Rodknock

Hi Guys,

Today after coming to a stop on a red light my van vibrated then started having problems when shifting from 1 - 2. It feels like a pretty hard shift that eases as you go to 3rd and 4th. It does sounds like the engine revs up really high before shifting from the lower gears.

Even when I stop then just let the van go by itself the engine revs up high before shifting by itself. Which I find to be very weird. Its almost like its accelerating by itself.

About a month or so ago I had the filter and trans fluid changed along with the gasket. The mechanic said the oil in the trans was so old it was gooey. Not sure what is happening. A few weeks after the change the change oil light came up. Turns out mechanic did not reset the oil tracker thing. I read the manual and showed him it and he did it and the light went away. Then a few weeks after that the light came up again and when I turn on the van the change oil light appears. It flashes just like before then it goes away. Makes me wonder if the mechanic put in the right trans fluid but at this point he won't remember.

Any suggestions?

Does anyone also know what type of transmission (Actual code names) the 2004 chevy express has? Wikipedia has 2 listed, but it has no actual name for them. I have no idea how to find it on the passenger side code sheet . Could someone help?

-edit-

after running the van some more it looks like the problem goes away after shutting off the engine for a while. Then when you turn it on it runs good until a few minutes in and the same issue arises going from 1 to 2nd.

canucklehead

With your comment about the oil being gooey, I would think of having the tranny serviced again. The new clean fluid might have washed some crap into the filter.
Have it road tested and checked for codes at a shop....

KChevy75

Which engine does it have?

It could be the 4L60e if it's the 5.3L or one of the v6 engines but might even be the 4L80e if it's the 6.0L.

Might be the pressure switch manifold. Could be the forward sprag is binding up due to damage.

My suburban with 202,000 miles has the 4L60e and started doing that after overheating due to low fluid. The fluid looked fine when I drained it but it was still shifting at high rpm from 1-2 and the forward sprag broke on a test drive after changing the fluid.

When I tore it apart, I could find nothing obvious wrong other than the broken forward sprag. The steel and friction clutches were within spec still. Nothing else was broken. There was very little metallic material on the magnet and no chunks of metal in the pan.

I rebuilt it myself using 7 friction clutches for the 3-4 clutch pack and a wide 2-4 band with new reverse input drum. I replaced all seals and bushings. I replaced the two shift solenoids also.

I put it all back together and I was still getting the high 1-2 shift and the same rough shift that broke the sprag originally. I went over everything in my head and the only thing I could think of was the pressure switch manifold. It's a $30 part that I told myself I should replace but I ended up just replacing the washers. I had to drop the pan to replace the pressure switch manifold. It drove beautifully after that.