Hi guys. I have a 2004 2500 with the 48re auto tranny and 26,000 miles on it. I'm having a problem when braking. The brakes work fine, but when coming close to dead stop, I feel like the truck pushes forward. It kind of feels like if the brakes let go at that moment, but today I tried braking in neutral and the symptom does't occur. This is driving me nuts, especially 'cause the dealer nearby doesn't have a diesel certified mechanic, so I would like to diagnose/fix it myself if at all possible.

 

My first thought was ABS, but you said it didn't do it in nuetral, so next guess is that trans is either not downshifting properly or TC is not unlocking when it should. Watch the tach when it does it. Do the rpm's drop very low then come back up as the surge occurs? Does the TC unlock if you slow down and accelerate again. Get the codes read, they should tell you.

 

I watched the RPM gauge and it stays steady. In fact, it doesn't do it if I put the tranny in neutral. When the vehicle is almost stopped, it kind of "pushes" forward. It's like if when coming to a stop, the brake was released at that very moment and pressed again. Very weird feeling, annoying . By the way, I still haven't changed the tranny's oil and filter or adjusted the bands. Any other thoughts???

 

Since the problem only occurs when trans is in gear, I'm leaning towards a trans issue. Either TC not unlocking properly or not downshifting. Does the brake pedal feel odd when this happens? Get codes read.
I wouldn't worry about band adjustment at only 26,000, but fluid change is good.

 

That's what it sounds like to me.


phox

 

If it just pushes forward a little bit that is normal! The trans is shifting into 1 st as you come to a stop! If it just started this or is very hard to stop you have a down shift or unlock problem!

 

Brake pedal feels normal...

 

Some years (can never remember which ones) you can turn the key on-off 3 times without starting, and read codes in the odometer window. Try that, otherwise hit Auto Zone, or other parts store and have codes read.
http://www.allpar.com/fix/codes.html For what the code numbers mean.

 

I agree with rick on this one. Just the tranny doing a final downshift.

 

As per Racer9 suggestion I read the codes from the computer. Got P1757. Looked up possible problems and pointed out to governor sensor. Went ahead and opened the tranny, changed oil/filter, replaced governor sensor and the transducer (the only two sensors near the valve body). Adjusted bands to specs, and tested...everything back to normal.

Checked with the dealer's technicians and they said those sensors commonly fail and they always replace them in pairs (for that reason they call them a "Combo")...

Just wanted to post this as it can be very helpful for people with similar problems and tranny acting up. The whole procedure took less than three hours.