Rebuilt 4L60E Transmission - Trans-FormationalA Rebuilt 4L60E Turns Our Low-Buck '96 Into A Tire-Toasting Terror From the January, 2010 issue of Vette By Jay Heath Photography by Patrick Hill
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While the transmission in... While the transmission in our '96 coupe performed flawlessly at wide-open throttle, it was prone to the occasional slip or indecisive shift in everyday driving. Factor in a copious ATF leak, and it was clear that restorative measures were in order. (Photo by Kevin DiOssi) Working on an older Corvette is a bit like playing a game of mechanical Whack-a-Mole: knock out one problem, and another one immediately pops up. In the case of our '96 Polo Green coupe, we've recently spent the bulk of our time concussing critters in the differential, the better to prep the car for a planned raft of power upgrades. The solution ultimately came in the form of a heavy-duty Dana 36 diff from Zip Products, which went in with a minimum of fuss and has thus far performed beyond even our admittedly high expectations. To minimize the car's downtime... To minimize the car's downtime during the rebuild, we obtained a used trans to serve as the foundation for the job. West Coast Vette specialists J&D Corvette sent us this low-mileage unit, which came out of a wrecked '94 model. Along with a vast inventory of new and used parts, J&D offers everything from light paint- and bodywork to complete Corvette restorations. With the diff squared away, it was time to focus our sanative attentions on the car's rebuilt 4L60E transmission. While the factory-issue trans was still cracking off rifle-shot upshifts under wide-open throttle, it had developed a barely perceptible slip when engaging Fourth gear in everyday driving. Around the same time, it sprang a festive fluid leak that left decorative Rorschach patterns on the garage floor. While neither of these issues demanded immediate attention on its own, together they constituted a clear indication that the 80,000-mile gearbox was nearing the end of its useful service life. All of TCI's Pro Super rebuild... All of TCI's Pro Super rebuild kits come with gaskets, seals, a high-volume filter, and everything else you'll need to perform a full, performance-oriented overhaul. Specifying the "Ultimate" version (PN 378955) nets you heavy-duty Alto Red Eagle clutches, power bands, and Kolene-treated steels in place of the standard-issue pieces. Since we'd also be adding a torque converter with a higher-than-stock stall speed, we decided to install one of TCI's Performance Coolers (PN 823500) as part of the job. Rather than simply overhauling the transmission with new stock components, we decided to load it up with race-spec hardware from drivetrain specialist TCI. The Mississippi-based company provided us with a full complement of severe-duty internals for the trans itself, along with one of its high-stall StreetFighter torque converters to enliven our C4's standing-start acceleration. To minimize the car's downtime during the rebuild, we also obtained a used stock 4L60E from Vette-parts specialist J&D Corvette in Bellflower, California. J&D shipped us an almost-new unit from a wrecked '94 model, which we turned over to local tuner AntiVenom for the freshening-up work. Once that was done, the AV crew headed back to Source Interlink's lavishly equipped installation center to perform the swap. Follow along now as we take a closer look at both the parts themselves and the highlights of the job.  The stock 700R4/4L60E sun...  The stock 700R4/4L60E sun shell is famously failure prone. TCI's "Beast" unit (PN 373900) is thicker than the factory piece and uses a revised spline area that's better suited to high-horsepower use.  With the car on a lift, AntiVenom's...  With the car on a lift, AntiVenom's Casey Willard begins the job by removing the exhaust system aft of the catalytic converters.  With a stall speed of around...  With a stall speed of around 2,800 rpm (stock is approximately 1,800), this 10-inch StreetFighter torque converter (PN 243106) should boost the car's off-the-line verve immensely. A full complement of beefed-up internals-including needle bearings, furnace-brazed fins, and a heavy-duty lock-up piston-makes the StreetFighter's roughly $580 price tag a relative bargain. With a stall speed of around... With a stall speed of around 2,800 rpm (stock is approximately 1,800), this 10-inch StreetFighter torque converter (PN 243106) should boost the car's off-the-line verve immensely. A full complement of beefed-up internals-including needle bearings, furnace-brazed fins, and a heavy-duty lock-up piston-makes the StreetFighter's roughly $580 price tag a relative bargain.  Next to go is the dust cover...  Next to go is the dust cover for the torque converter. You may have to do some creative wiggling to free it from the lines and wires positioned nearby. Take your time to avoid damaging these delicate components.  