Dog box on the street?

Vigo said:

If 5th is still synchro and you don't have super tall rear end gears i think you are actually going to be pretty ok. In casual driving with good low end torque a lot of cars can use 5th at 35mph or even less, so the majority of your driving will be in a gear with no extra 'lash'. Sounds good enough to me. The synchro 1st would be nice, but oh well. As far as spinning the clutch disc to zero, you can do that by shifting into 5th then into 1st at a stop. Maybe a little unnatural but also not really necessary unless you needed to stop and start in a really short time. Most people's clutch discs are closer to 3 lbs than 5+ anyway. 

My engine is an shiny happy person below 2k rpm, so I expect a lot of "trailer hitching."  I keep trying to mess with the tune to get it to be smoother down low, but I'm coming to the conclusion that I'm fighting a losing battle. 

snailmont5oh said:

My engine is an shiny happy person below 2k rpm, so I expect a lot of "trailer hitching."  I keep trying to mess with the tune to get it to be smoother down low, but I'm coming to the conclusion that I'm fighting a losing battle. 

Recently had this problem due to accel enrich changes. I found that if I disabled use of the TPS WOT curve it solved the problem, but I was worried about not getting enough fuel at higher revs, so instead I altered the TPS WOT curve (only used for accel enrich on a MS3 as far as I can tell) at low revs to reduce the use of accel enrich. Kinda hackish but it's definitely helping. If you have ECU-controlled ignition you could also try pulling timing in that area.

I got the trans in. And took it around the block. The banging into gear isn't as catastrophic as I thought it  would be. Even though it's helical, it's not as helical as a stocker, so it is pretty whiny in all gears but 4th. The backlash isn't unlivable. 

Now the good part: goddamn, does this thing SHIFT!  The shifter moves with a liquid smoothness and light weight, and you literally just *bump* the clutch and it's in the next gear. I can't wait for some dry roads so that I can spend some quality time with it. 

Edit: SWMBO hates it. 

So far so good! Make sure and post a follow up after you spend real time with it. I'm open to being sold on this. 

Oh I'm already sold on it.

I'm not terribly familiar with the G-force, is it T10 based or T5 based or something completely different?

Knurled. said:

Oh I'm already sold on it.

 

I'm not terribly familiar with the G-force, is it T10 based or T5 based or something completely different?

The one I got is t5 based. 

One thing to note is that one of the main reasons people hate dogboxes on the street is because most of the kits have straight-cut gears, producing the loud whining noise and amplifying the annoying bucking. Helical dog gears are available from some manufacturers - PPG has helical-cut gears for sequentially shifted Tremec 6-speeds, for example, which may be entirely liveable on the street. Since DSM/Evo123 gears aren't the strongest gears, my backup plan is to either get a helical dog kit from Albins, or a straight-cut synchro kit from PAR Engineering, if my built transmission fails. The two kits are probably on par with each other for useability in daily situations, but the dog kit would likely out-shift the synchro kit 10 times out of 10.

This video will show you how tame a helical dogbox can be: 

In reply to CanadianCD9A :

Straight cut gears are supposed to be stronger because the gear teeth actually pull the shafts closer together under load, in addition to not trying to spread the case.  In a marginal application like a DSM/early Evo, I'd think that would be good insurance.  Plus, if you never drive it because it is too obnoxious to live with, it won't break!

Noisy gears definitely seem to amplify any bucking because you will hear it long before you feel it.  NVH is all one concern because your brain interprets them all similarly, after all.

Knurled. said:

In reply to CanadianCD9A :

Straight cut gears are supposed to be stronger because the gear teeth actually pull the shafts closer together under load, in addition to not trying to spread the case.  

It's been a long time since I had a class on gear design, but I don't recall any type of gear that doesn't try to get away from its mate under load. The thing about a spur gear versus a helical gear is that they try to get straight away from each other, not at an angle, which makes the forces easier to control. Feel free to correct me if I have this wrong. 

General Update:

I did a hundred miles in it yesterday. It's not overly fun in stop and go traffic, or light to light.  As long as the earth-shattering "ka-WHANG" every time it shifts isn't hurting anything, I'm okay with it, though. Over time, I'll probably end up trying to figure out how to use finesse and better rev-matching technique to minimize noise.  Right now, the only tool I have in my box is "MOVE THE SHIFTER NOW!!"  It works, but can be unpleasant. It's probably better at higher engine speeds. I did have to give it some E36 M3 pulling out from a stop sign onto a busy highway into traffic, and it seemed to really enjoy getting the next gear at 6500 RPM. 

