Towing limit @ 50MPH for the 1st 500 miles?

[EZeis]

What's the reason for this limit in my owners manual? Manual states not to go over 50 MPH during the first 500 miles of towing. Something to do with break-in? Just playing it safe (liability) in case something happens to the drivetrain?



Earl

 

[betterthanstock]

That assumes a real new truck. If you have several thousand miles, you can tow faster, but if you hook up a boxy trailer, it takes a lot more hp to go faster, than slower. It's to protect parts that are not yet bedded down (gears, bearings) from too much sustained heat. I think it's mostly for the gears/differential, especially in hot weather.

 

[AMink]

It was explained to me that the 50mph is not for the engine but for the differential. It supposedly "marries" the gears together, getting them to wear evenly and take off any manufacturing inconsistencies.

 

[sag2]

It is for the differential. They run very warm even with no load for the first couple hundred miles. Gives the gears a chance to wear in a bit before you really load them up.

Unfortunately if you ignore the recommendation you will probably will not know it for many miles when the differential fails prematurely.

 

[EZeis]

Thanks for the info guys!



I figured it had something to do with the drivetrain. I have 3k on the truck now with no towing or hauling. Next weekend I have a camping trip hauling my 5th wheel (9k+ lbs) round trip of 250 miles. I'm taking a Route (55 MPH or less limits) instead of the turnpike so I can keep the 50MPH. I'll probably do 55 as not to cause too much road rage. Only problem is the route is mostly hills and mountains.



When climbing hills and mountains, should I keep the RPMs @ peak torque or peak horsepower? Not looking to get there fast, just want to do right by the truck during it's first tow.



Earl

 

[bighornram]

What's the reason for this limit in my owners manual? Manual states not to go over 50 MPH during the first 500 miles of towing. Something to do with break-in? Just playing it safe (liability) in case something happens to the drivetrain?



Earl

I didn't pull for 2000 miles, then under 50mph for the first 500 pulling. Fords passing me like I was standing still; it was tough to do. Now I fly by them on the hills. Never hurts to take precautions while breaking it in.

 

[AKaiser]

Basically, the gears need to wear in and be "lapped. " Essentially, the lapping process is to ensure proper surface "flatness" (better gear meshing) and roughness (less is better, of course). By keeping it under 50 MPH, you're preventing excess heat buildup and an improper lapping. Many would suggest that you change your gear lubricants after the first 500 miles of towing to remove metal particles.

 

[Money Maker]

I'd say you guys are be a little to conservative. If you were hooking up a trailer as you pulled the truck off the lot than maybe it would be wise to take it easy for the first 500 miles. But you guys have already gone well over 500 miles, your gears have been through many heat cycles and there is no need to worry about it, they are broken in. If you still want to be cautious at this point keep it under 75mph for the first 200 miles of towing, but I wouldn't worry about it. You have a warranty and your trucks will handle much more than you will ever put on them.



Your rings won't even hardly seat until you pull something heavy up a few hills and get the head pressure up.

 

[Sled Dog]

It is for the differential. They run very warm even with no load for the first couple hundred miles. Gives the gears a chance to wear in a bit before you really load them up.

Unfortunately if you ignore the recommendation you will probably will not know it for many miles when the differential fails prematurely.

Will let you know of any premature failure.

As I left the lot pulling a trailer with a F150 on it.

Then proceeded to drive 350 miles at 75 to 85 mph.

65K on the 05 now and No Problems.

 

[JHardwick]

Basically, the gears need to wear in and be "lapped. "

Burnish is what they are doing. Lapping is removing metal ever so slightly with an abrasive, burnish is moving and forging metal.



At any rate, I was very lax on this warning 300,000 miles ago :-laf

 

[EZeis]

I'm going to follow what they state in the owners manual. They have a reason for it or they wouldn't put it in there.



Earl

 

[AKaiser]

Burnish is what they are doing. Lapping is removing metal ever so slightly with an abrasive, burnish is moving and forging metal.



At any rate, I was very lax on this warning 300,000 miles ago :-laf

Well, technically, you're right, but the object is the same, to a point.



From http://www.engineershandbook.com/MfgMethods/burnishing.htm



"Burnishing is a cold forming process, without actual removal of metal, where a tool is rubbed on the metal surface of the part with sufficient force to cause plastic flowing of the metal. This allows the high spots to be flattened out and the valleys filled in. It is a new concept in finishing Components. This process eliminates Grinding and honing which are costlier processes while improving the surface finish, surface hardness, wear-resistance, fatigue resistance and corrosion resistance of a part. "



I bolded "cold" as this is why we don't want high temperatures caused by high speeds, which would be exacerbated by the freshly ground gears wearing in.