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Double Clutch or Not?

Discussion in 'Truck Talk' started by brann524, Feb 18, 2008.

  1. brann524

    brann524 New Recruit

    Am buying a M2 with Eaton-Fuller 10 speed. I looked on eaton fuller web site and they have a couple of videos on learning to drive a 10 speed tranny. They seem to suggest one should always double clutch when shifting gears. I used to drive a 10 speed roadranger and I only used the clutch when taking off. Has something changed or are they saying that cause they are afraid of new inexperienced driver who might tear up the tranny? Was I slowly destroying my 10 speed roadranger not using the clutch?
  2. arkjarhead

    arkjarhead New Recruit

    I was always told double clutching would wear your clutch out faster. Go figure. All the mechanics I've ever talked to always told me unless you were constantly grinding the gears it was alright to float the gears. I guess it depends on your style. Some may not agree with me. I've never known how to double clutch. When I was training I tried and my trainer finally told me to just float them because I did it better that way. He had 15 years under his belt so , as a rookie, I trusted him.
  3. piper1

    piper1 Active Expediter

    If when you shift without the clutch, the gears grind OR it seems like you have to push or hold the shifter a bit to force it in to should double clutch.

    If you can shift and the shifter just kinda falls into gear you can shift without the clutch. (this means you're doing it perfectly).

    Always a good idea to use the clutch when the transmission is cold first thing.

    If you have a smaller truck with a 6 or 7 speed, Don't double clutch. Your transmission is most likely fully synchronized (like a car) and double clutching won't allow the sychro's to do thier work. These transmissions can be shifted without a clutch as well but are much easier to abuse (the transmission won't fight back if you're doing it wrong). If you have a little transmission and it seems to need double clutching, it means she's all wore out on the inside.

    BTW, you're right about the Eaton video, they gotta assume that it's all rookie's watching it.
  4. arkjarhead

    arkjarhead New Recruit

    Correct me if I'm wrong Piper. Lets say you are shifting from 1st to 2nd gear. The first time you clutch is actually to disengage 1st gear, and then the 2nd time you clutch is to engage 2nd gear? Or is that wrong? It always had me confused.
  5. piper1

    piper1 Active Expediter

    You gotta it right Ark, double clutching is once to take it out of gear, release, clutch again to put in in the next. And all done fairly rapidly.
  6. brann524

    brann524 New Recruit

    So men what you are saying is that if I choose to shift without the clutch and Im not grinding the gears then Im not doing anything that would hurt the tranny at all right? I got the impression from the Eaton videos that only double clutching would suffice for their transmissions. Thats a lot of leg work, more than I plan on doing for sure.
  7. arrbsthw

    arrbsthw New Recruit

    I have driven an Eaton 10 speed for 10 yrs now and I shift
    either way. I can double shift when I want and shift with the
    rpms.. It has not effected the tranny in any way.
  8. nightcreacher

    nightcreacher New Recruit

    you push the clutch in to stop the sincronizers and gears from turning,taking the shifter out of that gear,pushing clutch back in gets the sincronizers,and gears lined back up so you can go to the next gear,raisng the rpms while dbl clutching lets you down shift,lowering rpm lets you up shift
  9. Crazynuff

    Crazynuff New Recruit

    I'm assuming you all know once you get rolling the clutch does not have to go all the way to the floor when shifting . Less than 1/2 way will do .
  10. Moot

    Moot Expert Expediter

    Transit 350
    If God gave you a left foot, use it! Unless of course you don't own the truck, then scratch away.
  11. cheri1122

    cheri1122 Expert Expediter

    I DO use my left foot: for picking up the stuff I drop on the floor, especially in the dark.:D The day I learned to float the gears will always be one of my favorites, and my left knee is eternally grateful, too.;)
  12. Jefferson3000

    Jefferson3000 New Recruit


    Weren't you drivin' an autoshift?
  13. greg334

    greg334 New Recruit

    I don't get it? Why double clutch a synchronized trans?

    I have to double clutch when I am really in a hurry (which is never) because my trans does not have syncros in it and as bad as this sounds, I like it that way.

