Hey guys, new to the forum and need some help from those with experience with this issue. I have a 2009 silverado 5.3L. It was my dads truck and I now have it. He didnt own it very long, bought used. It has 130,000 miles, in great shape.

I am having issues with the RPM fluctuating- anywhere from (50-300 RPM change up and down). I know this model has had issues with the active fuel management system. I have replaced all lifters and overhauled it, it now has a range technology chip that makes it V8 all the time. I am still having this issue. It will ONLY do it around 40-50 mph, in last gear, kinda coasting along. Any ideas, suggestions, or recommendations would be appreciated. I already have about 2 grand of repair in this truck and I want to get this fixed. Thanks so much for any input, any questions please ask.

 

If it’s only happening at highway/cruising speed, it’s likely an issue with the torque converter clutch not locking up correctly. Could be due to the transmission needing a fluid and filter service, the solenoid sticking, or a control circuit issue.

Go for a +/- 10 mile drive split somewhat evenly between highway driving and stop and go to get the transmission warmed up. Use a clean white cloth or paper towel to check the ATF level and condition. If you can read trans temp on the dash, an accurate hot level check starts at 180*F - below that temp, the level should at least fall between the hot and cold range markings.

Fluid should be clean and red - “the brighter red the better” so to speak but dark red isn’t necessarily bad. Check for a burned smell and heavy particle contamination on the paper towel.

If the level and condition are OK, check for codes. Even without a CEL, codes can be stored.

You can also try a product such as Seafoam trans tune that cleans varnish and debris from the internal components - if adding this improves the condition, service the fluid and filter ASAP. Those products are great for cleaning, but anything they clean stays in the transmission until the fluid is changed.

 

Thanks Gumby. I am unsure of the maintenance history, but am getting to the point where I am going to change fluid and filter anyways, despite the many people that say an initial fluid change at high milage will result in slippage.

Based on what I have read searching various forums, I was beginning to think it was the solenoid. I have to drop the pan to reach the solenoid anyways right? So I may do full replacement of fluid and solenoids. Is there a solenoid specifically designed for the Torque convertor lock up? How many solenoids are there? And is there a specific one I should be looking at. Thanks

 

Also, I have noticed my transmission temp gauge never gets above 140 degrees, which I thought was a little low

Fluid levels looked ok, not black but not red either

 

Depending on which transmission you have (4L60E or 6L80E - identified by the number of bolts in the oil pan but I can’t recall the numbers right now - there’s also an ID tag on the case behind the heat shield on the right side) there’s about 5 solenoids, 2 of which affect TCC control. They can be expensive, so I don’t recommend changing them just because you have access to them.

A fluid change can cause issues but it really just depends on the overall condition of the transmission. Keep in mind you’re only draining about 5-6 qts or fluid to drop the pan - total system capacity is about twice that. If the fluid is clear and doesn’t smell burned you should be fine doing a fluid and filter service.

As for temp while driving - the lower the better. I would consider 140 about normal unless you’re doing a lot of towing. Most of the time if a hot check is desired, I have to torque brake (brake stand) the transmission to get the fluid hot enough.

 

Thanks, I forgot to mention that it isn’t necessarily highway speeds, it does it worse in town and backroads. It has to be in the lugging or overdrive gear, and it only does it around 40-55 MPH, once I get above 60 it stops completely.

I got a more accurate reading of the fluid level today, and it appears to be overfilled to me. Not sure if that would cause the issue im having. Im still leaning towards the torque converter locking in and out, but im no expert by any means. Thanks for the input. I also think the fluid has definitely been changed before based on color. Just not sure what to do. I guess I could just start speeding in town more haha

 

To be clear - this is only happening when the transmission is clearly in gear and not during shifting, correct?

Back to fluid level - the transmission operates best when its fluid capacity is as close to completely full as possible. However, since fluid expands as it heats up, the amount of fluid needed to fill it can vary significantly depending on temperature, which is why a hot check is necessary.

The “cold” fill range is only there so you know it has enough fluid in it to drive it without causing damage to the transmission. There’s not really a defined temperature range for a cold check - it only applies when the engine is first started after having several hours to cool down.

After driving, but before the temp is high enough for a hot check, all you’re looking for is that the level falls somewhere between the high mark on the cold range and the low mark on the hot range.

A hot check needs to be done in the range of 180*F - 200*F per GM’s factory service info. At work I’ve always had to torque brake the engine to get the fluid hot enough - even on a blistering summer day and after a 20+ mile drive, the closest I’ve gotten it is about 160* - but that’s just cruising the highway without any real load. Personally I divide the hot range as best I can by temp with 180* as the low mark and 200* as the full.

GM also recommends shifting through each gear range for at least 3 seconds before checking the fluid level to ensure that the hydraulic circuits in the valve body are filled as well. I’ll usually just shift straight to low gear and then work my way back to park from there.

I also let it sit and run for a minute before checking the level as it allows time for the fluid level to stabilize in the pan, especially after adding fluid.

 

Gumby- That is correct, sir.

scenario: Say the light turns green, I give it normal throttle to regain speed, and am shifting just fine with the first 3 gears (4 speed). I am reaching my point of desired speed around 50 mph, so I begin to I ease off the throttle. At this moment I begin to feel the truck about to shift into its final gear (overdrive/lugging/cruise). As the truck enters 4th gear I leave the throttle right where it is- the rpm fluctuations then begin (anywhere from 50-300 rpm’s up and down, or bouncing you could say). If I let up on the throttle, it stops immediately. Or, I give it throttle, it downshifts and stops immediately.

As for the fluid level, it is above the high mark a half inch. I had driven the truck for nearly 45 minutes when I checked it, and temp was at about 145 degrees at idle. I didn’t get the desired temperature like you mentioned, but it was easily noticeably high.

Thanks

 

That is fine the 140 deg.

 

The high mark will be that cold, and or not running. What it sounds like is shift solenoid issue.