Auto tranny ?

Jacob_Royer

SCCoA Member
I've noticed that my 93 SC doesen't seem to have a lockup convertor... is this normal? or is it screwed up? or did somone swap it with a non-lockup unit? every other AOD car i've drove seems to have one.. i have 1st 2nd 3rd OD after the OD shift there is no aditional drop in rpms..
 
On an AOD, 3rd and OD are direct drive....they don't slip then lock up like the later model electronic transmissions.

David
 
In my car in first or second gear I can idle at low speed and hit about 1/2 throttle, the tach will flash to about 1700 and then the car pulls. If I'm higher up in the rpm's in 2nd (I can hold it because I have a lentech), I can hit it and it will jump revs just a bit not alot but maybe 200-300 before it will pull. In 3rd if I let off and get back on it, it won't jump revs at all, it's directly locked. OD is the same way. It's better for gas mileage this way, and you will pull higher MPH in the 1/4 mile with a lockup.

The factory AOD has a split path input shaft (hollow outer and thin solid inner shafts) When you shift to 3rd gear they lock and become "one". If you switch to a non-lockup convertor you must get a 1 piece input shaft.

The stock input shaft is a weak link, my friend broke one in his SC w/ only a 5% OD pulley, exhaust, and a Coy Stage 1 Cam and lentech valve body. Shifting from 2-3 it went bang and then CLUNK. Snapped the input shaft.

Notice how your car doesn't feel as strong down low in 3rd as it does in 2nd. Even around 2600 where the torque peak of this motor is (assuming mostly stock). I can feel the convertor lock on mine. It makes the 2-3 shift really harsh and it will get rubber. I guess when I get a non lockup convertor the 2-3 shift softens.
 
If you switch to a non-lockup convertor you must get a 1 piece input shaft.

Scott,

Lentech is one of very few companies that still sells a non locking converter for use with the stock dual input shafts. I'm using one on my 91 along with a hardned inner shaft.

David
 
If you switch to a non-lockup convertor you must get a 1 piece input shaft.

Scott... not a true statement. I have 2 AOD's with the non-direct drive converters and neither has a 1 piece input shaft. They both utilize the factory shaft configuration. As a matter of fact, neither uses a hardened direct shaft. One converter is a Lentech 11" 2400 stall and the other is a Dirtydog 12" 2400 stall. Depends upon your application whether a 1 piece shaft is necessary or not. Len at Lentech didn't feel either of my applications warranted the 1 piece or even a hardened shaft.

By going with a non-direct drive converter you will sacrifice around 1-2 MPG on the highway but you will gain torque multiplication in 3rd and 4th gears. I would never go back to the direct drive converter for street use again.

Bryan
 
By going with a non-direct drive converter you will sacrifice around 1-2 MPG on the highway but you will gain torque multiplication in 3rd and 4th gears. I would never go back to the direct drive converter for street use again

I wouldn't go back either, unless I was using a 4rw70 (or whatever the late model auto is called) and could use the computer to determine shift points converter lockup ect...

On an AOD non-direct drive is much more streetable. No more lugging/bogging in 3rd and it's quicker on the track. IMO, the additional 5% of power you lose at the wheels is a worth while trade off.

Add a Lentech VB to the package, and you will have a much improved AOD.

David
 
I always thought it pulls pretty good in 3rd down low.. not all that harsh going into 3rd eaither bit OD at high speeds thats harsh! I get rubber pretty good going into 2nd but never 3rd unless its extremely cold outside.. 5% gutted cats, K&N IC fan
 
So the inner shaft is the one prone to breakage? I didn't know that. I know B&M sells a convertor that will work with the dual path shaft. But I'd rather put a hardened 1 pc. shaft in and a non lockup convertor and a trans cooler and be done with it.
 
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