Synthetic transmission fluid for a manual transmission?

Discussion in 'General' started by abcdpeterson, Oct 11, 2009.

  1. abcdpeterson

    abcdpeterson Well-Known Member

    I felt something in my transmission go pop a week ago. The dealer found gears missing a tooth or 2, they have decided to replace the transmission instead of just the damaged gears. In warranty.
    So my question. Is Synthetic better in a manual transmission? And if so, Do I offer to pay for synthetic transmission fluid?

    Side note: more info on same issue.
    After I felt the transmission go pop into 5th gear it just did not feel right. Sliding it into gear was not as smooth, and when I got up to high speeds it would sometimes grind going into 5th. I found I could produce the grinding issue 100% of the time if I did this:
    6mph+, shift to neutral, let the clutch out, push clutch back in, shift to 5th gear.

    So now basically what they are telling me:
    “You should not double clutch a car with synchro’s, it could cause damage. Double clutching should only be done in large trucks without synchro’s”
    That sound like a bunch of bull shift to you also?
    I have driven a stick on and off for 30 years, from a VW Bug to large truck. I am shifting as I always have – sometimes leaving the transmission in neutral. This is the 1st transmission I have ever had any problems with. I do NOT see how double clutching can cause any issue. IMO it helps.

    If anyone can point me to any verifiable documentation on the issue of double clutching in a car with syncros PLEASE let me know. I would love to hand them verifiable documentation.
  2. KJSatz

    KJSatz Well-Known Member

    I don't think anyone here really wants to ask this you think bump starting or other hypermiling techniques could have contributed to this?
  3. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi KJSatz:

    ___No reason that anyone would ask that question but a broken tooth is a pretty harsh hit or a defect. Bump starting adds a few HP through the system but gears are already engaged. Its the clutch that absorbs the few HP of energy to spin the ICE up whereas a std. launch adds upwards of 100 depending on how harsh the average joe is driving. Then again, bump starting at 60 in second would not be to healthy either.

    ___On the highway, Hypermiling would place far less strain on a tranny than the average Joe drives given the higher speeds and rev to fuel cut to rev while not DWL.

    ___Good Luck

  4. 09Ranger2.3XL

    09Ranger2.3XL Well-Known Member

    As info: my 07 Mustang GT 5sp Manual came from ford with synthetic in the transmission & rear end.
  5. nervousmini

    nervousmini Well-Known Member

    Sorry to hear about your car, but I will try to answer your questions as best as I can. At least they are not arguing with you aver warranty coverage and just getting your car fixed.

    1. It sounds like you had a tooth failure of 1 gear and the resulting debris caused the remaining damage - not unusual. I can't think of any automotive application where a synthetic lubricant would not be preferred over a conventional version. If the repair center is willing to install a synthetic lubricant, by all means do it. I would suggest the appropriate product for your trans from wither Royal Purple or Red Line companies.

    2. I am not aware of any documentation regarding a preferred shifting method - with the exception of Full Race automotive transmissions ( X-trac ), or full size heavy trucks ( Peterbuilt ). I certainly don't see any potential for damage by "double clutching" a synchronized trans, I don't really see any benifit beyond matching engine to trans speed for a downshift though.

    3. I am not aware of any hm technique that would cause any damage or even accelerated wear to any component of a vehicle.

    I hope this helps.
  6. jhu

    jhu Well-Known Member

    I don't know. I'm doing a lot of P&G on the highway, and that has to be a little harsh on the clutch and transmission.
  7. nervousmini

    nervousmini Well-Known Member

    p&g loads on a transmission are very minimal as stated by Wayne. It is the large dynamic loads from a hard launch that are a killer to the trans, as are low/contaminated lubricants. Clutch wear shouldn't be an issue either so long as proper techniques are used - no excessive slipping.
  8. jhu

    jhu Well-Known Member

    What RPM discrepancy would you consider "excessive slipping"?
  9. nervousmini

    nervousmini Well-Known Member

    It's not really a factor of engine speed usually unless your are talking several thousand rpms ( in which case you should consider are you selecting the correct gear to downshift to ), but rather an issue of letting the clutch slip for an excessive amount of time. Allowing the clutch to clip for too long allows an excessive amount of heat to be generated which can damage or dystroy either the clutch friction disc, pressure plate or flywheel.
  10. msirach

    msirach Well-Known Member

    If your syncros are operating properly, double clutching is not necessary. The synthetic could help your transmission operate more smoothly. What kind of car is it?

    Dumping the clutch to start the engine shouldn't damage the transmission. If you're coasting 40 miles per hour and try to bump it in 1st gear could be some nasty strains.
  11. drimportracing

    drimportracing Pizza driver: 61,000+ deliveries

    They are right IF it is done improperly, even once could damage a tooth.

    You are right IF you never miss a gear.

    I searched for almost an hour and found nothing with authority and only a few amateur postings. I have double clutched Freightliners and military vehicles for a living in my nonpizza career but don't chance the damage to my own vehicles that don't require it..

    My personal experience has been that Japanese transmissions don't hold well to abuse compared to American transmissions:flag: but Japanese last longer if driven as intended per the owners manual.

    I've had two semi-pro drag racers do damage to a Honda transmission by speed shifting, no one will ever drive my cars again who have racing experience. :cool:

    I've worn out input shaft bearings in the Metros (prehypermiling) by high rev shifting, 4k rpms. They just can't handle the rpms and gear assembly movement.

    I would say accelerated wear is possible to the starter and flywheel when restarting from a complete stop at an intersection after a FAS on a non hybrid.

    Increased draw on the battery from excessive FAS will shorten the life of a non deep cycle battery. Like all day FASing in the city. ;) Alternator demise is currently suspect but not confirmed by excessive FASing.

