Trans break TH400

[68 C-10 KID]

Hello all. I Just installed a Th400 w/ tci trans break in my '68.
I have a 3500HD Hughes converter. Will this stall higher on the break than when I used to foot break it w/ my TH350?

2nd ? Can I get away W/ limiting the RPM W/ the 2 step if it stalls much Higher? I'm only running a 26x10 Hoosier @ 11.5 psi. I'm only guessing that much higher than 3500 it will just kill the tires.

Thanks for all info and replies.

[Marv D]

A foot brake can NO WAY get close to true stall. Your trans brake, with warm oil, the motor at WOT is the only way you will see 'true' stall rpm. The brakes are just not strong enough. So,, yes, you will see more rpm on the button than on the footbrake.

Typical setup is to set your two step 300-500rpm lower than stall on the button. That way you don't flash the convertor too hard and hit the tires easier. It's kind of deceiving. If you set your low side rev limitier to 1000rpm below stall, you will hit the tires HARDER than if you set stall close, or AT stall. Think of what happens when you release the button,,,, the engine has been sitting there trying it's best to gain RPM at WOT, but the ignition keeps dropping cylinders to make SURE it cant. You release the button, the engine starts spooling up and 'flashes' the convertor . Meaning somewhat like a rubber band wound tight, the inertia of the engine spooling up in rpms pushes past true stall some. How much,, depends on the convertor, torque curve, how quickly your motor gains rpm's, etc. Flashing the convertor can be a good thing, or bad. If you have traction it makes the chassis react faster, and improves r/t and 60' time. If traction is marginal,, it makes things worse with the added torque of flashing the convertor. (remember convertors are torque mulitpliers)

So.... start by warming the motor and trans, get out on the street and set the brake, go to WFO and pay attention to the tach to see what stall you get with your combination. Then start by setting your twostep 300-500rpm LOWER. If traction holds, set it 500-700 lower, if it still dead hooks, go 1000, or whatever it takes to start breaking the tires loose, then back up a few hundred RPM to dead hook.

Obviously the only way your going to see this is to have someone video your launch. Your not looking at the whole truck right now, just have them focus on the rear tire and body. Watch what the suspension does at the hit, and watch what the tire does. Suspension should drive the tires to the track, wrinkle the tire up, and slingshot the chassis forward.... in a 'perfect world' that is.

A friend (or two) with a video recorder is your best tunning tool for both launch rpm, and suspension settings and adjustments. If you eally want to get serious, pick up Dave Morgans book "DoorSlammers". Theories apply no matter if your tunning a 4link or a stock trailing arm C-10. Some interesting reading.

[Super73]

Marv,

Sound advise.. Morgan also has a DVD Seminar that you can find on Dragstuff.com Money well spent!!

To Marvs point about flashing the verter, my truck leaves hardest and cuts the best 60's leaving off the foot brake at almost idle when it holds. It's throwing the RPM up so fast and hitting the tires much harder than when stalled up. You would think it's the oposite, but it's not.. Think of it as inirtia or an object in motion, the faster it's going the harder it is to stop.

[68 C-10 KID]

WOW! That's some rad advice. Thank you guys so much for your time and your knowledge. I'll play with it a little today for the base set up. And 2 weekend from now I will be able to race it.
It sure is weird shifting back instead of forward.

Thanks much.

[Marv D]

Originally Posted by 68 C-10 KID

It sure is weird shifting back instead of forward.

Thanks much.

Haaaahaaha you want to watch something funny,, My Nova is a PG forward patern, my 66 PU is TH350 reverse patern, and I HAVE had both at the track at the same time. Nova leaves off top bulb w/ delay box and air shifted, Truck is transbrake, but no-E class and leave off the bottom bulb. I HAVE TO stop, look at shifter, tree, steering wheel for transbrake button, look for a delay box,,, EVERY time before I roll into prestage.
..... because ,,Yes I have launched the truck in 3rd gear off the top bulb before. Talk about feeling like a dumb@$$!

[68 C-10 KID]

I can't find the video at all

[Super73]

Originally Posted by Marv D

..... because ,,Yes I have launched the truck in 3rd gear off the top bulb before. Talk about feeling like a dumb@$$!

I found this sooo funny I tried to xplain it to my wife. She did this the whole time

[djracer]

I hate a reverse valve body. Here is what happens when a dumb@ss "me" down shifts with the gas on the floor.

[IMG]http://i129.photobucket.com/albums/p227/djrac...

this car was a handful to drive with a 3 speed and a 5.67 rear gear. you needed to do the 1 to 2 shift just as it was setting the front tires down. The best I got out of it this day was a 7.06 eighth but I talked him into letting me put a glide in it and it went 6.48.

I wish I had video of the first launch. The wheelie bars were up about 6 or 8 inches from where they are in this video. I turn loose of the button and almost needed new underwear. The guys at the track said you could have walked under the front bumper. Here's a better pass also.

[IMG]http://i129.photobucket.com/albums/p227/djrac...

[jgh64pkup]

well that must have been scary as hell