1999 chevy silverado rev/shift problem

[romi7612]

Hello all,
My truck was intermittently shifting really hard in first and second . I drained the tranny fluid and installed a new filter and replaced the fluid, I also changed plugs and wires. Tranny fluid is at the top of the hash marks on dipstick when hot and in park. When I come to a complete stop my engine 5.3 litre v8 revs up to about 2000 rpms but the truck takes off slowly like the tranny is slipping it is worse on an incline. If I dont come to a complete stop it shifts fine and takes off with good power. After it shifts to second it shifts normally and drives fine. tranny fluid looks clean and does not smell burnt. Also when driving on the highway if I am going 45 mph and punch the gas it wont rev past 2200 rpms like it is lugging down. when i shift thru gears manually there is no slippage what so ever and when in park engine revs to 6000 rpms no problem. Any help would be greatly apreciated as this one has me stumped also tranny is a 4l60e

[j cAT]

Originally Posted by romi7612

Hello all,
My truck was intermittently shifting really hard in first and second . I drained the tranny fluid and installed a new filter and replaced the fluid, I also changed plugs and wires. Tranny fluid is at the top of the hash marks on dipstick when hot and in park. When I come to a complete stop my engine 5.3 litre v8 revs up to about 2000 rpms but the truck takes off slowly like the tranny is slipping it is worse on an incline. If I dont come to a complete stop it shifts fine and takes off with good power. After it shifts to second it shifts normally and drives fine. tranny fluid looks clean and does not smell burnt. Also when driving on the highway if I am going 45 mph and punch the gas it wont rev past 2200 rpms like it is lugging down. when i shift thru gears manually there is no slippage what so ever and when in park engine revs to 6000 rpms no problem. Any help would be greatly apreciated as this one has me stumped also tranny is a 4l60e

normally harsh upshifting is the pcm/computer getting data suggesting that the transmission is slipping..this then causes the pcm/computer to command max pressure ...

this is usually worn clutches/sun shell....

how many miles, what is your fluid filter interval replacement cycle ?
what type tranny fluid do you use ?

[transman618]

Originally Posted by romi7612

Hello all,
My truck was intermittently shifting really hard in first and second . I drained the tranny fluid and installed a new filter and replaced the fluid, I also changed plugs and wires. Tranny fluid is at the top of the hash marks on dipstick when hot and in park. When I come to a complete stop my engine 5.3 litre v8 revs up to about 2000 rpms but the truck takes off slowly like the tranny is slipping it is worse on an incline. If I dont come to a complete stop it shifts fine and takes off with good power. After it shifts to second it shifts normally and drives fine. tranny fluid looks clean and does not smell burnt. Also when driving on the highway if I am going 45 mph and punch the gas it wont rev past 2200 rpms like it is lugging down. when i shift thru gears manually there is no slippage what so ever and when in park engine revs to 6000 rpms no problem. Any help would be greatly apreciated as this one has me stumped also tranny is a 4l60e

It sounds like it could be in limp mode. Have you had the computer scanned for codes yet?? If not, that should be your first step. Take it and have the codes read and post them here and we can take it from there.


transman

[romi7612]

engine and transmission have 217500 on them , the fluid has been changed every 30000 to 40000 miles I used tci fluid this time. I will Have the codes scanned this week and get back with you thus weekend , thanks for replying

[j cAT]

Originally Posted by romi7612

engine and transmission have 217500 on them , the fluid has been changed every 30000 to 40000 miles I used tci fluid this time. I will Have the codes scanned this week and get back with you thus weekend , thanks for replying

If this is the only transmission failure , it is because of your maintence interval which most recommend...

with this mileage I would be surprised if this would not need a rebuild..given your issue with it...



The drive train codes as mentioned should be gathered, then post back ,,,you will need a GM drivetrain scanner ..

[romi7612]

Hey All,
I got the codes scanned today and here are the results

P0161 02 sensor Heater ckt malfunction

P0332 Knock sensor 2 ckt low input bank 2

P0756 Shift sol B ckt perf stuck off

after reading around on these forums I watched a lot closer as what when i drive this truck I dont think it is downshifting as it should also I noticed that after my first complete stop after initial startup it will not shift into overdrive. If I come to a stop and turn the ignition off for a few minutes it shifts into overdrive, but if I stop at a corner and then take off it seems like it is only using one or two gears and it will not shift into overdrive or so I presume as at 55mph it is running 2300 rpms . When normally at 55mph it is running only 1600 rpms.
thanks for any help you may be able to give me

[j cAT]

Originally Posted by romi7612

Hey All,
I got the codes scanned today and here are the results

P0161 02 sensor Heater ckt malfunction

P0332 Knock sensor 2 ckt low input bank 2

P0756 Shift sol B ckt perf stuck off

after reading around on these forums I watched a lot closer as what when i drive this truck I dont think it is downshifting as it should also I noticed that after my first complete stop after initial startup it will not shift into overdrive. If I come to a stop and turn the ignition off for a few minutes it shifts into overdrive, but if I stop at a corner and then take off it seems like it is only using one or two gears and it will not shift into overdrive or so I presume as at 55mph it is running 2300 rpms . When normally at 55mph it is running only 1600 rpms.
thanks for any help you may be able to give me

the po756 tranny code is the 2-3 shift solenoid not working correctly. the VCM commands shift points and this valve/solenoid is not operating as commanded.

could be the seals or worn leaking

[transman618]

