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Old 07-28-2020, 09:03 AM
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Drag car transmission launch

Hello everyone, I'm still cutting my teeth on bracket racing and wanted to ask for some transmission advice. I have a th350 with a manual valve body with 2800 rpm stall. The rear end in my car has a 4:56 gear. I was wondering if launching the car from a footbrake in 2nd gear would help from busting the transmission as I need it to last at least one season.

I have contemplated switching to a th400 but that would mean I would have to shorten my drive shaft and I dont know the proper way to do that. Any ideas or thoughts would be appreciated.

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Old 07-28-2020, 09:07 AM
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will require some serious torque to get moving
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Old 07-28-2020, 09:11 AM
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I forgot to mention it's a 454 engine with approximately 425hp
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Old 07-28-2020, 10:00 AM
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Throttle Stop

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Originally Posted by 77nova454 View Post
I forgot to mention it's a 454 engine with approximately 425hp
Could you adjust your throttle cable to only hit 3/4 open? Since you are bracket racing, aren't you just trying to hit your dial in number? It seems to me like it would be more consistent, and easier on parts. That way you could take off in 1st.
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Old 07-28-2020, 10:05 AM
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I never really thought of that since I'm new to all of this.... its definitely worth a shot was trying to figure out a way to only shift one time without having to go to a powerglide.

I will try this out the next time I go to test and tune.... I'm on a tight budget lol.
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Old 07-28-2020, 10:20 AM
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Originally Posted by 77nova454 View Post
I never really thought of that since I'm new to all of this.... its definitely worth a shot was trying to figure out a way to only shift one time without having to go to a powerglide.

I will try this out the next time I go to test and tune.... I'm on a tight budget lol.
I'm no expert, but when I was in high school our auto mechanics teacher had a Super Gas Pinto. The car would go 8s, but he ran 9.90s consistently and was hard to beat! Thats what I remember him doing. It was a long time ago though. A bunch of these guys on here are regulars at the track and will probably have something better for you to try.
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Old 07-28-2020, 10:54 AM
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If you're bracket racing and not class racing, it doesn't matter if you run a 25 second E.T. and the transmission shifts 14 times, as long as you get to the stripe first and don't run under your dial-in. Put a block of wood under the accelerator pedal and save the old girl.
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Old 07-28-2020, 12:02 PM
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1st is not the weak gear in a TH-350....it is the 2nd gear roller clutch("sprag") that is prone to breaking right at the 1-2 shift.
Too high line pressure from a poorly designed shift kit/valvebody that slams the shift hard is what will break the stock sprag race.

If your manual valvebody deal has an aluminum plug that replaced the stock vacuum modulator...remove the plug and put the vacuum modulator back on it, just with no vacuum hooked to it, it will cushion the shift a little.

I'd say run normal 3 gears it till it breaks, if it does break you can then dive into the 400 swap. Start checking around now for someone who may do drive shaft shortening in your area...ask at the track, put out some feelers, somebody will know some one or of a truck service shop that does do it somewhere near you.

One of the worst things on the TH-350 trans is a 1-2 upshift in the water box with the tires just flying....start in 2nd and as soon as the tires are loose upshift to 3rd if you've got enough power to do it....if not , stay in 2nd...... and avoid a hard hook coming out of the water box.

Avoid doing any "dry-hops" after the burn out, hard on the trans and you are wasting that fresh tire surface you just prepped with the burnout and the best hook the tire is gonna have.....do the burn out and go right up to the stage area.
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Old 07-28-2020, 01:39 PM
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Lol I will experiment with it on Thursday night. You always make me laugh 🙂. One of the hardest things for me to remember is that it's all about consistency.
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Old 07-28-2020, 02:30 PM
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The Th400 is going to consume a lot of power if you go that direction. You would be better to build a 'Glide for that car, it eliminates a shift, the 1st gear ratio of it will lend itself to keeping the car more consistent and if the trans is put together right, you'll have a hard time breaking it with normal maintenance.



You're running 1/8 mile right, so with that gear you won't be shifting into high probably much before the first cone. Did you get the trans leak sorted out? What about the driveshaft loop?


Thursday night at Summer Duck?
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Old 07-28-2020, 04:39 PM
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The Th400 is going to consume a lot of power if you go that direction. You would be better to build a 'Glide for that car, it eliminates a shift, the 1st gear ratio of it will lend itself to keeping the car more consistent and if the trans is put together right, you'll have a hard time breaking it with normal maintenance.



You're running 1/8 mile right, so with that gear you won't be shifting into high probably much before the first cone. Did you get the trans leak sorted out? What about the driveshaft loop?


Thursday night at Summer Duck?
I did get the transmission leak sorted out. I'm still trying to figure out the driveshaft loop issue. They didn't say anything about it being 12 inches from the ujoint during tech.... I honestly thought they were going to measure with a tape.

They did mention that I needed to get the door bar fixed. I plan on having it welded up or installing a swingout bar this week. Yes, hopefully Thursday night at the duck ....
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Old 07-28-2020, 07:24 PM
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They did mention that I needed to get the door bar fixed. I plan on having it welded up or installing a swingout bar this week. Yes, hopefully Thursday night at the duck ....
What was wrong with the door bar?

Not steal your wind here, but can a door bar have a bend in it and still be legal or does it have to be straight?
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Old 07-28-2020, 08:08 PM
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They did mention that I needed to get the door bar fixed. I plan on having it welded up or installing a swingout bar this week. Yes, hopefully Thursday night at the duck ....
What was wrong with the door bar?



Not steal your wind here, but can a door bar have a bend in it and still be legal or does it have to be straight?
The person that owned the car before me cut the door bar to put a swingout kit on it cause he was a big guy and never finished it. I'll be honest I'd ask tech inspector ,Ericnova, or character about what's legal they have a ton of knowledge and have helped me more than words can say.
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Old 07-28-2020, 08:18 PM
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Yes the diagonal bar can have a bend in it, usually up near the upper arm area to provide additional room for the driver. I have seen one setup where the diagonal bar was crossed with another in the opposite direction making a "X" and it was leaned out at the top. We have "X" bars in the Monza but they are inline with the A-pillar bar and the leg of the cage hoop behind me.
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Old 07-29-2020, 09:02 AM
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Quote:
Originally Posted by 77nova454 View Post
The rear end in my car has a 4:56 gear. I was wondering if launching the car from a footbrake in 2nd gear would help from busting the transmission as I need it to last at least one season.
I would just try it on a practice run and see if satisfied with the overall performance... Theory is one thing, real world is another...
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