Mechanics... What makes shifting require more effort under engine load?

[altjx]

Sup guys!

So as many of you know, I'm pretty new to driving standard. This is my first ride with a standard transmission and I've had it for about a year now. Like some of you, it's my first real performance car other than the '15 GT I modded and sold for this one. I'm a tech nerd so I'm learning my car as I go.

Anyways, one of the things that I've been wishing I could understand a little better is why does it require more effort to shift when under engine load compared to when the car is parked? Long story short, I bought an MGW during the first few months of owning my GT350 because I kept getting locked out of 4th -- the gates were being misaligned or something. A friend tried explaining to me about the transmission torquing over under heavy engine load, sometimes causing this to happen. The MGW pretty much fixed this "alignment" issue under heavy load, but it makes me wonder -- why does it still require a lot of effort if the MGW is mounted onto the transmission instead of the car?

If you're unfamiliar with what I'm explaining, here's an example. While your car is parked, you can literally go from gear to gear with ZERO effort -- in other words, you could use your pinky to shift gears for you. However, when you're shifting at 7k+ (at least 8.5k for me), the delay in shifting gears is usually caused by me having to use extra energy and force to shift. Like shifting from 1st to 2nd at 8.5k takes a lot more effort than it is when parked. I'm guessing it's normal, but I'm wondering if there's anything I could do (if it's even possible) to make shifting require little to no effort at all even at 8.5k

Any thoughts would be greatly appreciated.

Sponsored

 

[DarkestHour]

that's because you're in neutral ...

 

[DarkestHour]

https://www.carthrottle.com/post/en...ual-transmissions-work-and-why-theyre-better/

 

[HISSMAN]

In basic terms. The faster the synchros and gearing are spinning, the more difficult it is to engage. But it really shouldn't be that much more difficult than being in park if everything is working as it should. A better fluid can help smooth things out a bit also. I have BG in mine, and it is like butta.

 

[EFI]

Simple physics...the engine is moving faster thus the transmission gears and components are also moving faster. Movement has energy, and when you're trying to change something with those parts eg. shifting gears you have to go through that energy.

Think of a spinning wheel and the effort it takes to stop it. Take your bike and flip it upsidedown on it's handlebars. Then get the wheel spinning slowly and see how much effort and friction it takes for your hand to stop it. The instant you grab it with a relax pinch it stops. Now get the wheel spinning much faster and see how much effort and friction it takes to stop it. Just by grabbing it like in the first scenario won't make the wheel stop, you really have to grab on to halt its motion.

Same with the gears, you have to take into account how much faster they are spinning so it takes more energy to counter the energy from the spinning gears.

 

[jasonstang]

Well yes and now. There are three things that affect shifting effort.
1. Shift collar alignment
2. Syncros
3. Shifter alignment

First, you will notice it's harder to shift into gear with engine off vs with engine on that is because shift collars need to be spinning to engage smoothly.
Second, at higher rpm, the syncros need extra effort to bring the shift collars up to the same rpm for it to engage.
Third, when drive train is under load, everything moves so if the shifter is not lined up properly, it will cause shifting issues. When I had my RX-8, the shifter would move about half inch when engine is under load vs neutral. That is a direct mount shifter meaning the shifter comes out of the tranmission directly.

 

[altjx]

that's because you're in neutral ...

https://www.carthrottle.com/post/en...ual-transmissions-work-and-why-theyre-better/

In basic terms. The faster the synchros and gearing are spinning, the more difficult it is to engage. But it really shouldn't be that much more difficult than being in park if everything is working as it should. A better fluid can help smooth things out a bit also. I have BG in mine, and it is like butta.

Well yes and now. There are three things that affect shifting effort.
1. Shift collar alignment
2. Syncros
3. Shifter alignment

First, you will notice it's harder to shift into gear with engine off vs with engine on that is because shift collars need to be spinning to engage smoothly.
Second, at higher rpm, the syncros need extra effort to bring the shift collars up to the same rpm for it to engage.
Third, when drive train is under load, everything moves so if the shifter is not lined up properly, it will cause shifting issues. When I had my RX-8, the shifter would move about half inch when engine is under load vs neutral. That is a direct mount shifter meaning the shifter comes out of the tranmission directly.

Simple physics...the engine is moving faster thus the transmission gears and components are also moving faster. Movement has energy, and when you're trying to change something with those parts eg. shifting gears you have to go through that energy.

Think of a spinning wheel and the effort it takes to stop it. Take your bike and flip it upsidedown on it's handlebars. Then get the wheel spinning slowly and see how much effort and friction it takes for your hand to stop it. The instant you grab it with a relax pinch it stops. Now get the wheel spinning much faster and see how much effort and friction it takes to stop it. Just by grabbing it like in the first scenario won't make the wheel stop, you really have to grab on to halt its motion.

Same with the gears, you have to take into account how much faster they are spinning so it takes more energy to counter the energy from the spinning gears.

Gotcha. Makes much more sense. Thanks a lot guys for the valuable information! So I guess mechanically there's really no way to get a "perfectly easy" shift during heavy engine load. Not to say it's extremely difficult, but noticeably more effort is required.

