TOWING AND RPMS

Finfever · January 19, 2004

Hi everyone,

Truck is an 03 ecsb w/ 4.8 and 3.42 gears. Truck has trans cooler installed. Tows my 17 foot Boston Whaler just fine. This summer Im helping a friend out by towing his 4000 lbs. boat 600 miles over the Grapevine. Steep long grades, hot as all heck. The killer of many cars and trucks. I will not tow in overdrive. Heres the gueston.

I know that in some parts of the Grapevine I will be down in second gear, speeds will be 55 - 60, and the RPMS will be 3500- 4000. The motor sounds very healthy and strong, is this hurting anything. Can the motor spin these kind of RPMS for a long period of time? What would be the max RPMS you would take it to such as passing trucks.

THANKS IN ADVANCE

MARK

robsawatsky · January 19, 2004

Well, more RPM = more wear. But, as for actual, immediate, short-term harm; as long as it isn't overheating coolant, engine oil or transmission fluid you should be OK.

I personally like to keep things at less than 3000 RPM for continuous driving but on hills 3500 - 4000 is often unavoidable if you want to maintain any kind of speed. I don't like going over 4000 unless I'm accelerating into traffic or for short passing bursts. Mostly because of noise and the fact that it will be sucking gas like crazy.

You will get many opinions on this but mostly it is a trade-off between speed and wear/fuel-economy so long as you aren't overheating anything.

Shaners · January 19, 2004

There may be some very minor wear issues, but as long as Temps are OK then I wouldn't worry about them. You will be in the "powerband" and the truck should run better and fluids will circulate faster.

Remember the vehicles years ago (before OD transmissions)? They were turning high RPM's all the time. It never seemed to hurt them at all!!!

My truck with 4.10's turns much higher RPM's then yours will with the 3.42's. I tow in "3" and don't worry about it at all.

QUIKAG · January 19, 2004

These trucks and engines in particular are tough. I wouldn't worry about a 4000lb load. These motors are designed to spin. My 5.7L LS1 in my Corvette (of which the 4.8, 5.3, and 6.0L motors are based) is very happy in high rpms when I'm roadracing it. I keep it above 4000 rpm and close to 6000rpm for 30 minute sessions at full throttle. I've run over 50 sessions like this with zero mechanical problems. Keep track of fluids and operating temperatures and you'll be fine.

JayMan · January 19, 2004

My truck is a special order, check my signature to see how it's equipped.

I routinely tow 7,200 lbs no problem, sometimes 9,200 lbs. Even empty, at slow highway speeds of 50-60 MPH, I leave the selector in "3" which results in 2,500-2,700 RPM.

I do this as the motor seems to have a "sweet spot" at this RPM. Empty fuel economy in summer 20 MPG average. I use Tow/Haul when driving empty in town, and use Tow/Haul all the time when loaded/towing. Almost 40,000 miles and zero problems.

Shaners must be an Old Coot like me! Yeah, those older SB and BB Chevy's hooked up to 4 speed sticks or TH400's also lasted a long time, and at highway speeds they were SCREAMING.

Some folks are Shocked I would drive in "3" instead of "OD." Unless the motor is constantly zinging over 3,000 RPM, what's the problem?? About the only high-wear item at high RPM is the camshaft, and the Vortec motors use Roller Lifters.

Roller Lifters provide dramatic reductions in friction and wear, which is why most large commercial diesel motors started using them years ago. Although the Vortec has needle bearings in the rockers, they still have a flat (Fulcrum) tip. Wish GM would have sprung for genuine Roller Rockers while they were at it.

If you're worried, look into what kind of oil you use. For many reasons I won't get into here, I prefer all synthetics. It's not so much how often you service the truck, but when you do the FIRST service interval (Shorter the better).

I did my first service at 600 miles, putting synthetics in everything but the motor. At 1,200 miles, after some towing, I changed the rear oil again and at that time switched to Mobil 1 for the motor.

Remember for the rear axle that the Helm shop manual recommends another rear axle fluid change within 600 miles of towing for the first time. You will generate more wear particles due to the R&P "wearing in" more uniformly under load.

intruder217 · January 20, 2004

Your engine has a broad flat torque curve that is just under 4000 rpm. Seems you'll be running in its sweet spot. Like the others said I'd be extra diligent on fluid changes if you tow alot.

Finfever · January 20, 2004

Thanks for all the moral support!

The oil was changed at 500, 1500, and at 3000 was switched to Mobil 1 10-30. Rear end was done at 5000. I havent done the trans yet but will get on it.

Truck has 10,000 miles on it and is smooth, quiet and powerful. Im very satified with it and would buy another in a HeartBeat. Thanks again for the replies.

Mark