Making a gearbox track-ready with crack checking a...

The Magic of Crack Checking

Scattered (really, neatly organized and cataloged) all through the GearFX Driveline facility are transmissions, rear ends and drivetrain elements from NASCAR and IMSA racers, classic racers, highway racers—any automobile that locations numerous stress on rotating and meshing elements. GearFX specializes in prepping these elements to carry out at their optimum and—this half is vital—to not explode.

Not exploding was definitely a trait we wished within the transmission of our C5 Corvette Z06 project, so whereas the gearbox was out of the automobile, we took it to the parents at GearFX to obtain their magic. After disassembly, the inspection course of is pretty easy.

“First we simply take a look at all the things,” Horton explains. “When you can see defects with the bare eye, you realize proper off that the half is not any good and must be changed.” The kind of injury can point out a necessity for additional inspection in associated areas, too: “Worn engagement rings generally is a signal of worn synchros; broken gear faces will warrant a detailed take a look at the shafts and bearings holding them; and so forth.”

After the visible test, it’s time to get a bit extra high-tech with a moist magnetic particle inspection. This technique of crack checking is included in the price of a transmission rebuild from GearFX. (When you simply have some unfastened elements you want checked, the service is accessible à la carte for $95 an hour—assuming the elements are clear and able to go.)

The method is usually known as Magnafluxing, a time period derived from a selected model identify of magnetic particle inspection gear that’s turn out to be ubiquitous in use, even within the trade. (The Kleenex and Band-Support individuals really feel their ache.) Regardless of the sci-fi identify, Magnafluxing is easy and excels at revealing cracks that aren’t seen to the bare eye.

1. Some cracks are simple to identify. The cracks on the root of those gear tooth may be seen by the bare eye, so the repair is straightforward: Simply toss the faulty half.

2. Different cracks are much less seen however can result in failures simply as devastating. That’s the place magnetic particle inspection is available in (aka Magnafluxing, because the Magnaflux model has turn out to be genericized). Handled with magnetic dye, this in any other case invisible crack turns into obvious underneath UV mild.

3. Crack checking is straightforward sufficient that no half ought to be excluded. This gear was hiding cracks not solely on the sides of the tooth, however on the faces as nicely. It’s a failure ready to occur.

First, the inspector magnetizes the half by passing a magnetic subject by way of it. Then, the half is drenched in a fluid that suspends microscopic magnetic particles, that are pulled into the cracks and fluoresce dramatically when hit with UV mild. The method takes just a few minutes however can stop a world of harm on the worst attainable time. For elements fabricated from non-magnetic supplies, like aluminum or magnesium, the inspector applies a fluorescent, penetrating dye that sinks into cracks by way of capillary motion. 

“We Magnaflux virtually all the things that comes by way of the door,” says Horton, “clearly any elements which might be coming off an current meeting that we’re going to reuse, however new stuff as nicely. It’s simply too simple to test all the things to verify one thing wasn’t broken in delivery or has the uncommon manufacturing defect that will imply catastrophic failure down the highway.”

How nicely did our transmission maintain as much as inspection? “There have been a couple of burrs right here and there that we may cope with on a case-by-case foundation,” Horton explains, “however nothing confirmed up throughout Magnafluxing that frightened us from a crack perspective.” He notes that common fluid adjustments and correct method—not placing any extra stress on the transmission throughout upshifts and downshifts than it was designed to resist—really go a good distance towards stopping longterm injury.

Shining These Inner Transmission Components

Whereas our transmission was aside, we figured that all the things deserved a correct shining. The method we used right here is REM sprucing: a really mildly abrasive course of that imparts a silky, virtually impossibly clean floor to mechanical bits. In our case, these mechanical bits had been the rotating, sliding and meshing elements of our transmission and differential. 

GearFX’s Jeff Horton explains that the outcomes of REM sprucing are removed from simply beauty, nonetheless. “Don’t consider it a lot as an influence adder,” he says, “however extra as an influence loss reducer.” In the end, the arrow factors in the identical course irrespective of the way you describe it.

So how does this all work? How does shining up a transmission’s innards lead to measurable beneficial properties in output? In keeping with the SAE-published analysis paper “Horsepower Retention by ISF (Isotropic Superfinishing) of Automotive Racing Elements,” the reply lies in lowering inside frictions. Give it some thought this fashion: Decreasing friction by smoothing these mating and sliding surfaces means much less vitality transformed into warmth, that means extra vitality despatched to the wheels. 

