I currently have this condition and Monday my truck goes in for the repair. They had to order parts. I can tell you this, if the condition exists it is easily reproduceable. I can make it happen every time and the tech saw it right away.
While backing out of the driveway, my 2002 Sierra (4x4 5.3L automatic trans) started revving uncontrollably. I pressed on the brakes and locked the wheels, and I was able to briefly stop the truck. Eventually, the engine revved high enough to overcome the braking, causing my truck to accelerate out of control. I have owned a 2000 Sierra (5.3L, auto, 4x4) and an other 2002 Sierra (4.8L, auto, 4x2) and not seen any problems like this. Has anybody else experienced this kind of problem?
I've never heard of this, but because my wife has an '01 Yukon with the same engine, now I'm a little worried. In any case, a vehicle's brakes will ALWAYS overcome the power of the engine so you should always be able to stop it. Even if you shut off the engine you should still have enough vacuum in the brake booster to easily stop the truck. If you ever figure out what happened please post here.
As an aside, I am sure GM would like to know how this happened too so they can apply this technology of powerful acceleration to the Cavalier. ;-) My sick humor. Sorry.
In any case, a vehicle's brakes will ALWAYS overcome the power of the engine so you should always be able to stop it. Incorrect. Always means that there are no variables in which it would never happen. The engine can and has over come the braking of vehicles. Especially the braking designs of todays vehicles.
The idle air controller has been the culprit of a few surges in rpm like that or the TPS signal malfunction can create problems like that. It is one reason that alot of training and manuals state specifically that after repairs, mechanics should avoid standing directly in front of the vehicle on initial start up.
I have a 96 GMC Sierra 1500 Extended Cab. Recently I took it in for service because I had noticed that it was over-heating. I added fluid and took it in for service where thye diagnosed it as the Intake Gasket. They replaced the Intake Gasket refilled with fliuds, but it has only been a few thousand miles and I have already taken back in becuase the fliud level was low once again. The dealer pressure tested, but could find no leaks. I am sure that fluids are leaking somewhere, but apparently the dealer nor I can find. Any ideas?
"It is one reason that alot of training and manuals state specifically that after repairs, mechanics should avoid standing directly in front of the vehicle on initial start up."
My 2001 GMC Sierra SLt, 5.3L engine, has had a vibration at about 700-800 RPM since new. You can put the transmission in DRIVE and hold the brake and rev it to 700 rpm and it vibrates enough that you can feel it everywhere, it even causes rattles under the dash like crazy. It does it also in PARK but not quite as bad. It seems to be a lot worse when the engine is cold than when hot. The local Service department disabled all accessories and then agreed that it was in the engine. It seems to be the strongest at the rear of the engine. They tried another 2002 vehicle on the lot and it had the same vibration. They then decided that it must be a normal condition and told me that they couldn't fix it. Has anyone else had this problem and if so is there any solution to the problem????? If not then does anyone have any suggestions about where to look for a solution (note...I lifted this text straight out of post #760 because I could not have said it better myself; just changed yr model).
Check the fluid level in the master cylinder reservoir. If ok, a scan tool is needed to retrieve any stored DTC's. Btw, post the year and model next time.
Brake fluid fine. Last month, dealer had to resurface all the rotors because of rust. [23,000 miles]. I want them to replace the rotors, but that is going to be a battle. I have an appt. on mon. to see if the computor picked up a trouble code.
Don't get your hopes up for a rotor replacement, standard practice is to resurface. As long as rotors are within GM specifications they won't replace, mine were resurfaced @ 17k because of a pulsation thru the brake pedal (slightly warped). They were still within spec after resurfacing so I could not get new ones as far as dealer was concerned.
Has anyone else had a problem with Power Window Regulators breaking in cold temperatures? New Hampshire temperature went to -12°F over night. While opening the passenger window, it went half way down & the regulator broke. It seems to be a popular replacement part, cost me $355.00 for poor design.
I had a slightly different problem, my door latch and lock mech broke, could open the door from inside or outside. They had to tear the door apart from inside the cab enough to get the door open...it was a circus. All covered under warranty thank goodness. Why would you want to drive with the window open at that temp? ;-)
To gvoigt: I lowered the window to check the traffic at a bad intersection. The window was not frozen in place but it was covered with ice, to a point which obstructed some visibility.
