[Ron]

Didn't build my transmission...didn't build my house either. But I earn enough money every year to purchase the best....and clearly you are not on that list.

Stop attending the friday night test and tunes and go to some real races to find out what technology is being used today.

[D. Miles]

Ron, other than from the PY board, I do not know you... John, I have met you a few times and have been watching your work for MANY years and have the utmost respect for you!!! PERIOD. I will go on to say that jakeshoe should not have called ANYONE an idiot, that's our wives jobs. I'm sure on any given weekend there are millions of quarter mile passes made with all the brands of 3 sp auto trans' being shifted into nuetral at the end of a pass without incedent. Short story of comparison: I had a 455 with Eagle steel rods and 60 cc chamber Wenzler Series II heads with .038 head gaskets, I ran Keith Black hyperuetectic CAST pistons that were .007 out of the hole, according to Wallace's and a few other compression calculators my compression was 13.8 to 1... I beat the crap out of that motor for 4 seasons running 9.70's in my 3300 lb. Wagon, wide open throttle on the three step burnouts I've pushed it to 6600 a few times it's seen 7200 with a few broken ring and pinions... Some guys can't get a set of KB piston through the engines break in period, some can't get 100 street miles on them, I made 700 HP for 4 years with them and they will be going back into my steel rod motor when the aluminum rod motor is done.

Case and point, what works for some can be catostophic for others. An automatic trans has planetary gears sets that CAN NOT be disengaged if the tail shaft is spinning something in that trans is spinning and the way planetary sets work at least in a T-350 and T-400 is when the tail shaft is being turned by the driveline, the internals of the trans can be engaged (i.e. the forward clutch pack and the direct clutch pack) which is otherwise known as high gear, all the rotating componants in the trans spins at driveline speed or driveshaft speed and the planetaries become non functional and do no further gear reducing, but when the trans is placed into neutral, all the clutches release but the direct drum is mechanically connected to the sun gear of the planetary set and do not "dis-connect" in neutral, the forward drum which is attached to the input shaft from the torque converter is connected to the rest of the driveline only through clutches and can be and does get "dis-connected" when in neutral. So if when in neutral the forward drum/inputshaft gets dis-connected and is allowed to slow down to the engines idle speed or stop completely if the engine is shut off, somethings speed has to be multiplied. Remember, when in low gear the planetaries when being driven by the input shaft/engine are in full reduction reducing rpm by simple division of the planetaries numerical ratio but if you let of the gas and the driveline/output shaft start to drive the planetaries then the inputshaft/engines speed is multiplied by the ratio of the planetary set, thats how you can let off the gas at say 30 mph and the engine is being held at say 3000 rpm even then you are off the gas. With that being said in a high gear going thought the traps scenario, since the direct drum is already spinning close to the engines rpm (except for converter slip) if the engine is allowed to go to idle in neutral the planetaries multiplication doesn't just go away so it has to go somewhere remember when the driveline rotates the output shaft it multiplies speed and the only way that multiplication gets stopped is if it is being locked or held by the clutches but that would be "in gear".

This is a very hard thing to describe in words and is better when seen but most guys don't have the whole internal assembly of a T-400 lying around to mock up on a bench and rotate it to see exactly how it all works. And using high end high horsepower NSCA and NMCA as well as Stock and Super Stock cars is a bad example of who neutralizes at the end of a run, most if any of those guys do not use stock components, why would a heads up racer who will spend tens of thousands of dollars looking for every ounce of HP skip on a $600 drum that could be and is often worth tenths of E.T. I've seen Super Stock trannies apart and those guys try every trick possible for that edge, a lot of them run 2004R internals some use TH-200 drums and internals as they have stamped steel drums and are super light, and I am most certainly sure that a 1000-1500 HP heads up car would have a trans with all the light weight and heavy duty aluminum, billet and titanium parts they can find or have made in the quest to go fast and have an edge, I can't see one of those guys building a $50,000 dollar motor, putting it into a $50,000 dollar car and using a $500 40 year old all stock internal T-400.

