jeff46614

I have a 2000 silverado 4.8 with 127000 miles. For the past 2 yrs now, the truck has problems upshifting when the weather gets cold (30ish and below). The kicker here is, the transmission starts to act up after it has been warmed up 20-30 minutes of driving. It is most noticable when I am driving between 25-35 miles/hr. The rpms will stay around 2300 until I hit 40ish, then you can feel it upshift. The local tranny shop flushed it last year and replaced the up and down shift servos. I have tried manually shifting it while it is acting up and tapping the brakes to see if the torque converter was locking. This is driving me nuts, because as soon as the warm weather comes back, the problem completely goes away. Any ideas?

FLT

iTrader: (1)

Jeff the issue you are having definitely sounds like the symptoms are TCC related. If I had to guess you might have an issue with a temp sensor. There are few different conditions according to my hydra-matic book for lockup. IMO just because your fluid temp is below 140* does not mean it a bad thing. As long as the TCC can function your fine. Below is some info from my book.

As long as the vehicle operating temps are appropriate for the TCC to be applied, the PCM provides the ground signal for the tcc circuit. Tcc function can happen after the engine is at 68*. The trans fluid temp must be around around 85* and will allow the lu to apply in 3rd gear. After 135* the tcc can be applied at all times in 4th gear, as apposed to having a scheduled LU apply.

I would probably get a scan tool on your vehicle that has data screens to see what the temps sensors are seeing and also what the commands are. This might help you figure out which direction to go. I hope this answers some questions. Vince

jeff46614

So I took my truck to my local tranny shop and we drove the truck around for a half hour on the scanner trying to figure out why it is holding 2nd to 3rd at around 30 mph. The scanner was showing around 150 for temp and all other conditions fine. He did pull up a bulletin that said transmission operation during cold weather has been revised to allow for faster engine and heater warm up. During initial key up, if intake air temp is less than 32 degrees, 2-3 and 3-4 upshift speeds will be affected. 2-3, if the throttle position is less than 37 percent, the 2-3 upshift will take place at minimum speed of 32 mph. If the TP is above 37 percent, the shifts will divert back to normal shift pattern. Ok, fine. But it is doing it after driving the truck approx 40 miles to work and engine temp steady at 176, tranny at around 150. He said that it is not the tranny, but maybe a computer issue or a temp sensor in the intake telling the computer the wrong intake temp. Any ideas??? This only happens when the outside temp drops below 40 degrees, not during the summer.

jeff46614

Anyone have any ideas????

08k1500_3

iTrader: (2)

That bulliten sounds familiar, how is that MAF sensor mounted with the charger setup you have? The Intake Air Temp sensor is part of the MAF sensor and have seen some issues with them at work

jeff46614

This is on my 4x4 silverado. It is completely stock, except for the tune I had done this fall. I have replaced the MAF sensor, but have not tried to replae the MAP sensor. Someone said that it could be the MAP sensor located on top of the intake. I don't know what intake air pressure has to doe with shifting, but I could try and replace it. Any more ideas? Thanks to everyone who has or will input on this issue.

Wesley Prince

i have a 1993 chevy c1500 pickup with a 4l60e auto transmission. here recently my reverse went out in it. all my other gears work just fine. when i try to put it in reverse it trys but wont go nowwhere unless im on a hill and shut it off and then it will begin to roll so i can park it. i even took this truck from arkansas to iowa and back and it ran fine no problems but still no reverse what could it be? can someone help me

Vince B

iTrader: (1)

Wesley your issue is either in the reverse input drum or in the low reverse clutch. If you have engine braking in manual low then I would say your issue is in the reverse input drum. Either way your transmission needs to be removed so it can be opened up and repaired. Vince

Beth Jackson

Did you ever figure out the issue here? I am having the same problem. I found an article on Transmission Repair Charlotte NC | Transmission Rebuild Charlotte NC that showed what some solutions are, but I wanted to know if you figured out a main reason? thanks.

Jerry Adams

I have a stock '99 Ext Cab 4X4 Silverado w/same problems described by Jeff; everything seems fine until temps drop below 30; I too had my tranny serviced and nothing major found. Just seems odd when it wont shift until 40 mph or so. Still looking for answers.