It shudders hard (can feel it through the cabin and the steering wheel goes back and forth a fair amount) at highway speed, but only when throttle is applied. If the foot comes off the gas, the shudder stops immediately. It also shudders less if maintaining speed (throttle applied lightly) and more if accelerating. Does not noticeably shudder at lower speeds, like below 40mph. Shudders quite unnervingly hard at 50-70 mph. Like, I'm afraid something's about to fall apart. I'm not really sure what to check, other than wheel bearings. What else should I check? This is a problem with my GF's 98 Forester 2.5L 4eat. It only started happening after we had towed a heavy trailer 100 miles with it. I ran it mostly in 3rd, but sometimes also in D. It was running pretty hot at first, so I kicked the interior heat on and after that it stayed at the normal point. It didn't shudder or do anything weird while pulling the trailer, only the next day when my GF drove it to work.
Get underneath it and look @ the driveshaft center hanger bearing. If its loose or the bushing is gone it will make a great shake. There is a fuse block on the passenger side shock tower with FWD printed on it, pop a 10 amp fuse in it, (its going to be FWD) see if the problem goes away.
Will do. I went for a highway ride with her after we were there on Fri, and its a lot worse than I was expecting. :eek3:
Negative on the driveshaft. Unless the acceptable tolerance is surprisingly small, cause it seems pretty solid under there. Still gotta try the AWD fuse.
wheel weight fell off? I know I am probably stating the obvious which you may have already checked. Doubt this would cause drastic shuttering but not happening at low speeds means it is centrifugal force related.
I didn't check, because the fact that it goes away as soon as the foot comes off the gas pedal rules that out. That's what has me confused. What would wobble the whole vehicle hard under acceleration, but not when coasting? Has to be something that spins (and spins faster as vehicle speed increases - vehicle speed, not rpm) only when throttle is being applied.
Interesting. I will check it, but it is as smooth as butter up to 40-50 mph. It really goes from ho-hum to holy **** quite quickly.
Inserting the fuse in the FWD location made no difference - it still shudders hard when it gets up around 50mph.
That would lead me to believe its in the rear wheels, time to take them somewhere to get balanced, I had an issue like this when I 1st got my impreza, it was out of balance rear wheels/tires.
Certainly cheap enough to check, and I told her to try to do that this afternoon. But, it doesn't pass the common sense test. The shudder really does go completely away as soon as you let off the gas. If the wheel balance was off, it would shudder the same regardless of whether one was accelerating or coasting. Right? One thing I should maybe try, is popping it into neutral on the highway and see if it still shudders (guessing it won't). I'd tell the GF to try, but who knows, she might hit R. :ugh:
not nessecarly.. Try the car going at 70 and then in neutral. also try revving it at that speed. if it does come when reved but not when rolling at 70 then id say engine mount or engine related..
Engine Misfire under load. At those speeds the torque converter clutch is probably locked and putting more load on the engine and putting more stress on a weak ignition system. Is Check Engine Light on/blinking? Front Axle Shaft's - mainly the inner joints. Torn CV boots?
Really doesn't feel like that. It doesn't lose power. Just shakes the piss out of the car. No check engine light. No codes when checked with a reader. I couldn't quite see the inner (closer to tranny) joints, but I'll be all the way under it this weekend and check. Outer joints on front and both on rear look actually very good, much much better than I expected given the age of the car, nearly new looking. Is it possible for a joint on the axle shafts to fail without any external signs like a torn boot? I also wonder what parts would be stressed from towing a load, since that's when the problem appeared. Obviously the tranny itself was worked pretty hard, but beyond that I'm having a tough time thinking what else. Unless its just coincidence that it appeared after towing.
A '98 Forester does not have the same capability of reading misfires that any of the newer cars do. It even still uses the older trigger pattern on the crank and cam triggers.
Finally got all the way up under her today (GF and I have opposing work schedules). The inner boot on the front driver's side axle shaft is torn wide open.
