-Just curious, I used to drive a Freightliner FL-70 with a Cummins and a 6 speed and was able to shift it pretty smoothly w/o using the clutch. Thanks!

 

I've never driven a manual you couldn't shift without the clutch.
All a matter of getting the rpm's right.

 

^ +1


As long as it's got synchros, you can get it done pretty easily without the clutch. I never do it, but it's totally possible.

 

Yep...as long as the rpm's are right it will work. but when it doesn't it make a lot of racket. btw...i dont do it

 

Yes, I drove mine for six weeks floating the gears because my clutch went out

 

The Freightliner probably wasn't synchronized...

The ZF6 is synchronized, while you "can" shift a synchronized box without the clutch, it is a lot harder on it and will wear the synchros out faster unless you are perfect with the revs as the transmission is still trying to "help" get into gear.

A non synchro box has no synchros to wear and you learn pretty quick what the right revs are lest you grind... that type of box requires double clutch techniques to shift properly, which shifting without the clutch accomplishes.

(I've driven both synchronized and non synchronized transmissions for years in trucks/tractors big and small)

 

^^^^^^^^^ What he said^^^^^^^^^^


Yes you can do it, but you'll wear the synchros out.

 

i know when i find the synchros right, that then, i could've floate it, but not will'n to try...

 

Yeah, I said as it would work as long as the transmission had synchros.

I meant as long as it does until you wear them out... shifting a transmission with synchros that are dead is worse than not having any to begin with.


But yeah, a tranny that doesn't have them to begin with is much easier to shift without a clutch....

 

Back in my truckin days I would float the gears in my Honda civic 5 speed mostly out of habit. I raised eyebrows with some friends, but all in all worked pretty well. (didn't know about the syncr wear till now) I just had to think where reverse was before attempting to back out of the garage.

 

I didnt realize that shifting a syncro tranny without the clutch wore the gears either. When I drive my fathers 01 f250 I rarely use the clutch, and he never does, except when starting. I drove my old civic and my old mustang like that all the time, oops!

My good ol western star doesnt mind it though

 

I don't see how it is hard on the syncros if you are shifting it without a clutch and not jamming it in and out of gear. With the correct rpms and speed it is smoother than using a clutch.

 

IF you can get the revs exactly perfect every time and shift with finesse as you mention, then you are not going cause undue wear, the problem is that the synchronizers still have to work anyways, and I guarantee that most people will not be able to always shift it perfect. The trans will still compensate for not getting the revs exact via the synchoes. Think of the potential wear if you don't put any effort in shifting (i.e. going 4th to 3rd and not rev-matching)

A clutched shift in a synchro box requires the synchro to only to slow down or speed up the input shaft on the transmission, an unclutched one requires the synchros to speed up or slow down the input shaft, whole clutch/pressure assembly, engine crank shaft and other rotational engine mass.

Now, clearly the trans can do it, but it's sort of like the difference between clutch wear pulling away on level ground versus pulling away on an upgrade towing a trailer. The truck can handle it, but one causes more wear than the other.

Yes the clutch does wear and it is moving parts too, the difference, and someone can correct me with $$$ figures if I'm wrong, but a clutch is way cheaper to put in than rebuilding the ZF6.

Echo the comment that a trans with shot/bad synchros is worse to shift than a trans with none. I've driven a F-SuperDuty 460 5-speed that the 3-4 and 4-5 synchros were shot, fun to even get it to shift especially with no tach.

 

Can you? Absolutely

Should you? Probably not.

 

My synchros in my ZF6 are shot in 1, 2, and 3 so shifting it period isn't much fun right now. Shifting from 3 to 4 and 4 to 5 without the clutch is smooth as butter at 1800 rpm's.