direct drive vs torqueflite

[krash]

a buddy has a direct drive trans for a big block chrys and swears it is the hot ticket. he ran it for years in figure 8's but i only run 3/8 mile dirt semi-banked
looking for all the pro's and cons i can get before i decide to switch

[340king]

I have and have run both(904 & 727). I currently have a direct drive 904 in my modified. It is valved to start in gear without jerking the trans. I think you need to maximize your effort at any track, regardless of size. The reduction in flywheel weight is probably the biggest thing I can think of. It is a real change to go from a stock 33lb unit to one about 3lb. It may take some time to get used to the car reacting faster, but when you do, you will never go back. The 904 is quite light in the rotating mass area also. My car winds up very quickly, even in drive with the car on the jack stands. A quick wack on the throttle sends the engine to 4,000+ rpm on the tattle tale tach (a little alliteration?).

If you do decide to run a direct drive auto, put a valve in the pressure side of the thing to allow it to move from a start without jerking. There are two ways to do it. One is to remove the rear over-running clutch (sprag), and tap the pressure port of the rear band apply piston with a 3/8" or larger line. Vent/return this line to the pan. With the valve closed the rear band can apply and start the forward motion of the car(the same is true for reverse). In essence you will use the rear band and valve as the clutch in this approach. The advantages are that you cannot destroy the sprag if it is not in the trans. The sprag is susceptible to damage if the tires break loose while it is locked up. It allows the rollers to jump out of place and break the transmission case.

The other way to do it is to drill a port into the pressure side of the front pump 1/2" pipe size. Then run this through the ball valve and into the pan. This removes all the pressure from the trans and applies the forward clutches and the rear band to begin forward motion. This is the way I have it on my car. I have a buddy in CO that runs one with the band apply method, either way works. In either case I recommend installing a new vent on the rear portion of the case where the extension mounts. The front pump vent has a tendancy to leak under circle track usage. I used the neutral safety switch hole for my return line. It takes quite a little tapping to get it to fit, but it works.

The last thing I did was to lighten my rotating mass by selected removal of some un-needed items in the trans. I use a manual valve body and remove the govenor and the other things attached to it. I am writing criptically, so the bowtie boys reading this won't catch on. There are some safety considerations when doing this especially in the pits and when loading the car.

Bottom line, I like the benefits of the direct drive auto.