Coasting up to lights - any problems?

[George7941]

I shift into neutral with my 5spd manual when I am approaching a red light and let the truck coast for a while.

I just want to make sure that I am not damaging the transmission. I don't think so, the input shaft is spinning bacause the engine is spinning, the output shaft and the counter shaft is spinning because the vehicle is moving. I don't see a lack of lubrication anywhere.

I have always done this. I did have two bearing failures in transmissions in two previous vehicles I have owned. I don't think it was caused by coasting.

Right?

And, please, no postings about how dangerous it is to coast in neutral.

 

[Dave Hess]

No damage will be done.

What vehicles did you have that had trans bearing failures ?

 

[VK56VD]

No problem but there is a more fuel efficient approach. You can use less fuel by keeping the car in gear and letting off the accelerator before you approach the light.

 

[mstrjon32]

You're fine coasting to a stop out of gear, but I like to leave it in gear until it's just above idle and then shift out.

 

[The_Jeff]

Could be interesting to read your owners manual on flat "dingy" towing... some automatics are real stern... 25 mph for 25 miles, no more. But few to no stick shifts.

 

[Steve S]

Originally Posted By: eljefino
Could be interesting to read your owners manual on flat "dingy" towing... some automatics are real stern... 25 mph for 25 miles, no more. But few to no stick shifts.
The engine is still running so there will be oil pumping.

 

[nickaluch]

Your going to go thru brake pads pretty quick, no engine braking to slow the car down

 

[George7941]

Originally Posted By: eljefino
Could be interesting to read your owners manual on flat "dingy" towing... some automatics are real stern... 25 mph for 25 miles, no more. But few to no stick shifts.


Owners Manual says "No towing of 2wd vehicles with rear wheels on the ground". It does not specify "Automatic transmission only". I assume the problem here is that the input shaft is not turning and hence the splash lubrication system in the transmission is not working the way it is designed to. When medium and heavy duty trucks with manual transmissions are towed with the rear wheels on the ground, either the drive shaft or the two rear axle shafts are disconnected to prevent damage to the transmission.



"What vehicles did you have that had trans bearing failures ?"
I had a transmission fail on my 1982 Mazda B2000 p/u that I owned from brand new. I also had a bad whine develop in the 4spd in my 1986 F250. It was time to scrap the truck anyway, so that is what I did in 2006 when the whine developed.


"No problem but there is a more fuel efficient approach. You can use less fuel by keeping the car in gear and letting off the accelerator before you approach the light"
I seldom exceed 2000 rpm, so I don't know if fuel gets cut off on overrun.


"Your going to go thru brake pads pretty quick, no engine braking to slow the car down"
I drive conservatively and get 100k mi plus from my front pads, even with 80% city stop and go driving.

 

[Drew99GT]

Originally Posted By: mstrjon32
You're fine coasting to a stop out of gear, but I like to leave it in gear until it's just above idle and then shift out.


That's what I do. There's enough engine braking to save the brakes. The only time I downshift to slow down is 5th to 4th, or down to 2nd to go make turns or something when a stoplight is still green.

I can't stand driving with people that downshift all the way to 2nd every time they slow down. It's murder on the clutch and syncros.

 

[mstrjon32]

Don't listen to anyone that tells you to downshift to "save your brake pads." That's insanity.

A set of brake pads costs $40 and takes 30 minutes to install. A new clutch kit typically starts at $300 and takes a full day to install, and on most modern FWD cars it costs a ton more than that.

There are many reasons to downshift, but saving brake pads is not one of them.

 

[Junior]

Other than increase syncro wear to get it back into gear, not a problem. Hold in the clutch, wear out the throw-out bearing. 6 of one, half dozen of another.

 

[mstrjon32]

I mean, presumably, if you're coasting in neutral, you've put your foot on the clutch, taken it out of gear, then released the clutch. You should never just hold the clutch in for an extended period of time for the aforementioned reason.

I don't see how increased synchro wear could result from either behavior (coasting in or out of gear), since you're not changing gears and presumably you're not coming off a light in 4th or 5th, and have to shift back into 1st anyway.

 

[AcuraTech]

I don't see any problem with coasting in neutral. The only time I would utilize engine braking with a manual transmission is on a steep grade.

 

[TallPaul]

All of this is a non issue with rear wheel drive because it is not near as costly to replace the clutch or throwout bearing in a rear drive vehicle. So, the lesson is, don't buy front wheel drive cars unless you consider it a throwaway item when the big stuff goes wrong.

I occasionally will downshift through most or all of the gears just for fun, but most of the time just one gear, then coast to near stop and pull the lever into neutral.

I often pull my automatics down a gear (out of OD) coming off the freeway for some engine braking.

 

[mechtech2]

Approximately 400 HP brakes vs 3 HP engine braking? Why bother?

Coasting down hills or up to lights is OK if the engine is running [stick shift]. Many auto transmissions are a different story.

 

[Junior]

Originally Posted By: mstrjon32
I mean, presumably, if you're coasting in neutral, you've put your foot on the clutch, taken it out of gear, then released the clutch. You should never just hold the clutch in for an extended period of time for the aforementioned reason.

I don't see how increased synchro wear could result from either behavior (coasting in or out of gear), since you're not changing gears and presumably you're not coming off a light in 4th or 5th, and have to shift back into 1st anyway.


If you stop in a gear with the clutch pushed in, all shafts in the transmission stop turning. Moving to a differnent gear is easy.

If you stop in neutral with the clutch out, the input shaft is turning. When you push in the clutch and jam it into gear, the syncros have to stop the input shaft to engage the gear.

Unless of course you wait long enough for friction to stop the input shaft.

 

[George7941]

Originally Posted By: mechtech2
Approximately 400 HP brakes vs 3 HP engine braking? Why bother?

Coasting down hills or up to lights is OK if the engine is running [stick shift]. Many auto transmissions are a different story.



I am curious as to why an auto transmission would sustain damage from coasting in neutral. With the engine running, the pump is working, gears and bearings are being lubricated. So, what is the issue?

This brings up a question about towing, I will start a new thread on it.

 

[TallPaul]

Then there are some folks who sit at a red light in gear, holding the clutch pedal down. That ought to make for some serious long term wear on the throwout bearing.

 

[ClarkB]

Originally Posted By: TallPaul
All of this is a non issue with rear wheel drive because it is not near as costly to replace the clutch or throwout bearing in a rear drive vehicle. So, the lesson is, don't buy front wheel drive cars unless you consider it a throwaway item when the big stuff goes wrong...


I think the average fuel economy of a FWD vs. RWD vehicle will more than pay for the extra money spent when the clutch goes south. The lesson would be better put into perspective (and more learned from it) when we consider the entire cost of ownership. I'll stick with my FWD "throwaway" car.

Clark

 

[Rooy]

I didn't see it mentioned, but you will use less fuel by coasting and leaving it in gear until just above idle. The fuel injection computer stops the injectors from pulsing when you're off the throttle and are above 1500rpm or so. If you just put it in neutral you're using as much fuel as it takes to idle.

Probably not a huge difference, but worth noting.

Don't know how long the revs will stay up if you leave it in 5th w/o downshifting though (coming off the highway, for example). I usually downshift to at least 4th, sometimes 3rd in that situation.