So my rig has had a vibration since I got it, and I still haven't been able to track it down. Here are the conditions. At first it was a narrow rpm band, about 2700-3000 rpm where it would happen, cruising. It sucks, because that is right where I am at when towing with the OD off down the freeway. It runs very smooth up until this point. When it happens, it's hard to tell where it's coming from specifically. It just rattles the whole truck really. I have checked all my u joints, and while I would like to replace them, I don't think they are the cause because it is rpm related, not speed. It seems worse under load, so if I put it in manual first and drive at that rpm, it's not as bad.
Does anybody have any ideas? The only thing I can think of is potential bad motor mounts, but I don't really know how to check that without replacement. The rpm band that it vibrates seems to have gotten larger, starting at maybe 2500 rpm and not really ever going away at high rpm like it used to. It seems to run right otherwise and has decent power, expect it also has a slight miss (I think it's a miss) at idle but it smooths out as soon as I start moving. I don't think it's related and am not worried about that one really, unless it turns out they are related.
If it helps, I know that this truck originally had a 5.9 and someone swapped in a 5.2. I have no clue why, and didn't know it when I bought it. They didn't don't a very good job, so it could be something uncommon that you wouldn't think of as a wear item or anything, or maybe the motor just wasn't aligned correctly.
Any ideas would be great. I want to keep it, but it makes me really uncomfortable towing with the vibration, and I seem to be towing lot with it and don't want something breaking on me
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I will check again to be accurate. Last time I checked I thought I could feel it, but it was hardly noticeable, to the point i wasn't sure if I was imagining it or not. I assumed because there was no load on the motor. Hopefully it will be more apparent since it's gotten worse
It could be motor mounts, or you may have even lost a weight on your flywheel. Also check your balancer, if the balancer looses its ability to absorb the torsional vibrations created by combustion forces you could be picking up pieces of your chranshaft off the ground.
I have recently discovered that the flexplate/torque converter (still haven't confirmed which one) is weighted on the 360 and not on the 318. I highly doubt the person who swapped motors realized this, and it could very well be my problem. My 5.2 is bolted to the wrong flex plate is what I'm thinking
The 5.9 is externally balanced where as the 5.2 is internally balanced. I can't remember how they balanced the 5.9 exactly, but I'm pretty sure it was balanced by the torque converter. If so, the 46re torque converter being installed will be your problem. If not, it may just be a matter or changing the flywheel? I can't remember what they used to balance the 5.9 so couldn't tell you for sure. If the vibration is rpm related, I can almost guarantee that the engine balance is your problem.
If you still wish to check the motor mounts tho, you can kinda check them this way by yourself. Lift the hood, start the truck, put it in drive, hold the brake hard and rev the motor, while revving it, watch to see how much the motor jumps. If you have a friend to help, get them to watch to see if the mounts jump to the safety catch. If they jump to the safety catch, they need replacing. You could also inspect the rubber for excessive cracking
__________________ My Daily Driver: 1993 Dakota LE 3.9L v6 Magnum, 42-RH 2WD (180 Degree Thermostat, V8 Throttle Body, Hughes Plenum Fix) My Project: 1981 Chevrolet 1500 5.0L (305ci) v8, Auto, 2WD Long Box Old Lady's Truck 2002 Durango SLT PLUS 4.7L Magnum, 545-RFE 4x4