In reply to snailmont5oh :

I just know what I'm told.  I'm sure the tooth form has a lot to do with it, as well.

Idle curiosity:  Can you smoothly drive a synchronized transmission without the clutch, up and down in the gears?  I mean, like rev matching/timing so the shifter drops in smoothly, not just leaning against the synchro until it falls in.

In reply to Knurled. :

Me, personally? I've only driven without the clutch when my clutch didn't work, mostly because I was told (and it made sense) that you were likely to cause damage to the  synchros while learning. So, I never practiced enough to say I was *good* at it, but I could do it, and when I did do it, I always tried to only move the shifter at the right time. If it gave me resistance, I'd change something and try again. 

I've also driven heavy trucks (tractor only, no trailer) up and down through the gears smoothly, which is easier than it is with my car because the huge engines take much more time to change speed. 

According to Billzilla, the straight cut gears transfer the power more efficiently than helical cut gears because the helical cut gears try to push the shafts in opposite directions, creating load (heat, power loss) on the bearings, while the straight cut gears transfer the power without that side load.  Straight cut gears are also nosier than helical.  It's been a couple decades since I read his web site, but I think he also said helical are stronger.  He said that they make custom gear sets with less angle helical cut gears so you can have some of the best of both worlds.  He also had some general directions on how to swap stuff around in a Toyota T50 box and get a closer gear ratio, but with the side effect of a weird shift pattern.

snailmont5oh said: As long as the earth-shattering "ka-WHANG" every time it shifts isn't hurting anything, I'm okay with it, though. . 

WonkoTheSane said:

snailmont5oh said: As long as the earth-shattering "ka-WHANG" every time it shifts isn't hurting anything, I'm okay with it, though. . 

 

You got the reference. 

In reply to Dr. Hess :

Yes, straight-cut gears only try to get straight away from each other, while helical gears try to get away at an angle. This means that your supports and bearings for a helical set must be able to take much higher thrust loads. 

Another day, another 5 hours in the car. I've come down to the idea that it's gonna be okay. I think that extremely rapid, clutched upshifts is the ticket for all situations, and double-clutched downshifts when time allows. About 3/4 of the time, I manage to nail a double-clutched downshift silently, the other third, there's a little crunch, but it's much less catastrophic-sounding than a normal slap-downshift. 

I think this is gonna work. 

So, if the actual lash between the dogs isn't annoying and you can rev match appropriately it's livable. Good to know! What's your clutch disc anyway? Material, sprung hub? That probably has some minor impact on how harsh it feels to engage the dogs. 

In reply to Vigo :

Lash doesn't seem like a problem.  It's barely noticeable, what with the rod ends all over the place in the rear suspension. If you intentionally jump on and off the gas, you can pick it out, but a modicum of smoothness seems to keep its noise in the "manageable" range  

If's got an organic disk with a sprung hub.

Latest update:

A few months in, and I'm pretty much getting through all the upshifts smoothly, and quickly enough to not hold up traffic, by careful throttle modulation, and no clutch whatsoever. Sometimes, if I let off the throttle too fast and am lazy with the shifter, I miss the opportunity to get it out of the lower gear and have to start over. The most annoying part is trying to remember to pick up the throttle *while* moving the shifter into the higher gear, not after, for smoother acceleration. Fast upshifts are still about bopping the clutch and the shifter at the same time. They're getting pretty slick, too. Downshifts are mostly of the double-clutch/rev-match variety, which only bothers me because I'm rev-matching the shift, not the clutch coming out. It's not horrible, though. 

I just put it away for the winter, so I'm sure I'll suck again by spring. 

In reply to snailmont5oh :

Reminds me of a Certain Ethnic joke I heard when I was a little kid and this sort of thing wasn't banned.

You know why they don't give elevator operators lunch breaks in Certain Ethnicland?

So they only have to train them once a day.

I think of that every single time I forget how to do something utterly simple.

Knurled. said:

In reply to snailmont5oh :

Reminds me of a Certain Ethnic joke I heard when I was a little kid and this sort of thing wasn't banned.

You know why they don't give elevator operators lunch breaks in Certain Ethnicland?

So they only have to train them once a day.

 

I think of that every single time I forget how to do something utterly simple.

As long as Certain Ethnicland is in Europe, specifically Northern Europe, you're okay. <*end of anything remotely political*>