    Clutch disc from bump starting, Every use of the clutch diminishes material so bump starting rather than leaving it in gear increases the wear.

    High psi in tires can cause punctures by sharp rocks on gravel roads when otherwise softer tires can passively resist damage. ($35 replacement tire is a lot of gas, glad it wasn't on my FSP)

    There is no free lunch. Something has to wear when two surfaces contact. You've just got to decide what is the most economical technique.

    For instance slowing a car down with the transmission or the brakes. It is cheaper to replace brake pads than clutch discs. So coasting to a slow roll and minimal use of the brakes is superior to downshifting in all instances that don't warrant emergency stopping maneuvers.

    I use all hypermiling techniques and note part replacement so I can be better informed about wear on components. I am usually unbiased by nature and will let my experiences and observations guide my opinions even if they reveal results not popular to myself or others. Your results may differ, I drive 600 city miles a week.

    Oh yeah, I use synchromesh in my GEO transmission and it works great. :D - Dale
    Last edited: Oct 11, 2009
  12. abcdpeterson

    abcdpeterson Well-Known Member

    Thanks Dale!

    I think your saying you don't double clutch if the vehicle doesn’t require. And that brings up the question of the semantics of term “Double Clutch”

    That makes me think of using neutral at all.

    Accepted definition of “Double Clutch” is quickly letting the out and back in again while passing through neutral. So… How about it someone is letting the clutch out not to accomplish a “Double clutch” but just to keep off the trough-out-bearing during a long glide?

    That is the category I fall into, I am not “Double Clutching” I am putting the car in neutral.

    In when you look at what happens “Double Clutch” and Using Neutral are the same. I can’t imagine the dealer saying I should not use Neutral. Can you?

    Do most here use neutral?
  13. drimportracing

    drimportracing Pizza driver: 61,000+ deliveries

  14. abcdpeterson

    abcdpeterson Well-Known Member

    Same here,.:Banane35:
    Again Thanks Dale.
  15. npauli

    npauli Well-Known Member

    I concur that I wouldn't expect double-clutching to hurt anything (though I still don't understand how it helps either).

    For what it's worth, I put synthetic in the engine, tranny, and xfer case one day and immediately felt a difference - just felt smoother and slicker, even with clutch keeping the engine out of the equation. So the difference I felt was either the synthetic tranny fluid, xfer case, or the placebo effect.

    I'd probably prefer to let them fill it with whatever they want, then change to synthetic after a while. That way, you can shop for a good deal on the best fluid, can tell the difference when you change, and most importantly, can let the tranny break in with the fluid you're about to get rid of.
  16. KJSatz

    KJSatz Well-Known Member

    I guess I'm not entirely sure what you're saying. So like, do you always restart with the starter, and once your in neutral, do you not go back into gear until you're fully stopped? Or how do you get back into gear? Then what exactly do you mean by rev matching and slip shifting?
  17. abcdpeterson

    abcdpeterson Well-Known Member

    I LIKE the idea of getting that break in fluid out first.
  18. abcdpeterson

    abcdpeterson Well-Known Member

    I think your thinking the same as me. Using Neutral and Double clutching are the Same.

    Only difference I can see:
    Double Clutch you only stop in Neutral long enough to let the clutch out then back in again.
    Using neutral you leave the clutch out and in neural for some unknown length of time.

    Only issue with double clutch is it’s easier to mess up a shift as your trying to do more in a small amount of time.

    I cannot think of a reason to use double clutch in a modern car, Hypermiling or not. Using nutria I can understand.
    Odd isn’t it, same but kinda difrent.
  19. drimportracing

    drimportracing Pizza driver: 61,000+ deliveries

    Double clutching is done quickly where you want to shift to another gear immediately timing the input shaft to the gear your trying to get into.

    Excerpt from the link on double clutching I posted above from wikipedia:

    The purpose of the double-clutch technique is to aid in matching the rotational speed of the input shaft being driven by the engine to the rotational speed of the gear you wish to select (directly connected to rotating wheels). When the speeds are matched, the gear will engage smoothly and no clutch is required. If the speeds are not matched, the dog teeth on the collar will "crash" or grate as they attempt to fit into the holes on the desired gear. A modern synchromesh gearbox accomplishes this synchronization more efficiently. However, when the engine speed is significantly different than the transmission speed, the desired gear is often unengageable even in a fully synchronized gearbox. An example is trying to shift into a gear while traveling outside the gear's speed or directional range, such as reverse while moving forward.

    Slip shifting is done with an unsynchronized transmission. It's where you only use the clutch to take off from first gear and rev match all of your gears whether going up or down without touching the clutch pedal. Lets say that your going from 1st to 2nd and your engine rpms are at 1100 in first and you have to find the sweet spot of 2nd gear which may be 800 rpms so while in first you lightly bump the throttle, pull the shift lever out of 1st gear and allow the engine to slow rpms to say 750 while in neutral and bump the throttle again to 820 and drop the lever into 2nd gear as it hits 800, all without using the clutch.

    Slip shifting is done to prevent leg fatigue from constant shifting in heavy traffic and if done properly will prolong the life of the clutch disc. Big trucks with manual transmissions are tough on your legs and back. If slip shifting is done improperly often you can damage the gears within the transmission and will probably hear about it from the mechanics.

    I've tried to slip shift a few times with a synchronized transmission and it didn't perform as well as I liked so I personally won't do it with my cars. I thought that it would be easier with the synchronizers but it wasn't.

    Any good explanation for this is beyond my knowledge. :D - Dale
  20. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Are we equating double clutching with "slip" or "clutchless" shifting??

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