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View Full Version : Transmission Problems - '97 Chevy 1500



Gearheadtom
06-01-2013, 10:45 PM
So I've been having trouble with the transmission not shifting quite right on my truck. To start, the truck is a '97 chev 1500, 2wd, 305 vortec, and 4l60e trans I think. The trans works good under normal city driving, but if I get hard on the gas, or on long upgrades above about 80 km/hr, I start noticing that the truck won't shift right. Basically, if I get hard enough on the gas that it'll downshift, it won't upshift again until I let off the gas to about 1/4 throttle. It'll just keep accelerating until 4000 rpm, then stay there.
I'm thinking more an electrical problem rather than a mechanical problem with the trans. Only code that came up when I scanned it was for the maf sensor, but I've dealt with that.
Trans fluid it still a good red color, not burnt, and I have yet to do a fluid and filter change. The truck works perfect otherwise, only dash light on is abs, and that's because I pulled the fuse ( I hate abs).
Anything else to check before I start on trans specific issues?

Scootertrash
06-02-2013, 08:48 AM
I believe you are correct that it's a 4L60E. You may want to run it to a shop so they can do a deeper scan on your computer. Are you just using one of those auto store home mechanic scanners?

Gearheadtom
06-02-2013, 10:31 AM
I believe you are correct that it's a 4L60E. You may want to run it to a shop so they can do a deeper scan on your computer. Are you just using one of those auto store home mechanic scanners?

Ya, that's all I've been using, just to see if any codes come up. That's what I've been thinking about doing, taking it to a shop so they can use their scanners with it running and see what kind of reading each sensor and such is giving. I've been putting that off tho due to lack of money haha.

Gearheadtom
06-02-2013, 11:02 AM
I did have some more codes come up again, the maf sensor one came back, two different 02 sensor codes, and an egr code that I dealt with a year ago came back.
I had replaced the maf sensor with a junkyard one, I'm guessing now I have a wiring problem, or an air leak. All of them came back within a week or two of me checking it last.

Gearheadtom
06-02-2013, 08:40 PM
Got an email saying mts made a post, but now I can't see it... I'll answer the questions he asked tho...
The truck has about 180,000 km's on it, no shudder's or anything, at least not from the trans (I've got out of balance tires, and warped rotors haha).
It shifts perfectly normal if I drive it normal, but when the motor gets under a load either from climbing hills at highway speeds, or if I accelerate hard is when it hangs in gear. It does the same thing at lower speeds to, like if I hit it hard at about 40 km/hr it'll downshift, and rev like normal, but just keep accelerating and reving.

Gearheadtom
06-02-2013, 10:11 PM
I've been doing some more reading on the problem and talking to a buddy of mine, and I guess the intake gaskets going are common on these vortec engines. So that would explain the maf sensor code coming back, and explain why the truck seems to run better with the maf sensor unplugged. Some people have reported having shifting problems as well with the intake leaking. Usually they either leak coolant out, or into the motor, and my truck has been doing neither.

MTS
06-02-2013, 10:20 PM
sorry i deleted the post after re-reading yours a few times, The intakes are known to leak they will suck oil up the intake tract too, and air out the top depending on what gaskets are in there, and with 180km im sure they have been changed at least once. it could be the problem, throwing your maf,map, and tp sensor out causing it to not shift right under a load and a few otherthings. Just a fyi the dist gear wears out too and throw's the timing out several degrees causing poor running, somethin to look at. also your descrtiption sounds alot like my truck with a 700r4 i have to back out of it to upshift from 3rd to 4th when layed on but that's a complete differnt set up that im working on.

Gearheadtom
06-02-2013, 10:43 PM
Okay, thanks. I thinking that an intake leak is the problem, that also explains the intermittent little shudder I feel at idle sometimes, just big enough that I notice it a bit. I've got another distributer here anyway in case the gears are worn, but like normal, where the screws go in for the cap is broke haha.

max
06-03-2013, 04:01 PM
Most likely engine performance issue. Fix your engine problems first!!!

Mosh
06-03-2013, 04:19 PM
It sounds to me as if the cats are plugged partially. This will cause the O2's to hang rich and not read correctly, force excess exhaust backpressure through the EGR system, and wig the m.a.f out since it can't draw air into the engine, due to the exhaust restriction. Remove the front O2's and rent a vacuum gauge and O2 port tester from a parts store. Install the tester into each 02 port and start the engine and let it idle. There should be no pressure on the gauge. If you have even 1/2 lb of pressure or more, say a 1lb or over, you cats are plugged. Also rev the engine while watching the gauge, it should not build any pressure. It is a classic symptom and problem for that vehicle with that mileage. If the tool is not available or testing is to complicated to do, drop the Y pipe and see if your symptoms go away. If so cats are clogged. When they clog up slightly, it causes the trans not to shift until you let off the throttle some.

