truck torque

OT as I have an older work truck which I can use to pull me and my junk around fine. Problem is I bought a four door chevy with 6.0l gas to haul may family and small camper camping. All was fairly well even after we upgraded to a much larger camper. It was loaded, but I could hit the Interstate and run at a very good speed and it would not excessivly shift out of overdrive if I pushed it reasonably. The thing is, my muffler went bad and I replaced it with a Flowmaster. Ever since it sure seems like I lost any margin I had and it drops out of overdrive on grades I use to think I could pull in OD. In all fairness, it could be my imagination and or the fact that the recent trips have been longer and we have loaded everything we own including the kitchen sink.

What do you think, could I have really lost noticeable low/midrange torque by switching to a low back pressure muffler designed to increased horsepower? Also considering 410 rear versus 373, thoughts here?

saw it happen before on a friends car I would go back to the orig. muffler

I was told by a transmission mechanic that it's not a good idea to pull a trailer in overdrive. The are some small planetary gears in the transmission that don't stand up it. The extra you pay for decreased fuel mileage is nothing compared to a transmission job.

Did you put the tow/haul switch in haul? This changes the shift points in the transmission.

You have to remeber there is no 'free' lunch. All actions have an opposing reaction. Etc, etc.

That said, you will lose something somewhere IF you are getting more total power (presumably only at high revs).

Maybe also you have been inflating your tyres to 0.1 to 0.2 bar less than previous (perhaps the airline where you check the pressure has been 'adjusted/changed)?

Maybe you have changed tyres on the drive wheels to some which are slightly taller in section or higher rolling resistance?

Have you changed grade of gas, as this can alter things? Even the engine oil can have a slight effect.

It might be that things have just tipped the balance, including your gross vehicle weight, and that just makes it unable to keep up without shifting more often.

I think you need to keep an open mind when assessing, and pin-pointing, the reason if it has dropped in torque. Often things that you obviously changed are the main subject of attention and others just 'slip by'.

Just remember they get 7-800 HP out of a 3 1/2 litre engine for F1 but they wouldn't pull even a small 'van, at normal soad speeds, let alone a plough!!

Regards, RAB

stop towing in OD!!!!!

Push the "tow" button button. If it shifts up and down too much try dring 3-5 mph faster or 3-5 mph faster.
I re-programed the VCm on mine so it wouldn't drop into 2nd gear on moderate grades.
You are not going to ruin the overdrive on a 4l80 transmission.

I'm wondering if maybe the incorrect muffler was installed? Or maybe it was installed incorrectly?

I really don't think going to the 4.10 gears is a good idea for a highway cruiser. I have the 4.10s in my dually, and 60 to 65 mph is just about as fast as you want without making the engine scream. The truck is a lot more comfortable at 55 mph.

"upgraded to a much larger camper". Please do yourself and everyone else on the road and buy a 3/4 or 1 ton truck with a diesel engine to tow with. I see many different vehicles towing campers on the road and most of them are VERY overmatched with the camper they are towing. Most are just a few MPH away from a serious fishtail and a crash.

At the least, consider your family's safety and upgrade. Once you've done that you won't worry about being able to pull.

Hello matthewh.
Do the math and see if your fuel mileage has changed. Muffler may have been installed incorrectly. Do yourself and the trasmission a favor, DO NOT TOW ANYTHING ON OVERDRIVE!.
Pull down your viser( that is where FORD puts the warnig!) not to use overdrive while towing, as it may cause the transmission to kick down all the time!
The owners manual will say the same thing, DO NOT USE OVERDRIVE WHILE TOWING!
Guido.

Sorta the same thing happened to me yrs ago only instead of changing the muffler I put on a rebuilt carb (same size) and the next time we pulled the new camper the truck seemed to loose all its low end torque I was wondering if the carb had smaller jets or something till we were half way thru the weekend and I realized the wife had loaded about 800 lbs of extra junk in all that newly aquired "extra space" we had. Just something to think about.....OCG

I agree and think I am good. What I did not say is a started with a very small camper.

I have the base HD chevy truck. The combination is well within max trailer weight and GCWR (trailer marketed to be towed by standard 1/2 ton - that would be loaded to the max). Even though not duals, with the 3/4 heavy suspension and stock E load rated tires inflated properly at 80psi it is very solid to drive, definately not on the edge, no sway, no sweaty palms, handles/stops very well

Interesting enough, the diesel only adds 600 lbs to the GCWR. Performance though is a different story. Yes, I would like to have the Duramax. Overall, I am very pleased, perhaps surprised, at the performance of the base 6.0l gas (same base engine also used in the 3500 1 ton). I can go pleanty fast enough and then some not to be a traffic hazard.

Thanks for the safty concern.

I think I will. It will cost a hole lot less than this fancy muffler I bought.

tks

very good chance you are right. Think I am going back to stock muffler anyway. thanks

yes, incorrect muffler more or less. Low back pressure 2 chamber fairly noisy Flowmaster brand. Thought I would tolerate the sound for better performance. Their web site talks about increase horsepower and better millage. No doubt it may breath better at max rpm and increase hp. But that is not where I drive it. Think I will go back to stock.

You hit it dead on. Faster helps which is the main reason I am considering going to 410 rear. The RPMs are so low at 70 mph that if you let it spin on up, it get in a better zone.

I never have a problem dropping into second unless the grade is very steep.

I have a programmer, but have never considered changing the shift points as I know not what I am doing. Suggestions appreciated.

In your opinion, did going to low backpressure muffler hurt me on low RPM torque or is it my imaginatio?

most always use tow/haul when heavy loaded.

tks

I remember turning up the idle on a lot of old cars when they blew muffler and had no back pressure, because they would stall a lot and idle too slow. What does this mean? Maybe you need backpressure. Wonder if you disconnect batt for 5 minutes and reconnect will computer relearn according to lower backpressure. Don't cost nothing to try.