This winter I will be buying an ATI aluminum direct drum so that I will be able to shift into neutral at the end of a run to save my aluminum rods. but like my example earlier of making 700 HP successfully with KB CAST pistons for years and 100's of passes, what works well for some could be catostophic for others, in my years of racing, I have seen MANY T-400's come apart in the lights when the driver goes to neutral, I repeat MANY! so it's not like there is no risk here for anyone who wants to do it, some will do it their whole racing career with no incedent while the next guy might lose a limb or crash their car or at the very least oil down the track when the direct drum explodes. The warning is here, the pictoral proof is here so take it as you will. I would have to say I side with jakeshoe and screamingchief here by putting the warning of what can and does happen with hope of keeping just one incedent from happening... Thanks D. Miles

[Skip Fix]

KO I meant in regards to the neutral shift deal. They are well over $2K for most also.

[KO]

The TH400 direct drum is heavy, large diameter and cast iron that has alot of intertia and doesnt fare well at 12000+++++ RPM

[Nickv]

Interesting. I've been shifting to neutral after every run with my 67. I have over 250 drag strip runs on the tranny. I guess I've been lucky or stupid, but I see alot of drag racer shift to neutral after a run.

[mchell]

Originally Posted by Nickv

Interesting. I've been shifting to neutral after every run with my 67. I have over 250 drag strip runs on the tranny. I guess I've been lucky or stupid, but I see alot of drag racer shift to neutral after a run.

ditto that.....MANY hundreds of runs on my original trany....never thought there would be any multiplication when going to neutral....gonna have to re-think my habits..

I assume the direct drum is still spinning at very high rpms when I go from neutral back into gear at the turn off point.....what is slowing it down when you put it back in gear?....or is it purely the driveshaft rotational speed that compounds the direct drum speed?.........stupid questions I know....I need to study up on th400's

[KO]

In high gear the direct drum connects to the drive shell which connects to the sun gear. When in high gear the direct clutch and the forward clutch are both engaged causing the transmission drive drain to be locked up and turn as one. When pressure is released the forward clutch drops out and the output shaft then can turn the planetaries with mutlipication to the direct clutch suddenly accelerating the direct clutch to output shaft speed times first gear ratio. 5000 RPM times 2.48 = 12000 RPM and that is only 5000 RPM. 7000 RPM = 17000+ PLUS the inertia of the heavy drum probably more. This is very common in TH400s I have personally witnessed two. A 2.2 first will reduce rpm a bit.

[screamingchief]

Problem is,parts of this debate are based mostly on myth,superstition,and supposition.

And other parts are based on direct physics and mechanical principles.

So clearly there are two sides.

There are those that say neutral it and save the engine wear and tear.

And there are those that say dont neutral it and save the trans.

Here's how I see this,stay with me a second or two folks.

I've seen lots and lots of evidence that proves that putting it in neutral can cost a trans,and occasionally cause an injury and/or crash as well,seen plenty of fragged trans,also seen plenty of pictures of the same,and heard (or read) plenty of direct testimony from hardcore racers that have learned this lesson the hard way.

Now the flip side of that,I've seen virtually zero solid proof that putting it in neutral during shutdown is somehow saving wear and tear on the engine.

I've yet to see any solid evidence of a single engine failure that can DIRECTLY be attributed to leaving it in high gear for the shutdown.

No pics of such,no rods that I can see clearly pulled apart from those extensive forces,no proof that a bearing failure was due to this,nothing.

So IMO the "neutral" guys are taking it on faith that their engine guy is right.

And the "no-neutral" guys are making their decision based on visual proof and direct testimony.

Ask me,it's a waste of time trying to debate a given topic with a person who's taking their side based solely on faith.

If it's so hard on the engine to leave it in high gear during shutdown,where's the proof of this???

Please,enlighten us if you have such proof,just dont try to feed us simple soundbites to support that argument,as such offers us no viable evidence to make any sound judgements upon.

You guys say thousands click it in neutral every day,well the flip side of that is thousands dont click it in neutral every day,so by ya'lls logic there should be literally thousands and thousands of guys out there stretching their rods like taffy and blowing up their $#!t due to that situation,but I just dont see that's what is happening out there.

In the end,neither side is 100% right,nor likely is either side 100% wrong,like everything in life,we hafta make our choices as best we can,and then we live with the consequences of that choice,and these choices dont always affect just us,often they will affect the lives of others around us.

Just try to make those choices based on the best information you can get.

And I wanna clear one last thing up before I leave this thread,I'm not "pro" or "con" on this subject at all,frankly I dont give a rats ass what any of ya'll do,you make your choices,I'll make mine.

But I do feel that folks need to hear both sides to make that informed choice.