Gearheadtom
06-03-2013, 04:32 PM
I thinking I might have a look at the intake gaskets first, it would be the easiest to do considering everything underneath the truck is rusted to badly. Y-pipe bolts aren't recognizable, and the O2 sensors don't look much better.

Gearheadtom
06-03-2013, 05:53 PM
I tried the carb cleaner trick to see if I had an external intake leak, and found nothing, but I didn't notice that before I even started, the intermittent slight shutter this has at idle was back, and after spraying carb cleaner around the idle got progressively worse, but that may or may not have been from the carb cleaner.

EngineBob
06-04-2013, 11:44 AM
I work on a lot of these trucks and when they have a problem like this with multiple codes like O2 sensors I check fuel pressure and change the filter. They are very pick on the pressure.

Gearheadtom
06-04-2013, 04:39 PM
I might have a look at that first then. I changed the fuel filter a few months ago, but I know my tank is getting rusty on the inside, and my last filter only lasted a year until it started to clog and the truck started acting up a bit, never had a shifting problem before tho, just rough idle and sometimes wouldn't start up as quick.

Gearheadtom
06-06-2013, 06:13 PM
I've been noticing something else odd with this truck as well, if I unplug the maf sensor, the truck seems to have more power, and be sharper off the line.
I also tried to see if this truck would lay a patch of rubber as well as it did last summer, and now all it'll do it give just a few chirps if I hold to to the floor pulling out of somewhere.

Gearheadtom
06-09-2013, 10:23 PM
The truck took a turn for the worse over the weekend. Gradually lost power from friday night until saturday night. Now it will only rev from 3-4000 rpm with the pedal to the floor in neutral or park. Doesn't missfire or spudder, just won't make power. Driving it, it seems to make the most power and accelerate the best at 1/4 throttle. I tried another tps sensor and another coil, no difference.
I'm thinking fuel problem right now, I'm going to see if I can borrow a fuel pressure gauge from someone tomorrow, or buy one if I have to.

belly
06-10-2013, 12:44 AM
It's very common for the fuel pumps to go out on those trucks. If it is the fuel pump, make sure you get the upgraded wire harness. They're prone to keep moisture inside and short out eventually. good luck!

Larry T Moore
06-10-2013, 05:11 AM
take the radiator cap off....slide a new truck under it....:lol:

Gearheadtom
06-10-2013, 06:28 AM
take the radiator cap off....slide a new truck under it....:lol:

That's my plan once I get the money saved up haha

I have heard about the fuel pumps in these trucks. They say the factory ones are the best until they die, and a lot of the aftermarket ones don't last long, but maybe the ones with the upgraded harness are better. I was planning on not getting the cheapest one if I buy one, I don't want to drop the tank in another year haha

Mosh
06-10-2013, 06:48 AM
Not trying to be a jerk. Have you done anything other than plug and unplug sensors and just keep driving it? If you want to throw a 300$ fuel pump at it go ahead. But I strongly urge you to perform the tests I suggested last week first. I really feel your converter was partially clogged last week and now is fully clogged. You keep running it that way and you can add a 200$ egr valve to the parts list too once it melts down from the exhaust restriction.

atc300r
06-10-2013, 07:33 AM
Speed control sencor could also be your trouble. Cats like mosh said could be your trouble a friend of mine had a plugged cat on his s10 he replaced it and the muffler says it runs like new.Im having trouble with my 97 s10 4.3 v6.Mine shifts good starts hard sometimes.

Gearheadtom
06-10-2013, 11:50 AM
If I could just unbolt the y pipe and drop it I would. Unbolting my y pipe would include snapping off every stud, no amount of heat or oil will prevent this, then pulling the manifolds to replace the studs.
I put a fuel pressure gauge on it today, and got 50 psi at idle, and it got up to 60 when I reved it. I also swapped in a different coil and tps yesterday with no difference.

briano
06-10-2013, 12:31 PM
Cut the cats off, that is going to solve your problems. Just put a piece of pipe in their place to try it.

