My rear pinion seal didn't like the recent dyno runs / test drives, and decided to $#!^ the bed. I'm thinking about going ahead and doing 4.10's in the rear and getting the front end done late this fall. What do you guys think? Should I go Ford Racing or Yukon? I don't think Ford offers a reverse 4.10 do they? If I can't spring for the Eaton True Trak right now, should I just wait until I can?

I found Ford Racing 4.10's for $165, but they are 4:10 and Yukon is 4.11. Are they the same thing or what? Also would I need a master install kit that includes axle shaft bearings & seals or no?

 

if im not mistaken you can run .01 off in the front and rear. but im not sure so 4.10 and 4.11 wouldnt hurt.
im not 100% though

you would need a master install if the last one went it might have taken some stuff with it

 

What size tires?

 

32.6" ProComp XAT's. Nice and heavy. Keep in mind I have the 5-speed. 4.10's would be equivalent to 4.56's in an auto. I'm just worried about traction issues if keep the open diff. How well do the TrueTrak's and other limited slips handle acceleration while cornering?

 

yes 4.10 and 4.11 are the same, some companys/manufactures or even depending on the diff itself will call it different. i think the general rule is to keep the front and rear ratio within .03. basically 4.09 4.10 4.11 and 4.12 are all the same.

 

Yeah, I wouldn't go taller than 4.10s with those tires. Should pull nicely with the manual.

If you're thinking about a LSD then may as well do it all at once since you're in there anyways.

I had the Ford Racing LSD. It's pretty tame compared to most of the aftermarket ones. But it was very "streetable" and didn't make any noises or chatter or anything.

My current truck has a Torsen geared-type. It's good and transfers power well, but I get a little wheel scrub in tight turns...and I've got a 145-inch wheelbase (quad cab, 8-foot bed). If my truck was shorter like a normal truck I think it would scrub more on sharp turns.

 

What is a fair labor charge on the rear end?

If I can't spring for the TrueTrak right now, what should my second choice be?

 

Have you looked at Auburn?

 

My local shop said they swap in a lot of Auburn units in the Stangs if not the TrueTrak, but I think they still cost a lot.

I'm actually considering a Ford Racing Traction Lok with carbon clutches. It's the one that came factory in 03-04 Cobras. Any opinions? At half the cost, I think I could live it.

 

Is there really a "break-in" period with re-gearing when they're setup properly? If so, how do you handle the front diff's break-in?

 

To break in the rear, just drive it easy, but not too easy for the first few hundred miles. Some people will change their fluid after those first miles, I don't think it really matters. As for the front, just use it when ever you need it. Since the front isn't the primary driving diff that always pulls all the weight around, it wouldn't be worth the wear and tear on other componets to drive in 4x4 on pavement.

A muddin trip would give you an excuse to test out the new gears and LS

 

Just wanted to make sure I can get away with changing the rear gears only for now, then the fronts in a few months...I don't see why not, but wanted to double-check.

Also, the factory diff fluid doesn't get changed after a break-in, so I don't think I'll worry about it. I'll probably pickup a diff cover in the next year, so I'll take care of it then unless someone thinks that's a horrible idea or something. Can't wait to see how this wakes up the truck.

Here's my current and projected RPM's with my 5-speed tranny on 32.6" tires.

3.55
70 mph / 2075 rpm (indicated)
75 mph / 2200 rpm (indicated)

4.10
70 mph / 2396 rpm
75 mpg / 2540 rpm

...I think 4.56's would be too tall, considering I mostly drive 75-80. I may have considered 4.30's if an IFS were readily available.

If my button mashing is correct, with 4.10's I'll effectively be equal to an automatic running 4.30's on stock tires.

 

Yes, you can get away with it, but do NOT UNDER ANY CIRCUMSTANCES engage the 4WD.

 

Do the rear and don't engage 4WD until you get the front done...won't harm anything unless you engage the front driveshaft.

When I had my gears done (DiffWorks in Riverside, very well-respected), they said to drive it easy for 500 miles, change the fluid, then have at it. I followed this advice.

The owner's manual in my current truck (not a Ford) said to avoid towing for the first 1,000 miles to let the rear-end break-in...but didn't mention changing the fluid. I followed this advice as well.

Unless your installer tells you otherwise, I'd take it easy for a few hundred miles for sure. Change the fluid for peace of mind if you want.