I'm probably going to try changing fluids soon since it seems like someone here mentioned that was an improvement for them.

 

[DarkestHour]

Gotcha. Makes much more sense. Thanks a lot guys for the valuable information! So I guess mechanically there's really no way to get a "perfectly easy" shift during heavy engine load. Not to say it's extremely difficult, but noticeably more effort is required.

I'm probably going to try changing fluids soon since it seems like someone here mentioned that was an improvement for them.

Unfortunately not. Would be nice though!

 

[altjx]

Unfortunately not. Would be nice though!

Agreed!

 

[TexasRebel]

When you're stopped with the clutch disengaged and in gear there is nothing spinning in the transmission.

Shifting effort just has to overcome the detent springs on the splined collars to come out of gear. It also has to be enough to roll the alignment gates up to 1/2 tooth (worst case misalignment).

While you're moving, the output and lay shafts are always spinning, and every gear pair has a different rotational velocity. With a 6 speed transmission 4 gear pairs are fixed to the output shaft and 3 gear pairs are fixed to the lay shaft (depending on the transmission, the opposite might be true). Gear pairs are then paired to splined collars. Gear pairs on opposing legs of the H pattern share the same splined collar. So in the S550's 1&2 are together, 3&4 are together, and 5&6 are together while R is off by itself.

Direct drive is always simply coupling the output shaft directly to the input shaft. So the 5&6 coupling immediately follows the input shaft, while the others can be in almost any order that radial load on the bearings allows.

Anyway, when shifting from one gear to another the rotational velocity of the splined collar must be brought into synchronization with the corresponding gear pair. If their rotational velocities are mismatched the splines will clash and the blocking rings will prevent engagement. This is what most people call "grinding gears"... you're not really grinding gears in a synchromesh transmission, but grinding the bronze blocker rings.

The blocker rings are usually integrated with the synchronizers. Synchronizers are cone shaped wet clutches (sometimes dual or triple) that match the rotational velocity of the input and output sides of the transmission. Not all transmissions have synchronizers on every (or any) gear.

Which brings me to crash boxes... in the S550 you don't really ever shift gears. You shift collars to select gears, but the gears are always meshed (called a constant-mesh transmission). Get on and old tractor or into an old Semi... even a Willys Jeep and now you have a sliding gear on a splined shaft. Synchronizers? HA! It's up to the operator to get those gears rolling at the same rate or crash teeth. This is where double-clutching is absolutely necessary.

clutch disengaged once: shift to Neutral
clutch engaged: get input side of transmission to desired RPM using engine
clutch disengaged twice: shift into desired gear
clutch engaged: GO! (or stop if you're engine braking)

 

[Wriggly]

[MENTION=22579]TexasRebel[/MENTION] why are the MT82's so damn crappy.

 

[jasonstang]

[MENTION=22579]TexasRebel[/MENTION] why are the MT82's so damn crappy.

Tolerances as well as choice of material but I don't think they are that bad. I have had worse.

 

[Wriggly]

Tolerances as well as choice of material but I don't think they are that bad. I have had worse.

I had a 13 GT and pulled it into the garage and parked for the night. Next day I go to back out of the garage and it kept jumping out of reverse. Ended up having to get it towed to the local Ford dealer. Trans needed to be rebuilt. It had exactly 1000 miles and 30 days old. I was 63 years old at the time and have driven manuals my entire life, including many different types of trucks professionally.

A buddy has a 14 Boss and has had to have his trans repaired three times in 13,000 miles. Just last week he told me his fifth gear was out.

I have had a couple of cars with Tremec transmissions including my current GT350 and they shift like butter.

 

[jasonstang]

I had a 13 GT and pulled it into the garage and parked for the night. Next day I go to back out of the garage and it kept jumping out of reverse. Ended up having to get it towed to the local Ford dealer. Trans needed to be rebuilt. It had exactly 1000 miles and 30 days old. I was 63 years old at the time and have driven manuals my entire life, including many different types of trucks professionally.

A buddy has a 14 Boss and has had to have his trans repaired three times in 13,000 miles. Just last week he told me his fifth gear was out.

I have had a couple of cars with Tremec transmissions including my current GT350 and they shift like butter.

The S197 MT-82 had some issues but the S550 should be much better.

 

[mustang1]

... the delay in shifting gears is usually caused by me having to use extra energy and force to shift. Like shifting from 1st to 2nd at 8.5k takes a lot more effort than it is when parked. I'm guessing it's normal, but I'm wondering if there's anything I could do (if it's even possible) to make shifting require little to no effort at all even at 8.5k

Any thoughts would be greatly appreciated.

best not to use extra energy and force to shift unless you don't like your synchros. It should shift with minimal effort. If not, you are probably outrunning the synchros.

I'm probably going to try changing fluids soon since it seems like someone here mentioned that was an improvement for them.

I doubt you will improve on the GT350 gear oil. You can change it just for fun, but I wouldn't expect that to magically make the transmission shift a lot faster.

Sponsored