I know automatics are no longer called slushboxes and haven’t been for quite some time now. But when I was unspeakably young, that’s what people called them because they shifted (or so it seemed) as if there was slush inside them instead of bands and drums and the occasional planetary gear, which is to say they pretty much sucked behind any engine with balls. For that reason, hot rodders preferred stick shifts for their immediate and positive engagement.

This doesn’t exactly bring us to the 4L60E/65E four-speed overdrive automatic that churns in Red Dog’s belly, so just call it poetic license. There are millions of these transmissions throughout the universe (with their favorable 3.06-, 1.68-, 1.00-, and 0.70:1 ratios), most of them in need of better internal gizmos–even when new. Remember, the manufacturers surely anticipate that you will be buying parts in the not-too-distant future, so just about everything is planned for failure. When you increase torque, as we have with the Red Dog’s 5.3L, the inevitable creeps that much closer.

Vinci Hi-Performance has put 350 hp and 360 lb-ft of torque to the Silverado’s wheels so far–and expects to add another 80 to 100 of each with the addition of a positive displacement supercharger, so it only made sense to incorporate a stronger, more viable link between the engine and the rear axle, along with the proper torque converter to liven things up. For this, we whistled 20 minutes up the pike to Monster Transmission & Performance.

Our conference clustered around several salient issues. We didn’t want a high stall-speed converter that would take lots of throttle to get the truck moving. We didn’t want part-throttle shifts that would constantly test the link between spine and skull. We didn’t want the tires to chirp simply by dropping the lever in Drive. We didn’t want to put drag slicks on it. We did want a smooth-shifting transmission composed of premium parts capable of withstanding 500 lb-ft with composure. We did want the full Monte when we flattened the throttle to the floor. Barking back tires is just fine with us.

Monster listened. Monster interpreted. Monster gave us exactly what we wanted. All the while, the original transmission felt strong enough but didn’t shift up (especially the 1-2 exchange) to our liking. Despite the reprogrammed upshift quality via the Crane Powermax handheld programmer, the transmission would always hesitate a little before completing the shift. Though annoying, it more or less signaled that the transmission was beginning to slip, but this wasn’t really palpable until the day we’d driven Monster’s rendition.

The stock torque converter has a stall speed of 1,650 rpm. The upgraded performance converter that Monster recommended pushes the limit to 2,300 rpm and, unless you make a point of it, behaves exactly like the OE unit. No heavy lurch against the motor when you pull the shift lever from Park to Drive. At 800 rpm, it’s tight enough to crawl through a traffic light. When you mash the loud pedal, the thing hooks up and leaves without hesitation. Keep the pedal planted and the bulbous 295 Goodyears squawk their hearty approval on the 1-2 shift. Part-throttle upshifts are firm and immediate but never obnoxious, never embarrassing, never a jolt you didn’t expect. Build on the brake a little and the back tires spin with ease. Is this a good thing? We don’t know…but we like it. On the road, the revitalized tranny feels like it means it. Everything happens quicker and snappier, giving the truck that “of-a-piece” crispness.

The object of this lesson is to familiarize you with the things Monster changed in the 4L65E, rather than a step-by-step rebuild, which has been the subject of numerous tech journals and we have neither the space nor desire to recount it here. The Mega Monster lists for $1,895 with free shipping and no core fee. If you want something that will deal with 500 lb-ft day in and day out, that figure is pretty much in line. While some aftermarket tranny builders test their stuff on a type of dynamometer, Monster takes it a long step further. It runs in the real world. That ratty, road-rashed Monte SS with the scabby wheels, aka the perfect street race sleeper, has a 500hp 383 and is the test bed for every transmission Monster builds. More about that whole deal later.

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