aod manual shifting

ThunderDave

Registered User
I had posted something about this in the non tech forum and thought I'd post it here to try and get a little more info. On my 91 SC, I can shift from 1st to drive and then back into 1st and it will hold it in 2nd till I shift to drive again, like an actual 3 speed trans. would do. My question is, is this normal and is it bad or hard on the trans.? I thought it was kinda neat to be able to run 2nd gear out a little longer than the auto shift point does, but I don't won't to damage the trans. doing this if it's bad for it. Does anyone have any info on this???


Thanks,

David
 
This is normal ... Pretty cool huh

Do it all the time... Up and down shifting... No reason to be in OD in a super coupe unless you are rolling above 75mph...

I like to drop it it low when I am rolling down above 30 mph this will keep the trans from shifting into 3rd.. Then you can rap out second but you have to ease into the throttle depending on speed or it will down shift into 1st automatically When you get down to around 5 to 10 mph it will automaticly shift into low... Course if you speed up and want to go into 2nd you have to shift into drive.... Back and forth back and forth...

Yes you can strech the gears out in a SC for sure....

Wouldn't say it is good for it would say it is bad either If you want it to last longer than it is best to be easy on it...Normal wear and tear..Sometimes from a roll you got to have the power and the tork to get out of the whole so you need to down shift...
 
You can drive around town in 2nd just don't " Shovel Shift" it to OD I only use OD when I'm on the highway trannys been good for 163,000 think the B&M helps a tad :D


My .02 Rick in FL :cool:
 
This was posted by Vernon some time ago.


"What some don't understand here is that the SC was built with two different auto trannys and the poster has the "other" one. Bottom line: manual shifting in '89-'93 = busted tranny, manual shifting in '94-'95 with O/D off = firmer shifts and no problems when done with common sence and caution (see J57ltr sig).

The '94-'95 4R70W is a wide ratio version of the AODE. There were many significant changes over the previous AOD that allow manual shifting including a 1-2-D/OD shift pattern. Also I've noticed and this has been discussed at Corral.net to great length that turning the O/D off on the AODE and 4R70W also causes the EEC to use a different valve body calibration with quicker and firmer shifts, it's a towing / performance feature on all those trannys. For those who've never been in one of the later auto SC's the O/D button is mounted on the shifter down below the main shifter detent release button. It's pretty small and hard to see. I drove my '95 about three times before I noticed it.

Here's the reason you don't want to shift the AODs yourself:

I have seen some mention the 1-3-1 shift pattern for drag racing and used to do it myself to the tune of two burned out OD bands on AODs. I will put out this info so all can decide if the small, though effective and thrilling, gain is worth it.

What this does is make the shift into 2nd hard (rubber with stock AODs) and then keeps it in 2nd until you put it back into drive. This was discovered a long time ago on AODs. I figured it out on a '80 model T-bird work car before I even had an SC. The problem is that the AODs have no 2nd gear position in the shift mechanism. One thing to be aware of is this technique while effective is extremely detrimental to the overdrive band. Here's what’s happening in the tranny as told by Len Bertrand of LenTech.

Len tells us that the 1-3-1 shift habit of AOD racers is very detrimental to the life of the transmission and explains why. During full-throttle upshifts, when the shifter is moved to the Drive position, the direct clutch (third gear) begins to engage before the intermediate clutch. This is partially due to the capacity modulator valve, which meters the fluid feed to the 1-2 shift accumulator. The capacity modulator valve is programmed from the factory to provide smooth shifts, but even changing its calibration won’t allow the intermediate clutch to engage before the direct clutch because of the arrangement of the gearsets.

When the shifter is moved back into First, the overdrive band is engaged. This occurs because OD-release servo pressure is dumped while the OD-apply servo pressure is maintained. Prior to pulling the shifter back to First, both the apply servo and release servo are energized, which keeps the OD band disengaged. After the shifter is returned to Drive, the OD band must release to allow third gear to engage.

This chain of events creates two problems. First, the partial engagement of the direct clutch under full throttle eventually causes it to burn out. Second, the OD band release action for third gear engagement cannot occur fast enough to avoid wearing the band. The eventual result is a burned-out band.

By the way Len discovered a way to modify the shift shaft that provides a (OD-D)-2-1 shift pattern. It’s very simple to duplicate and comes standard in all his AODs and shift kits. This way the tranny can be shifted at the track and not wear out.

Vernon"
 
it's kinda like throwing it in park to stop the car. be nice to your AOD. They are made of glass and shouldn't be beat on to save 1/10 of a second. it costed me $900 the last time to rebuild mine and if I had that money to put under the hood, I would be going a lot faster. :D
 
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