Anyone running a 904 behind a 340?

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My point, I have no point, you asked why buy a better sprag, and I have tried to explain the reason for it. Because in some situations, poorly prepped track, it is still possible to hurt the sprag. I understand how the release of the brake works by releasing the front clutch, even that varies by manufacturer. Some release much faster than others. The griner brake and it’s derivatives are very popular because of the speed of there release. I have met many racers of the 904 who switched to a power glide because they claim they could not keep the roller clutch from breaking. For some applications there is a need for a stronger roller clutch. That’s all I was trying to say.
My point was that just upgrading the sprag is not the be all to end all, especially when you look at what they were originally designed to do.
A lot of people think that just going to a TCI bolt in sprag will immunize them form having a sprag failure, when obviously it won't.
 
I think this is where the confusion started;

First your saying the band is on, then your saying it's not on, it's a little confusing.
That's why I made the comment about the non band apply VB's.
Actually you brought up a very good point. Many on this forum, myself included are confusing the term low band apply. What does it actually mean?
As was explained to me, all torqueflite brakes apply the band when you push the button.
All brand do this. Not all of them leave it on till second gear. So which version is considered low band apply? They all apply the band.
 
My point was that just upgrading the sprag is not the be all to end all, especially when you look at what they were originally designed to do.
A lot of people think that just going to a TCI bolt in sprag will immunize them form having a sprag failure, when obviously it won't.
Agreed !! My 904 has the ati 30 element sprag, an aluminum front drum and a billet brake that leaves the band on till 2nd gear, solid a&a low reverse servo kit to speed release and John Copes recommendation for a double wrap low band adjustment of 1-1/2 turns versus the factory 4 turns to speed the release of the band.
 
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Yes. it's a little confusing.
A Manual VB with Low band apply will hold the band on until second gear is selected. With or without a Transbrake being part of it.
A Manual VB without Low band apply generally will not engage the rear band while in first. But if a Transbrake is also fitted ,it can utilize the rear band while the car is stationary with the Transbrake on, to take the load off the sprag while being loaded up on the start line..
This would help with bumping a car into the lights..
Problem is with that design is that as soon as you launch,( brake off) the band is released and if you load, unload the tires then the sprag gets a hammering.
May as well just keep the band on all the way to second gear.
 
Agreed !! My 904 has the ati 30 element sprag, an aluminum front drum and a billet brake that leaves the band on till 2nd gear, solid a&a low reverse servo kit to speed release and John Copes recommendation for a double wrap low band adjustment of 1-1/2 turns versus the factory 4 turns to speed the release of the band.
Yes, lot's of little things make them work more efficiently.
It can be hard to make VB's work exactly the same way on transmissions when they have all different types of bands, clutches, clearances and spring loads. That's why a Manual VB install usually requires a transmission overhaul as well to get the most out of it.
Glad we sorted out the confusion.
 
Yes. it's a little confusing.
A Manual VB with Low band apply will hold the band on until second gear is selected. With or without a Transbrake being part of it.
A Manual VB without Low band apply generally will not engage the rear band while in first. But if a Transbrake is also fitted ,it can utilize the rear band while the car is stationary with the Transbrake on, to take the load off the sprag while being loaded up on the start line..
This would help with bumping a car into the lights..
Problem is with that design is that as soon as you launch,( brake off) the band is released and if you load, unload the tires then the sprag gets a hammering.
May as well just keep the band on all the way to second gear.
Yes that’s been the problem. But apparently these new billet valve bodies along with high low servo return spring pressure have figured out how to get a clean shift with the band on till second gear. I have one of those but have not tried it yet.
 
Yes, lot's of little things make them work more efficiently.
It can be hard to make VB's work exactly the same way on transmissions when they have all different types of bands, clutches, clearances and spring loads. That's why a Manual VB install usually requires a transmission overhaul as well to get the most out of it.
Glad we sorted out the confusion.
Hopefully we have educated others as well.
As I said this was explained to me by others.
I understand how the trans works, but it is these valve bodies causing the confusion.
 
Well, if your talking with John Cope, then you can't go wrong.
 
I would like to see video proof of that 10k plus action.......while your at it you may as well include the I was going 185 mph speedo shot too
Well we weren' t filming it but 2 FABO members were in the car when it kicked down into second at 100 mph and spooled up to over 105 before upshifting so you do the calculation yourself wise guy . 323 rear end , 145 2nd gear with 275/60/15 Nitto NT555R tires .
 
interesting reading…..
I’m at 84 passes on an amazingly stock component 904 trans. A&A front clutch spring pack and Pro Trans t-brake about the only “jewel-ray” in the build. I also went with the A500 pump gears. Was going to pull it at 60 and take a peak, but just dropped the pan and serviced it instead. Oh…. and we went 9.09 last weekend and had a 148.6mph slip too :).

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Factory 904 converters can crack in the pump drive neck area. A chromoly pump drive can prevent this, but some people also elect to go with the A500 style flat inner pump gear and A500 converter pump drive as to avoid having any problems.
 
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we’ve had 904 hub issues in the past so i just decided to go to a set up to totally eliminate the possibility…. matter of fact the pump lugs broke off on my old 727.

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Stock shafts, all thrust washers no bearings, not even a lightened sun shell. Front drums do have oil relief holes drilled in them. Chuck Lofgren built this for my dad back in the 90’s when he was running our low 11 combo. It had been laying around for 20+ years. I’d long since sold the Griner t-brake that was in it in favor of my pro trans unit. I’m actually surprised that I haven’t broken a shaft as I know quite a few people that have snapped them. I really plan on getting a more robust build and keep this one around for a “backup”. Not a cheap endeavor, but I feel like I’m dancing in a minefield right now. It was unfortunate that I swapped intakes at the same time I did the trans swap from the 727 as it really picked up quite a bit of ET. Would have been interesting how much was trans related.

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