Longer lasting engines?

[Ausfahrt]

I have a theory about engine longevity that I have had for a number of years. In my experience, engines mated to manual transmissions seem to run better and last longer than A/T engines.
My thinking is the difference is at idle. The engine in a car with an A/T probably spends hundreds of hours at idle and in DRIVE with the drivers foot on the brake during its life. That means that the engine is churning against the transmission at its lowest RPM and lowest oil pressure. Add in A/C on hot days and its like lugging the engine.

On the other hand, those hundreds of hours at idle in the engine with the M/T are "freewheeling" with the transmission either in neutral or in gear with the clutch engaged.

I don't have any proof other than personal observations and a gut feeling but I would like to know what you BITOG'ers think. Am I on to something or (as my wife says) do I have too much unsupervised time on my hands?

 

[The_Jeff]

Torque convertors are pretty loose at idle so I doubt it's that.

I wonder if it's more of a mechanical empathy on the part of an owner who deliberately, and as a minority, chose a stick shift. They'd be less likely to gun it when cold etc.

Give someone an auto and they just know one pedal makes it faster and the other slower... they don't feel the engine being sluggish from thick oil etc.

You'd be way more likely to find a remote start in an automatic car-- good thing if they hammer it, bad if they idle it forever to get heat/AC.

 

[exranger06]

I think most auto-equipped cars are in the junkyard sooner than their manual counterparts because the auto transmission took a dump, not because of the engine. Manual transmissions tend to last a lot longer.

 

[Johnny]

I think your wife is correct.

 

[daves66nova]

Originally Posted By: bigdreama
Add in A/C on hot days and its like lugging the engine.
doesn't the engine kick up the rpm's when the a/c is on?

 

[d00df00d]

Good points on all accounts.

Also, don't forget this point on the other side of the argument: nobody shifts perfectly, which means there is usually more shock loading on the rest of the drivetrain with a manual transmission.

 

[SuperDave456]

Also remember that something like 6% of the cars sold last year were manuel.
The reason that the Army is requesting all new vehicles are automatic is that they are tired teaching kids how to drive a stick.
Lowest common denominator says that a Automatic will be more abused than a stick.

BTW, both myself and my wife drive an automatic. Both transmissions are serviced regularly. I expect them to last longer than average because of the maintenance we do.

Do I expect the majority of people to do this?
No.

The Transmission place my family goes to has been in business since the 50's. He says the majority of people never have their transmissions serviced, until it totally goes out.

A lot depends on the driver, and the driver is the one who normally determines who buys the car.

 

[GMFan]

I'd say it isn't really true, but I have seen some more high mileage stick vehicles compared to automatics. My guess is that the automatics died before the manual transmission did.

If there was a noticeable difference, I'd say it is because more manual transmission drivers are more mechanically inclined, and thus spend more quality time with their vehicles. I know way more manual transmission drivers who change their oil than their automatic counterparts.

I've worked construction, and I'd say 50% of them drove manual transmissions. I guess people who work with their hands for a living enjoy the stick shift more than others.

 

[mstrjon32]

Originally Posted By: eljefino
I wonder if it's more of a mechanical empathy on the part of an owner who deliberately, and as a minority, chose a stick shift. They'd be less likely to gun it when cold etc.


I gotta say, I currently own one of each and don't hesitate to drive the snot out of either. If anything, I'm softer on the automatic.

If there is truth to this, I'd say it's because automatic transmissions tend to fail sooner than manuals, and when the failure is at 150K+ miles, for many people its not worth fixing. That doesn't mean the engine lasts longer, though.

Maybe its because automatics never seen engine braking and don't get opposite pressure on the rings? I know occasionally when I'm almost home, I make the last turn towards my house and then run it up to redline in second, and then let it coast back down to 1,500 before releasing the clutch. It's kind of fun and I tell myself it cleans the carbon out of the engine. The automatic doesn't get this treatment.

 

[Quest]

In terms of trannie, M/T does last longer than A/T due to wear-n-tear issues on the A/T clutch friction plate materials. As transmissions age due to mileage and service wear,A/T will begin to slip; whereas M/T tends to whine more due to wear on helical gearings.

On engine, however, it all depends for in A/T equipped engines, provided that all things equal, A/T equipped engines should theoretically lasts longer due to the lack of "lugging" and also "thrust bearings" that typically comes with M/T gearbox.

Ultimately, the longevity of engines are pretty much boiled down to the following:

-matellurgy, machining and design
-owner maintenance and servicing (OCI, tuneups, etc.)
-operational conditions (dusty or excessively high-load conditions tend to wear out your engine)
-user's means of operation (if you are a frequent "lugger" of M/T equipped gasoline engine then obviously you may wear out your big-end/rod bearings sooner.

There maybe more to go along with this so feel free to add points.


Q.

 

[PT1]

I think Johnny is correct...

 

[ClarkB]

Originally Posted By: mstrjon32
If there is truth to this, I'd say it's because automatic transmissions tend to fail sooner than manuals, and when the failure is at 150K+ miles, for many people its not worth fixing. That doesn't mean the engine lasts longer, though.


