OK i just got a '97 K1500.

It was my younger brother's truck. He only had it 3 months before it got taken away, so I've only ridden in it a few times.

It has 3.42 gears w/235k on it. I know NOTHING of the previous maintenence so I will be giving it a tune-up and changing all the fluids.

On the highway it will not downshift or even unlock the convertor until the mph drops at least 10 mph or more.

Its also throwing P0147 code. From researching that it sounds like its not the 02 sensor itself but somewhere in the wiring?? He took the thing mudding almost daily and it took about an hour at the car wash to get most of it out. Could that have caused it??

Thanks.

 

Lots of things could cause that...someone installing it wrong, four wheeling cut a wire, age of vehicle, etc etc.

I'd try to get the code taken care of first then worry about the late shifting. Almost sounds like a tuning issue with the shift but I could be TOTALLY wrong on that one.

Only other thing to think of is mechanical issues with the tranny!!

 

One thing I forgot to mention is that it wouldn't downshift from the day he bought it. It will downshift if you put your foot in it. It hesitates when the cruise is set.

 

this doesn't really address your shifting issue. but you mentioned it has 235k on the clock. I wouldn't change the trans fluid unless you know it's been changed on a regular basis. Alot of transmissions have been known to go boom after being flushed if they've never been flushed before.

See this thread regarding changing the fluid.
https://www.performancetrucks.net/fo...d.php?t=404982

 

Could be several things but the first thing tat come to mind is the TPS not working so the truck dosent know throttle position. The trans itself has no control over when or wether it downshifts . This is controlled stricly by the PCM , I would data logg the TPS or just replace it and see what happens

 

That's what I'd look at.

 

How do I data log?? I don't have any scanning tools. Can Advance Auto do that?? Right now its at the body shop, so it will be a few days.

Can this issue hurt the transmission?? At this point its more of an annoyance than anything. Also what do you think of the change/not change tranny fluid on a high mileage vehicle??


BTW, I dunno if you recognize the s/n but I just had a Level 2 along with a PT4000 (for my Z28 - not the truck) installed from you guys and it works great so far. Its in storage now, but I will be getting a upgraded rear end over the winter. Then I won't be scared to thrash on it.

 

Ok, somewhat of an update. I got it back from the body shop today. They disconnected the battery so the Check Engine light is gone. Before I gave it the tune up I took it out on the highway and it did unlock the converter going up a hill.

When I tap the brake pedal the converter unlocks. I changed the fluid and so far from the little driving I have done, the issue seems to have disappeared.

Everything seems cool now....I will keep in touch on the situation.