Rick,
My trans was built by Chuck Lofgren, who has been building Torqueflites for racers for 40 years? He put all the needed upgrades in this trans, for my power level at the time. The next step only requires tougher shafts.

My 727 still has stock shafts in it. Haven't broken one yet, but it wouldn't surprise me if it broke on my next pass.
3850 lb car, 575" hemi on nitrous...Mid 5s at 127 mph in the 1/8. Should be somewhere in the 8.6-8.7 range in the 1/4, I just haven't run at a 1/4 mile track in a while.

Thanks Shawn. That tells me a lot. How do you launch and what tires are you running?

It was just Shawn's event, not me, lol. That's why his name is on the photo.
3k off the transbrake,. 295-65 drag radials.

Chip

I broke an output shaft at 700 horse at 3350 pounds.
Some guys get lucky, some don’t.
The fact is, the stock parts are 50 years old, they can break with pretty much any decent power. No way of knowing.
To the OP, seems like square peg round hole. Sensible thing is to go to a glide that can handle the power, and make the car way more consistent.
It’s never gonna be a world record holder, being consistent, not breaking and having fun seems logical to me

Rick Allison recommends anything 900hp or over to have hardened shafts.

Call Rossler and get a glide.

Don't get me wrong, if I had the budget, there'd be a powerglide in my car. I'm not recommending stock shafts either...I know mine is a timebomb. Just stating what I've done.

I assumed what you stated. I know i am skating close to thin ice, but i have backed myself into an empty race budget with the new motor and total rebuild of my trans . Originally i had planned to stay at 550 cubes, but a great deal on a longer arm crank came my way and i couldn't resist. Soooooooo, as mentioned earlier i plan on leaving soft and will upgrade to the input shaft and hub. Hopefully it will live a while. But i just remembered i have the GM bolt pattern, so that is one little item out of the way for a changeover to glide, ahould i need to go that way.

I still run a 727 but the only thing not billet was the output shaft but it's back at my trans builder getting new gears and a billet output shaft and the car is 3800 lbs on 275 radials. I'm similar to you as in I've backed myself into a corner with this box with the amount of money that's been spent on it. If I had to do it again it would definitely be a GM style trans, similar money ( bit dearer), but more ratios to choose, SFI cases and especially over here more parts availability.

Just for info, the H/D O/P shafts don't have the worm drive machined in for the speedometer. Just something to take into consideration if you have a car that does any street duty.

New hi strength input and hub showed up today! I am going to stay with the stock output shaft for now.

My 904 is doing pretty well at 6.08 and 112 in the 8th mile. 1.3 at 60'

Mine is a 540" B1 deal fwiw. It can run well into the 8's at 3600lbs and has never had any issues so far. As for consistency it seems prett good, nothing related to the trans anyway there. More the ability to keep the fnont end down has been the issue for me as we try to put the power in it. Still pulling fair amount of timing at the hit to tame that down, but slowing trying to ad it back. Hopefully new front shocks will be the ticket.

Need new shocks to calm the front rise and moreso the bounce when she lands. Then maybe I can put more power in it and one day maybe try something bigger than the single 4150 carb This was a low 9 teen pass here in Vegas problem is I was dialed 9.09

Wow, that wheelstand did get out of hand quick haha. One beautiful car. Love the 64-65 Plymouths.

Something I did not see posted much on here when it comes to taming down the launch while still running a torqueflite is a 1st gear change. Rick Allison sells a 2.28 helical cut rear planetary while maintaining the same second gear ratio of 1.45. Rick also sells a 2.28/1.45/1:1 straight cut planetary set but they are pricey. I have the 2.28/1.45/1:1 straight cut planetary in my trans but I have a backup torqueflite which I intend to one day put in the 2.28 helical cut rear planetary.

The 2.28 helical cut rear planetary is way cheaper than switching to a glide and it does help keep the launch more controllable. I have considered the glide as well but its very expensive to switch over. Especially since I have two very expensive torqueflites from A&A transmissions along with 2 torque converters from turbo action and I have a very expensive Precision Performance Products shifter.

I think the 2.28 first gear compared to a 2.45 first gear is a good thing for cars that leave hard with higher HP. Granite, I do not have the 572+ cubic inch and 572-13 heads, but my car has always left very hard even when it was footbrake car. When I switched to the transbrake I put the 2.28 trans in and it was very consistent 60' and much more controllable.

1.18 60' best
1.21-1.22 60' regularly
2835lbs
528 Wedge
440-1
71 Dodge Demon

Pull a 727 apart then lay the stuff out on a table, now do the PG the same way. Compare the parts for differences. imo it’s the aftermarket cases where most of the strength is found. One can buy better shafts, drums, gears, sprag but you still have that flexible case.

There are a number of gearsets available for a Proflite. Mine is and F1 2.24/1.48. Choices go from first gears of 1.78 all the way to 3.20, why they are so popular in Comp, SS and Stock. We have two transmissions for the Vette one is an F8, 2.18/1.48 the other is and an E8 2.25/1.51. The parts to run this stuff are not cheap for sure and from my experience they work great for higher HP stuff but when the torque numbers start going up they can become a problem. Some friends with a TS car tried for about 6 months to make one work for their combo with one of the big name shops in the end they just couldn't take the torque and they went to a TH400 based unit

I wonder if a 727/Proflite can handle near 1300HP? How would it perform against a 2.10 first T400? What would the difference be in cost? Assuming you'd bellhousing the 727 for a larger converter?

I am certainly not familiar with the proflite but I have heard of guys going to T400 for many reasons. Guys I race with, including myself, have said if we ever had to switch from 727 it would be to a T400 mainly cause the availability of parts, first gear ratios, and SFI case.

Lonnie Johnson runs a proflite in his comp car using an ex pro stock motor. Last when I spoke with him, he had 150 passes on it and was going to rebuild as needed soon. That motor has to be making over 1300 to maybe 1400 Hp.