Trans brakes
09-18-2004, 08:20 PM
#1
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Location: Darlington. England (Northeast)
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Trans brakes
Hi Guys.
Anybody frquenting this site who uses a trans brake? Is your car over 3500lb? how do you make it live? what problems would I come across in a 3900lb car and 730ish HP. OH... I maybe moving up to a 572ci in a season or 2 which should have at least 100hp more,need to keep that in mind.
Cheers. Tig.
Anybody frquenting this site who uses a trans brake? Is your car over 3500lb? how do you make it live? what problems would I come across in a 3900lb car and 730ish HP. OH... I maybe moving up to a 572ci in a season or 2 which should have at least 100hp more,need to keep that in mind.
Cheers. Tig.
09-22-2004, 04:35 PM
#2
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Location: Darlington. England (Northeast)
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Ok, I've asked around and surfed the net to find out some stuff on 727's and trans brakes. So I've sort of answered my own question. Here's what I found if anyones interested.
As we all know the inherent weak point on a 727 is the interference fit, one-way bearing ( sprag ). On most manual valve body's, the the low band on the rear drum isn't applied. This means that all the power and torque is applied to the sprag in 1st gear. To counteract this, the better manual valvebody's available have low band apply. Also bolt in sprags are available, some bolt in sprags are better than others having 16 rollers to spread the load rather than the stock 12. The high line pressures these valve bodies can generate means that other stuff has to be toughened up. Billet servo's, HD band struts and lower ratio kick down arms ( 4.2 or 3.8 ) rather than the usual hemi 5:1 arm. The must is to have an Aluminium or billet steel front drum. If the sprag goes this means that the front drum can rotate at 2 times engine speed. The front drum is not usually reliable at over 9000rpm and the result of this is not pretty. A rollerised rear support for the output shaft is also advised, its just stronger and takes some of the loading off the rear bush. Also advised are billet pump gears, stock ones are apparently sintered metal and the tangs can crack or break off. Also the converter has to be up to the job. So once you've got all that, remember that the rear ring and pinion should be the "soft" type to absorb some of the shock due to backlash, normal street gears can chip. This was recommended just for my 750hp 3900lb bracket car. If you want to run a 727 behind anything with forced induction you've got to start talking about billet input and output shafts, fully rollerised, STEEL 5 pinion planataries, Ali front and rear drums etc. Big money! I've decided to build a tough box with a bolt in sprag and aluminium front drum and a few other trick pieces, a transbrake will not be included
Cheers ..Tig
As we all know the inherent weak point on a 727 is the interference fit, one-way bearing ( sprag ). On most manual valve body's, the the low band on the rear drum isn't applied. This means that all the power and torque is applied to the sprag in 1st gear. To counteract this, the better manual valvebody's available have low band apply. Also bolt in sprags are available, some bolt in sprags are better than others having 16 rollers to spread the load rather than the stock 12. The high line pressures these valve bodies can generate means that other stuff has to be toughened up. Billet servo's, HD band struts and lower ratio kick down arms ( 4.2 or 3.8 ) rather than the usual hemi 5:1 arm. The must is to have an Aluminium or billet steel front drum. If the sprag goes this means that the front drum can rotate at 2 times engine speed. The front drum is not usually reliable at over 9000rpm and the result of this is not pretty. A rollerised rear support for the output shaft is also advised, its just stronger and takes some of the loading off the rear bush. Also advised are billet pump gears, stock ones are apparently sintered metal and the tangs can crack or break off. Also the converter has to be up to the job. So once you've got all that, remember that the rear ring and pinion should be the "soft" type to absorb some of the shock due to backlash, normal street gears can chip. This was recommended just for my 750hp 3900lb bracket car. If you want to run a 727 behind anything with forced induction you've got to start talking about billet input and output shafts, fully rollerised, STEEL 5 pinion planataries, Ali front and rear drums etc. Big money! I've decided to build a tough box with a bolt in sprag and aluminium front drum and a few other trick pieces, a transbrake will not be included
Cheers ..Tig
09-22-2004, 07:59 PM
#5
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Originally Posted by Tig
I use a trans blanket, even though the car doesn't need it to be race legal 
. In the UK trans blankets are only required on cars running quicker than 9.99
. In the UK trans blankets are only required on cars running quicker than 9.99 My car runs 12's, but I've had a blanket on my 727 since it was running 15's.
It's cheap insurance, in my book.
09-23-2004, 06:46 AM
#6
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I've been racing seriously since 1997, I've never seen, or heard of a 727 blowing a front drum in the UK. Though thats not to say it's never happened. I've heard of plenty of sprags throwing in the towel though.
09-23-2004, 07:22 AM
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