Lock out shifting from 3rd to Second when cold

[spike021]

Originally Posted by Ultramaroon

Someday I'll crack open my original transmission to shim the input shaft bearing like we discussed. Will be interesting. Both of my transmissions are super picky about downshifting into first.

3/4 rod overtravel? Sounds like I need some schoolin'

I've never been able to get my transmission to downshift into first really, except _maybe_ from 3-4mph, like right around where the car would lug in 2nd if I let it.

[RACECAR go brrr!]

Originally Posted by spike021

I've never been able to get my transmission to downshift into first really, except _maybe_ from 3-4mph, like right around where the car would lug in 2nd if I let it.

It's super weird that there's apparently such a wide variation, and so common. I'm also glad mine don't have that issue, lol.

[NoHaveMSG]

Originally Posted by Ultramaroon

3/4 rod overtravel? Sounds like I need some schoolin'

I saw this and all those, "what is this ball stuck to my drain plug?" threads made more sense.

https://www.jackstransmissions.com/t...ervice-brz-frs

When the 3-4 Shift Fork / Gear Slider overextends on the gear hub, there is a chance that the small synchro spring and detent ball can pop out, causing additional issues. We correct this issue by replacing the gear hub detents with a much more robust style. We also install heavy duty bronze rail bushings to keep the shift rails from wobbling around inside the transmission. This results in more precise shifting.

[Ultramaroon]

Originally Posted by NoHaveMSG

I saw this and all those, "what is this ball stuck to my drain plug?" threads made more sense.

https://www.jackstransmissions.com/t...ervice-brz-frs

Aha! Gotcha. Thanks!

[Ultramaroon]

Originally Posted by RACECAR go brrr!

It's super weird that there's apparently such a wide variation, and so common. I'm also glad mine don't have that issue, lol.

It's not a bug. It's a feature.

Originally Posted by spike021

I've never been able to get my transmission to downshift into first really, except _maybe_ from 3-4mph, like right around where the car would lug in 2nd if I let it.

Perfectly normal. Keeps less attentive drivers from money-shifting into first and potentially wiping out.


edit: To clear up any doubt, here's a page from the service manual with the relevant IPB. Scroll to the bottom. It's called the "1st shift restrict ball."

[RZNT4R]

The location of that ball reinforces the importance of the oil.

On this transmission the 1/2 shift hub is on the layshaft, submerged when the car is parked, and very likely soaking wet with it's toes in the oil bath even when running and flinging oil around the case. If you've that OEM fill GL-3 goop in there that's a lot of jelly that little ball, and that shift ring and synchros have to push out, and a lot of warming up to do before it gets as smooth as a more high tech oil.

[Ultramaroon]

Not specifically that ball, but yes. It's also the reason timing is especially critical for the cold 1-2 shift. That jelly quickly drags down the speed of the whole gear set anytime the trans is in neutral with the clutch disengaged.


Pro tip; shift with a quick gentle open-fingered flick from first to second without pausing in neutral. With good technique, even stone cold, it just falls into gear.

[humfrz]

Originally Posted by Ultramaroon

Not specifically that ball, but yes. It's also the reason timing is especially critical for the cold 1-2 shift. That jelly quickly drags down the speed of the whole gear set anytime the trans is in neutral with the clutch disengaged.


Pro tip; shift with a quick gentle open-fingered flick from first to second without pausing in neutral. With good technique, even stone cold, it just falls into gear.

Also, with better technique, you don't even have to use the clutch -

[soundman98]

Originally Posted by RACECAR go brrr!

Hmm. Well here's a video I made many years ago after getting into an argument with someone on Facebook about it, lol. I downshift into 1st at 15 and 20 both without double clutching. I'll also note I had to have a new transmission installed at 40k (because my 5th gear synchro went wonky) and that transmission also doesn't require double clutching. So I'm 2 for 2 on the "defective" 1st gear lockout if that's the case.

i've got a weird theory that either my clutch drags slightly, or i unintentionally drag the clutch.

my car definitely has a 1st gear lockout, as it won't fall in unless the revs are first matched or over-reved before the shift. but i've never double clutched.

normally when i'm going 2-1 at anything other than a stop sign, it's at the upper limit of 1st, and i intend to rotate the rear around the corner(not always sideways, or skidding, many times just enough to roll the tires over).

it's almost automatic at this point, but i'll rev-match 4-3-2, line up for the corner, then clutch-in, drop out of 2nd, rev up while holding towards 1st until it drops in, and then release the clutch(not pop) as it's falling into 1st...

both of my early '14's operated the same.

though as long as i'm under-reved for 1st, it will refuse to go in.

i do wonder if it's my/your technique that's working around the mechanical 1st gear lockout, or there's enough clutch dragging to keep the input shaft spinning to follow the rpm jump.

personal technique would make more sense, as we're both a sample size of 2 different transmissions operating the same way, and the odds of mass manufacturing skew against us.

of note, i never down shift for the first mile-ish of use, the fluid is too cold, and nothing wants to work.

[Ultramaroon]

Originally Posted by soundman98

i've got a weird theory that either my clutch drags slightly, or i unintentionally drag the clutch.

Even with the clutch fully disengaged, there's always a tiny bit of contact somewhere on the friction disc. Maybe even windmilling. It wasn't until getting into a discussion with another forum member here that I ever tried just revving up in neutral with the clutch disengaged. It actually works when warm. There isn't enough contact to overcome the viscous drag of cold lube. If it did, I would suspect something was not quite kosher with the clutch.

I've driven a couple which were super easy to downshift into first, even without doing anything special to spin up the input side.

[humfrz]

Originally Posted by Ultramaroon

Even with the clutch fully disengaged, there's always a tiny bit of contact somewhere on the friction disc. Maybe even windmilling. It wasn't until getting into a discussion with another forum member here that I ever tried just revving up in neutral with the clutch disengaged. It actually works when warm. There isn't enough contact to overcome the viscous drag of cold lube. If it did, I would suspect something was not quite kosher with the clutch.

I've driven a couple which were super easy to downshift into first, even without doing anything special to spin up the input side.

Yep, in my NC Miata, I could shift into first gear at 40 MPH. The thing was that you could only let the clutch out once per car -

[Ultramaroon]

Originally Posted by humfrz

Yep, in my NC Miata, I could shift into first gear at 40 MPH. The thing was that you could only let the clutch out once per car -

lol

[redvee86]

I find that if I get the revs up to just over 4k after a cold start and shift 1st to 2nd it is a smooth shift. Generally lower rpms will make a crunching noise.

The difficulty shifting 3rd to 2nd after cold start is frustrating!

[redvee86]

So is there a consensus on the best oil to use for the transmission?