Lock and nonlock 904 case the same?

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john27pa

john27pa

74 360/904 Duster
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My lockup 904 case busted a chunk out at the bellhousing area. I have a nonlockup trans sitting here. I want to keep the lockup setup. Are the 2 cases the same? I will be doing a complete transplant.
 
The case won't be a problem. It's my understanding that the main differences are in the pump and valve body. The swap has been done often , but I don't know if any specific, individual parts need or don't need to be swapped or modified. My trans people swapped non-lock-up guts into lock-up cases many times for my race cars, which sometimes had the 2.74 low as opposed to the standard 2.45.
 
I'm no guru but I have discovered that
there are three 904 style transmissions; the A904, the A999, and the A998.

AFAIK the A999 has always been a loc-up with the 2.74-1.54-1.00 ratios.
AFAIK, the A904 was never a loc-up, and always had the 2.45-1.45-1.00 ratios.
AFAIK, the A998 could be had either or; that is to say, could have had either gear ratio and could be had with or without a loc-up.
The lock-up in the early years was hydraulically controlled. In later years it was electrically controlled.
So
If your case has provision for electrical loc-up, and you need it, then you can only use another case that has the same provision.
But
If you have a hydraulically operated loc-up, then you should be able to use any 904 case.

I noticed some differences over the years around the accumulator, in the routing and shapes of various passages. I do NOT know if this will be an issue. If your broken-one and your swap-candidate are the same in this area, then I would swap the guts and air-test it. If it passes the airtest, then the VB should also work. so long as both cases are for use by the same loc-up activation method.
Either gear ratio can be swapped into either box.

BTW
that case is aluminum, as you know, and easy to weld up.
 
AJ/FormS said:
I'm no guru but I have discovered that
there are three 904 style transmissions; the A904, the A999, and the A998.

AFAIK the A999 has always been a loc-up with the 2.74-1.54-1.00 ratios.
AFAIK, the A904 was never a loc-up, and always had the 2.45-1.45-1.00 ratios.
AFAIK, the A998 could be had either or; that is to say, could have had either gear ratio and could be had with or without a loc-up.
The lock-up in the early years was hydraulically controlled. In later years it was electrically controlled.
So
If your case has provision for electrical loc-up, and you need it, then you can only use another case that has the same provision.
But
If you have a hydraulically operated loc-up, then you should be able to use any 904 case.

I noticed some differences over the years around the accumulator, in the routing and shapes of various passages. I do NOT know if this will be an issue. If your broken-one and your swap-candidate are the same in this area, then I would swap the guts and air-test it. If it passes the airtest, then the VB should also work. so long as both cases are for use by the same loc-up activation method.
Either gear ratio can be swapped into either box.

BTW
that case is aluminum, as you know, and easy to weld up.
Click to expand...
If I cN find the broken piece
 
The cases also have different mounting points for the shifter linkages. My 72 B body has a 68 904 in it and the column shift linkage isn't happy.
Good luck!
 
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