Re: Ford Automatic Trans (AODE) - 3-4 (overdrive) shift problem -- After installing a shift kit and new overdrive servo, the 1-2 and 2-3 shifts are fine, but the trans seems to shift into neutral during the 3-4 (overdrive) shift. Prior to the shift kit, the trans failed/shuddered on the 3-4 shift. I have installed shift kits before without any problems. I’m wondering whether the shift kit has “uncovered” a pre-existing problem, or if this is possibly a problem with the MLPS. Any suggestions?

What was the condition of the tranny before kit install? Weak shifts ? How many miles?

Perhaps the OD band is worn out

If you did not hold the OD band in place when installing the new OD servo, & verified the servo pin hit the band strut ......you missed the band. A very common thing on a shift improver install in the AODE / 4R70W

Lets say you verified the servo pin hitting the band strut..... which servo did you install? there are two sizes.

AODE & 4R70W use a smaller servo with a sleeve that slides into the OD servo bore. An early AOD design servo ( larger) slides into the bore with NO sleeve..... small servo with NO sleeve means a big pressure leak

IF all of the above is found to be A-OK..... re-check every thing on the install


Early MLPS could cause a tranny to seem to go into neutral when they were actually telling the PCM to command 1st gear..... year of your vehicle? Model?

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If you find yourself in a ditch.... down shift!

Thanks Crosley, this is VERY helpful!

Vehicle Information
Year: 1994
Make/Model: Ford Thunderbird
Mileage: 78K miles (actual – I’m the original owner)
Trans condition prior to kit install: Only problem was overdrive failure/shudder. A few years ago at about 50K, I fixed an erratic 1-2 shift with a shift kit, but the overdrive problem remained.

This time around, I added a few more “improvement” parts – e.g. the Sonnax Sure Cure Kit and a new OD servo. I used the “small” OD servo with sleeve, but I was unaware of aligning the OD servo pin with the band strut. So, I probably did miss the strut. Since I’m doing this work with the trans in the vehicle, I suppose there is no way to make sure the pin is properly aligned. Drat!!