Gearheadtom
06-10-2013, 04:24 PM
That would actually be easier, and I might try that. I can't see why the cat would plug up tho, I've known many people with these trucks over 300,000 km's on them and not a problem. Would that cat plugged explain the surging I get at about 30 km/hr, if I'm just barely on the gas? It goes away if I get on the gas harder.
How well do these Vortec's run with the cat gutted long term? I know it'd probably trip some engine codes, but will it turn it into a fuel thirsty pig that runs like garbage?

briano
06-10-2013, 10:16 PM
It should run fine, if not get high flow cats for it, they are universal and relatively cheap compared to the exact fit

Dirtcrasher
06-10-2013, 11:14 PM
MOSH really knows this stuff inside and out. Keep him in the loop and he is always willing to help people; Just be nice!!

Gearheadtom
06-11-2013, 05:14 PM
A plugged cat does make some sense, but the way the truck acts feels like a fuel problem, mainly because of the surging. The cat doesn't seem to get to overly hot, I figure if it was plugged bad enough to make the truck run as bad as it is, the cat would get pretty hot.
I'm going to see if I can borrow one of them infrared thermometers from someone to measure the the temp of the cat on each end, they say one end is supposed to be cooler that the other, I forget which end is supposed to be hot/cool tho.
I checked my fuel pressure again today, just key on it hit 60 psi until the pump stops, then it drops to 55 immediately, then leaks down to 50 in just a couple seconds. I've heard these trucks are sensitive to fuel pressure because of the popet vavle injectors.
I also forgot to mention before that I can hear it spark knocking a bit when I get hard on the gas, but from what I've read, a lean fuel mixture, or a clogged cat can cause that.

Slingblade
06-11-2013, 06:29 PM
If the cats are clogged you should get a code for the downstream oxygen sensors. A clogged cat could cause your problems but so could many other things, or a combination of things.

Fuel Pressure Regulator, Bad injector(s), o2 sensors, spark plugs, wires, dist cap, bad ground wire, bad plug or bare wire in harness, map sensor, MAF sensor, How exactly did you deal with that?

When you drive with stuff unplugged (MAF) The PCM runs in open loop with a predetermined Air Fuel Ratio, usually really rich. This will in turn screw with your other stuff, o2 sensors, etc.

60 psi should be good for that Vortec. One more thing, when you unplug stuff and plug it back in this screws with the pcm, it has to go through a resetting process.

I would suggest plugging everything back up, remove the battery cable and let it sit a few mins. Drive it a few miles, let the pcm learn it's stuff and see what codes you get.

Or take it to someone with a good GM scanner and let them see what it's doing in real time. I know this stuff gets frustrating, Hang in there, You'll get it. Good Luck.

Gearheadtom
06-11-2013, 07:27 PM
Everything's been plugged in since saturday. I did swap on another good cap I had, and no difference. It doesn't act like ignition, there's no spuddering or missfireing, except for the surging, but that feels like I'm on and off the pedal, like the motor loses and gains power.
When the maf code first came up (almost a month ago), I cleaned it, the code came back after a few days, and the same thing when I swaped in another one. The EGR code I had about a year ago was just because the valve stuck open just a hair because it was just gummed up. After cleaning, the code never came back until now.
After I had the maf code come up, the downstream O2 sensor code came up, then a week or two later, one of the other O2 sensor codes ( one of the two just before the cat) came up, along with the same egr code that I had a year ago.
I've pulled the EGR valve, and it was still clean, and not sticking at all.

Slingblade
06-11-2013, 07:40 PM
If your getting o2 codes and egr codes, Theres a very good chance your cats are clogged.

Gearheadtom
06-11-2013, 07:50 PM
I might try swapping in one of those hi-flow universal cats this weekend, that's if the local candian tire still carries them.

Dirtcrasher
06-12-2013, 12:15 AM
Listen to mosh!!!!!!!!!!!!!!!!

Gearheadtom
06-12-2013, 06:42 AM
Listen to mosh!!!!!!!!!!!!!!!!

I am, I'm going to gut/swap out my cat this weekend... only thing I'm not gunna do is do the tests he said... just swaping the cat will be easier than the tests he said to do, because of all the rust...

Gearheadtom
06-14-2013, 10:35 PM
So I decided that I'm just gunna gut the cat, at least for now. I started at it tonight after work, I got the flange that's downstream from the cat unhooked, then spent the rest of the night drilling out the broken bolts haha. I looked up in the pipe with a light, and the cat looks good, but I figure the upstream end of it must be all melted and globbed together.

Gearheadtom
06-15-2013, 02:39 PM
Well I partially gutted it today, I didn't clean it out all the way just to leave some back pressure, and now the truck has more power than it ever had, and shifts like it should. I guess the reason it wasn't shifting was that it wouldn't reach a high enough rpm to shift when I was on the throttle hard.
Thanks so much for the help everyone, I'm sorry I doubted you! I should have listened to what you guys had to say first thing, I guess I'm to stubborn haha