TH350 shifting in burnout box - Chevelle Tech
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post #1 of 13 (permalink) Old Jun 27th, 11, 10:38 AM Thread Starter
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TH350 shifting in burnout box

Ive heard not to start your burnout in first gear and shift from 2nd gear with a TH350. Is this proven? I know all the major transmission shops say it. I just recently heard this but I have been doing this for 4 years or so without a single issue. We run a fairly stout sbc with around 600HP and a TCI Competition TH350, trans brake, reverse valve body, etc. 9" 4500 stahl B&M converter. Whats everybodys thoughts? Like I mentioned Ive been doing this for quite some time and never had an issue. Is this a ticking time bomb? Whats the theory behind this?
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post #2 of 13 (permalink) Old Jun 27th, 11, 10:53 AM
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Re: TH350 shifting in burnout box

I have sbc th350 t/b from ati . They said to start the burn out n shift to 2nd because your wheel speed is faster n its easy to maintain a lower rpm while you heat your tires up . Nothing to do with blowin the trans just heat the tires up quicker so not as long of a burn out needed to get the same amount of heat in them

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post #3 of 13 (permalink) Old Jun 27th, 11, 11:56 AM Thread Starter
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Re: TH350 shifting in burnout box

Quote:
Originally Posted by redlightrookie View Post
I have sbc th350 t/b from ati . They said to start the burn out n shift to 2nd because your wheel speed is faster n its easy to maintain a lower rpm while you heat your tires up . Nothing to do with blowin the trans just heat the tires up quicker so not as long of a burn out needed to get the same amount of heat in them

On ATI's website it says with a TH350 start your burnout in 2nd and shift to 3rd. Just curious to why this is.
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post #4 of 13 (permalink) Old Jun 27th, 11, 11:57 AM
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Re: TH350 shifting in burnout box

I just leave it in 3rd and do the burnout. Keep the rpms where you wanr them. With 600hp you shouldnt have a problem doing this.

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post #5 of 13 (permalink) Old Jun 27th, 11, 12:03 PM
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Re: TH350 shifting in burnout box

It i generally accepted that shifting 1-2 in the burnout can lead to intermediate sprag failure. I'm sure if you did a google search you would find hours of reading on the subject.

I've broken 2 th350 intermediate sprag outter races in the burnout over the years. But they were stock sprags with just the hardened outer race. With the 34 element spags i've never had a problem.
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post #6 of 13 (permalink) Old Jun 27th, 11, 12:08 PM
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Re: TH350 shifting in burnout box

They said in 2nd or third you can control the motors rpms easly n you have a faster wheel speed . So the tires are spinning faster in 2nd n evan faster in third at the same rpm as you would in first . It realy just heats the tires quicker n lets you do a shorter burnout while heat up the tires the same as a first gear burnout n more control of over reving the motor in the burnout box .

72 chevelle best et 10.45 on spray 131 mph 1.42 60ft still tuning
70 ss 396 4 spd #s matching (500 rwhp & 503 tq)
http://m.youtube.com/watch?v=SsY4WCfBQEE#
http://m.youtube.com/watch?v=_K_u1VHUb6A#
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post #7 of 13 (permalink) Old Jun 27th, 11, 12:47 PM
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Re: TH350 shifting in burnout box

Quote:
Originally Posted by redlightrookie View Post
They said in 2nd or third you can control the motors rpms easly n you have a faster wheel speed . So the tires are spinning faster in 2nd n evan faster in third at the same rpm as you would in first . It realy just heats the tires quicker n lets you do a shorter burnout while heat up the tires the same as a first gear burnout n more control of over reving the motor in the burnout box .
You can do it in any gear you want, But just advoid making the 1-2 shift in the burnout and your intermediate sprag will be much happier.

If you need to start in 1st, wait till the engine rpms stabilize before you shift, if the RPM's are still on the way up and you shift it's even more shock to the sprag.


(and by "you" i mean the general automotive public, i'm not singling you out)
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post #8 of 13 (permalink) Old Jun 27th, 11, 1:16 PM
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Re: TH350 shifting in burnout box

I've got the TCI h/d drum with 34 element sprag in mine, been 1-2 shifting for 4 years now. As has already been stated, the 10 element stockers don't care for it. With nice parts, it'll live.

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post #9 of 13 (permalink) Old Jun 27th, 11, 1:20 PM
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Re: TH350 shifting in burnout box

I agree . Just throwin out what ati told me when I got the trans . They said same thing start in first but said as soon as tires spin hit 2nd . just how they told me is all . Plus I had them way over build my trans for hp I make .

72 chevelle best et 10.45 on spray 131 mph 1.42 60ft still tuning
70 ss 396 4 spd #s matching (500 rwhp & 503 tq)
http://m.youtube.com/watch?v=SsY4WCfBQEE#
http://m.youtube.com/watch?v=_K_u1VHUb6A#
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post #10 of 13 (permalink) Old Jun 27th, 11, 1:46 PM Thread Starter
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Re: TH350 shifting in burnout box

Just got off the phone with TCI and they said I have a 36 Element sprag in my trans. Good to hear
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post #11 of 13 (permalink) Old Jun 27th, 11, 2:40 PM
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Re: TH350 shifting in burnout box

I am no expert at all, but the experts explained to me the weakest link on a TH350 is the sprag. The sprag is used in second gear if I remember correctly and this is what fails. Its not from the burnout, it is from catching traction in second gear coming out of the burnout box (maybe also if not enough rpms). It does not like backlash however that occurs. Hope that helps.

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post #12 of 13 (permalink) Old Jun 27th, 11, 3:09 PM
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Re: TH350 shifting in burnout box

Been shifting the 350 in the box for years. As said 2nd is the weak spot but its gonna happen or it aint. Just put a new TH350 in and the builder said just keep doint what I have been.The new one also has HD sprag though.

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post #13 of 13 (permalink) Old Jun 27th, 11, 3:35 PM
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Re: TH350 shifting in burnout box

I start in 2nd and immediately shift to 3rd. I do it for the same reason. Seems the consensus is the trans will live longer. Mine is still holding up so far so plan on keep doing the same thing.
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