coasting in neutral good or bad

Leecbr · #1 (**permalink**) 11-04-2010, 03:18 PM

Hey guys, I was wandering if coasting down a large hill in neutral would damage the Transmission over time. I know it's illegal and can be murder on the brakes. I only coast with no cars ahead to make sure i don't use the brakes. I would imagine the transmission fluid would still be in there if it's a short stretch. Especially with the swirling motion from the driveshaft.

For long distance towing I know it's important to unhook the driveshaft.

I mainly coast for the engine to cool...maybe save some gas...Perhaps the engine cools but I am putting wear on the tranny...

I've always done this in any manual vehicle. Never had a problem..

Is this good practice or should I avoid it.

What's your guys thoughts on this?

Fordzilla · #2 (**permalink**) 11-04-2010, 03:26 PM

I'm not a tranny expert but I don't think an automatic tranny pumps any fluid when in neutral. (hence removing the driveshaft for towing) So I would say it's not a good thing to do. I'm sure the tranny experts will chime in...........

blykins · #3 (**permalink**) 11-04-2010, 03:41 PM

If the engine is running, then the torque converter is turning, which means the front pump is turning.

As for removing the driveshaft while towing.....if the rear wheels are spinning and the driveshaft is turning, then the output shaft is turning, which causes the speedometer cable to turn, which could cause the odometer to rack up miles.

I wouldn't worry about letting the engine cool....I'd let the engine help on the braking. It's not like you're constantly driving down a hill for the life of the car anyway.

bobcowan · #4 (**permalink**) 11-04-2010, 03:46 PM

An auto will pump fluid while in N, no problem.

For a manual, if the engine is still running the input shaft is still turning. That will keep the rest of the parts lubed.

I don't see any problem at all. I do it too.

Z-linkCobra · #5 (**permalink**) 11-04-2010, 03:53 PM

Like Brent said...if the motor is running the pump is pumping. When you tow with an automatic tranny the drive shaft is spinning but you have no fluid because the pump is not pumping. Eventually the planetary runs dry and...BOOM.

Excaliber · #6 (**permalink**) 11-04-2010, 07:23 PM

I'm assuming were talking about a manual trans here, auto's vary but for the most part, drop the drive shaft. Leaving the motor running (atuo trans) is an interesting option though. That could be an easy solution for a short to medium tow distance with an auto trans!

As per Ford, all manual 4X2 and 4X4's can be towed for an unlimited distance without dropping the drive shaft. I don't know about GM, but I bet it has similiar guidelines for their manual trans.

Leecbr · #7 (**permalink**) 11-04-2010, 09:03 PM

Sorry guys, Manual Transmission. Thanks for some feedback.

I actually called a transmission shop. I was told by AAmco Transmissions ( located in downtown SLC.) that it is not good to idle a vehicle down hill in neutral. They stated it is bad for the brakes and is illegal..We already knew that.
The mechanic there said it will damage the transmission. Apparently there is some fluid thrown around while the drive shaft spins but not enough to fully lubricate the moving parts. Which done in excess will eventually wear down the parts and ultimately damage the transmission. leaving it in 5th or 4th gear on the descent doesn't use that much gas plus no damage to other parts.

I guess saving a little gas and cooling the engine a bit, really isn't saving if we have fix or replace the brakes and tranny.

Bob In Ct · #8 (**permalink**) 11-04-2010, 09:22 PM

One other potential problem is that when you're coasting in neutral for any distance, all the coolant in the radiator is getting to ambient. When you start spinning the engine again a lot of cooler than normal fluid enters the engine very quickly. This rapid cooling of various components could possibly cause some damage. This will happen even with a thermostat since the thermostat will not close until the coolant makes its way to the top of the engine.

Just my $0.02 worth.

Bob

Excaliber · #9 (**permalink**) 11-04-2010, 10:03 PM

Eh,,, the Ammco guy is throwing out GENERIC politically correct advice that covers all transmissions of all makes and models under any concievable condition. A nice CYA approach to customer advice,,, but he didn't answer the question. Is it OK to coast YOUR manual trans?

Actually coasting would be better than towing!! When coasting you got the input shaft turning with the running motor (as was mentioned earlier) and the tail shaft turning from the rear end gears! Ford doesn't seem to care if the input shaft is turning or not (manual trans), there OK with just the tail shaft turning.

Ford says all manuals, no limit on towing, therefore, no limit of coasting!

Leecbr · #10 (**permalink**) 11-05-2010, 08:32 PM

Very cool...great information Excaliber. I guess it's good either way. In gear you get the benefits of safety and proper braking.. Neutral coasting seems to be harmless with manual transmissions in fords. Thanks guys.