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Mechanical Maintenance (Oil, Fluids, Break-In, Servicing) Everything related to the mechanical maintenance of the FR-S and BRZ


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Old 03-21-2018, 10:48 PM   #1
Fuergrissa
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bad driveline vibration when accelerating at low RPM

I recently replaced my throw-out bearing after the factory one had failed which involved removing the drive shaft and dropping the transmission. I replaced the trans oil at the same time.

After the work I am getting a severe vibration when accelerating at low RPM when the engine gets bogged. This is the only time the vibration is present but it is very severe. I know TOB's are a common job, has anyone encountered this before? Not excited to drop the trans again without knowing exactly what I'm looking for. I'm assuming something with the clutch or the DS carrier bearing but really don't know.

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Old 03-22-2018, 12:05 AM   #2
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Did you install an aftermarket lighweight flywheel/clutch kit?
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Old 03-22-2018, 12:14 AM   #3
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Chances are something is not torqued down properly.
Could be tranny mounts, drive shaft, who knows. It's one of those things where you just need to put a wrench and feel what's loose.
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Old 03-22-2018, 12:43 AM   #4
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Quote:
Originally Posted by Fuergrissa View Post
I recently replaced my throw-out bearing after the factory one had failed which involved removing the drive shaft and dropping the transmission. I replaced the trans oil at the same time.

After the work I am getting a severe vibration when accelerating at low RPM when the engine gets bogged. This is the only time the vibration is present but it is very severe. I know TOB's are a common job, has anyone encountered this before? Not excited to drop the trans again without knowing exactly what I'm looking for. I'm assuming something with the clutch or the DS carrier bearing but really don't know.

Thanks
Welcome to the group, there, Fuergrissa ..........

So, you didn't have this vibration before you replaced the TOB .. ??

Did you take off the pressure plate and or replace the clutch disk .. ??

Did you do the work or did someone else do the work .. ??

Come back.


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Old 03-23-2018, 08:27 PM   #5
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Originally Posted by EndlessAzure View Post
Did you install an aftermarket lighweight flywheel/clutch kit?
No, they were not removed

Quote:
Originally Posted by Mr.ac
Chances are something is not torqued down properly.
Could be tranny mounts, drive shaft, who knows. It's one of those things where you just need to put a wrench and feel what's loose.
You are probably right, this was my assumption

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Originally Posted by humfrz
Welcome to the group, there, Fuergrissa ..........

So, you didn't have this vibration before you replaced the TOB .. ??

Did you take off the pressure plate and or replace the clutch disk .. ??

Did you do the work or did someone else do the work .. ??
No, it wasn't present before. neither pressure plate nor clutch were removed, just pulled the trans off, replaced the TOB and retaining clips, greased the fork pivot (was squeaking), and reinstalled with new trans fluid.

I did the work.

I marked the DS alignment to the differential so it went back on the same way, but the front yoke may have gone into the transmission with a different orientation.

It may be a few weeks before I can put it back in the air and investigate, so I just wondered if anyone had some different ideas. I don't think it's a balance issue because it does not increase in intensity with RPM. and if it were a harmonic resonance it would occur at the same RPM during all operating conditions. The fact that it is only in a certain RPM and only a certain operating condition (under load) makes me think it is probably something mounted too rigidly or not rigidly enough. Checking all the bolts is probably to best way to figure it out, but if anyone has another idea I would love to hear it.

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Old 03-23-2018, 08:53 PM   #6
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I'll summon ol @Ultramaroon ...... one of out transmission experts, to see if he has any input.


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Old 03-23-2018, 09:19 PM   #7
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Quote:
Originally Posted by Fuergrissa View Post
No, they were not removed



You are probably right, this was my assumption



No, it wasn't present before. neither pressure plate nor clutch were removed, just pulled the trans off, replaced the TOB and retaining clips, greased the fork pivot (was squeaking), and reinstalled with new trans fluid.

I did the work.

I marked the DS alignment to the differential so it went back on the same way, but the front yoke may have gone into the transmission with a different orientation.

It may be a few weeks before I can put it back in the air and investigate, so I just wondered if anyone had some different ideas. I don't think it's a balance issue because it does not increase in intensity with RPM. and if it were a harmonic resonance it would occur at the same RPM during all operating conditions. The fact that it is only in a certain RPM and only a certain operating condition (under load) makes me think it is probably something mounted too rigidly or not rigidly enough. Checking all the bolts is probably to best way to figure it out, but if anyone has another idea I would love to hear it.

Thanks
Ah, gotcha.

I have a similar issue when I lug the engine between 1k and 2.2k as well as when I'm engine braking from 2.6k down to 2k.

However, I changed my clutch and flywheel plus added a transmission bushing.

I'll keep an eye on on this thread too.
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Old 03-23-2018, 10:07 PM   #8
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Do you hear it, feel it, or both?

How did you support the engine?
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Old 03-25-2018, 08:20 AM   #9
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Quote:
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Do you hear it, feel it, or both?

How did you support the engine?
For my part, a little bit of both.

I don't recall supporting the forward part of the engine during the process
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Old 03-25-2018, 10:19 AM   #10
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Dont assume its driveline. Low RPM vibrations are often an indication of an engine problem.
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Old 03-25-2018, 01:58 PM   #11
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For my part, a little bit of both.

I don't recall supporting the forward part of the engine during the process
The engine and transmission together balance on the engine mounts. When separated the engine will flop forward pretty hard. If you didn't support it, the exhaust pipe must have kept things in place. Perhaps a heat shield was bent then? Also, the engine bottom cover can make a hell of a racket if the screws back out. Once they've been removed, it seems like they don't like to stay tight. I use blue loctite on them.

Just a couple ideas. Try to record it for us. It might help.
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Old 03-26-2018, 11:00 AM   #12
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Quote:
Originally Posted by Ultramaroon View Post
The engine and transmission together balance on the engine mounts. When separated the engine will flop forward pretty hard. If you didn't support it, the exhaust pipe must have kept things in place. Perhaps a heat shield was bent then? Also, the engine bottom cover can make a hell of a racket if the screws back out. Once they've been removed, it seems like they don't like to stay tight. I use blue loctite on them.

Just a couple ideas. Try to record it for us. It might help.
I'll try to get a recording this week.

I didn't remove the front aluminum undertray/shield so the engine may have had some minimal support during tbe process.
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Old 03-26-2018, 01:03 PM   #13
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When I did my TOB I didn't support the front on the way off and spent almost 2 hours trying to get it off the lower studs. It wasn't until I said fuck it and pushed the jack aside and man handled it (not a good idea) that it came off. Once it was finally off I realized how far forward the engine tips which explained my difficulty getting it off. I supported the engine before putting it back on and WOW what a difference. I jacked it up enough and get it on the lower studs and then a single gentle push of the jack and the thing went right on. I could kick myself in the ass for skipping the front engine support.

Anyways, I feel sorry for anyone who does that job without jacking the front of the engine.
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Old 03-26-2018, 01:17 PM   #14
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Anyways, I feel sorry for anyone who does that job without jacking the front of the engine.
After I get the back of the transmission separated, I wrap around the front of the engine and tie to the tower braces with a big fucking strap.
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