Sometime hand model Willard...  Sometime hand model Willard unbolts the universal joints to free the driveshaft. (Note stylish Katech Performance work glove.) It's best to use a traditional lift-rather than the dyno variety shown here-for this phase, since you'll need to rotate the rear wheels to access all the U-joint bolts.  Once the driveshaft is out,...  Once the driveshaft is out, the torque arm can be unbolted and removed. If you're following along at home, be sure to support the trans with a trans jack before you complete this step.  After an extended bout of...  After an extended bout of painful-looking contortions and creative scatology, Willard is finally able to unhook the radiator lines and begin lowering the trans out of the car with the trans jack. Although this phase of the job should be a piece of cake by comparison, the long-tube headers on our C4 serve to complicate matters immensely. Another hour of fun ensues before Willard manages to finagle the trans body out through the narrow tangle of header pipes.  Removing the speed sensor...  Removing the speed sensor while the trans is still on the jack makes it easy to catch any fluid that drains out. Frustrated though you may be at this point, fight the temptation to toss your old trans on the scrap heap: Assuming there's no structural damage to the case, you should be able to get at least $150 for it as a rebuildable core.  Here's a look at our used...  Here's a look at our used J&D trans in post-rebuild condition. After finishing up the internal freshening, the guys at AV hit it with a coat of black caliper paint to give it a natty new look.  Yes, that is a Sawz-All, and...  Yes, that is a Sawz-All, and yes, he is using it on our newly rebuilt transmission. After the earlier trauma of the removal process, Willard decided to lop one of the aluminum "ears" off of the case to ease reinstallation. While we don't recommend your duplicating this step at home, in our case it proved to be a shrewd time-saving move.  Here's a look at the speed...  Here's a look at the speed sensor before it gets cleaned and reinstalled on the rebuilt trans. Forget this step, and all your fresh transmission fluid will spill right out on the garage floor as you pour it in.  We decided to use Royal Purple...  We decided to use Royal Purple Max ATF (fully synthetic) in our refurbished 4L60E. According to RP, Max ATF's low coefficient of friction and high film strength can reduce heat and wear as compared with conventional fluids. Our StreetFighter torque converter consumed exactly three quarts of the merlot-colored stuff.  After the converter is rotated...  After the converter is rotated into place on the transmission's input shaft, AV's Greg Lovell uses a cutting-edge measuring implement to ensure that it's fully seated before tightening up the bolts.  While Willard jacks the new...  While Willard jacks the new trans into place, Lovell takes a few moments to give our torque arm and converter dust cover a quick hosing down in the parts washer.  Fresh from their dousing,...  Fresh from their dousing, the old arm and cover look as good as new. Too bad we can't fit the rest of the car in there.  As is usually the case, the...  As is usually the case, the reinstallation process is simply a reversal of the teardown procedure. You may wish to take a few minutes (days?) to compose yourself before you get started, as you'll have to battle those damnable radiator lines again.  Once the trans is bolted up,...  Once the trans is bolted up, Willard reinstalls the driveshaft followed by the torque ar and, finally, the converter dust cover. Double-check to make sure you've reinstalled all the transmission lines and wires, then move to the top of the car for the final steps.  An empty 4L60E will hold between...  An empty 4L60E will hold between 11 and 12 quarts of transmission fluid, depending on the size of the torque converter. After adding five quarts via the dipstick tube (remember, we've already put three in the converter), we fire up the engine and run the shifter through all of the gears. Willard continues to add fluid until the dipstick reads "Full," then moves back underneath the car to check for leaks. When he finds none, we lower the lift, back the car out of the garage bay, and take a quick spin around the parking lot.  Although follow-up dragstrip...  Although follow-up dragstrip testing will have to wait until our next installment, it's clear that our '96 coupe's starting-line reflexes have been significantly sharpened by the fresh trans and high-stall converter. Even moderate throttle applications now send the tach needle twirling into the high-2,000-rpm range-right near the crest of the LT1's plus-sized torque curve. Assuming we can still get the car to hook up, a real, live 12-second e.t. seems a distinct possibility. Stay tuned.
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