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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain.


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Old 05-15-2020, 04:07 PM   #15
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My point is that if you truly want to learn about the transmission, humility is your greatest asset. Do you want to learn about your transmission, or are you here to have your preconceptions validated? If it's the latter, I'll kindly excuse myself.
If you believe someone needs knowledge, then why did you offer ridicule instead of information.
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Old 05-15-2020, 04:11 PM   #16
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So back to the 1 -> 2 and 2 -> 1 change issues, this is also a function of the ratios and the engineering of the gearbox itself. All modern OEM gearboxes I've come across have 1st and 2nd sharing a shift fork. Same with 3rd and 4th, then 5th and 6th.

The info I had in this italicized space was all wrong because I didn't think through my logic and flipped a calculation super duper early which led to correct assumptions validated by incorrect data. Thanks to @Ultramaroon for reminding me torque multiplication is the output side, and rotational speed is the input side, hence why we get the wonderful money-shift. Per his later post:
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The lower the gear, the greater the mechanical disadvantage through which the syncro clutch must drive the input. The viscous drag of the gear oil is amplified in the lower gears, and the syncro clutches in this transmission are as compact as possible for a conventional gearbox. There's more to it. The layout of the gearbox with respect to what the 1-2 syncro clutches must drive also plays into the picture.
We can't do anything except be nicer and give more time, or be forceful and send the teeth mashing together. Eventually things loosen up doing it the second way.

Additionally, on downshifts a rev-match while the transmission is decoupled gains some benefits from friction. The selectors are all spun up a bit by the output shaft speed as you give the input shaft some extra RPMs. It's not perfect, but in a 2 -> 1 shift it makes it a lot easier.

In my 86 it's easy to hear the faint whrrRRRRRR of gear teeth speeding up as rotation is matched when selecting 1st from any other gear with the clutch in. Not sure if that will last forever, but there was a similar thread a while back where someone else mentioned they had the noise and mine still does it 30,000 miles in.

All that said, you can't fight math and physics, especially friction in a cold gearbox (even room temp is a little cold for a transmission) vs an operating temp gearbox. The only real suggestion I have is to be a little more patient or drive it like a 5 speed using only 2nd through 6th. That way you skip the massive delta and associated notchiness that comes with selecting 1 -> 2 or anything -> 1.

Last edited by anticubus; 05-16-2020 at 11:11 AM.
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Old 05-15-2020, 04:14 PM   #17
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I read a number of posts about the benefits of changing the transmission gear oil. When I changed the oil I did have some metal on the drain plug as it said I would. I added three quarts of Lucas synthetic gear oil and thought I was all set.


The issue is now when the transmission is cold first tot second, second to first changes are very notchy. To the point of difficult shifting. Once it warms up it is much better. Additionally when I'm on the power and pulling hard it becomes difficult to shift. I have the Edelbrock SC so pulls are harder than stock would be.


Why would this have happened when changing the gear oil? Would changing back to the stock oil or another brand solve the problem?
Because Lucas Oil sucks and you used too much of it? Basically exacerbated the 1-2 shift issue that's common, and now it takes longer to warm up because there is more mass to heat.

Also, I too am curious as to why FI would change how a manual transmission shifts. Please explain why that would make a difference.
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Old 05-15-2020, 04:36 PM   #18
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If you believe someone needs knowledge, then why did you offer ridicule instead of information.
It's not up to me. We all benefit from knowledge but it must start by being receptive to it. The OP is thick with bravado. I'm getting that shit out of the way as quickly as possible so we can get down to the real learning. The elephant in the room, if you will.

I think it worked. There's some really good stuff here already.
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Old 05-15-2020, 04:37 PM   #19
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Also, I too am curious as to why FI would change how a manual transmission shifts. Please explain why that would make a difference.
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Old 05-15-2020, 05:43 PM   #20
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Take a 1 -> 2 shift at 4000RPM before we account for final drive:
1st gear output is ~14400RPM (~3.6 x 4000RPM)
2nd gear output is decoupled. 2nd gear input is spinning at 4000RPM, so the output gear that the fork will mesh to select is spinning at ~8400RPM. Adding in the connection to the wheels, you need to account for the engine speed that matches the rotation of the wheels after final drive, and that's the sweet spot for each rev-match up or down.

That's a 6000RPM output speed drop, and not only that, but the selector fork will have all the momentum from 1st gear output spinning it at 14400RPM as it gets slid over the 2nd gear synchro and against the mesh teeth spinning at 8400RPM.
First off, thank you. Let's talk about the gear ratios. That 3.6-to-1 ratio is 3.6 revolutions of the input shaft for every single of the output.

input 4000 -> output 4000/3.6 = 1111 (ish) RPM. Follow down for the rest of the gears.

