Breakin LD vs HD

[camperbob]

Something I have always wondered, and hoping to gain some insight. If you read many new truck owners manuals, they recommend not pulling a trailer, or loading heavy within the first 1,000 miles or similar. While I understand the reasoning, why don't Heavy Duty Class 8 engines get the same "disclaimer." Its a given that from the day it leaves the showroom, a class 8 or similar engine is going to be worked.

What am I missing here?

 

[SteveSRT8]

These days "break in" is more about the drivetrain than the engines.

Frankly in an engine the rotating assembly is either right or wrong from birth. The rings and such seat very quickly, and load is actually good as the gas pressures force the rings outward into the cylinder wall for a great seal. Many larger engines are run in for a time on a dyno, thus no care required.

It's the transmissions and rear ends, etc., that need a break in to seat well...

 

[4wheeldog]

I am not so sure that the admonition not to tow is related to the engine.

Differentials need to run in, even more than engines. If they are heavily loaded early in life, they will run quite hot, and some parts can overheat in small areas.

Engines need to go through some heat cycles, but it can be even more critical for some other drivetrain parts.

So......Depending on how overbuilt the rest of the truck is, the break in instructions can be different.

 

[camperbob]

Originally Posted By: SteveSRT8
These days "break in" is more about the drivetrain than the engines.

Frankly in an engine the rotating assembly is either right or wrong from birth. The rings and such seat very quickly, and load is actually good as the gas pressures force the rings outward into the cylinder wall for a great seal. Many larger engines are run in for a time on a dyno, thus no care required.

It's the transmissions and rear ends, etc., that need a break in to seat well...


Case in point back in the early part of 2000 we saw many 7.3's at the dealership that were well maintained, and in for stupid stuff. At the same time along comes the railroad with 300k and more coal dust on the engine than could manage, even the air filter was sucked into the box...yet they started quicker and ran better than the average joe. Im sure this isn't across the board, but I fully agree its either right, or not

 

[HerrStig]

VW used to run their flat four bug engines for half an hour on natural gas before installation.

 

[Cardenio327]

I worked for a company that had mostly 12.7 Detroits, rebuilt in house with genuine GM rebuild kits. We would typically get 900,000 miles on bottom ends between rebuilds.

The mechanic that did the rebuilding would tell the first driver out on a fresh rebuild to run the truck harder than usual if possible, wide open throttle with a full gross weight of 105,500 lbs. I think they would even make sure a pre-loaded trailer was ready and waiting to avoid driving the truck around empty before the break-in.

No special break-in oil was used, just the same bulk 15w-40 for everything.

 

[jrmason]

As mentioned its mainly the rear ends. Towing generates pressures and temperatures that are much higher than the lapping that takes place at the factory. If the gear set is not allowed to work harden at low temps and work loads the mettalurgy is altered which will cause premature failure.
I'm not involved in class 6 and 8 trucks but I can only speculate the manufacturing process is different for heavy duty rigs. Heavy duty trucks are designed for one thing and that is work and have to be ready to do so the day they are bought. This likely means superior components and manufacturing (and costs) compared to light duty vehicles.

 

[TiredTrucker]

You will not find anything from heavy truck OEM's regarding light loading, even for the drive train, on heavy commercial trucks. They go from dealer, to owner, to work. Many of them, their first load is gross weight. Except for the occasional lemon that happens with any brand, size, etc truck, these trucks starting out of the gate going right to work with what they will be doing for their entire life are doing just fine. With the majority getting into 1 million mile territory with no major component rebuild.

My pickups, I just operate them right out of the gate just like I will be operating them over the entire life. Have never followed the light loading philosophy in over 40 years of owning various vehicles and heavy commercial trucks. i have never bought into the drive it like you stole it philosophy either. I just operate it like I always will.