RPM's & towing
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Junior User
Joined: Apr 2003
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From: Coos Bay, Oregon
RPM's & towing
Hey all,
A lot of times while towing, I'll come across hills steep enough that I cannot run 4th gear. My question is, how hard can you safely run the 300? My truck, at 55mph in 3rd gear, turns 3600 RPM. Usually I'll back off somewhere between 45 and 50, simply because I don't feel comfortable spinning that many RPM. Am I just being paranoid? Is it safe to run it that hard for 3-5 mile stretches?
A lot of times while towing, I'll come across hills steep enough that I cannot run 4th gear. My question is, how hard can you safely run the 300? My truck, at 55mph in 3rd gear, turns 3600 RPM. Usually I'll back off somewhere between 45 and 50, simply because I don't feel comfortable spinning that many RPM. Am I just being paranoid? Is it safe to run it that hard for 3-5 mile stretches?
Elder User
Joined: Dec 2002
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From: Metro Detroit
With that info if you regear to 4.11's, 4th gear should be around 2500-2600 at 55mph. I'm assuming that in 4th right now it's around 2200-2300 rpms.
Last edited by Lectrocuted; Apr 8, 2004 at 04:12 AM.
Elder User
Joined: Aug 2003
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From: philly pa
Originally Posted by KAS300
Hey all,
A lot of times while towing, I'll come across hills steep enough that I cannot run 4th gear. My question is, how hard can you safely run the 300? My truck, at 55mph in 3rd gear, turns 3600 RPM. Usually I'll back off somewhere between 45 and 50, simply because I don't feel comfortable spinning that many RPM. Am I just being paranoid? Is it safe to run it that hard for 3-5 mile stretches?
A lot of times while towing, I'll come across hills steep enough that I cannot run 4th gear. My question is, how hard can you safely run the 300? My truck, at 55mph in 3rd gear, turns 3600 RPM. Usually I'll back off somewhere between 45 and 50, simply because I don't feel comfortable spinning that many RPM. Am I just being paranoid? Is it safe to run it that hard for 3-5 mile stretches?
you're loosing power at that high rpm. the 300 peaks its torque at about 2200 rpm's. 3500 is the peak horsepower, so it will go faster, but wont be able to pull as much. if you don't mind the slower accelerating keep the rpm's a little closer to 2200 rpm's.
the engine should be able to handle 3500 rpm's w/no problem.
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Elder User
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From: McChord AFB
while mud racing my 4.9L 4,000rpm isnt uncommon and i have had it blip up to 4,500rpm. Its still running strong, and for oil im running semi synthetic 10w30. As far as towing goes, i have found mine does its best at 1800-2500rpm. Im running 33" tires and 3.00 gears so that puts me right at 60-70mph and i have had no problem towing 4,000lbs.
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Post Fiend
Joined: Jan 2000
Posts: 5,860
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From: Metro Detroit (Redford)
I'd say the 300 is puttin down pretty good torque all the way from fast idle up to 3400 rpm. So by running higher rpms you are jacking up the horsepower which is needed to get the work done faster. Get yourself some high quality oil, maybe synthetic and not too thin, probably minimum 10w30, maybe 15w40. There used to be a company that used the 300 I6 in industrial applications like generators and their spec sheet said max sustained rpm, I think was 3400.
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Junior User
Joined: Apr 2003
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From: Coos Bay, Oregon
Thanks for the replies!
2200 RPM would mean driving around 50mph in 4th gear. Obviously thats not possible, otherwise I wouldn't have to shift to 3rd. If it would pull 4th I'd use 4th. Driving at around 30-35mph in 3rd equates to around 2200 RPM, but then whats the point? Doesn't matter to me if its fallen off the torque curve, as long as it can still accelerate and pull faster, I'll rev it out.
At 55mph in 4th, she's spinning about 2400 RPM. But then again, if I hit the base of a hill at 65mph in 4th, its turning about 2700 RPM, and it will still fall on its face, and I'll be in 3rd by the top of the hill. I think 4.10's would just prolong the inevitable for a few more hundred yards.
I think from now on, I'll try to curb my paranoia and let it rev a little more (and maybe keep a close eye on the heat guage
).
you're loosing power at that high rpm. the 300 peaks its torque at about 2200 rpm's. 3500 is the peak horsepower, so it will go faster, but wont be able to pull as much. if you don't mind the slower accelerating keep the rpm's a little closer to 2200 rpm's.
the engine should be able to handle 3500 rpm's w/no problem.
the engine should be able to handle 3500 rpm's w/no problem.
With that info if you regear to 4.11's, 4th gear should be around 2500-2600 at 55mph. I'm assuming that in 4th right now it's around 2200-2300 rpms.
I think from now on, I'll try to curb my paranoia and let it rev a little more (and maybe keep a close eye on the heat guage
).
Elder User
Joined: Dec 2002
Posts: 695
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From: Metro Detroit
Yeah. I got to thinking the same. My math was off a little. Pretty much at the limits of the old six. Need more power, Scotty. Keep your eyes on the gauges and your ears open. She's a tough old warhorse.
Hotshot
Joined: Oct 2002
Posts: 18,488
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From: The Big, Oregon
I ran (am still running) 10w40 Castrol. That is all this engine has seen the whole time I have had it.
At the time I did that, I was more concerned with doing 80+ than pulling a trailer. Although, on the way out here, I was turning about 3200 most of the time, six days straight. Everytime I got back on the highway, 5k was seen in first and second. I also did a few long pulls in second gear at 4k plus.
These engines are a lot more stout than they are given credit for, and if some breathing mods are made, they make decent power at the top end.
With a good balance job, and major intake and exhaust port and valve mods, I am looking at turning 7k out of my 300-6TT.
At the time I did that, I was more concerned with doing 80+ than pulling a trailer. Although, on the way out here, I was turning about 3200 most of the time, six days straight. Everytime I got back on the highway, 5k was seen in first and second. I also did a few long pulls in second gear at 4k plus.
These engines are a lot more stout than they are given credit for, and if some breathing mods are made, they make decent power at the top end.
With a good balance job, and major intake and exhaust port and valve mods, I am looking at turning 7k out of my 300-6TT.
Post Fiend
Joined: Jan 2000
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From: Metro Detroit (Redford)
Originally Posted by Ford_Six
I ran (am still running) 10w40 Castrol. That is all this engine has seen the whole time I have had it.
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