ruwafl

at lower speeds, 30-40 mph, i can release the gas pedal and the truck begins to slow, and then it will seem as though the engine just disengages and goes to a complete idle and then if i give it gas the whole thing re engages. then today, in that same speed range, the truck started acting as though it were shuddering or shifting gears, but i didn't notice the motor speeding up when it was doing that. and the problem is completely random. i could power my way out of it or if i just steadily gas on it it wouldn't do it, just a steady speed or very lightly increasing speed.

i just changed the transmission fluid about a month ago. this problem existed before the fluid change(the motor feeling as though it were disengaging). i had hoped it would take care of the problem, but not so. i also drained the torque converter at the fluid change. the fluid level is full and looks clear and clean and does not smell burned. i used mercon v which was the recommended replacement fluid. the transmission is a auto 3 speed c6. when i pulled the xmission pan, there was a gray residue which i wiped out when i cleaned the pan.

thanks in advance!

dirtcrew51m

Is the vacuum modulator hooked up?

ruwafl

i just looked and the vacuum hose is connected. i assume that it is the only piece under there with a vacuum line.

dirtcrew51m

Might be a dirty valve body, usually when the converter goes, its gone.

ruwafl

will try replacing that. is that replaceable from the outside of the transmission? a screw off and on type replacement?

dirtcrew51m

Pull the pan, let trans drip for about 1\2 hr, makes less mess, remove filter, remove the rest of the bolts it should come down, but be careful when assembling and pay attention to the bolt lengths, some are different, when installing be careful not to over tighten the bolts, snug them and give a little more, and line up the shift detent pin with the notch in the valve body barrel valve.

ruwafl

thanks a mil. will maybe try to tackle that tomorrow. hopefully will fix the problem.

ruwafl

another question, looking at the parts store website, there are three different modulators having different color bands. looking at the modulator on the truck now, i see no color bands or perhaps they have worn off over the years. how do i determine the correct modulator?

also, i pulled the vacuum line off and got a couple of drips of transmission fluid. sure sign of a bad diaphragm.

dirtcrew51m

Yes bad modulator, I remember 3 colors black, purple and green, the colors depend on the weight of the vehicle, I used to get big block truck\car transes and they used a black one, and truck transes used a green one, so possibly the green one will be ok, they are also adjustable.

ruwafl

thanks for your direction and thoughts on this dirtcrew. i replaced the modulator this morning with a green banded modulator and all seems well at this point. took it out for a test drive and she responded superbly. hopefully i won't have any sort of a relapse on this problem as in it is masking a larger problem.

anyway, it was about a 2 minute job. it has a set of fingers that hold the modulator in place as it pulls out and pushes in. one bolt to loosen, pull the old modulator out with a little twisting motion and the other goes back in the same way.

thanks again!