The TCI press release does mention that they disengage the forward clutch allowing the engine to idle, but I don't see anything about retaining fluid pressure to the direct clutch.
Has it been decided? - Yellow Bullet Forums
Steve Griner:
Assuming the shift pattern is PN123N, and referring only to TH400 and 727's
The words clean and safe mean two different things. Let me try to explain.
A clean neutral is where the last neutral position dumps all the fluid pressure to all the rotating parts. The way planetary's work there is no way to control the internal parts from spinning out of control. This is can be dangerous especially with cast iron parts, for it is possible to explode the transmission.
A safe neutral directs fluid pressure to the high gear clutches while in that last neutral position, this locks all the rotating parts to the engine during the shutdown keeping all the internal parts spinning under control.
You must remember that the engine must remain running during the shutdown, A safe speed is achieved before the engine can be shut off (at least 2/3 of the speed must be scrubbed off.) Shutting off the engine to soon stops the transmission pump, this is the same as dumping the fluid, raising the risk of A transmission explosion.
Also, another interesting post from Steve Griner:
"Clean neutral" why? - Yellow Bullet Forums
Originally Posted by
grinertech View attachment 1715397648
I will go into a little more detail, You was being offered to purchase a valve body that would do exactly what you wanted including neutral at the finish line. What if the transmission exploded and you was badly hurt and your car was destroyed. Could that possible cause for legal action ?
You 400 turbo guys , listen up!
Next time you have one on the bench, assemble the transmission up to the center support. now mock up an empty high gear drum and the clutch hub in the transmission. take a
magic marker, and in a straight line, mark the drum, hub and a spot on the case. Now with one hand turn the output shaft one revolution in the direction of engine rotation (refered to as Drive Shaft).
and hold the hub from turning (refered to as Engine Idling). and watch what the high drum does. It overdrives over three times to one of the drive shaft.
Now, lets do this in real time across the finish line.
8000 RPM,s Drive shaft
1000 RPM,s Engine Idling
7000 RPM's Differential RPM,s
21000 RPM,s Overdriven Clutch Drum (over3 times)
The clutch drum explodes somewhere between 12000 and 15000 RPM,s
You say, The forward clutches come off when I put it in neutral. Your lucky, and I will take no bets.
Oh! and want A explosion prone drum more likely to explode.
Install heavier springs and drill A 1/16 air bleed hole in the high drum like they do for A transmission brake.
Just leave it in gear unless you have a safe neutral valve body that has the proper oil circuits to do this.
