Moparts Tech Archive
904 or A999 question?gary white
Registered: Nov 2001
posted 06-27-2002 06:11 PM
I am looking for the low gear 904 trans in local yards and wanted to know what year cars,trucks,or vans to look in.found a van vin #2B7G13T8EK311492 with a a999 trans and a lock up torque convertor.would this have what I am looking for thanks for any input
You will have to convert it to a non lock up if you want it for a performance application.
Check '80's model M bodies. Most used the 999 and are relatively low milage.
so does the 999 version mean it is a low gear set or is it a differant trans all together?
Would an '81 R-body with a 318 4-barrel have a 999???
The A999 was brought out in '74 to be a beefier transmission to put behind the 360. It has a 5 disc front clutch pack. The 999's came with either a 2.45 (standard ) or a 2.74 1st gear ratio.
Some 1980 cars had the 2.74 1st and all 1981-1988 had the 2.74 and 5 clutch direct drum. Look in Diplomats, 5th Aves, Grand Fury, etc. Most were lock-up converters, but you can swap the gear set into a non-lock-up tranny. John
Originally A999s were behind 360s and 998s behind 318s. Did this change?
The production of the 2.45 low gear sets was dropped after the 81 MY, any tranny of the 904 family has the 2.74 gear set from then through the present MY, even the mitsu and amc trans. If I remeber right the 998 got the 5 plate Fr clutch but not the double wrap L&R band.
what parts do you swap over from the a-999 to the a-904 if you want the non-lockup type of tranny?
Basically, you need to swap either the input shaft and/or the input shaft forward drum assembly because the input shaft has 26 spline for lock-up and 27 spline for non-lock-up. Also, the front pump is unique to the lock-up. The valvebody needs to be swapped also. You can simply swap the gear set into a 904 trans. However, if you also want a 5 clutch direct drum, you need to get a pump with a bevelled back that will allow the wider drum to fit. In addition to that, the forward drum with input shaft needs to have a 1-1/8" wide clutch hub to allow 5 clutches to engage inside the direct drum. Normally, the 4 clutch drum 904's use a 1" hub on their forward drum with shaft assemblies. So, it's easy to swap the gear set by itself. But, if you want the 5 clutch drum, you need to find the correct bevelled back pump and 1-1/8" forward drum. There was a sealing ring diameter change in 1978+ and both lock-up & non-lock-up transmissions had this. So, after 1978, you can look for a non-lock-up tranny for the larger sealing ring stator support and forward drum. The best transmission to use as a core is the 1975-1977 A999 used behind 360's. This trans used the 5 clutch drum, but no lock-up. So, if you find a trans in this year range, simply swap in the 1981+ 2.74 1st gear set in, and you are set. You can use the thinner rear clutch frictions in the direct drum which will allow 5 in a 4 clutch drum for a little easier swap. John
all info provided by board members listed above.