Magna 2001 TJ 3.5l V6 Auto
Following what I suspect was a broken wave spring, subsequent pump failure and then death I have replaced the Auto trans (with a qualified mechanic).
I suspect the trans was from an earlier model, still a F4A51 but it had a filter where the original didn't.
I have searched the forums but cannot find a similar problem.
The car starts moving in D but falls out of 1st into neutral. You can drop to L and manually change to D after you hit 15km/h and all fine. All other gears work well. When you stop or slow below 15km/h it falls into neutral and you have to manually drop to L again.
If you accelerate after it drops to neutral, it triggers a Code 41 (N flashing) but drives probably in 3rd limp mode.
I have had it scanned - Solenoids all OK - code 41 is all that it shows
Q: Is the trans completely incompatible, or could it be an electrical or ECU problem???

Hi, have look at below: (from the mitsu workshop manual)
Code No. 41 1st gear incorrect ratio
If the output from the output shaft speed sensor multiplied by the 1st gear ratio is
not the same as the output from the input shaft speed sensor after shifting to 1st
gear has been completed, diagnosis code No. 41 is output. If diagnosis code No.
41 is output four times, the transmission is locked into 3rd gear as a fail-safe measure,
and the N range light flashes at a frequency of 1 Hz.
Probable cause
 Malfunction of the input shaft speed sensor
 Malfunction of the output shaft speed sensor
 Malfunction of the underdrive clutch retainer
 Malfunction of the transfer drive gear or driven gear
 Malfunction of the low and reverse brake system
 Malfunction of the underdrive clutch system
 Noise generated

Thanks Dazmag, That gives me a couple of things to check out!

What model do you have, TE-J are fine to swap aroaund, TL onwards HAVE to be the correct box as the TL uses a different output shaft ring to allow the ecu to run the speedo

Edit, should have read the initial line, the trans you have should be fine, check the connection to the output shaft sensor and the sensor itself.

The car is a TJ -2001 model. And I assume the replaced trans was an earlier model ( has filter). Speedo works fine. Drives fine except for in Drive below 15km/h.

Thanks Madmagna.
I have cleaned both the Input and output shaft sensor connections. Both sensors were swapped from original trans and using original harness - Given they were not faulty before, I assume they are not now. Problem still not solved.

The trans filter was deleted around on TJII iirc, so about 2002. What sort of mileage was on the replacement box when it went it?

I dont know the mileage unfortunately. But the original was a 2001 and was without filter. So I am guessing it was pre-2001.

The trans filter was deleted around on TJII iirc, so about 2002. What sort of mileage was on the replacement box when it went it?

The external filter was deleted before the TJII , I have a 2000 KH Verada and it has the internal filter

Thanks Madmagna.
I have cleaned both the Input and output shaft sensor connections. Both sensors were swapped from original trans and using original harness - Given they were not faulty before, I assume they are not now. Problem still not solved.

Hi just wondering where the Input and output shaft sensor connections are?