1999 Sub c1500 5.7 problems but no codes

[ChevyGirl77]

First, I am new to this forum. I apologize if this is a rerun. lol Hopefully you can link me to other thread or combine them if they are related.

I have a 1999 Chev Sub c1500 5.7L 2WD Automatic

I first thought I had a transmission problem, as it would bang hard when shifting into 2nd gear. Then the truck started acting like it was slipping in and out of overdrive while driving and sometimes between shifts (most noticeable when shifting from 2nd to overdrive), it will rev way up and you have to back off the gas to get it to shift into the next gear.

I have had it to two different transmission shops, and both came back saying Transmission is fine. There is a slight gap in something in the transmission that caused it to shift hard into second, but there really isn't a fix for that.

I work for the municipal garage, and the mechanics there seemed to think it was a solenoid issue.

Well, after the second trip to tranny shop, the guy said he believes it is an engine problem, because fluid is nice and clean and no codes are showing. We left it plugged in and he had me get on it pretty good.

Now, if it was an engine issue, I would assume I would get a check engine light. Ran the codes on engine and they also come up empty.

I was wondering if it was a computer issue, and I even thought maybe it was fuel related. However, after popping the hood and reving the engine to about 2500 RPM, there was no hesitation, no stumbling, and nothing that indicated any type of fuel system issue or misfires. Haven't used a fuel pressure gauge on it yet, but that is because the problem is intermittent and I figured if it was fuel related it would be consistent.

This is what I know:
Front brakes, rotors, bearings, seals, pads - 10 mos. ago
New water pump - 10 mos. ago
new thermostat - 10 mos. ago
cooling system flushed - 10 mos. ago
all new felpro gaskets from the intake up - 1 yr ago
Transmission fluid & filter changed - 2 mos. ago
Oil Change - 2 mos. ago (conventional oil used)


AC does not work. I am going to see if one of the mechanics will hook a scanner to it at work tomorrow. It has not worked since I got it 1 yr ago. Probably just needs charged, but I am more concerned about the slipping issue (if I can call it that).

I hope that was enough information. I will hang up and listen now. Thanks in advance.

[ChevyGirl77]

Also, I think it needs new drums on the back. It does make a clunking noise sometimes if I brake hard. Once fully stopped, it will clunk. Will it clunk after taking off, too, if they stick? That may be the issue with the banging, but I need to figure out why it is hesitating. I am worried it will die on me when I am driving it.

Trying to figure out what it could be that would not throw out a trouble code. Fuel related? Drive-line? I am at a loss here.

[ChevyGirl77]

Well this forum is not very helpful

[Cusser]

OK Girl: with the AC, first thing is disconnect the battery, wait 15 minutes, then reconnect, see if that helps. Second would be to read R134a pressures, as pressure switch will prevent operation (to save the compressor) if the refrigerant is too low - refrigerant helps move the oil. If the refrigerant is low, look for oily residues at AC fittings, the high pressure line from compressor to accumulator, the compressor body itself, etc. If R134a pressures are OK, then check for 12 volt positive voltage at the connector to the compressor, engine and AC "on". If voltage is there, CAREFULLY tap the center of the compressor with a wooden hammer handle, see if it pulls in ("engages"); if it does, then the AC clutch gap likely needs adjusting smaller, like pulling out a spacer. If there's voltage there and you can't get the clutch to engage, the AC magnetic clutch may be bad. If there's no voltage there, get a wiring diagram and work your way backwards, and it's pretty complicated.

[ChevyGirl77]

Originally Posted by Cusser

OK Girl: with the AC, first thing is disconnect the battery, wait 15 minutes, then reconnect, see if that helps. Second would be to read R134a pressures, as pressure switch will prevent operation (to save the compressor) if the refrigerant is too low - refrigerant helps move the oil. If the refrigerant is low, look for oily residues at AC fittings, the high pressure line from compressor to accumulator, the compressor body itself, etc. If R134a pressures are OK, then check for 12 volt positive voltage at the connector to the compressor, engine and AC "on". If voltage is there, CAREFULLY tap the center of the compressor with a wooden hammer handle, see if it pulls in ("engages"); if it does, then the AC clutch gap likely needs adjusting smaller, like pulling out a spacer. If there's voltage there and you can't get the clutch to engage, the AC magnetic clutch may be bad. If there's no voltage there, get a wiring diagram and work your way backwards, and it's pretty complicated.

Thank you.

May have a leak or just needs refrigerant. Will be running a dye through it tomorrow to check for a leak.


My major concern is the hesitating/shifting hard issue. Lifted rear end. Seems to have a lot of play in the pinion shaft... This could be the clunking. I am wondering if that will cause hesitating or going in and out of OD... I guess if gears in the rear axle were not grabbing, it could?

[chuck's]

Don't know if you have gotten the tranny shift issue corrected,but one repair for a poorly shifting tranny could be the ignition switch.I have replaced mine because the dash was acting weird.Tranny wasn't affected at that time and there were no codes.Also at my work,a fellow mechanic had to troubleshoot a 2000 p/u for poor shifting and found out that the ignition switch supplies the power to the solenoids.Replaced the ignition switch and the shifting problem disapeared.I hope this will be of use.
chuck's

[ChevyGirl77]

Originally Posted by chuck's

Don't know if you have gotten the tranny shift issue corrected,but one repair for a poorly shifting tranny could be the ignition switch.I have replaced mine because the dash was acting weird.Tranny wasn't affected at that time and there were no codes.Also at my work,a fellow mechanic had to troubleshoot a 2000 p/u for poor shifting and found out that the ignition switch supplies the power to the solenoids.Replaced the ignition switch and the shifting problem disapeared.I hope this will be of use.
chuck's

That is interesting. I replaced the transmission and the torque convertor, because OD would just wind. The transmission was toast, and it was evident by all the metal shavings. However, after replacing the tranny, i ran into another problem. Truck seems to hesitate. At first, only in OD. So i started using 3rd. That made it better. Now it is hesitating in 3rd. Glad i got a warranty. :-(