New to the forum! Regearing to 4.56 questions

BamaToy1997 · Mar 6, 2015

Mach375 said: ↑

x2

Even going 3.73 to 4.56 isn't a huge difference. Noticeable, yes. But not huge. Big differences start at 4.88, but then you're building for a lot more than just getting back in the power band.

As for parts:

Most basic parts needed for the most basic ratio change are matched ring gear and pinion gear, gear oil (new gearset requires dino oil, not synthetic!), and RTV gasket maker. This approach is if you know FOR SURE that everything is in new condition. (For example: I just replaced my blown 4.56 gears. I did this Most Basic approach because I had replaced everything else [bearings] less than a year prior, so I knew they were 100%......after close inspection, of course!)

The next most basic adds bearings (four sets: 2x carrier bearings, front pinion bearing, rear pinion bearing). This approach is pretty much the standard if you are handing parts to a shop and having them do the work. The assumption is that the shop has the necessary shims to get the numbers and pattern where they need to be.

After that, the next step is for the person doing the work hirself, and adds shims and marking compound. This approach is for the person with the tools and know-how to do a proper setup, and will be doing 100% of the work. Tools needed include a shop press, a very strong air gun, an inch-pound torque wrench, and micrometers. (This is what I bought a year ago, so I had all the shims I needed for when I just recently had to re-do it)

About the only next step that does not include a complete, ready-to-go third member is swapping the carrier. This is usually considered a separate part, because the only reason one would replace the carrier is to add traction-controlling capability. The options are myriad: multiple versions of Limited Slip, multiple versions of Lockers (auto and manual), and of course, the Big Gun: the ARB Air Locker. If one is *also* swapping the carrier, then one would need the full shim/bearing/gearset as well; if one is keeping the current gearset, but swapping only the carrier, then that person would need at least a set of shims, and it would be recommended to also replace the bearings (again, unless they're already near-new).

The top list of parts is really only one part: a complete third member, ready to install. This is for the person who either has no clue how to rebuild a diff, doesn't have a good shop in the area that can rebuild a diff, wants a warranty, or who wants the least downtime. A complete third includes new bearings, shims, matched gearset, and labor of setting it all up 100%. The only work required of the buyer is to install it, add gear oil, and properly break it in*. If the buyer has ever done a complete brake job, then s/he can install a third member.

*= New gears MUST be broken in properly! Install, add oil, then drive gently for 20 miles, then park it overnight (that's an end-of-the-day roundtrip of 10 miles!) (if you touch the diff just after that 20-mile drive, you'll immediately understand why only 20 miles- it gets HOT!). After that initial 20-miles, drive gently for the next 500 miles (NO TOWING!!, and no beating on it...like rock crawling). At 500 miles, change the oil, taking note of major pieces of metal (larger than 1/16"). If no significant bits off metal are found, and the oil doesn't have a severely rank burned smell (you'll know it!), then you're good to go. Keep up regular oil changes every 15k on dino, 30k on synthetic. If you swapped to a Limited Slip carrier, make sure the oil contains friction modifier (Redline synthetic does, Lucas does not).

Again, now is the time to decide if you're going to upgrade the carrier. I would personally recommend it, if your budget allows, even for the street (it's amazing how big a difference in wet-weather driving a simple LSD provides!). Nothing like having to rebuild a diff twice because you changed your mind later.
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I have to respectfully disagree with you on the breaking in process. I have installed several hundred gear sets on 2wd and 4wd trucks. After the installation was completed we would go out and drive the vehicle for a good 40 miles, making sure that we had several opportunities to accelerate steady up to 55MPH, then coast down to 20MPH. (Automatic trans shifted into manual 4th or 3rd depending on model, manual transmission just letting off brake, letting engine braking slow it down) and after that was done, we returned it to the customer to drive normally, with no towing until at least 500 miles was completed, and vehicle was returned for a fluid change.

I have almost never had a gear set come back failed, and have done it this way for over 20 years. I see absolutely no purpose or reasoning behind driving only 20 miles, then parking it overnight.

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BamaToy1997 Wheel Bearing Master

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#21 BamaToy1997 Wheel Bearing Master

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BamaToy1997 Wheel Bearing Master

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