the trailer I bought. It is a 22ft enclosed race car trailer probably weighing around 3800 lbs empty.

This was my first towing experience ever, but you can definitely feel the trailer when you are towing. Others had told me you can't feel a trailer that is less than 6500 lbs, but I guess either my truck is weak on horsepower or I was too sensitive. The truck had no problem doing 55-65 mph of course, but it definitely did not feel like it was unloaded either.

BTW, the prodigy controller is amazing, nice smooth stops.

Parking the trailer into the storage slot was the most fun part of course. It took me a good 20 minutes getting in there, but I did not hurt the trailer or the truck :D

Please tell me it gets better parking.

Bora

[motovet]

Tudge, I will have to agree with Mr. Burton. SLOW DOWN man! I know these trucks feel pretty comfortable at speed while towing but most any unfortunate event at that speed would be disasterous. The previous comment was correct; the going is easy, stopping is not! The downshift you experiance is normal as I had the same towing 10,000#. I used to turn the tow/haul off also in order to get the tranny to shift back to 5th. One thing I learned however is that after more towing miles with the tow/haul on the tranny shifted much better. Would shift to O.D. sooner and not want to shift so often. It is LEARNING. The ultimate weapon to combat the downshifting is an Ez Amp/Juice. I did some extensive testing on a trip this weekend over some mountain passes and it WORKS. Never knew what anyone meant when they say they can't even feel the trailer behind them, obviously a figure of speech. Parking gets better.

[bora]

At least here in CA, the speed limit for autos with trailers is 55 mph, I figure a 6500 lb truck plus a 10000 lb trailer, I would probably be around 55-60 mph most of the time. I have kids and wife in the car when I am towing. Safety first!


Bora

[Brucec]

Tudge, Yes the downshift I also get, MAN 80MPH I have a 36 foot 5th wheel 13,600 gross and I never go over 65 and sometimes I think that's to fast.

[hoot]

Punching addt'l holes in the airbox. Isn't the latest GM airbox mod drawing in hot underhood air?

I towed a car on a dolley 250 miles the other day. I guess what, 4-5000 lbs. I'm running the Powershot propane setup. I ended up turning it off going up the steepest hills cause the boost gets up but the rpms don't. Since the PS2000 is boost controlled, it unloads lp big time and puts out the fire. Result.... noisy pinging and reduced power. Cure? More airflow? Higher rpms? or readjust the PS2000 for towing.

I know the instructions tell you to adjust it for towing which I failed to do so don't count this as a mark against the PS2000. I just wanted to present my experiences.

Towing this load with no lp my egt's always stayed under 1100. Mostly 900-1000. No matter how hard I ran it.

I turned the lp back on on the long highway runs. I love the crisp power with it on.

Shifting over all was excellent. Granted it wasn't a big load but I was very happy. No strange happenings. Be hitting 30,000 miles soon.

[ 05-30-2002: Message edited by: hoot ]</p>

[RWHP]

Tudge,

Ignore these old men on here, you almost got it right. 80mph is a good start but these truck like 85 even better. Next time cruise at 85 and you will NOT downshift unless the hill is a very high grade.

You will also see much more downshifting and slowing down at lower speeds, just the way GM decided to program these trucks. Keep the speed at 80+ and you will be fine, you may also want to take it out of cruise on the heavy hills and modulate throtle with your foot to keep from downshifting.

[hoot]

Keep the speed 80+ and the red and blue lights start blinking.