Myth and mystery solved HERE TODAY:
...this is bad for stock units and it is DIRRECTLY linked to the VB and no other part. The OD band is not a fualt (not really anyhow)
The OEM VB doesn't alow the OD servo to exhuast fast enough before the 3/4 clutch engages and this burns the OD band when you shuffle into D range for 3rd gear. And acting as a double edged sword...since the oD band is binding it slows the 3/4 engagement and makes the dirrect slip more than it should.
Combine these events with a 89 or older AOD with the case bore accumulator and you got a pretty messy shift.
Shift kits provide some reliefe though....and so do kevlar bands (less burn)...the kits are designed to prevent any shift overlap between the OD Band and the dirrect engagment by increasing OD servo disengage fill rate and increasing the dirrect piston engagment. Both are done by increasing size of sperator plate holes.
It is kinda tricky though also, if you exhaust the band too fast before engaging the dirrect you would get a flare that would let the RPM raise and then slip the dirrect as it engaged. And obvisouly if you do the opposite it will burn the band again.
Note that the 1D1 is also bad on the DIODE...as it was never intended to see as high RPM as we push them too That is why the 7 element AOD diode has such a bad rap. And the Extra RPM you push it too increases the chances of tossing the snapring.
Some FACTS:
The OD band ONLY applies durring the MANUAL 2nd (D-1) and the OD (4th) range. The OD band is the DRUM BRAKE so when you let off the gas you have engine braking - or in transmission terms called: Overrun. If the OD band is burnt or not engaging you will FREEWHEEL and have NO engine brake in manual 2nd and also have a nuetaling effect in 4th gear. Note that the 1D1 shuffle also USES the OD band more than regualr use...meaning, Ford never intended you to manual 2nd the trans alot - therefore by doing the 1D1 shuffle you are accualy cycleing the OD band more times in it's life cycle than what Ford intended you to do so...this is just an excuse, but it does have merit.
The D range does not apply the OD band on the 2nd gear shift, cause as you know, the second you let off the gas it shifts to 3rd.....Ford didn't find it neccesary for you to hold 2nd gear. However Baumann first invented what is today known as the EPOXY mod and allows manual 2nd but however does not apply the OD band in 2nd therefor it freewheels. Today's aftermarket VB builders have invented ways to control the OD band application and use it for manual 2nd now - along with the ability to lockout OD....very nice!!
Now that I spoke about the 1D1 UPSHIFT, now consider the manual D2 downshift. NOW if you were in 3rd and you slap the shifter back into manual 2nd to slow down or force the downshift. The OD band is applied and the dirrect disengages and this IS a reason for concern of the 1D1 shuffle as well. using it as a brake to slow down is bad, but manual downshift for performance is okay, but still not fast enough on the band apply - if you have c/b servo, you are asking for trouble.
Manual first....forward clutch engaged and REVERSE BAND...the reverse band allows engine braking....if you find that you feewheel in manual first, you more than likely don't have reverse either due to a burnt band. Often reverse bands are burnt up by people who race around in manaul 1st alot and coast down to stopsigns alot or pull back into manual 1st to help stop the car. The Reverse band does not engage in D range much like the OD band doesn't as well.
Note that some FREEWHEELing can be expereinced if the VB is sticky and not allowing the proper valves to work freely...often due to age, sitting months, useing Type F, iregular service, trash in system, dirty fluid.
So...to recap...shift kit = good and better manual 1D1. AT LEAST keep the TV pressure high for the 1D1 on a STOCK VB. Those that have 89 or older VB's...just stop now! Those that have 90+ VB's, you are accelerating the invevitable.
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------------------------- Dan Gilsdorf ---------------------------
