Transmission Fit Options

All the A9xx series autos come in just two patterns; either SBM(Small Block Mopar) or slanty.
The A999 and some to most A998s are a wide-ratio trans with ratios of
2.74-1.54-1.00, compared to the standard A904 ratios of
2.45-1.45-1.00.
Some A998s have the standard ratios.
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IIRC; ALL A999s have a lock-up convertor, but NOT all A998s do.
The A998s are heavier duty than A904s, and A999s are heaviest of all.
You cannot mix parts from one, willy nilly, with parts from another; some parts have to be kept together.
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The ratios do not look that much different until you work out the percentages. For example; 2.74 is 11.8% deeper than 2.45; which is the same as going from 2.76 to 3.09 rear gears., or from 3.23 to 3.61s.
As for Second gear; 1.54 is 6.2% greater than 1.45, which is the same as trading 3.23 rear gears for 3.43s
In other words, you engine will feel more powerful by the % differences before changing rear gears. So then,with the wide ratios, your 225 will feel like 252 in First gear, and like 239 in Second, then fall back to 225 in Direct-third.
The loc-up feature is worth about 3 to 5% rpm or 100/150 rpm at 65mph, so dropping your slipping3.23 that might rev like a manual trans with 3.33s to 3.40s, back to a true 3.23. The rpm-drop is worth about half the percentage , in mpgs. So say 2% or 1/2 mpg with 3.23s
None of this comes free because with the wider ratios, the engine rpm will drop lower for the same shift-rpm. This can be bad news if you chose a cam with a narrow powerband. For example; shifting at 4500, and using the A904, in First gear, the rpm will fall to 2655, whereas with a wide-ratio, the rpm will fall to 2529; a difference of 129rpm, usually no big deal . You can easily overcome this with more than stock stall. I really liked my 2800.
All in all, this is IMO, a very desirable improvement.