vibration/rumbling at certain rpms
 

i've recently been getting a light rumbling and vibration around 2200 rpm and then againa round 3500 rpm. i can feel it in the shifter and pedal and certain trim parts rattle a little.

other than vibrating, the engine delivers good, steady power. the vibrations happen with the clutch in or out, parked or moving. other than these two rpm ranges there are no toher vibrations.

engine has 10k on a rebuild and pulling perfect compression/vacuum. engine and transmission mounts are new oem.

i'm stumped and will be putting the car up on the lift tomorrow to see what things are looking like in mount-land. some ideas about what to look for would help.

do you experience vibration at 0 mph at those rpms? if your vibration is both speed and rpm related you may want to look at the driveshaft. after more than a decade the stock 2 piece driveshafts will loose strength at the u-joint and the car will vibrate at times, usually at a certain speed or rpm range (only when moving). if vibration only occurs when moving then the driveshaft is a potential culprit.

nope, this is not a driveshaft issue

i put it up and couldn't find anything wrong with the mounts. i also jiggled the engine and heard no slop. i'm really starting to get worried here... i hope this isn't internal.

i also put an ebay front downpipe on it to try and get rid of an exhaust noise i've been hearing near that area. it seems to have just made the noise different and slightly more obnoxious! i originally thought it was because i had a gutted cat up there, but now i have no idea!

ahhhh! it's definitely been a bad month for the 7...

i was thinking aboutthinking about the problem: since the vibration happens only at certain lower rpms it is not an internal balance issue... and it happens independent of the transmission...

it's either an accessory problem or fuel/ignition.

anybody know if fuel/ignition problems can cause vibrations without causing hesitation? could i be leaning out and detonating without running problems? it doesn't seem possible, but this is the only explanation i can think of.

i took off the transmission crossmember to see if the mounts were good, which they are.

i then put spacers on the stud that hangs down and goes through the middle of the crossmember to tighten it up between the plate and transmission. i have a bushing that i made in there right now, because the old one was dead.

apparently tightening up the stud made me able to hear every transmission noise very well. i had heard it all before, but not as loudly. there is a constant whirring noise, some oscillating gnawing noises, and all kinds of clunking! it sounds like complete shit since i tightened up that crossmember stud.

so, i guess the transmission is toast... but how would it cause vibrations just as badly in neutral with the clutch disengaged? and how could it run and shift fine with all that horrible noise? input shaft? the thing has almost 200k on it.

i'm so confused.... this car is kicking my ass at the absolute worst time! i hope it gets me to my poker game and back lol. we'll see!