transbrake with caltracs, help

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deepockets

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i have a 69 dodge dart with mild 440 with auto trans and 430 rear gear. i have caltracs bars, springs, rear 9000's, and there 90/10 front shocks. the rev limiter is at 2400 rpm before it flashes to 3600 rpm. the car pulls the front tires off the ground about 3-4". i have new hoosier 28-10.50 slicks. some where after takeing off it unloads the chassis and the back hops up and down a couple of times. it does not do this if i footbrake the car. i have eletronics in the car and really want to keep them. any body else have any ideas or suguestions. the car has glass hood and deck and front fenders. 6 point cage and no back seat with kirkey front seats. thanks for any help
 
hi I assume you have a throttle stop? does it come on shortly after launch?
If it does, then you're unloading the chassis, makes it hop up and down.
what are the rear shocks set on? do you have any preload on bars or no preload? which hole is bar set in? the lower hole would prob be better for trans brake. trans brake is like a stick car. no preload on suspension. it shocks it hard. I have my rear ranchos on # 7 setting. what tire pressure you run? how wide is the wheel? prob should use a wheel as wide as the tire if not litle more wider. on a stick car usually run a wider rim compared to the tread width. it's like anything else, takes work to figure out what the car requires or likes.just foor forthought
 
My wild guesses:

Sounds like the shocks might be set too stiff, or the shocks are dropping the front end too fast, or your front suspension doesn't have enough travel.

Why are you setting the limiter so much lower than the stall?

What is your pinion angle? Have you tried both sets of holes in the Caltracs?

Where do you have the 9000s set?

Tire pressure?
 
wow that quick on response guys. i was running 13 lbs of pressure. the rims is 10" wide. i did have 2 flats of preload with driver in car. i have only used the bottom hole for the bar as the upper hole is not accessable since the spring is up high in the relocater mounts. the bars have 4-5 degrees of angle upwards to the front. i was told by calvert to run 1000 rpm difference from the two step to the converter. i tryed middle and stiff setting on the shocks and it's worse. i did just get the front end to where it has 5" of front seperation. it did have 3-1/2 and then 4-1/4. calvert said it must have 5". i'll take it out this thursday and see if the increased front travel helps. still open for ideas. how much rpm difference should i have from the two step to the flash on the converter?
 
the car has the stock heigth springs, the shocks that i have are 99113 that are 20 inches long and 13.25 colapesd. sitting in the car there is 3 inches of shaft exposed. do you thing these things separate that much? also why does is separeate so much? i dont see chevys or fords doing this. thanks
 
Seems you probably have enough travel. Does the front rise a little before the car moves forward? Does the rear rise a little or squat?

Got any videos of it launching?
 
i'm going to video it this thursday and then try to figure how to download it, i''l keep you posted. thanks
 
Get some real good focused shots from the side as it launches, and mark the tires with some white shoe polish so you can see if it spins. If you know how to edit the video, slow it down by 2x or 3x.
 
hi,why is the front spring mount up so high? calverts are made to work with stock front spring heights. pinion angle is relationship of pinion to driveshaft.
not to the ground or trans. If your front spring mount is way high, your instant center is way off. it's way short and too high. a short and too high instant center cannot lift the nose. and keep tires planted. best thing is to graph the complete suspension on graph paper. its a lot of work, you will know where the instant center is and can relate to pinion angle. theres a couple good books out there about suspensions . dave morgans is one. it looks like your bars and front half of spring are aimed up. just food for thought.
 
deepockets said:
the car has the stock heigth springs, the shocks that i have are 99113 that are 20 inches long and 13.25 colapesd. sitting in the car there is 3 inches of shaft exposed. do you thing these things separate that much? also why does is separeate so much? i dont see chevys or fords doing this. thanks
Click to expand...


It's my understanding that it is caused by the geometry of the rear springs. The front part of the spring acts like a control arm. The back part of the spring (which is much longer), working with the front, torques the car and causes lift......this also forces your tires down into the road....pretty cool.

Leaf_springs_mopar.jpg

Look how far forward the axle mount area is from center.
 
I had a similiar problem with my Dart. What was happening was the shocks were reaching full extension when the front end was in the air. I also use Cal Tracs and Rancho 9000. I firmed the rear shocks all the way to determine that was the problem. I then backed (softened) the shock off until it launched right. Most tracks, I have them set on 6 or 7. Hope this helps
 
perfacar, i had done that as to bring the rear down some, also the rear part off the spring is on a slider thats mounted flush with the frame that brings it uo as well
 
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