Trans Gurus, Why no TH400 'Brakes with Auto/Modulator function

[jakeshoe]

Wondering why no one makes a VB with transbrake for a TH400 that retains auto features and modulator?

Basically,
Street strip car, mostly street. Sees some dragstrip duty but lazy drivers like myself don't want to manually shift ALL the time.

Is it feasable to take a stock VB,
do normal shift kit type mods (dual feed directs, HD PR spring, etc..)
then plumb a 'brake onto it?
Plumb into the line pressure then feed the int. or directs to lock it down while you have it in manual low.

On the surface it all seems simple enough to do but obviously I'm overlooking something.
Not a trans guru like you guys just know the basics.
wish I understood the hydraulics better.

 

[WE4]

It is hard to...

explain in a short form but the very basics are the fact that the fluid paths and apply and release of high drum for the brake would not allow the circuitry to support an automatic function.
Line pressure is is greatly affected. Govenor pressure is a little different than our 2004r. Ever notice how transbrakes are reverse pattern? There is a reason for that.

Let me add that I know of three I have seen and worked with in my life, that years ago a company called "Lamb" made an external brake on the back of a 400. That would work but I haven't seen or heard of one in many , many years. Chris, Greg, Alan? Any you guys remember these or have any more info on this product these days?


Bruce
WE4

 

[jakeshoe]

I've heard of using the intermediates to operate the brake, would this simplify it any?

 

[WE4]

No ,

Intermediate would be a not such a hot Idea. It is already the weak point by blowing the lugs out of the case. I have a fix for that that puts and end to ever blowing the case but it takes some time to do but makes it almost impossible to blow them out. I pin the plate through the case. Works great. But for the brake , it would be slow and not work well in my opinion. Years ago I worked for ATO Racing and they did extensive testing on the 400 brake. He tried many things and I beleieve that was one of them that was scratched. Jim used 2nd gear for his brake for the C4 and it worked great.
My opinion anyway.

Bruce
WE4

 

[jakeshoe]

Thanks for the info,
Just got home from work and when I get on this forum I go into tranny think mode.

Where do you guys learn all the hydraulics basics, tricks, cause/effect stuff at?

I can rebuild a transmission, I can read a hydraulic diagram, I understand the principles of hydraulics, pressure, etc..
But where can I read about all the voodoo

 

[WE4]

Well

As They all will tell you, Alot of time and alot of breaking stuff. To learn you have to be hands on. Book smart and application smart are two different things. For a fee I will fly you out and teach you., ROFL

Alot of time and alot of frustration. Not everything thing you think will work does. Not everything you think will not, just might There are alot of theories that are applied.

Bruce
WE4

 

[jakeshoe]

Definately,
I agree.
I've done some of that breaking stuff
I broke my Th400 when I first got my car going. Int sprag.
S I went back into it and went all out.
HD Low sprag, HD int sprag, etc..
Put the low sprag in backwards. was looking at the ATSG and checked rotation but the manual confused me. Backed car out of shop, put in gear, voila. I had a TransBrake. Unintended one.
2 hours later I was driving home.

 

[jakeshoe]

If I ever win the lottery,
I'll come work for free just to learn more from those that know.
For the moment (last 3 weeks) I've been aligning new Peterbilt trucks at the plant.
Gm dealership was more exciting but I got 3 hungry kids to feed and flat-rate mechanicing is too unpredictable.

 

[HOTTOGO]

Re: Well

Originally posted by WE4
... Alot of time and alot of frustration...... Bruce
WE4

you mean even the big boys get frustrated from time to time...... LOL!!!

I always thought it was a God given gift with never a mistake, just always perfection... ?!

 

[6PacktoGo]

Yes, it was Lamb

Roger Lamb, the guy who gave you the drag racing four link, and the strut frontend. It was CO2 operated originally. He had one for the PowerGlide too. No one I know if is making an external brake anymore. Roger Lamb made a lot of neat stuff, but the external brake was not among the best of his work.

The reasons for the lack of an automatic transbrake VB for the 400 are too numerous to list. Fluid flow, the need to use the direct clutches for the brake, and some of the other modifications to install it are just the most well known. And using the intermediate clutches is a very bad idea. As Bruce said, it stresses the case. Also, the intermediate clutch pack and sprag is in fact the weakest part of the 400 anyway. We've never ripped the lugs out of a case, but we've done damage to everything else in second gear.

 

[6PacktoGo]

Originally posted by jakeshoe
If I ever win the lottery,
I'll come work for free just to learn more from those that know.
For the moment (last 3 weeks) I've been aligning new Peterbilt trucks at the plant.
Gm dealership was more exciting but I got 3 hungry kids to feed and flat-rate mechanicing is too unpredictable.

Peterbilt huh. Denton Texas or Nashville/Madison Tennessee? I used to be a proto type tech for a Peterbilt supplier.

 

[chris718]

hey jake .we make them from time to time like that but no one buys enoug to keep them in production. all our ck performance pro series brakes use the 2nd gear clutches ,forward clutches and the band to lock the output shaft however it took a while to stop blowing case apart until we dropped line pressure to 160 psi,added 12 stiff springs and increased second gear clutch clearance to increase clamping force lost by dropping line pressure.a solenoid off the v body puts line to the intermediate clutch with a pipe ,much like our manual automatic 2004r brake.however if you apply the brake in hi gear it wont work because the band stays on until you make a manual 1/2 shift and the oil dumps out at the manual valve .i thought i was the only reject who was making them.i would love to see those other designs however .i would feel like an archaeologist discovering atlantis. i like valve body design , function , theory and execution.

 

[jakeshoe]

Chris,
Thanks for your input.
I thought I had heard of people using the Intermediates.
I see a little more of the inside theory here.
I had thought that maybe the pressure of the brake engaging a clutch pack was backfeeding into other circuits causing problems with automatic operation, so the need for a specific manual VB, etc..
Yes all the trickery of the VB is interesting to me. The guts can be figured out USUALLY with normal mechanical and engineering principals. But the VB requires some VooDoo.

I every once in a while build a Th350 or 400 for some racing buddies. I don't know all the tricks but have a few I use and most for the TH's are so commonyl known that not really a closely gaurded secret anymore.

It's hard to convince people that that BANG shift ISN'T what they really need. Nothing wrong with firm shifts but when it gets to the point of being a bind-up just so it'll always chirp going into 2nd it's detrimental to the trans.
Mine leaves scratch in 2nd but it's AFTER the shift. kinda hard to explain but you guru's know what I'm talking about. Car shifts then the tires break a little from torque. My 3rd gear shift ended up a little firmer than expected. Nice comfortable shift under light throttle but it hits pretty hard under WOT. Probably not gonna hurt the 400 since it's just a clutch over clutch shift.

Chris,
I'll try to call you. I thought about the mail system the other day. You had a problem getting the VB here. My mail carrier sucks and probably won't walk to my apt. to deliver it. Lots of stuff gets fouled up so I usually use UPS instead of USPS.

6pack,
Denton, TX.
I was working at a large GM dealership. Enjoyed the work but the slow times kill me. Not a great money budgeter...
Also the sole income so nothing else to rely on, except an occasional side job.
A few plusses though. I work evening shift so now I can take some college classes. 1 class away from my Associates so need to get after it.

Alright next question.
I understand the 200 has an "exhausting checkball" type governor. How does this function?
I'm familiar with the TH types and understand how they work. What differs with the 200?