I recently got a new 740 that required tons of maintenance and Everytime I fix something, it reveals a new issue. It had bad vibration ever since I got it because the carrier bearing needed replaced, as well and engine and transmission mounts. Since then I have done all of those.

The transmission mount was the last thing I replaced and when I did so, all seemed perfect. All vibration was gone, it ran super quiet and smooth, I thought all was great. However, upon test driving it after the mount was completed, I took it on the highway so I could get a feel for just how well it ran. When I got on the highway I started accelerating slowly, feeling out the car to make sure there weren't any sounds or anything that would cause an issue. As soon as I was on the highway, there was a bit of a hill I had to climb so I started giving more gas. Once I reached around 50-55mph I engaged the kickdown cable because it didn't feel like I was getting much power, once engaged, rpms went up, got a small boost but then I immediately lost power. I realized it had just shifted down to first gear and wouldn't shift back up.

I pulled over on the side of the road and put it in park. That didn't fix anything. I cruised the rest of the way to the next exit on the shoulder. Found a parking lot and turned the car off so I could inspect it, I found nothing obvious. Once I turned the car back on so I could meet my friend down the road to see if he had any advice, the transmission seemed to fix itself. This was 4 days ago and I haven't had any problems since. I've driven it up a mountain and to and from work every day.

Given that this only occurred after engaging the kickdown cable, could this just mean I need a new cable, or could it indicate much larger issue.

I'm going to drop the transmission pan later this week to do some cleaning and replace filters, gaskets, etc, and am hoping to also do the kickdown if I have time. Hoping this will also allow me to get a better look at the condition of the transmission. Just wanted to know if there was anything else that would specifically cause this because I couldn't find anything specific about the kickdown cable cause the transmission to have a stroke like it did. Any advice would be greatly appreciated, thank you.

 

Old kickdown cables get rusty inside and stick - You accelerated and opened the throttle pulling the cable out - I suspect it stuck out when you opened the throttle wide and later retracted "fixing" the problem.

Turn the throttle roll with your hand - pulling the kickdown cable out all the way - see if it sticks. If it does stick or is reluctant to retract, loosen the cable from the throttle roll and using the penetrant/lubricant of your choice, try to get some lub between the inner and outer cables - hopefully getting enough in to keep you from having to replace the cable.

 

Update: I flushed the fluid and replaced the cable about a week ago and I haven't had any issues yet. Except engaging the cable while going up a hill, however not as bad as the first time the transmission crapped out. It will give me a boost then feel like it shifts back. I'm pretty sure I can blame that on the cable being a little loose as I think we left just a little bit of slack when installing.