Bret P.

[grandville455]

I always just slowly let off once thru the traps, 700 Runs not one problem doing it that way plus... I like my feet

[KO]

I have witnessed it personally twice. I have heard of many more. I have only seen this on TH400s. I have HEARD it happens on 727s and they have large iron drums like a TH400 It wont happen on a Powerglide or a Proflite due to lighter smaller drums and numerically lower first gear ratios. The best thing to do is click the motor off

[taff2]

I run used ali rods in my 400,have done for 7 years or so, I come off the throttle slowly at the top end and have hundreds of 7000rpm runs on these rods, I've never shifted into neutral at the top end either

[screamingchief]

Originally Posted by KO

I have witnessed it personally twice. I have heard of many more. I have only seen this on TH400s. I have HEARD it happens on 727s and they have large iron drums like a TH400 It wont happen on a Powerglide or a Proflite due to lighter smaller drums and numerically lower first gear ratios. The best thing to do is click the motor off

Just to be 100% clear here.

I asked where's the proof that it's hard on the engine to leave it in high gear during shutdown.

I (like you & others here) have seen firsthand the proof that putting it in neutral can lunch a trans.

And yes,I've also seen/heard lots and lots of secondhand proof of such as well.

Just wanna avoid any confusion based on my comments.

Bret P.

[KO]

A case of ATF under the car at 100+ MPH isnt fun either

[Ron]

The only proof I have is my motor is still together....however I attended a seminar where the late Buddy Morrison was one of the speakers and he was asked about putting the motor into neutral to reduce/eliminate engine loads...his reply was yes because keeping the motor in gear and allowing it to coast could cause engine failure. He went on to explain why but I didn't pay that close of attention because at that time I raced a high 11 second low 12 second GTO and never had plans on anything quicker.

[Probird]

Put me on the list of putting it in nuetral at the finish line. I do it with a Powerglide with a pro tree brake which has a clean nuetral. I have noticed that when I do this the engine rpms don't drop to idle immediately they hang out around 3000 rpm's until my speed gets down to around 30 or 40 mph or so. I always kind of wondered why but never really thought too much about it. And not that it makes any difference but I do build my own transmissions and haven't seen any ill effects of doing this. I wouldn't reccomend it with a th400 though.

[jakeshoe]

As has been stated the issue is with the direct drum.

A clean/safe neutral valve body releases all the clutches except the direct. It releases the forwards and intermediates.
When you release the forwards it is essentially like mashing the clutch on a stick car. The engine is unhooked from the trans and can return to idle.

The direct stays engaged to the forward drum and sun gear, so it continues to spin input shaft speed, not being driven by the output shaft.

I have put all the geartrain together for a TH400 and looked at the way the direct drum is driven by the output shaft. Those who are curious should do this sometimes because you will find it doesn't do exactly what you expect and overdrive to 2.5 driveshaft rpm.
However what it does do will cause it to grenade and that is why I mentioned clutch release rates earlier because I believe that how fast the directs release has a profound effect on whether the drum stays together or not.

I do not disagree with the philosphy that decel is harder on the rods. My understanding and experience indicates it is the initial change from accel to decel is where they see the most load and that is why you shouldn't snap the throttle at the end of the track.
We've all seen/driven a motor with a rod knocking and you can hear it get worse on the intial decel and then continue to hammer, light accel and it oftentimes goes away.

However hard decel if it can be avoided is a good thing. Simply less wear and tear on parts.
That is why there are VB's made for it and that is why transmission builders recommend them for applications where they are needed such as aluminum rods or extremely high rpm applications.

I have built Stock Eliminator transmissions. TH350s and 200 3 speeds.
There are some neat tricks there.
Most of those guys want the lower (higher numerically) gearsets. 2.75 in a TH350 and the stock 2.74 ratio of the 200s.
In a TH350 one trick of many is to leave out half the pinions in a planetary and use lighter parts from a TH250. Lower pump pressures.

200's have stamped steel drums and are lightweight.

Scott McClay is well known for his 200's.

[Dragncar]

I build my own engines and T400s. Nothing too fast, just 11 flat on pump gas.
But I have never hurt a engine or blew a tranny apart doing both. Letting off the gas at the end or just clicking it into neutral.
The last pass I made the car spun but I kept my foot in it and the car crossed the line at 7000+ RPMs and I just clicked it into neural.