Amen to that. When Toyota and Honda started getting a reputation for really well made engines in the late '80's, many of their cars were still very prone to rust. So if you're in the rustbelt, add in the fact that your car is a rust bucket at 150K+ and you really don't want to sink any money into it.

Clark

 

[andrewg]

I can't speak for how others drive their auto's or manual shift. I baby both. Rarely do I 'slam' gears or lug an engine when in manual. As far as my auto...well, I'm confident that it will last just fine with the way I drive it. I wouldn't be surprised if my auto vehicle outlasts my stick car. Why?? Because the auto vehicle has already proven to be one of the world most long-lived engines in the world. It's a Mercury Grand Marquis (same thing as a Crown Vic....taxi, police, etc.). Those cars drive hundreds of thousands of miles in the WORSE traffic possible. Tons of idle time and stop and go driving, the transmission constantly shfting up and down, loads of heat generated, erratic and sometimes terrible driving habits, and yet they last forever.
So at least in the case of a Crown Vic/Merc Grand Marquis....I would say that an auto transmission causes no shortened longevity.

 

[Cutehumor]

Originally Posted By: exranger06
I think most auto-equipped cars are in the junkyard sooner than their manual counterparts because the auto transmission took a dump, not because of the engine. Manual transmissions tend to last a lot longer.


I'm going through that now with my 96 sunfire. I'm babying the trans right now.

 

[Ausfahrt]

Thanks alot Johnny.

Lets just keep this between you and me. Wifey doesn't need to know about it.

Oh. And stop encouraging others, willya?

 

[Bamaro]

I dont know for sure but I have always heard that an A/T is easier on the engine than a M/T. No lugging and no banging of gears. Also I think that people who drive sticks 'tend' to be harder drivers.

 

[labman]

I don't think engine longevity is much of a concern. I think most cars go to the scrap yard for other then engine failure Fram filter, iffy lube, and all.

 

[UNC017]

I don't know, I would think that any advantage an engine picks up from a manual trans not loading it at idle would be more than offset by the impulsive loads during shifting and the constant banging of the throttle open and closed. Yes, a good driver can avoid most of that during shifting (I consider myself a pretty decent stick driver, my passengers don't bob their heads every shift anyway) but an automatic is still 10 times smoother. And the throttle just stays open and the engine sees a nice constant load. Of course the newest computer controlled automagic transmission controllers actually do throttle the engine back during shifts and wait until the sensors indicate that the RPMs are pre-matched before engaging the next gear, which is the smoothest method imaginable short of a CVT.

Another issue is the transmission system ITSELF. Manual transmissions rarely outright fail, although synchronizers tend to get iffy beyond 150k miles or so, but they always need clutches well before an automatic will need an overhaul. In my experience automatics always last well to the high side of 150k miles unless the automatic has some defect. A manual trans clutch replacement is a pretty big deal since the transmission (or engine, depending of the drivetrain layout) will have to be removed to replace the clutch. A neighbor just sold her Mazda 626 with only 124k miles on it because the clutch was gone, the front end was getting bad, and it was going to be a $700+ job for the clutch alone.

All that plus the fact that the vehicles I've run out the absolute highest mileages (300k, 250k, and over 400k miles) have all been American v6 or v8 engines mated to automatics leads me to believe that automatic-transmission cars probably have the longevity edge.

Besides, there's something positively stone-age about rubbing a piece of un-lubricated friction material on a spinning metal plate to get a car moving... even though I wouldn't trade my stick Jeep for an automatic for anything.

 

[mstrjon32]

Originally Posted By: andrewg
It's a Mercury Grand Marquis (same thing as a Crown Vic....taxi, police, etc.). Those cars drive hundreds of thousands of miles in the WORSE traffic possible. Tons of idle time and stop and go driving, the transmission constantly shfting up and down, loads of heat generated, erratic and sometimes terrible driving habits, and yet they last forever.


I have no evidence to back this up, but it's my feeling that RWD transmissions last longer than FWD ones, as a general rule. That's not to say that there aren't some decent FWD's, but the RWD automatics take a beating and keep on going. FWD models always seem much more fragile and failure prone. Not to mention more expensive to repair. Give me a TH350 any day.

 

[UNC017]

Originally Posted By: mstrjon32


I have no evidence to back this up, but it's my feeling that RWD transmissions last longer than FWD ones, as a general rule. That's not to say that there aren't some decent FWD's, but the RWD automatics take a beating and keep on going. FWD models always seem much more fragile and failure prone. Not to mention more expensive to repair. Give me a TH350 any day.


Well, a TH350 (or in my case a TF904 or 727) is definitely more reliable than *any* FWD transmission, but its not really a fair comparison. A TF727 or TH350 is just way simpler than almost any FWD transmission made. Yeah, there were a few early 3-speed FWD automatics that were universally horrible, but today they're all 4, 5, and 6-speed computer controlled things. You'd have to compare a 4L80E or a 545RFE to a modern front-drive to get a real comparison.