Front Diff Build

[SALEEN961]

I've rebuilt plenty of differentials over the years, but building one from all new parts has been very annoying and I ran into way more problems than I ever could have anticipated. First and foremost Ford's quality control is terrible, I'm used to parts missing from their ring and pinion kits, but this was a new low. Of the two housings I ordered, one had a damaged bearing race, and the other had razor sharp burs and machining debris everywhere. One pinion gear had a few chipped teeth, and another wasn't machined to the proper size so the outer bearing didn't fit.

The good news is that after trying a few different pinion shims, I got a pattern that I'm happy with. With our front diffs running on the coast side of the teeth so often, getting a good pattern on the coast side of teeth is even more important than usual. In the end the drive side reads as the pinion being slightly shallow, and the coast side reads as the pinion being slightly deep, but I don't want to make the coast side pattern worse by chasing a better drive side pattern or vice versa. Both patterns have a fairly large contact area, and they are fairly well centered on the teeth.

With everything assembled my backlash is 0.0105", the spec is 0.0080"-0.0120". My pinion turning torque is 25 lb-in, the spec is 16-29 lb-in. I also made sure to add 0.008" to each carrier shim to establish bearing preload, my stock diff had shims that were way to thick and I think that is what caused my very low mileage carrier bearing failure.

Drive side gear pattern:

Coast side gear pattern:

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[FaaWrenchBndr]

Hadn’t really considered the coast side pattern much in the past. The coast side pattern concern is very valid when considering the advent of 4A and the Powerboost model.

Certainly an eye opener for sure…..thanks

 

[SALEEN961]

My brand new diff is together and ready for install with one minor exception, the factory never installed the pressed in barb for the vent hose, but on a positive note they did drill the hole. With today being a holiday I probably won't be able to get that missing part until Friday.

 

[ThumperF150]

What diff cover is that?

 

[SALEEN961]

What diff cover is that?

It's a stock Ford Raptor R front diff cover, NL3Z-4033-A

What made you go with bolts and washers? Why not use the factory bolts for that cover

With the thicker aluminum diff cover, the stock bolts only grab a few threads. I wanted to use longer bolts that maintain the same amount of thread engagement that my stock bolts had with the stock cover.

 

[SALEEN961]

These are what are factory installed and don’t work?

What part number are you seeing? The only thing listed in the two parts catalogs I have access to is in the picture below.

 

[SALEEN961]

PB3Z-4346-A for the single bolt

PC3Z-4036-AA for the gasket kit which is a bit more cost efficient. However this is if you really care to be OEM with bolts.

The catalogs I have access to show those part numbers fitting newer Super Duty trucks and Broncos, but I suppose those bolts would work if they are 5/16"-18 thread.

 

[ThumperF150]

It's a stock Ford Raptor R front diff cover, NL3Z-4033-A

How much lift do you have on your F150 with that cover? I’m curious about the cover the steering clearance.

 

[SALEEN961]

I retract what I said. I just spoke to someone and those aren't what are used my apologies. It's a bolt and washer setup and I am not sure if there is an available part number. They're a niche item during assembly at Sterling Axle. I thought they were just ordinary bolts from Super Duty due to sharing an assembly plant


EDIT:

This is what was given to me for a part number 6L1Z-4346-AA

Those are expensive, but as you said it is a niche item.

How much lift do you have on your F150 with that cover? I’m curious about the cover the steering clearance.

The Raptor R cover fits great on a stock F150.

 

[ThumperF150]

Those are expensive, but as you said it is a niche item.



The Raptor R cover fits great on a stock F150.

Wish I had known this before I had a drain plug welded into a stock diff cover.

Not sure there is enough time to get that Raptor R cover before my gear appoint on the 8th.

 

[TheGoatman]

Wish I had known this before I had a drain plug welded into a stock diff cover.

Not sure there is enough time to get that Raptor R cover before my gear appoint on the 8th.

Takes a dealer 2-3 days

 

[SALEEN961]

The new front diff is installed and getting broken in over the next week. The old diff with the damaged housing and gears is getting torn down to salvage the Torsen and a few other hard parts before getting rebuilt with new gears and a new housing.

My hope is that if I have a fully built spare diff just sitting in my garage, I'll never need it; but if I keep pushing my luck by launching in 4H with the converter stalled up past 3200RPM, something is bound to fail eventually.

 

[SALEEN961]

I put 100 miles on the new diff so far and to be blunt I think I may have messed up. Coasting the gears are so silent that you can't tell any difference between 2H, 4A, and 4H, but under acceleration there is some NVH right around 40mph. It's not terrible and it might go away as the gears wear in, but I'm starting to doubt the decision I made. Maybe I should have chased a better drive side pattern at the expense of the coast pattern, or tried a different set of gears in the hopes that they wouldn't require as much of a compromise between the two.

 

[ThumperF150]

Mine goes in Tues for gears. My guy did a great job on my jeep. I sure hope he can do the same on my truck.

 

[SALEEN961]

Mine goes in Tues for gears. My guy did a great job on my jeep. I sure hope he can do the same on my truck.

I'm sure you'll be fine, to be honest my biggest blunders and struggles have always been on my own vehicles. I drive them like they're stolen and I think they hate me for it. I'm just happy that this happened on my own vehicle and not on a customer's vehicle. I'm not happy about eating the cost or the lost time, but at least no one else was inconvenienced by my decision.

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