Technical Why Chrysler urged drag racers not to do a neutral drop

Back in 2000 my old boss had a 1969 barracuda with a B1 headed 440 that someone put a TH 400 behind. After running a mid 9 second pass he put the trans in neutral in the shut down area only to hear a massive explosion. The entire case disintegrated. The pan came off when we dropped the blanket.

 

I think that was Ron mancini's Super Stock in the first pic.been posted 87 times in the Drag Cars In Motion thread.
NHRA immediately prohibited the practice, if you look close in ( I think ) 66-67 there is a small sigh by the ;tree that says"no Neutral Starts:.

 

I believe this is why Hurst came up with the Line Loc.

 

In high school, my stupid brother worked for my uncle at his wrecking yard. A pretty decent Chrysler came in and he wound up buying it for his daily. 383/at powered hardtop Newport. One day after school we were headed home and he turned onto our long driveway and nailed it. Throttle stuck wide open headed straight at our house. Instead of turning the key off, he threw the shifter handle up. I have no idea what gear he landed on (P/R?) but that beast went Kaboom and screeched to a halt. Figured it was a goner and didn't even try to start it, we got out and pushed it the rest of the way. Later he decided to see what was up with it so he turned the key and it ran just as well as it had before and went through the gears fine. Different day he had the hood open and gave it some gas. Engine damn near jumped out of the bay. Both motor mounts were completely broken- assume it happened instead of grenading the trans that day.

 

Had a G/F knee the column shifted th400 into reverse once at about 50-60mph. Thank God it was a long straight stretch & no traffic. Instantly locked the rear wheels up, & did a perfect 180 degree J-hook. Never said a word, dropped it in gear & drove away. Had the trans rebuilt several months later, not that I ever abused it myself...

 

Almost all the drag strips in the mid to late 60's had a no neutral starts signs. Before that you would see a Mopar racer staging with one hand on the wheel the other hand over by the push button controller. The lights would come down and they would hit the button and if it held together they left quick.

 

Brings back memories of a kid in my high school class that did a neutral drop in a '51 Olds at a stop light. Those of you who know early hydros can probably guess what happened as he pulled the shift lever a little too far. The guy behind him got a big surprise that day!

 

I've killed my share of Mopar automatics, but the only one that ever broke the case was the one that lost a rear u joint first. (I won't count the one that caught the car on the guardrail and kept me from going down in that deep ditch.) I learned very early not to do the big N drops, the ones I did early on just killed the rear axles. I was probably pretty lucky.
I had a pretty big pile of broken parts back when I was younger. I never met a trans or rear axle I couldn't break, and the process of breaking those usually resulted in additional broken stuff. Gene

 

1989 or 90, at Bremerton Raceway, we were having a Nostalgia race put on by Flyin' Phil Elliott. My job with the Handler's was the primarily as the Starter. The Wayne Harry camp had come up from Vancouver, Wa with their Willys Pickup and a Willys Coupe. These were Gas Supercharged cars, and I knew what Torqueflites were known for. The Willys Coupe was making a single pass in the right lane on our setup day, and rather than throw the switch from beside the car, I stepped back to somewhat behind it. Tree came down, and BOOM!!! Transmission exploded all over the place, and those blankets can't contain everything. Took us a while to mop up all the ATF, pick up the pieces of transmission scattered all over, and then a couple gallons of methanol set on fire to burn off the rest. The actual race got rained out the next day, and Flyin' Phi was completely beside himself; he had a lot of his own money wrapped up in the race, and there was no way the Handler's could work him back into another regular race-date. Saw a little FED with an injected SBC, bolted up to a Torqueflite, explode the transmission at Seattle International Raceway once. That car was a real mess inside, and all the body panels were bulged out and full of holes; the crew had taken the driver to the hospital, and left the dragster beside the trailer unattended. This was before the Powerglides/race converters really came into their own. Torqueflites DON'T need to be "neutral dropped" to explode; the front drum takes most of the abuse during first gear operation when torque multiplication is the greatest. If the drum is weak, worn, or damaged, it can come apart taking the rest of transmission internals with it. I've heard that if a "sprag race" in a Torqueflite lets go, it allows the front drum to spin at double-triple it's normal speed; and they can't sustain that for long; BOOM!!! Don't really know much about Torqueflites, other than my 70 340 Dart had one; the only non Chevrolet I've ever owned.
I am Butch/56sedandelivery.

 

I had a friend that ran a dirt late model with Mopar power. He had another car that he used for static display for advertising. It had a warmed up 360 with a torqueflite. One day he was warming it up to load into to his trailer and luckily he was standing outside of the car. He revved it a little because it was cold and the carb stumbled, he took it to about 4500 when the trans let go and destroyed the interior cockpit of his late model. He is just lucky he was standing outside of the car when it came apart and it was in park when it happened.

 

If I understand this right, Torqueflites (and most other classic American automatic transmissions - they generally all follow the same pattern) will explode when the front clutch is subject to more centrifugal force than it can handle by suddenly being spun to ±10000rpm. There are two situations where this can happen: 1. first gear sprag failure on launch, and 2. engaging neutral at a high road speed. Both these conditions can be eliminated entirely by ensuring that the low/reverse band is always applied in neutral and first gear. This renders the sprag almost redundant. There are valve bodies that do this, for this reason.

 

N-drop... the poor man's stall converter....

 

If that was a Power Glide it would have just went PING! At least that's what mine did.

 

Powerglides (cast iron AND aluminum Powerglides) just snap the spindly, little input shaft on neutral drops, and even with stall converters. I am Butch/56sedandelivery.