Truck vs car manual tranny

Shux Howdy Folks!

I've been driving Big trucks with non-synchro manual transmissions from seven to eighteen gears for many years, -- double clutching AND floating the gears, and I shift as smooth as a hot knife through butter, both up and down shifting. BUT, after reading all these explanations I have to admit --- I'm more confused now than I've EVER been!

 

I hear ya, AfterShock.

Going back to the poster's original comments...

You can float a car/light truck whether it's synchronized or not... you just have lower mass than a big diesel in the moving parts, so it's easy to overspeed or underspeed when adjusting RPM for the next gear.

But listen here, driver... if you're shifting right in a car or a truck, you're already matching your RPMs perfectly for every up and downshift you're making, and you don't need the clutch.

USE THE FORCE, FLUKE!!!!

 

I will say that in light vehicle applications, some engine/trans combos are far easier to shift clutchless than others.

I.E. my old VW GTI VR6 didn't care for me to skip the clutch, no matter how careful I tried to be... but my Tacoma 4-cyl truck has few complaints. Yeah, every now and then if I'm not paying close enough attention, I'll get a buzz from 4th... but most of the time I shift up/down w/o clutch in this truck.

As for my comment about should already be matching RPMs, I mean if you upshift, you shouldn't be pushing your right foot to the floor before letting the clutch out (because an upshift requires the engine rpm to drop) and you shouldn't be pulling your right foot off the gas and letting the clutch out in a downshift (because a downshift requires the engine RPM to rise).

If you're doing your shifts right, you can "forget" the clutch and nail a smooth shift every time.

FTR, I've driven a lot of light trucks and cars, and have found few that didn't care for my technique in float shifting... and have rarely ever had transmission issues, and those issues existed before I owned/operated the vehicle. I.E. my old VW Bug in high school liked to jump out of 2nd when I bought it... but I could still float every gear. my 1970 jeep CJ5 with it's 3-speed would float fine, but years of abuse and neglect before I bought it caused the trans rear mainshaft bearing to self destruct.

With BOTH those vehicles, I lost my clutch either due to a snapped cable (in the case of the VW, that happened often) or due to a frozen throwout bearing (on the Jeep). In both cases, knowing how to float the gears saved me a tow truck... when stopped, kill the engine, put it in first and when you're ready to go, put your foot on the gas and crank the engine... float up and down until you stop and repeat.

YMMV... don't sue me if you push a lever and shred a synchro or drop a transmission. It's not my fault if you can't control your equipment.

 

Some may be rationalizing that they can float their car's transmission, but that could lead to significant damage. A truck's sliding gears will give a little warning if the rpm is not correct. A truck transmission is tough and forgiving.
550hpW900L referred to the straight cut gears in a truck. I am not an engineer, but believe the shape of the gears in heavy trucks, motorcycles and some race cars allow floating without damage.
http://www.edmunds.com/ownership/techcenter/articles/46029/article.html

 

A version of this video is sometimes shown during mechanics' training to break the boredom.

http://youtube.com/watch?v=rLDgQg6bq7o&feature=related

 

Thanks for that video. There is another one, look for it. I searched youtube for "techno babble electronics" and it was like the second result. It's more convincing, I think, and mostly the same words!

Anyhow. I follow what you're saying though, heyns.

And you guys, I know we're deviating here- I hope folks don't mind... if y'all ain't figured yet, I like to talk, and I type about as fast as I talk- so I'm sorry for the long winded posts.

Here's the thing. If a driver of a synchro gearbox is trying to float, the transmission won't "open the gate" (i.e. can't even move it towards that hole) until the rpms matched enough. Now, a tendency may be for some drivers to slip out of neutral (which is easy and does no damage... just slack the load and push out) and then push it towards the next hole while the rpm drops, hoping to catch the synchro as the engine drops down thru that range. That "pushing the gate" will wear the synchros quicker than using the clutch. The synchros aren't made to handle that.

Now, if the RPM is dropping too fast (or rising for downshift) then it's likely that once that gate opens, the rpm will drop too far to engage once it's "in the gate". If they follow thru with that pressure, they will experience a hard THUNK and probably see shiny parts bouncing on the pavement out their rear view. So, if that gate opens up within 250 rpm of the target speed, and you're still holding it about 150 rpm too fast or slow, you'll find your familiar telltale sounds and behaviors like you mention, I think. (whines, groans, buzzes... not loud unless you push too hard, just like a crash box, right?)

Now, on the other hand, a motorcycle gearbox is sequential, with only one neutral- thus you can't "float" it... but you CAN shift it the same way many drivers use their splitter. Throw the switch, slack the throttle, throttle down. Motorcycle shifts the same way. When you hit your splitter, you are applying shift pressure to the gear fork. If you pull up on a motorcycle shifter, you are doing the same. When you slack the throttle in both applications, the gear can suddenly pop into place. There is no neutral, because you didn't pull it out of that hole, you just toggled the splitter.

The difference here, at least w/ a crotch rocket type bike, you may have a span of 4500 RPM between torque and HP, and it's geared to handle it... that's a few RPM difference more than what most you guys see when you hit the splitter, am I wrong?

Now, for racing... I don't know all types of racing, and don't care for all types of racing... but I'll tell you what- with enduro, hill climb, motocross and those types of bike racing, if you're not slipping the clutch, you're not getting power. But a motorcycle also typically has a wet multiplate clutch, and they are very resilient to slipping, because they're cooled by oil. (I know right... how does a clutch work submerged in oil!? It does! Well!)

Like I said before- follow your gut, don't do what you don't feel comfortable with. Your Mileage May Vary. Some limitations apply. Don't sue me if a house falls on your pig. Do as I say, not as I do. One size does NOT fit all. God Bless America.

 

I began floating the gears in my SuperDuty wrecker since my syncs are shot to hell. Pretty easy in that truck. Shift out at 2500 rpm and the next gear catches at 1500