Originally Posted by romi7612

Hey All,
I got the codes scanned today and here are the results

P0161 02 sensor Heater ckt malfunction

P0332 Knock sensor 2 ckt low input bank 2

P0756 Shift sol B ckt perf stuck off

after reading around on these forums I watched a lot closer as what when i drive this truck I dont think it is downshifting as it should also I noticed that after my first complete stop after initial startup it will not shift into overdrive. If I come to a stop and turn the ignition off for a few minutes it shifts into overdrive, but if I stop at a corner and then take off it seems like it is only using one or two gears and it will not shift into overdrive or so I presume as at 55mph it is running 2300 rpms . When normally at 55mph it is running only 1600 rpms.
thanks for any help you may be able to give me

You might not get anywhere replacing the "B" solenoid however it could be faulty. This particular code is a performance code. There is a service bulletin on this. I'm not at the shop right now but when I get there either later today or tomorrow, I'll look it up and post it here if I can. I know for sure that there was a problem with the separator plate between the valve body and the transmission becoming plugged up in one of its orifices. So either way the valve body is going to have to be removed to check this particular orifice for debris. The orifice is so small and plugs up easily. Do one thing for me, really easy. I want you to check the range switch. This is the gear selector switch mounted on the side of the transmission. All you need to do is idle the engine, drop the gear selector down one by one into the different gear ranges and make sure the proper gear is achieved. For instance When in "R" the truck should move backwards, "N" is neutral, "D" starts in drive, L2 and L1 and so on. Make sure the transmission is starting off in the proper gear. Let me know what you find out.


transman

[romi7612]

I checked the gear selector switch as you asked reverse works fine an L1 L2 and L3 you can burn out in all these but as quick as you put it into D drive it seems as if its either lugging down or slipping until it makes the first shift then I have plenty of power

[Blue Bowtie]

Sounds like insufficient pressure to activate the low clutch. There could be numerous causes for that, including the separator plate issue described above, as well as insufficient friction material to make the clutch bite, worn steels, internal leaks on the piston or shaft seals.

...reverse works fine an L1 L2 and L3 you can burn out in all these but as quick as you put it into D drive it seems as if its either lugging down or slipping...

Operating in a manually selected range other than D will bypass the PWM pressure control and provide full line pressure to the appropriate hydraulic circuits. This additional pressure is often adequate to force engagement of a worn or slipping clutch or the band servos which would otherwise not have sufficient force in automatic mode. The manual ranges also bypass the solenoid valves, so your results MAY indicate a problem with hydraulic control and not friction surfaces - MAYBE.

Fortunately, this can usually be diagnosed and possibly serviced in the vehicle. A mechanical pressure gauge can be connected to the test port on the LF side of the trans to monitor actual line pressure during all ranges of operation. An extension hose/tube can be used to place the gauge in a visible location for analysis while driving as long as the gauge and extension are rated to 300 PSIG working pressure. The pressure transducer below the valve body cannot be relied upon for this kind of diagnosis, so a scanner reading of line pressure may be misleading and is useless.

[Blue Bowtie]

And at the unavoidable risk of offending someone, even though there is no intent to do so, I have to ask...

Dude - COLON, Michigan? Seriously? I had to Google it just to see that it actually exists and that you weren't colloquially referring to Detroit (which, upon reflection, would have more appropriately been "Sphincter, MI" instead). That's not meant to be a huge slam on Detroit, since we here in Ill-Noise often use "Armpit, IL" to identify Chicago. I didn't start it, only repeating it. Everyone knows some of the more colorful names of towns, like Hell, MI, but until now I'd never heard of Colon.

Actually, it looks like a very nice area, with a few lakes and woods around, and plenty of space. I've been in and around Kalamzoo and know people in Berrien County and Big Rapids, and have seen that the area is nice. I'm guessing you regularly have some fun with the name, even though it's pretty likely you pronounce more like the town in France and not the intestinal tract feature.

Sorry, but I had to ask.

[romi7612]

Nope not like the french sounds just like it is spelled and trust me us people in this town are the [BUTT] end of a lot of jokes about this town. It is a very nice place to live though and quiet a hell of a lot better than Detroit. Thanks for your post. What pressure should the tranny have in drive also would it be worth a shot to replace the B solenoid or does it not have anything to do with takeoff in first.

[Blue Bowtie]

The "B" solenoid (2-3 shift) should be energized in 1st and 2nd ranges. The valve is normally open and allows pressure to bleed through. It requires power to close to allow line pressure to build behind it into the forward accumulator and against the forward accumulator valve. This pressure activates the forward clutch. Once pressure builds in that line the oil pressure forces the low/overrun valve forward and engages the low/overrun clutch ONLY if there is a manual range selected. This is why line pressure is higher in manual ranges.

A test pressure gauge should show 55-65 PSI in Park or Neutral. In OD range and with the vehicle not moving (it should be in 1st at that point) the line pressure should be 65-80 PSI. In a manually selected 1st gear the line pressure should be about 160-190 PSI.

[romi7612]

Hey all
Replaced b shift solenoid , knock sensor and oxygen sensor truck runs and shifts like it is new again thanks everybody for their help it was greatly appreciated

[j cAT]

Originally Posted by romi7612

Hey all
Replaced b shift solenoid , knock sensor and oxygen sensor truck runs and shifts like it is new again thanks everybody for their help it was greatly appreciated

so what do you think was the issue with the solenoid ?