Hey guys, trying to figure out what I screwed up here. Did a full transmission service on my 1999 B3500 with the 5.9 and 46RE. Service included:

• Fluid and filter
• Front and rear band adjustments
• Governor pressure solenoid
• Governor pressure sensor
• Gaskets
• Lock up & overdrive sensor
• 3-4 accumulator spring

Before the service, if the van sat for a while (a couple weeks), the next few times I drove it, it would occasionally seem to "lock" into 3rd gear. It would really load the engine and barely maintain speed, but you could power through it after a few seconds. Once it "let go", it would drive normally until the trans cools back off. That being said, I've taken it on 2 long trips, over 400 miles each, and it did just fine.

Now, I took it for my first test drive, and the 1-2 shift was buttery smooth (better than it used to be), reverse worked great, but after shifting into 3rd, the van falls on its face and begins slowing down. It feels like something is dragging HEAVILY and I can't keep speed. Had to put it in second to turn around and limp home.

Any thoughts on what this could be? Adjusted a band incorrectly? Too much fluid? Bad sensor? I'm not even sure where to start. Any insight is appreciated!

 

Could be a band is too tight... What specs did you use to adjust them?

Fluid level good? (gotta check it in neutral, checking in park gives an artificially high reading.)

 

Bands were torqued to 72 in-lb, then the front band was backed out 2.5 turns, the rear band was backed out 2 turns, per the Cascade Transmission video on YouTube. It's possible the rear band isn't exact, as the fastener is a ~5/16" square head, so I can't get a torque wrench with a socket on it. If anything, though, it's adjusted loose as I was very conservative with the tightening. Also, it's my understanding that the rear band is for reverse, but I may be incorrect.

Fluid level should be good, about 7 quarts came out and 7 went in. It's in the low/high range on the dipstick when hot and idling in neutral.

I'm slightly concerned that the old wives tale has come true and changing transmission fluid on a dying transmission just speeds up the inevitable. It feels like the same issue I used to have, but worse.

 

Sound like the trans is suffering a band fight where it is basically not releasing the one gear and trying to engage the next gear. When it happens just back off and don't try to power through it. I had this happen in my T/A challenger and it took a rebuild to fix.

 

That's what I was afraid of. Thanks for the insight.

 

It's more of a self-fulfilling prophecy than a wives tale. Most people ignore their transmissions until something doesn't feel right. So in turn, they then change the filter, fluid, adjust bands, etc. A short while later the tranny fails, which it would have anyway, except now the repair work gets the blame.