Why aren't 998 and 999's more popular?

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D

DQ81

'73 Dart
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From what I've read this evening online just about the facts they have steeper 1st and 2nd gear for better acceleration but a 1:1 3rd like a 904 or 727 for good highway cruising.

Seems like the ideal solution for fun street car application if you want to keep mild rear end gearing?

Do they have a critical flaw or do they not fit?

Aren't they just a 904 in a 727 case with different gears?

If they are any good anyone know what years are best and where to source one, what vehicles where they common to?
 
I think they are a 904 (in a 904 case) with 5 clutch packs instead of 3. Why aren't they more popular? Maybe they aren't as plentiful as they would have been an option. I don't know about the gearing in them.

I have one in an M body that I plan to put in my Duster. Still quite a few old M body cop cars with 998/999 in them.
C
 
just change the 904's gears... that makes sense. lol

For those who are interested.

Basically from what I can find, they have a steeper 1st gear and 5 pack 1/2 clutchpack...

But building up your 904 makes sense.
 
doug 371 said:
2nd is lower also...
Click to expand...

from the Wiki:

For 1980, a wide-ratio gearset was released for the A904, A998 and A999, with 2.74:1 in first, 1.54 in second, and 1.00 in third. (these 904's appear to be of the lockup variety)

the regular 904 has:

2.45:1 in first, 1.45:1 in second, and 1:1 in third.
 
904 is /6 trans with 3 cluthes in forward and rear drum
998 is 318 trans with 4 clutches in forward drum and rear drum
999 is 360 trans with 5 clutches in forward and 4 in rear drum

gear ratios are interchangeable as a unit...

lockup has nothing to do with drivetrain and gears....lockup is in the converter and valve body...and input shaft...
 
THere is a mod for the LU function that allows it to stay unlocked for longer, thus making it act like a poor mans 4 spd AT.
 
and you can fit five in a 998 drum, and stick it in a 904, just need the right thickness thrust washer.

butI'm not a tranny guy, I red the manuals as I go when foolin with them.
 
kick down levers can be what ever you want it to be....

i put 5 clutch disc in 4 disc drums...

the later trans offer steel planteries...but i have 904 that has used the same aluminum planteries for 16 yrs now...been running in the high 10s with transbreak also...16 yrs..
 
never heard of any other gear from the factory except 2.45 and 2.74

2.66 is first gear in 833 4 speeds....manual trans
 
Junkyard is the best place, just buy a whole trans for less than the individual pieces would cost. Also the reaction shaft is different in lockup transmissions making the actual conversion a little more difficult than it seems. Late style 2 ring non lockup input shafts are hard to come by, at least that I've found. And the early style single ring input shafts don't fit the late reaction shafts, neither does the rear clutch drum. A late 5 disc front clutch drum won't fit an early reaction shaft either, they rub on the backside.

I know it all sounds very easy at first glance but in reality it's a little more difficult to locate the late style non lockup parts. You can modify a lockup reaction shaft to a non lockup style by removing a check ball on the inside where it bolts to the pump. You'll have to compare the two to see which one to remove though, it's difficult to explain without visual aids.
 
Why would you convert a lock up to a non lock up? Would that be a racing application?
For daily driver application wouldn't the lock up be better?
C
 
abodyjoe, not to be a smartass - what makes it better? Help me understand. I thought the lock up torque converter was an "improvement" over the non-lock up for fuel mileage.
I will admit that I know next to nothing about auto transmissions. Is there a web site or "small book" that can be recommended to school me on them?
Thanks
C
 
Lockup converters have never been favored for high performance applications and as such converter selection for performance usage is limited. If you are building a mild street car then maybe it's a good choice. If you are building for performance and don't care about fuel mileage than it's not a good choice. In addition NHRA does not allow lockup converters in many classes of race cars so there is another reason the aftermarket doesn't support it.
 
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