vibration 1700-1900 rpm

[speedracer]

My truck has a resonance type vibration (not real bad, but noticable) which seems to come from the engine. It happens under heavy throttle(especially when pulling a trailer) between approximately 1700-1900 rpm. The truck has about 23k on it.



Is this abnormal? Is it hurting the motor? Do any of you guys have this noise? Should I be concerned?



Thanks for any input.

 

[JohnB]

Mine will growl and vibrate under hard pull at those lower rpm, but I also have a more ringing resonate sound mostly in 3rd and 4th gear coming from under the truck (not the gear-train above). Haven't been able to locate.

 

[Texas Diesel]

Me too, mine "vibrates" under load anytime RPM is <2000. I think that we are feeling the combustion impulses.

 

[GLASMITHS]

It would appear that you are lugging your engine (if you have a 24V). When pulling a trailer (mine) a 16500# Kountry Star, I never let the rpm drom below 2000, and upshift at 2600. If it gets below that it will vibe big time.



george

 

[Vaughn MacKenzie]

I never give mine more than 1/3 throttle under 2000rpm. . . if it vibrates you ARE lugging it! Like Glasmith says keep er above 2000 when accelerating fast or towing!! Very hard on driveline for sure

 

[GLASMITHS]

Thanks MAC. I learned a cheap lesson, before my transmission temp got installed. Went up a biiiig hill in OD, ok ok. Anyway the transmission was slipping so bad it barely got me into the campground. I just knew the next morning would be wreacker time. But it acted like nothing happened. The fluid looked ok, so off we went. So 45,000 miles later it is still popping.



The moral -- keep it out of OD and don't lug it especially pulling a heavy load. I have a GV and lots of stuff now----

 

[John Berger]

Keep it at 2000 or above. If you are below that, don't mash the pedal, do like Vaughn says and feather it until you get up to speed. If you are on a grade, downshift. I have the resonating sound as well. I think it's the exhaust, but don't know for sure.

 

[Steve M]

This thread caught my attention. My '95 auto did this only in 3rd or O/D with the TC locked up. Dodge put a drive shaft in with a vibration damper on it. problem solved. My '98 5spd did it and I had to keep the rpm above 2100 while pouring on the coal to keep the vibration noise tolerable. It resonated in the cab big time. My new 2001 auto has more torque and hp than either the '98 or '95 and it doesn't have a resonant vibration at any rpm. I notice looking back up the page that you're all driving standard trannies. Could it be that the standard trannies pick up the vibrations more? Even my old "94 Ford (only had it a year) with it's 5spd did it under load at about the same rpm. It was a 300 I6 gasser.

 

[Steve Campbell]

I agree that the RPM's need to be above 2000 when "pouring on the coal". I feel that the transmission/driveline parts are trying to move anyway they can to get out of the way of all that torque and thus the "vibration". Bruce Mallinson talks about this problem with the "large cars" when they build 855's up to 700-800Hp and 1800-2200ft/lbs of torque.

 

[speedracer]

Thanks for the responses.

I would think if it was lugging, the vibration would be more pronounced and would occur at all rpm below the point at which the engine is happy with the load, not just in the narrow band 17-1900. I'm not saying it isn't lugging, just wondering if there's another explantion. Also, those of you with timing boxes; does the timing advance feature exacerbate the problem?

 

[dodger22]

All:



I have a very harsh resonance at 2000 rpm in overdrive (about 72 mph) without any noticeable vibration. This is pulling a 10,000lb trailer. The truck is accelerating so I don't think I'm lugging it. I am able to "feather" the throttle past this and it's fine.



Would someone please comment whether this is lugging or something else?



Thanks

 

[Steve M]

It's not luggin at all. It's normal pulses from the motor resonating through the driveline. The damper on the drive shaft of my '95 automatic cured it on that truck. I would have liked to try one on my '98 5spd. It was way worse and very annoying. But it is normal pulses from the motor under load. Just not too good for the drive train and migraines if you're like me.