That doesn't invalidate your observations overall, especially the whirring sound you hear and resistance felt when downshifting into second and especially first. The reason that sound is important is because for any shift, the input shaft is being driven by the output via the syncro clutch. The lower the gear, the greater the mechanical disadvantage through which the syncro clutch must drive the input. The viscous drag of the gear oil is amplified in the lower gears, and the syncro clutches in this transmission are as compact as possible for a conventional gearbox. There's more to it. The layout of the gearbox with respect to what the 1-2 syncro clutches must drive also plays into the picture.
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Old 05-16-2020, 11:06 AM   #21
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First off, thank you. Let's talk about the gear ratios. That 3.6-to-1 ratio is 3.6 revolutions of the input shaft for every single of the output.

input 4000 -> output 4000/3.6 = 1111 (ish) RPM. Follow down for the rest of the gears.

That doesn't invalidate your observations overall, especially the whirring sound you hear and resistance felt when downshifting into second and especially first. The reason that sound is important is because for any shift, the input shaft is being driven by the output via the syncro clutch. The lower the gear, the greater the mechanical disadvantage through which the syncro clutch must drive the input. The viscous drag of the gear oil is amplified in the lower gears, and the syncro clutches in this transmission are as compact as possible for a conventional gearbox. There's more to it. The layout of the gearbox with respect to what the 1-2 syncro clutches must drive also plays into the picture.
Ugh you're right, torque multiplication is the output side calculation, not speed. Not the first or last time I'm gonna flip those . My way would mean we would never need to deal with a money shift, and all our wheels would be the size of pebbles. I never said I'm a mechanical engineer because I actually live in the friction free world of software. I'll go back and update it all.

My takeaway is I can't be trusted to write this sort of technical post in layman's terms during my lunch break. Thanks for keeping me honest.
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Old 05-16-2020, 04:39 PM   #22
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I actually live in the friction free world of software.
LOL... Your writeup was excellent. By your description, I can tell that you're visualizing the mechanics perfectly. It's just a dumb arithmetic error. I made almost the same mistake yesterday scaling up the quantities of chemicals for our cheesy, above-ground pool.


Now let's see whether or not we still have OP's attention.
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Old 06-01-2020, 09:39 PM   #23
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My point is that if you truly want to learn about the transmission, humility is your greatest asset. Do you want to learn about your transmission, or are you here to have your preconceptions validated? If it's the latter, I'll kindly excuse myself.

I'm not sure why you're tasking me on humility. What have posted that I am boasting about? Is it the supercharger? I thought that was necessary information being that I was asking about shifting under load. With the SC the load on the drive train would be higher than a stock car would experience. I received valuable information about the mounts flexing. Which would be worst with the increased load.



Every car I've owned has it's own idiosyncrasies. Understanding how a transmission works or responds in one car doesn't it will be the same in others. So I am here asking questions on a subject I don't have experience with. It doesn't mean I don't know how a transmission works.


Sorry for the misunderstanding.
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Old 06-01-2020, 09:48 PM   #24
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I want to thank everyone for their input. The driveline moving under load I will have to address later. The main issue was caused by over filling the transmission. I got it back down to the correct level and now it shifts great. I swear I read it was 3 quarts. I knew I could count on the community to help solve the problem.
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Old 06-01-2020, 10:03 PM   #25
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The OP is thick with bravado.
Please point out where and how.
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Old 06-02-2020, 12:52 AM   #26
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I'm not sure why you're tasking me on humility. What have posted that I am boasting about? Is it the supercharger? I thought that was necessary information being that I was asking about shifting under load. With the SC the load on the drive train would be higher than a stock car would experience. I received valuable information about the mounts flexing. Which would be worst with the increased load.

Every car I've owned has it's own idiosyncrasies. Understanding how a transmission works or responds in one car doesn't it will be the same in others. So I am here asking questions on a subject I don't have experience with. It doesn't mean I don't know how a transmission works.

Sorry for the misunderstanding.
It took guts to come back. The problem is that you want it to be about the supercharger. It has absolutely nothing to do with it. I explained succinctly why that is the case but you glossed right over my point. You continue to gloss over literally all the correct responses. Humility has everything to do with it. It takes humility to open up and consider opinions that do not fit with what we want to be true.

It takes humility to admit not knowing. Your claim that it takes special vehicle-specific understanding is an easy tell. Understanding how a manual transmission works comes before discussing idiosyncratic differences. Explain the increased load of a disengaged clutch.

"Sorry for the misunderstanding." is not an apology. It's a passive-aggressive swipe. I save my apologies for things which I can take responsibility.
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