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- - Shifting (https://www.dieseltruckresource.com/forums/24-valve-engine-drivetrain-89/shifting-18250/)

My husband is an ex-truck driver and wanted to know if you are able to float or skip gears?

I've heard its not good on the trans, and sincrinizers. ( spelling) Kimrey

i do it on mine and haven't had any problems alltho they say its not good. i just dont force mine

Hubby can float shift the Dodge, but he shouldn't. Why not? Short answer is - it's bad for the synchronizers. Long answer follows: In a heavy truck trans like a 10 or 13 speed, there are no synchros, just toothed rings known as dog rings. When you float shift a 10 speed, you're actually making an educated guess as to what combination of gear, road speed, and engine rpm will line the teeth on those rings up. If you're wrong, you get negative reinforcement in the form of nasty gear grinding noises, but unless you try to jam the thing in gear you won't hurt anything. Synchros, on the other hand, are brass cones with teeth on the outside. The teeth are always inside a spinning (at road speed) collar that the shifter slides back and forth between a set of gears (1st & 2nd, 3rd & 4th). The collar also slides over the end of the gear the driver selects. What the sychro does is this: as you push the shifter into gear, the cone shaped part of the syncho pushes into a corresponding cone shaped recess on the gear, synchronizing the speed of the gear to road speed. So what does this have to do with not float shifting? The synchro will try to make the truck go into gear even if you do the float shift wrong. This makes the synchro wear out very fast. You can't know if you're really shifting properly, you will just know you've done it very wrong when it won't go into gear. I know this will be very disappointing to your husband, but if it makes him feel better, double clutching on the way down is easier on the synchros and will extend their life.

nice explanation wannadiesel! :) Tim

WOW!! Wannadiesel, good heavens! That was an excellent INDEPTH overview of shifting. I can't wait to show the hubby. He will be disappointed to know that it isn't the greatest as far as wear and tear on the rig. Those truckers though, just want to have it all!! LOL Thanks for all your input, it was really helpful, I am still waiting for more responses on my other post of Looking for Advice. I expected everyone to just post their fannies off. ???

Wannadiesel you are right and wrong in my opinion. As another extruck driver we dont guess but use the RPM split difference to find that(clutchless) float spot. This manuever is based on experienced listening, feel and that silly guage called a tachometer. The synchromesh units are to make up this difference to enable miss-matched component RPM's for the ease of driving, however excessive force even with the clutch continously will drastically shorten the life of those little teeth. If driven with care up shifts and down shifts properly aligned by the driver matching components will make the wear ratio very low. Technically if everything is lined up the transmission will shift with NO resistance and the synchro hubs are just along for the ride just like a twin counter shaft transmission. I dont recommend it on our trucks because the split is a lot wider and harder to control in which case you are correct. I do drive it with the clutch using the same method as the big truck as it makes my 6 spd shift like butter. If some of us were a little more patient and careful the infamous 6spd gear clash would simply vanish by trying to more closely match the engine/driveshaft speeds in each gear. PK

PK, as a current truck driver, that's what I meant when I said [glow=red, 2, 300]educated[/glow] guess. I may be educated, but I'm still guessing. I don't guess wrong often, but I'd be lying if I said I never miss a gear. And I agree, properly executed float shifting won't harm anything, it's just that it's difficult to know when you've done it right. You make an excellent point about taking one's time and shifting the trans how it wants to be shifted. Getting the shift timing right is a big adjustment for people used to driving a car. They're used to shoving those little tiny gears around however they please, but the big heavy gears in a six speed shove back if you don't let them move at their own pace. Then they complain that the trans is hard to shift. Hopefully this will allow us truck drivers to buy their Dodges on the cheap.

I agree with P Kennedy.....IF and that is a GREAT BIG IF you match the rpm with the road speed and the proper gear selection it will slide into the right spot. If not, well, you know the story. I am also an ex-truck driver and only used the clutch for getting it rolling. Never had a tranny problem. The only clutch problem was when I got one the clutch wouldn't release completely. Turned out the first disk wore half way though the input shaft. We had a bugger of a time pulling the transmission. BTW do you guys know what the FIRST sign of a tired driver is? They will miss a shift. Tom

Went through this on another forum with others and they all blamed the truck for not shifting properly. Realisticly less than 5% are actual tranny problems but driver education is the key and Wannadiesel your are right we "ALL" miss a few. I now use a different approach to this problem, I know what worked for me 25 years and "I" drive my truck what you do with yours is your business. Ask me my successful method of minimum breakdowns I will share, but practice on your own equipment. Just finished rebuilding NV4500 for a guy that 5th gear let go said he could not understand why it came apart twice in 6 months. He took us for a test drive with the rebuild and well like you said it ain't no Camaro, we directed him to the local DC dealer for any further problems. MnTom this is another common problem of trucks shifted without the clutch, the clutch disc(s) very seldom move except to start and stop start wearing into the input spline and then hang up on the wear lip. Mountain trucks shifted clutchless and jaked a lot are much more prone to this. Tomorrows shop lesson is on John Deere 2020 gas engine rebuild- I know were having fun how about the rest of you. PK

Thanks for all the information you guys!! ;D We will keep all of your comments in mind when we shift! I just love this forum not only because it is informational but it is also fun. It is pretty bad when you find yourself laughing at the computer after reading some of the answers given on other topics. [laugh] Thanks again, Tina