4. Friction results in warmth, and warmth results in failure. We polished lots of our transmission’s interfacing elements to scale back friction and put on.

5. Sharpening with the correct media is vital to the perfect end. A very good tech chooses media that matches the job necessities.

6. Our transmission’s guts, prepared to return collectively, regarded shiny and slick.

Not less than that’s the speculation. However the writers of the SAE paper confirmed that principle by precise dyno testing with an engine hooked to a NASCAR-style T101 transmission. Within the assessments, the baseline, unmodified transmission persistently produced about 5 horsepower fewer than one with REM-polished internals—from 383 horsepower inventory to 388 with the shiny guts. We’d be pleased to see these beneficial properties from an even bigger {hardware} change, like a cold-air consumption or cat-back exhaust system.

The sprucing course of advantages the transmission in a number of different methods, too. The diminished thermal load is healthier for bearings, and the diminished sliding friction of interfacing surfaces makes for smoother shifts and diminished likelihood of fatigue-related failures in these elements.

Not like Magnafluxing, this course of requires some specialised tools. Components are loaded into a large vibratory tumbler with the REM media and given a very good spin. After some time, the elements come out shiny and clean as glass. The entire sprucing course of for a five- or six-speed transmission prices round $500.

Whereas it sounds easy, there’s an artwork to the science. “Realizing what exact media to make use of and for the way lengthy to get the outcomes you’re in search of, that’s the place the expertise is available in,” Horton says. “I’ve totally different blends of styles and sizes of the ceramic-based media that we are able to use and mix for various durations and at totally different speeds to get perfect outcomes. It’s a comparatively easy operation, however it takes some ‘really feel’ as nicely. You may throw the stuff in and flip the swap and it’ll shine up good, however an skilled operator can actually produce some wonderful outcomes.”

A Little Transmission R&R

In fact, having the technicians at GearFX polish all the things and test for cracks could be pointless in the event that they didn’t additionally substitute all of the worn bits. Our transmission really regarded higher than most, however there was nonetheless seen proof of wear and tear on some essential synchros and kit engagement rings, like third gear. We had undoubtedly skilled poor engagement on various events in third, and a fast visible inspection confirmed that it wasn’t fully due to our driving.

7. The 1st step to opening up a T-56 transmission: Hit with hammer. GearFX’s skilled hammer techs did a much better job than we ever may.

8. Our transmission internals regarded good however not nice, displaying largely typical put on—just like the burrs on the tooth of this cog.

9. As soon as all the transmission was disassembled, it was time for cleansing and crack checking.

10. These outdated synchro rings confirmed warmth injury and extreme put on on the inside floor of the blocker rings.

11. These heavy-duty replacements function extra sturdy carbon pads on the within of the blocker rings for longer put on.

12. Changing the inventory shift fork pads with bronze fork pads is a really useful improve for any Tremec that may see harsher shifting than regular each day avenue driving. These examples present a typical put on sample. The decrease two pads are severely worn and cracked. This may be attributable to localized warmth from worn blocker rings or compelled shifting. For the reason that pads push the synchronizer, as soon as they begin to put on, it takes extra fork journey to have interaction the synchro meeting. This turns into a compounding challenge. The bronze fork pad improve helps guard in opposition to this and in addition offers a extra exact shifter really feel, particularly in high-performance functions.

So all the transmission was handled to an upgraded rebuild equipment which dropped proper into our current case with none modification or machining. The $1599 bundle contains bearings, bushings, seals, synchros and upgraded carbon blocker rings. The equipment additionally replaces the inventory shift fork pads, that are susceptible to degradation from age and laborious use, with bronze items. 

Due to the entire sprucing and rebuilding, the refreshed transmission additionally requires no devoted break-in interval as soon as it’s again within the automobile. Simply fill it up with the manufacturer-recommended Dexron 3 or a very good high quality artificial transmission fluid and let the joy start.

We didn’t simply rebuild and shine our T-56 transmission, we threw some upgrades on the rear finish as nicely. A Wavetrac diff and polished gears now reside contained in the rear finish housing, able to put energy to the bottom. We’ll be discussing the loopy physics of torque-biasing differentials in a future installment.

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