I repeat:
No full synthetic for 1000 miles to permit the rings to seat. Vary speed to prevent narrow wear patterns on gears. Motorcraft semi-synthetic 5w20 is fine for 95% of us. Full synthetic is ok, just not necessary unless you need extra protection at start-up. Change your oil and filter at the recommended interval or sooner. (through the warranty period - after that do whatever you want - it's your engine and your dime.)

 

No matter how many times you say it...
No matter how strongly you word it...
No matter how many ethereal "authorities" you cite...

This remains what it is: shadetree mechanic stuff from the carburetor era.

The fine clearances in the engine of concern are not the gears, they are the wrist pins, piston rings, and such. These have clearances on the order of 8 µ and seating is important, but it happens in the engine far faster than you give it credit for and the lubricant used, so long as it is a mainline lubricant (and without additives), makes little difference to this process.

It just happens far faster in the engine than the axle wear in process where you are wearing in the 90º hypoid, spiral type gears and the faces and loading need to be virtually perfect.

I believe that the axle break-in is the limiting element in the recommended break-in period that OEMs publish. Remember that they only tell you the most limiting break-in. The shorter and less limiting ones will take care of themselves.

As I mentioned: I put my money where my mouth is on two Fords and they both run like a top... I keep my cars for the long haul.

 

BW:

I had a '79 Toyota 4WD and the manual said to lock(manual hubs) for the first 300 miles. My '86/'97 Ranger 4WDs had the self-locking front hubs, so that prevents any front end locking without switching into 4WD because it unlocks in reverse after 10'. That blows a hole in your ring/pinion break-in theory for some vehicles.

How are you doing oil analysis yourself?

 

Different engineering for different brands; I owned a 2003 Honda CR-V, and the Honda owners website specifically said NOT to change the factory oil until 7500 miles (longer than the 5K severe cycle), because the factory oil had additives that helped break in the engine. I don't recall exactly what they said the additives did...

 

If the factory guarantee is that specific... follow it, if you want to keep the guarantee good... No sweat. I would do just that, as I do keep the guarantees good.

Be tight on this. Some say words to the effect of: there is no need to change oil before... that is not the same as: do not change the factory delivered oil & filter.

If the guarantee says to use a good quality oil then Mobil One is as good as any other mainline brand, and in my opinion is better for the reasons I've gone over.

 

Regarding the differential gears: what I said is not theory, just look through any shop manual that shows how to set up a rear end and you'll see precisely what I'm talking about.

Clearly you don't have a clue as to why they specified what they did and without knowing what kind of axles you had I wouldn't hazard a guess as to why they specified what they did. I speak from the axles I had including the one I replaced and then broke in.

Oil samples: I fill up a small bottle and mail it off. A lab does the analysis and emails me the results. For example:

Date Miles Mailed Rcvd Al Cr Cu Fe Pb Sn
9-Apr-07 198142 10-Apr 18-Apr 10 0 4 42 4 6

Si K Na Mo H2O Oxidation Visc Glycol Fuel Nitrates TBN
31 28 23 84 0.2 8.6 7.5 0.0 0.0 6.0 4.8

I couldn't get the sample results to line up even thought they did in the post winndow.

 

I'm questioning the fact the the differential gear set is the limiting factor in a vehicle break-in period bacause the automatic locking hubs on some 4WDs make it impossible for it to be the limiting factor. That was on Ford Rangers from at least 1986 to about 2000 or so when they went to the constant engagement like on the F-150s.

Now a days because of new machining and lapping technology of a ring/pinion sets when installed in a new vehicle wouldn't need any break-in period. I worked in maintaince at Ford's Sterling Gear/Axle for +35 years. I maintained the machines that cut the ring/pinion sets, lapped them, assembled the cases and carriers. That's all the preload testers, shim selectors, ratio verifers, pattern checkers, carrier balance, etc. I do know a bit about ring/pinion sets and matching them.

I've setup ring/pinion sets where the ring gear was 2' in diameter.

I doubt if a Ford dealer rebuilds any rearends these days. I know that the '09 FE/FEH WorkShop Manual states the rearend other than replacing oil seals is unserviceable and I have no idea who builds that.

The '97 Ranger had a Dana 35 front end and the rearend was built at Sterling.

 

First, I disagree with your automatic locking hubs idea.

Second, you may be well acquainted with setting up rear ends in the shop, but it is clear that you do not understand the required break-in of gears that require fine alignments. Particularly those gears that carry potentially heavy loads across wide gear faces.

...And yes the shop manuals do have sections devoted to reworking and aligning rear ends.

I just do not agree with your conjecture.

 

Don't just disagree, tell me how you think that it works? When 4WD is engaged through the driveshaft/gearing the wheel sense this and locks up. If you disengage 4WD, drive in reverse at least 10', the wheels disengage. Now, if you don't back up, the wheels stay engaged! I had problems with my '86 Ranger because it was a 5-speed manual. If at a stop on a slight incline, clutch in and rolled backwards just a little bit one wheel would disengage. Makes a lound buzzing sound.

I'm refering to the '09 FE/FEH that states that the rearend is unserviceable. I had hoped to see what the ATC unit looked like and found nothing because of this!

Speaking of a FE/FEH 4WD similar to a constant engaged frontend 4WD. When in 4WD your driving on the tooth's drive side of the ring/pinion set. If not in 4WD which is the majority of the time, the wheels are driving the ring/pinion set on the tooth's coast side although without much of a load.

You interjected the rearend break-in as a limiting factor, so this is about new vehicles or shop assembled rearends/frontends and not rebuilts.

If there was a rearend/frontend break-in period, I'm sure that Ford would want you to drain/replace the fluid. The Scheduled Maintainance Guide shows that at 105K if you have a Dana unit but refers you a exceptions section. It states that a Ford-designed rearend is lifetime synthetic. The Escape 4WD listed as non-synthetic, so if you do lots of towing, etc., every 3K or three months, it states. Sounds like what's suggested for the transmission under towing.

 

Billy- When I ordered my timers, (about $25 each ) I ordered online. I did one of those rookie mistakes and clicked on check-out twice.

I wanted 2 runtime clocks, and they sent me ( and billed me ) for four.

I have two more clocks at home just sitting there.
The hardest part was finding a wire that is only powered (5v to 25v ) when the engine is on. The only wire I found was the oil pressure switch. So I had to tap this wire under the hood and run it to the dash. That took the most effort.

If anyone wants my other clocks, mounted on a clear plexiglass plate, I'd be happy to make another. I have the parts, if you or someone else has the patience to tap into the oil pressure switch, or find another 5v to 25v source of power that is only on when the engine is on.

The timers have a permanent ( like odometer ) that cannot be reset, and also a "trip" meter that can be reset.
The toggle switch toggles between trip and cumulative meter. The black pushbutton resets the trip meter only.
( The trip meter will save for as long as you want between pushes of the button. )
The left is key on time, the right is engine on time.
-John