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Lower engine-rpm driveline 'vibration' or more accurately, engine shudder, is acceptable overhead with a Diesel engine - not so noticeable in an 8-cylinder engine, it is more evident in a 6-cyl, and very pronounced in a 4-cyl due to the large angles between power-stroke thrust events: 8cyl = 90* for 4 power thrusts per rev, 6cyl = 120* for 3 per, 4-cyl = 180deg for only 2 thrusts per 360* crankshaft revolution - an automatic trans hides the rotational violence fairly well with the fluid coupling and by keeping the rpms up where the strokes are better averaged per unit of time - would be very noticeable in a clutched manual transmission drivetrain, where the driver may be remiss in shifting to a lower gear to get engine rpms up - me, within self-imposed limits, I enjoy that shudder in my big Dodge\Cummins rig, as indication of the tremendous torque output at low rpm - the VM Motori 2.8L was given twin balance shafts to help hide that (so as to appeal to the girly-man segment), and the TCM won't let the 545RFE stay hooked-up at lower rpms, but it's there, and I enjoy the occasional event when things work together righteously and the mild shudder on acceleration can be felt - 'course, I do have the non-worrisome Suncoast TCC, and maybe the day will come when that 545RFE bad boy can be locked-up in 5th at 30mph for better fuel economy - on that event, it would be a pleasure to downshift to 4th to reduce the shudder somewhat, while still in TCC lockup
Far as determining vibration\shudder source, if vehicle vibrates in 5th but not in 4th, or 5th and 4th but not in 3rd at same mph, then it's engine, with possible probability of oem TCC - if it continues to vibrate in any lower gear, then it's drivetrain, such as u-joints, rubber eng\trans isolator mounts, or rotating component balance, even tires\wheels\rotors, including loose lugnuts - can also be simple as exhaust hanger deterioration, since the KJ has no separate rubber-isolated frame to hang that component assembly from - that wierd-looking chinese finger-torture device in the exhaust pipe adjacent the transmission was designed to reduce engine shudder into the KJ's short-wheelbase exhaust system - remove it during exhaust system 'upgrade', and yer on yer own..............
_________________ '05 CRD Limited Pricol EGT, Boost GDE Hot '11; EDGE Trail switched SEGR; Provent; Magnaflow; Suncoast T\C, Transgo Tow'n'Go switch; Cummins LP module, Fleetguard filter, Filterminder 2.5" Daystar f, OME r; Ranchos; K80767's, Al's lifted uppers Rubicons, 2.55 Goodyears Four in a row really makes it go
Last edited by gmctd on Thu Dec 18, 2008 6:26 pm, edited 2 times in total.
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