So I'm driving behind my friend who also has a third gen Camaro. His car is running a 350 with 400 crank hp, in front of a rebuilt turbo 350 trans with a pretty high stall convertor. He runs a 13.1 @ 104mph all day long. So a crotch rocket comes up behind us, passes me and gets up next to him. They race from 60mph till my friend Josh hits 5500 rpm in third, lets of the gas and shifts into nuetral to coast. Well he does this, and I see his torque convertor cover go flying off and 2 seconds later so much white smoke I can't see 10 ft in front of me. I pull up behind him, having to swerve around his front half of his driveshaft laying on the road! When we got his car home, we noticed the bellhousing of the trans was cracked in half about 4 inches behind the engine. All we can think of is that the tranny completely locked up for some apparent reason. He looked at is further the next day and said it looks like fluid forced its way out of case just below the pump, in front of the pan. Anyone heard of anything like this before??

 

NEVER neutral a 3 speed auto!

Providing nothing was destroyed inside the transmission, which I doubt,, that can still be saved. A JW Ultra Bell can be installed on that case. For the price of an Ultra Bell, it might be easier to just install another transmission. It depends if the old one is worth it or not. Ultra Bells run around $230.

 

Stephen, I am just curious exactly what happens when you neutral an auto at speed. I read in a post on another forum somewhere where people got into a giant flamewar over it (Alot of people were talking about neutraling out after the 1/4 to avoid TDC stress under deceleration, and some guy mentioned that when you neutral a trans at speed, since the trans is disengaged from the engine the internal speed is then determined by the driveshaft @_@. Not sure how much merit there is to this, was just wondering exactly what happens when you do this.

I did this once on the interstate at 70MPH by accident. thought it was in third and went to shift to fourth, but really it was already in fourth :smackhead:. I was able to shift right back though without anything bad happening. The trans did die months later though from old age.

 

I hope it's not too dumb of a question, but why not? What does it do mechanically that causes such a potential for damage?

 

When you neutral a 3-speed trans, all clutch packs disengauge, leaving the input shaft to "freewheel" down with the motor, BUT also leaving the output shaft to "freewheel" at driveshaft speed. Since no clutches are holding, the low roller support is not holding, nor is the sprag, thus the planetaries gearing hyper speeds the direct drum to around 2.5 times the driveshaft speed.

I've seen plenty of trans tunnels, windshields, and even roofs with holes perforated in them due to the direct drum exploding. That's if you're lucky and everything goes straight up or down, not towards your legs/torso/etc.

Most full manual valvebodies do not have engine braking, thus there is no need to go to neutral anyway. The engine will come down on it's own. Even with engine braking, the stress of decelerating the engine is far less than the disaster waiting to happen of putting any comon valvebody in neutral at speed. - The Griner "clean neutral" valvebodies are an exception to this, as they have neutral all the way at the back of the pattern, and are designed so that the direct clutch stays engauged, but everything else dumps. By dumping the forwad pack the engine can fully "freewheel", but by keeping the direct engauged the drum will stay at input speed.



It is highly likely the harmonics caused by the drum hyper-speeding is what lead to the case breaking as it did. It could have been much worse.

 

There was a discussion on another forum about the damage done. It's unlikely this tranny was neutralled. typically when it blows up from netralling, the clutch hub explodes and goes through the case. With the type of damage see in those pictures, there's a high chance the tranny was put into reverse instead.

 

at the end of a roll race, best to leave it in the last gear you used, the engine braking is a good thing. The engine will come down pretty quickly otherwise, and if you're carbureted, may want to stall if you didn't leave it in gear. No, there's no sense in shifting the trans at all at the end of a roll-race like that. That's little-16-year-old-kiddie B.S.

 

Usually a bell breakage on a th350 or th400 is either from flex(motor and/or chassis) or from driveline vibration. At the speeds a drum can obtain when "neutraled", it can easily cuase a significant vibration; this vibration/harmonics is usually what causes the drum to fail/explode.

I've seen pieces of the drum exit clear through the roof, after going through a shield and the floor. I wouldn't want my legs near it.


All things considered, this could easily be from either situation(neutral or rev). Either way he will be lucky not to have hurt any internals, and even luckier to have not had a more catastrophic failure. "Hard lessons learned."

 

Interesting topic, we're pretty sure the trans was not shifted into reverse, but I never heard of it being bad to pop it into neutral. The trans has not been taken apart yet, if it ever will, who knows. The only reason he shifted to neutral was to avoid smoking, since his engine has a little bit of an oil control issue under high vacuum. I wonder what actually locked up in the trans. The output shaft felt normal as far as end play and I could slightly rock it back and forth. The cracked case was most likely caused by the twisting force when the trans locked up. Him and I both will not be ever shifting into neutral at speed after this. He's lucky the driveshaft broke instead of locking up the tires. I wonder how his rear end is after this. Stephen- where is this other discussion? I would like to check it out.

 

just for $hits & giggles... wat would happen with neutraling a 4speed auto like the 700r4? im not totally sure why anyone would put it in neutral at a high speed and want to use there brakes to stop. i would just downshift if i wanted to slow down with brakes.

was that the stock steel DS? lol geez.

 

Probably the same thing. The only auto that can be safely neutralled is a powerglide and I don't even neutral mine at the end of a 1/4 mile.

 

4L60/700R4's are very different inside than a 3-speed. There is no "direct drum", and the planetaries are not only in the back linked by shafts. Due to the set-up, they is nothing to "hyper speed" when neutralling a 4l60. - Still no reason to do so.

The Griner "clean neutral" valvebodies can be shifted to neutral at speed, but they are very different than other valvebodies, even the pattern is different(rev manual is PR123N). Again, they release the forward clutch thus allowing the motor to freewheel, but they hold the direct clutch thus keeping the drum at driveshaft speed.


I have always felt that it's better to leave it in gear. If for any reason something happens, it's good to be able to throttle the car. - Not sure about on this forum, but there are several threads about "neutralling" in the trans section of YB.

 

Turns out the front U-joint of the driveshaft might have been what caused all this. The bellhousing might have just cracked from the severe vibration of the driveshaft with the u-joint failing. Everything in the trans and rear end was ok.