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i need a little input on this one...


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hey everyone. this problem is a little out of my league and i was wondering if anybody could help me diagnose this problem. i have a 1990 legacy wagon with an automatic transmission. this morning i noticed when i dropped my car into 3 out of D to help slow it down, the car began to shake as if i were driving over speed bumps. i tried it again at a lower speed, and it didn't happen. it seems to only happen when i am doing about 50 mph or faster, and only when i put it in 3. 2 and 1 don't do it. does this problem sound familiar to anyone?

 

thanks in advance!

bnb

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Originally posted by intrigueing

Automatic? :eek: My guess is that you dropped it into a lower gear at too high of RPM'S, and were bouncing off the rev limiter. Do yourself a favor and don't downshift at such a high speed.

 

No. Third gear in the Auto should be fine WAY beyond 50. Hitting the rev limiter is not the problem. I have very little experiance with automatics but I'd guess it isn't actually the trans. Check all the motor and trans mounts for excess play.

 

Also, do you feel the vibration in the steering wheel at all like you would if the rotors were warped?

 

Keith

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I was taught that brakes are a lot cheaper to replace than a transmission although I admit using the engine as a brake on long down hills. I can't remember for sure, but I assume I down shifted to 3 at highway speeds with no ill effect.

 

If you've been doing this since routinely since 1990, I have new respect for the 4EAT. Like intriguing says don't downshift at high rpms.

 

Someone more knowledgeable than I can correct me, but you may also have some half shaft wear that shows up when you reverse the force on the driven components.

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now that you mention it...i can feel it a little bit through the steering wheel. the vibrating is not quite as bad in the steering as if the rotors were the problem. it's quite strange because the entire car shakes as if i had just gone over some sizeable speed bumbs. it is not a violent shaking though...they are more evenly spaced apart rather than just a mess of shaking.

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I had a similar problem though with a Toyota Camry; around 50, horrible shaking; slip it out of gear, shaking stopped; get on the gas again, more shaking. Turned out to be a rear wheel bearing needed replacing and a tire that was seriously out of round. I suspected the tranny at first, then motor mounts, but the bearing and tire took care of the problem.

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On the FWD autos, 3rd gear is good to 120 mph.....so you're good there ;)

 

I downshift into the third to slow down.....some may say it will prematurely wear the tranny....it may....I don't care....prefer the control.

 

As for your problem. Is it intermittant, or pretty consistant now? I had a weird vibration under decel...went away. I'm pretty sure it was cv axles. After replacing axles, I have not had any reoccurances, also, the car doesn't have a vibration it had before at higher speeds.

 

Other thing to look at is your trans mounts, and possibly motor mounts.

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