Help with a transmission...

[MT_D]

I decided while I'm installing a newer engine in to my YJ I'll go ahead and rebuild the transmission. I have a '89 YJ 4.2 3speed auto. I did lots off research and discovered I have a TF999. So I go to the parts store to get the rebuild kit and they dont list the 999 for my YJ. I go and research deeper and I am more than confident that I have the 999, but I did find that sometimes they call the 999 a 904. I want to make sure thats right before I go waste money on a rebuild kit that wont work. So, is the 999 and the 904 brothers or just distant kin?

 

[Saddle Tramp]

From what I know you should have a TF999, it was used in YJs from 1987 to 1991 behind both the I4 & I6 and in fact an updated version of the transmission was used in TJs as well. The TF904 was only used by Jeep behind the I4 except for the wimpy 2.8 (V6). The 909 is a 904 with a lock-up converter. As far as the trannies being brothers I am not an expert here but if Jeep only used the 904 behind the I4 and the 999 behind both the I4 & I6 my nod would have to be to the 999 for strength and say they are not interchangeable.

 

[carnuck]

The rear band is bigger on the 998/999 than the others and the case is slightly bigger to accommodate it. A few other internals are beefed up too.