Dual feeding direct, LU vs NLU
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If you were building and selling transmissions would you guarantee that there wont be a direct failure without dual feeding in a high hp application? I have seen them last a long time in 125mph cars but they usually dont forever. Once its dual fed and forward drum has been replaced with a a billet shaft its indestructable from what ive seen. Other parts start breaking from the violent apply of direct.V6RACER said:Never had a problem years ago with well over 500 hp and no dual feed.Yes, it is a good thing to dual feed the direct, but it isn't the end all for direct clutch failures.
Considering it is a FREE mod, and commonly accepted to be standard fare for building Th350's and 400's, there is really no reason not to do it IMO.
Sure,
we can jack the line up to 300 lbs and make the clutches live, but why stress the pump and sealing rings?
Sure,
we can jack the line up to 300 lbs and make the clutches live, but why stress the pump and sealing rings?
It doesn't necessarily make the apply "violent". It can be adjusted by the orifice sizing of the direct feed and the band release.
Usually direct feed needs to be an approximate size anyway, doesn't matter whether you dual feed or not. Say a .125" feed hole for a good firm shift.
On a non-dual fed trans the band release hole would typically be in the .100-.110 range.
On a dual fed unit, it may need to be as large as .140".
Dual feeding allows the directs to have much more apply area, so more pressure is applied on the directs. Pretty simple hydraulics.
However it gets complex because the drum may need a bit more oil to apply, and the way trhe fluid is routed, the 2nd servo gets "kicked" off for the trans to shift to 3rd. It also acts as an accumulator for the 3rd shift.
If you kick off the band too fast you get a flair, if you don't get it disengaged soon enough you get a bind-up.
On a 200-4R a flair is a momentary return to 1st gear, not really a slip, but it can be because you are making a 2-1-3 shift, instead of a 2-3, and it causes the directs to take a beating when they do get applied.
A bind-up is the trans trying to be in 2nd and 3rd at the same time. This WILL snap the forward drum. You basically have the input shaft twisting the forward shaft, while the directs drum (being held by the 2nd band) is trying to prevent movement of the remainder of the forward drum.
On a dual fed unit with proper calibration, you will have positive shifts. A positive shift is the result of more "overlap" of the band release and direct apply. Too much overlap causes the bind-up previously mentioned, not enough overlap causes the flair.
The trick is tuning the trans to have the perfect amount so as not to create undue stress.
A bind-up puts stress on the forward drum but also on the band and directs.
A flair puts stress on the directs.
You can calibrate a proper shift by mainly playing with orifice sizing. However the shift timing is affected by direct clearance, band clearance and return spring tension, and oil flow.
Usually direct feed needs to be an approximate size anyway, doesn't matter whether you dual feed or not. Say a .125" feed hole for a good firm shift.
On a non-dual fed trans the band release hole would typically be in the .100-.110 range.
On a dual fed unit, it may need to be as large as .140".
Dual feeding allows the directs to have much more apply area, so more pressure is applied on the directs. Pretty simple hydraulics.
However it gets complex because the drum may need a bit more oil to apply, and the way trhe fluid is routed, the 2nd servo gets "kicked" off for the trans to shift to 3rd. It also acts as an accumulator for the 3rd shift.
If you kick off the band too fast you get a flair, if you don't get it disengaged soon enough you get a bind-up.
On a 200-4R a flair is a momentary return to 1st gear, not really a slip, but it can be because you are making a 2-1-3 shift, instead of a 2-3, and it causes the directs to take a beating when they do get applied.
A bind-up is the trans trying to be in 2nd and 3rd at the same time. This WILL snap the forward drum. You basically have the input shaft twisting the forward shaft, while the directs drum (being held by the 2nd band) is trying to prevent movement of the remainder of the forward drum.
On a dual fed unit with proper calibration, you will have positive shifts. A positive shift is the result of more "overlap" of the band release and direct apply. Too much overlap causes the bind-up previously mentioned, not enough overlap causes the flair.
The trick is tuning the trans to have the perfect amount so as not to create undue stress.
A bind-up puts stress on the forward drum but also on the band and directs.
A flair puts stress on the directs.
You can calibrate a proper shift by mainly playing with orifice sizing. However the shift timing is affected by direct clearance, band clearance and return spring tension, and oil flow.
recent testing has shown that when dual feeding with our methods and ALL OF THE PARTS INCLUDED in the recalibration kit(2 holes for the 3rd apply already pre drilled to .140") that drilling of the 3rd accumulator hole is not necessary.it can be left stock.
JDSfastGN
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- Jun 16, 2001
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- 3,506
chris718 said:
I've got two trannys running this setup(CK shift kit and dual fed) and am very pleased. Both are not overly harsh or snappy at part throttle cruising, but at WOT they a very positive shift that really snap. Neither has a flair or bindup. I definitly am a believer in dual feeding as my directs would never last before I did this mod.
Thanks for all
the replys and good information guys. Been a long time since a ran a 200-4R but the track days and the turbo 400 are over, back on the street
we could get the 200 to live at 500 hp on the 3.8 before we gave up on it but the 600+ on the Stg motor was a horse of a different color
9sec.
the replys and good information guys. Been a long time since a ran a 200-4R but the track days and the turbo 400 are over, back on the street
we could get the 200 to live at 500 hp on the 3.8 before we gave up on it but the 600+ on the Stg motor was a horse of a different color
9sec.
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