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CLUNK during acceleration
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Old 07 Jun 2013, 02:59 PM   #1 (permalink)
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CLUNK during acceleration

I'm not a mechanic. This question will be written as a non-mechanic newbie -- I'll do my best

1993 Subaru Impreza sedan (automatic, 2-wheel drive "L" model, 1.8liter engine). During acceleration, big CLUNK ("ouch that hurts my neck") between automatic gear shifting.

Several years ago, when going from "stopped-at-a-stoplight" to full speed, I slowly depress the gas pedal. The car revvs and increases speed. When it automatically shifted to next gear there would be a BIG CLUNK (not a transmission noise) then as I would continue to revv ("revv" = hold pedal down to increase speed), there would be ANOTHER huge clunk as the car automatically went to the next gear.... and another clunk for the next gear. I know it sounds like all I do is revv my car, but the reason this is such a big issue for me is the place I work. I constantly have to run errands for an internet based textbook business (I work at a place where students sell textbooks and between processing books and keeping up w/ supplies, that's a lot of driving!)

ALL the mechanics said either I needed a new Tranny (I went and got one!), or a dumb-ass lame "Oh all subarus do that, they shift rough." One mechanic mentioned the TPS! So I bought a new throttle positioning sensor and VOILA! It worked!

It worked! But, only for the LAST few shifts (higher speeds). Now, no matter how hard I depress the gas pedal, it would shift SMOOTH AS BUTTER!!!!!!!!! So ALL THAT TIME, I just needed a NEW THROTTLE POSITIONING SENSOR!

What's the problem then? The problem is it did not help for the lower speeds. For example, being at a stoplight, accelerating to normal 35MPH city speeds. No matter how gingerly I apply the gas to accelerate, I'll get at least 2 clunks for both the lower automatic gear changes.

Any ideas?

Last edited by Shayna; 24 Jun 2013 at 01:14 PM.
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Old 07 Jun 2013, 06:51 PM   #2 (permalink)
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Re: CLUNK during acceleration

could the "clunks" be from the gearbox and it needs a oil change ?
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Old 07 Jun 2013, 09:44 PM   #3 (permalink)
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Re: CLUNK during acceleration

Quote:
Originally Posted by Technical_Bob View Post
could the "clunks" be from the gearbox and it needs a oil change ?
Technical_Bob, hi, I like your name -- it makes me think if anyone is going to help, it's going to be you! (LOL -- my name would be "NotTechnicalAtAll_Shayna" haha)

Anyway, no, all my oils are changed (everything else in my Subaru has been broken and fixed/replaced/restored -- everything from the shocks, axles, transmission,sway bars, differential housing,rear main seal, every thing).

In fact, the "symptom" plagued my car from the day I got it. For several years it clunked during ALL gear changes, but after I replaced the TPS, it only clunks during the lower/slower gears.

I'll try to "re-describe" (i.e. "articulate better") the symptoms. In my car, 10 minutes ago, here's what it did:

I'm at a stoplight, the light turns green. I step on the pedal. The car accelerates. 3 miles per hour, 5mph, 10mph, then around 15mph or so, time for a gear change.... CLUNK... my neck gets whiplashed, so I ease off the pedal because I know to eventually reach "cruising speed" of 35MPH, I got one more gear change coming up. Slowly my car continues to accelerate, 22MPH....25MPH....30MPH....here it comes.... here it comes.....CLUNK! AAAGH!!

Did I do a good job describing it?

Every mechanic I've been to just shakes their head. Like I've seen a UFO or something.

If anyone can help, I know it's someone like you with the word "Technical" in their name :-)

P.S. THIS IS IMPORTANT: When I say "clunk" I don't mean I just "hear a clunk." What I mean is the whole car jerks. The jerk (which snaps my neck) is accompanied by a clunking sound.

In other words, a pair of earplugs won't solve the problem...

Last edited by Shayna; 08 Jun 2013 at 12:23 AM.
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Old 08 Jun 2013, 06:39 AM   #4 (permalink)
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Re: CLUNK during acceleration

So there is no clink, it misses ? Like fuel cut at gear change
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Old 08 Jun 2013, 03:53 PM   #5 (permalink)
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Re: CLUNK during acceleration

There is a clunk sound and there is a huge jerk/lunging. Instead of a smooth transition from one gear to the next, the car clunkingly "snaps."

I hate to throw in a guess because I'm not a mechanic, and I don't want my "guess" to skew responses from actual mechanics, but if I were to guess, I would say the "transmission is loose" and "the transmission needs to be tightened" and "it needs to be tighter so the transmission doesn't slip" and "there's a big gap between the transmission gears."

BUT.... those are just "newbie guesses" that I know are NOT true, becuase I said all that to the tranny shop guy that said "Okay we will completely rebuild your transmission," and after a $2500 transmission rebuild (he said "it's perfect now") the car STILL did the clunk thing.

That's when I replaced the TPS. Replacing the throttle positioning sensor COMPLETELY CURED the clunk/lunging/jerk for the higher speeds (i.e. 40 to 65mph). But just driving around town (i.e. from stopped at a stoplight to 35mph city driving) I have to deal with the horrible clunk.


P.S. LOL -- this is fun -- I have both Bobs -- "technical" Bob and "bugeye" Bob both helping me. That's cool! (Unless they're the same Bob -- the 'technical' Bob now has bug-eyes after seeing my problem hahaha

Last edited by Shayna; 08 Jun 2013 at 03:55 PM.
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Old 08 Jun 2013, 06:30 PM   #6 (permalink)
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Re: CLUNK during acceleration

Jerky Gear Changes - General technical - UK Legacy Forums

seems common on auto Subaru`s
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Old 10 Jun 2013, 12:02 PM   #7 (permalink)
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Re: CLUNK during acceleration

Cool -- even in the UK there are subarus that clunk LOL.

So, any suggestions please? I've put a lot of time and effort into describing the issue, I would hope that is enough information to start seeing some suggestions.

Thank you!
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Old 24 Jun 2013, 01:18 PM   #8 (permalink)
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Re: CLUNK during acceleration

Hi, okay I'm almost ready to "give up" on finding a solution. I'll leave this thread with one thought: perhaps the problem is not in the actual transmission (the gears, belts, or whatever makes transmissions work haha), but perhaps in one of the many electronic sensors. Remember, the Throttle Positioning Sensor originally helped with the higher gears... maybe there is some sort of sensor that tells the engine to let off on the gas in the lower gears. This is "impossible" to do on my own.... if I really super-carefully "feather" the gas pedal during acceleration from a stopped position to full city driving speed (35MPH), I can almost avoid the jerk/clunk symptom.

thanks!
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Old 24 Jun 2013, 08:14 PM   #9 (permalink)
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Re: CLUNK during acceleration

have you had the codes read at all,any CEL light coming on??...could it be a bad earth or electrical short causing the issue?
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