    Which reminds me, I have to adjust my clutch.
  14. FIS53

    FIS53 New Recruit

    You know all these years of building transmissions and they haven't built one that works the way we drivers want. I'm positive the guys who desgin these things have never driven one in slow hour traffic on a highway through a city.

    For me it always was clutch when cold and slide it afterwards and only clutch when stopping or reversing. Otherwise once rolling in first and not in a hurry I've slide the shift to every other gear up or down and haven't blown any standard trannys after my first one when I didn't know (teenager) about sliding it right when the clutch went. After that no more broken standards. Autos now that's different. I even shift those things.

    All the truckers I know either slide it when rolling alright or slip the clutch a little (half or less depression of clutch pedal). Even when using the split shift they usually in traffic only slightly depress the clutch to let it change. Now several have hundreds thousands of miles on their transmissions and no problems.

    I guess we do what works for each of us.
  15. piper1

    piper1 Active Expediter

    Just remember folks, even though your Eaton 8 speed and up has synchro's in it, it is NOT a synchronized transmission.

    The only fully synchro transmissions are the 7 speeds and under, the model numbers all start with "FS". These puppies do not need to be double clutched unless they are wore out or you are trying to powershift your FL70 like a dragster.

    Sorry greg, couldn't resist the dragster FL70 jab.

    cheri, you can pick stuff up with your feet while you drive? That's the kinda talent my grandpa woulda seen and said "she's a keeper".
  16. greg334

    greg334 New Recruit


    That's good......but....... the Spicer manual says I need to shift between 1900 and 1950 (see attached file) and nothing about double clutching. I got to try power shifting at that speed and see what happens.:p
  17. piper1

    piper1 Active Expediter

    Guess I should've said the Eaton model numbers start with FS. If you have a Spicer 5,6 or 7 spd it is fully synchro as well so no double clutching req'd.

    Let me know how the powershifting turns out. Quater mile times in the high 50's maybe:D.
  18. Broompilot

    Broompilot New Recruit

    Learn to Float em, not gona hurt anything and one will also pick up more MPG.

    I float up and down, it takes a while to learn this, just a little push on the accelerator and it comes right out of gear if not your going to fast for that gear anyway example 35mph for 8th for that 10 speed should be top of the line for that grear time to float out of 8th and into 9th 32-35mph should be your range with rpms at 1,500 thats the secret right up to 1,500 and go up, going down when you drop to 1,150 or 1,080 thats when you float back to a lower gear give the accelerator a little goose and it should come right out than down shift. Accelerate the RPMs to match the speed while downshifting and she will slip right into the lower gear for you. Sounds easier than done but once you learn this it makes driving a 10 speed enjoyable instead of fighting it all of the time.

    After a while and some gear grinding aint gona do enough damage so beware your gona do it but it makes the drive train easier to adjust no bounciing or rocking the truck no racing to next light thus improving your MPG. If you have always been the first away from the light than your not Float N em and your paying $ for the privledge of being first at the next light while I am coasting and timming the next light to change so I try to never come to a stop at the next intersection. It takes lots of fuel to get a truck to get up and go from 0-5mph vs 6mph to up shifting into 4th.

    Take off always in 3rd gear with full load maybee 4th in a Straight Truck. While I am light or empty I can pull away in 4th or 5th loaded 3rd.

    Hope this helps.
    Last edited: Feb 24, 2008
  19. Moot

    Moot Expert Expediter

    Transit 350
    Starting out in 4th or 5th is also a great way to keep from wearing out gears 1, 2, and 3. Those gears can be saved for special occasions, like Fridays during lent.
  20. greg334

    greg334 New Recruit

    I did low 50's but ..........

    By the by, I have a spicer ps-110-7b, it is a non-syncro trans with 6+1 forward gears. I know that it has straight cut gears like my 1929 Chevrolet because the other one I have sitting over my father's house has no housing cover on it. Oh and it weighs somewhere between 735 and 760 lbs because my dummy of a brother-in-law decided to move it and used my motor stand that had a rating of 750 lbs, which now the motor stand needs to be fixed.

    Now for something completely different - what is the difference between the KW 2120 and the 2000?

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