manual transmission damage with EOC?

[GasSavers_Red]

In a FWD transmission setup where the diff and the tranny are in one unit, the ring gear could provide enough lubrication, however what about those of us utilizing a RWD or 4WD setup? Doesn't the output shaft have an oil slinger on it? Else how would you flat tow something?

[omgwtfbyobbq]

Here's a good read on the subject.

The only problem is that, for most manual transmissions, the output shaft is the shaft with the freewheeling gears and shift sliders. The countershaft is solely driven by the engine, and is also what slings the lubricant around. With the engine off, the output shaft doesn't get any lubricant. (As mentioned earlier)

Front wheel drives can be much different. Saturn transmissions, manual and automatic, are designed such that they can be flat-towed indefinitely. Quite handy for the RV crowd!

So RWD should be o.k. for shorter distances too, but I'd probably tow my pickup long distance w/ the driveshaft disconnected, as opposed to my fwd car, because the r&p, input, and output shaft are always in oil with the fwd car, while some spinning parts of the rwd trans may not get lubed properly on a long journey due to the countershaft being below the mainshaft.

[repete86]

Considering how long I've been EOC'ing with an auto that has more miles on it than most autos last, I think that all of these claims of destroyed trannies are unfounded. Has anyone had a problem apart from people doing things like towing cars for thousands of miles at high speeds, or are these people focusing on hypothetical situations? I think that it's the latter.

[atomicradish]

Originally Posted by repete86

Considering how long I've been EOC'ing with an auto that has more miles on it than most autos last, I think that all of these claims of destroyed trannies are unfounded. Has anyone had a problem apart from people doing things like towing cars for thousands of miles at high speeds, or are these people focusing on hypothetical situations? I think that it's the latter.

I'm EOCing in my Metro now, and honestly, I wouldn't have done it if you hadn't had so much success with it. If there were a lack of lubrication would the transmission not emit a screeching noise when coasted? I have yet to hear any such noise, and the car drives fine.

[omgwtfbyobbq]

Originally Posted by atomicradish

I'm EOCing in my Metro now, and honestly, I wouldn't have done it if you hadn't had so much success with it. If there were a lack of lubrication would the transmission not emit a screeching noise when coasted? I have yet to hear any such noise, and the car drives fine.

Nah, it's the metal on metal of the needle (or ball, but needle bearings aren't as sturdy) bearings that'll eventually kill them, which should be relatively quiet. But like repete said, most autos probably won't last long in the first place, so if the clutch packs need to be replaced every 150-250k miles, and the bearings will last that long in limited EOC'ing with an auto, it's not a big deal.

[JanGeo]

There is no load on the parts and the bearing are getting enough oil to not be harmed. I do get a whine when coasting in neutral with the engine on may be caused by no loads on the shafts.

[Gary Palmer]

I would agree with the starter and clutch possibilities, but I don't think I can buy into his assesement on the manual transmission. As long as you have the right amount of oil, in a reasonable weight, I don't think that coasting, engine on or off is going to cause any appreciable damage to a manual transmission.

The only problems I have encountered in manual transmissions is failures due to not having enough oil. I am not particularly comfortable with running to light of an oil, but my expectation is that in most cases that is even Ok, because to a large extent people are not loading the daylights onto the transmission, because of their efforts to get better mileage.

Additionally, on a manual transmission, you can minimize syncro wear, significantly, just by shifting at a speed that the engine input and the gear you are shifting into are spinning at the same, or close to the same speeds. If you are careful and reasonable, you can shift through all of your gears, by a little wise use of the gas pedal and speedometer, without using the clutch at all. You can also shift into neutral, without using the clutch, if you just let up on the gas a little and slip the shifter into neutral, without forcing it.

Anyways, a little wordy, but I don't think their is a problem.

[cems70]

I did massive amounts of engine off and engine on coasting for all 225,000 miles of my Civic VX ownership. And before the VX, even more EOC coasting w/ my '86 CRX hf which I bought used w/ 40k miles and put 100,000 miles on. Both cars saw both short and very long coasts (i.e. 1,2,3,4+ miles at a time when the hilly/mountainous or exit ramp conditions were present). I never replaced a clutch or starter in either car. And I never had any transmission problems in either car.

[lca13]

Originally Posted by Coyote X

There are very few manual transmissions that will be hurt by engine off coasting. Just look at the cars being towed behind RVs they never have trouble out of the transmissions. The ring gear is big enough that it throws more than enough oil at anything important when the engine is off while the car is moving.

Most of those have the driveshaft disconnected.... keeping it connected is a no-no for RV towing.... actually, a look at why this is a no-no on the RV forums might give additional insight... but I do recall complaints of screwed up transmissions after being towed in with the driveshaft attached.

[Drew1d]

Wait, so, if the gears aren't turning why are you so concerned about lubrication? If your in engine off or engine on, if the clutch is pushed in why exactly would this matter?

This doesn't make sense to me at all. Unless you were starting the car by dropping the clutch in 4th at 60mph, or if you constantly were on the starter, I really don't understand the harm.