Tranny Doesnt Want to Downshift

[6.0DSLPWR]

I was driving last night and I noticed if I am accelerating, once I get up to around 80km/hr and let off the accelerator to just cruise around that speed the rpm will drop from around 1800 down to 1200 rpm. I am not sure how this tranny works but I assume it is either going into lockup or shifting into overdrive for better fuel economy while cruising on the highway?

Anyways if I get back on the accelerator to pass someone or climb a hill the truck would normally downshift and take off. But last night it wouldn't downshift and I kept pressing farther on the accelerator and it got to the point that the truck started to surge/buck but wouldn't downshift. It did this many times and I was just wondering if anybody has had a similar problem and what it ended up being?

The tranny never got hot, tow/haul never flashed. Other than that it shifts fine.

[shu873]

Sounds like your converter stayed locked up. Mine does that when daily driving my race file, but if I stomp on it, it will down shift. If I roll in to it easy it just stays locked and digs. What file are you running on your X3?

[6.0DSLPWR]

Originally Posted by shu873

Sounds like your converter stayed locked up. Mine does that when daily driving my race file, but if I stomp on it, it will down shift. If I roll in to it easy it just stays locked and digs. What file are you running on your X3?

Yes if i roll into it easy it stays locked up and digs. I didn't try stomping on it but i did press maybe half throttle and when it started to surge/buck and didnt feel like it was happy I let off cause I was afraid of messing something up.

I am not running my X3. I was running erics xtreme street and matts srl only for about 15,000kms. I haven't had a tune on the truck for about 10,000kms now.

I will see if it still does it today and if so I might try disconnecting the battery's and letting it relearn and see if that helps. If not something must be going south in the tranny.

[shu873]

It shouldn't act like that on stock programming, and it definitely shouldn't shudder or surge.

[6.0DSLPWR]

Originally Posted by shu873

It shouldn't act like that on stock programming, and it definitely shouldn't shudder or surge.

Thats what I was thinking. I did quite a bit of driving yesterday and although it didnt shutter or surge anymore. It seems like it takes more for it to come out of lockup if that makes sense. But this morning I am going to disconnect the battery's to reset the computer and let the tranny relearn and check the fluid level.

Do you know what the correct way to check the fluid level in this tranny is? I havnt looked in the manual for a answer yet but most of the class 8 trucks with automatics that I work on at work say to check the fluid with the tranny cold at an idle in neutral?

[6.0DSLPWR]

Well today I disconnected the battery's and let everything reset. I then went for about a 30 km drive and let the computer relearn. The tranny felt like it shifted much better and when I am going 80 km/hr and the converter is locked I get on the throttle and it unlocks right away and takes off. Definitely feels much better.

After i went for the drive I checked the fluid while it was hot and the truck idling in Park. It was in the Cold on the dipstick so I added half a quart of SP and will check it again tomorrow and if it isnt up in the Hot I will add a little more untill it is.