Hey guys I really need help diagnosing whatever the hell is going on with my truck.
It's a 91 short bed 1/2 ton 4x4 truck.
I have a 300hp crate 360 magnum in it, I have a non lock up A-518 trans in it.
I have a very strabge vibration issue going on, in every gear I get a vibration that comes on at about 2500rpm and it's at it's worst at 2500-2800 rpm then it some what smooths out if i step on it a little more, but it's still there, at higher rpm it just seems like it takes longer to circulate if that makes sense.
This vibration at 2500 rpm is like a quick womp womp womp womp type vibration, I can feel it in the gas pedal and in the steering wheel.
For the longest time I thought it was drivetrain related, but I'm realizing that isn't the case because of how it's rpm sensitive and speed sensitive.
It still vibrates the same even in park or nuetral.
Transmission was re-built a few years ago and the dumb asses at the shop put the wrong converter on it, they put an la 360 converter on it and I caught that fairly quick.
They then put the correct converter on and I thought all was well there, trans shifts fine, no leaks anywhere, I don't see any abnormal amount of wobbling at the converter and flex plate while idling or while holding it at 2500 rpm.
I don't hear any strange noises coming from the transmission area and converter area.
I'm at a loss with what's causing this.
Brand new alternator and ps pump and brackets, new belts, I've removed the belts and the vibration is still there, new radiator fan, no fan clutch, I don't see any strange wobbling at the harmonic balancer and it is the original
Balancer that came with the engine from mopar.
I'm about ready to pull my hair out over this vibration and I don't know where to start.
I was thinking start at ignition since that's easy and cheap, I tested my ignition coil which is a crane cams lx91 e-core style coil, the numbers are .07 for primary resistance and 4800k for secondary resistance.
The ignition is brand new, crane cams hi-6 cd ignition, rev limiter is set to 6200 rpm.
Distributor is a brand new firecore 50, timing is 16 initial and 32 total.
I'm out of ideas and need some advice or some strategy to pin point whatever this is.
Oil pressure on engine is good, don't hear any strange knocking sounds or anything like that.
The last warm compression test I did each cylinder was at 150 psi, that was done while engine was at operating temp and last time i did it was a couple years ago.
I can perform another one if need be.
Please help.