After the new regulator was installed, the window seemed to open more slowly than I thought it should. When I took it back, the dealer lubricated the window tracks with silicone spray. That made a big improvement. The regulator is a very frail design so a little silicone spray could save others from the same problem & expense.
hope someone can help-dealer says no problem. had to have a new alternator installed by dealer while on vacation {go figure} about 6 months ago. Now when ddriving vehicle during darkness, headlighs dim intermittenly and voltmeter pulses from 14 volts to under 14. dealer says nothing wrong-does not want to replace gmc warrantied one
I have a similar problem on my 2001 5.3L Z71 SLT GMC. When sitting at a light the lights in the dash flicker and so do the head and tail lights. When I hock up any of my trailers it gets worse. One evening in a driving rain I stopped at a light, the wipers were in high speed mode, all lights on, brights too, radio on, heater fan running high speed and the engine was pulsating with the wiper motor. Dealer said “Couldn’t duplicate the problem.” When I got in the truck at the dealer there was a light rain so I duplicated it for them and they connected a computer thingy and still said there wasn’t a problem even though the thing was pulsating with the wiper motor right in front of them. I drove down the street to another dealer and showed them the same thing and they said it was a bad design of the voltage regulator in the alternator. “It wouldn’t fix the problem if we change out the alternator because they all have the same design.” What the @#$% is a man to do about such blatantly badly designed junk!!??? Also I have made a point to look at the lights of other GM truck when sitting at lights. I have observed the same problem with them. Everyone that I see does the same thing. Please let me know if you all observe the same thing.
I'm glad to report that my GMC Dealer ,still unsure of the location of my oil leak,traded me out of the truck with a 03 Bonneville SSEi.And I didn't loose one dime.I'm very happy with the Bonneville and will buy from this dealer again in the future.
PS It was late Summer when I got the Bonneville,sorry for the late post.
When I try to put my truck into four wheel drive while it is moving it just grinds. It will not go in. I took it back to the dealer and they said there was nothing wrong with it the first time. Then I contacted GM and they told me to take it back so the second time they put some sort of pump in the transfer case. That didn't work either. Just wondering if anybody else had a problem like this.
i own a 1995 gmc sierra 1500...the fan for my heater/ac only works on the high setting....no other setting works...could someone please help the new guy?...thanks
I had the same problem, it turned out to be the latch mechanism was totally fried. Had my edlerly father in the truck and he was trapped inside, luckily we were able to get him out the drivers side. Mr Goodwrench said it was a common problem they had seen. They had to disassemble the door enough while closed in order to release the latch to open it to repair it completely. Took about four hours. Waiting for the drivers door to do the same thing.
i appreciate your help alcan...how are you on brakes?...ha ha ... the last two days my emergency brake suddenly engages while i was backing up...i pushed the e-brake pedal down and puled the handle, but it was still engaged...then it just lets loose.....could this be a result of low brake fluid level perhaps?
is hanging up for some reason or the p. brake cable is getting stuck within it's protective cover (water/freezing). You'll need to get under there and have someone work the parking brake to see what's happening. If frozen get out the wife's hair dryer and thaw out the cable housing.
A friend of mine had the same problem in a 96 Jimmy. I got in the truck with him to see if we could replicate the problem. It turned out he was not letting the engine decelerate before trying to engage the 4wd. Thus the the transfer case was trying to shift while the engine was still under load. He pretty much was frying his transfer case. I told him to wait 1-2 sec after pedal release prior to pushing the 4x4 button and he has not had a problem since. I hope this works for you. If not I would insist on a whole new transfer case.
I finally got the dealer to replace my transfer case and guess what, it fixed the problem. Too bad it only took me three times to get them to fix it. Thanks for the advice.
From Post #717 You state that your 1999 Z71 OD engages at around 40mph and that your motor sounds dead.
As you know it is dead, turning around 1000rpm with the OD engaged is silly, I wish GM would wake up.
I have a 1999 Z71 Silverado 5.3, 4x4 XC. I ran across a GM TSB that fixes this. It absolutely turns the truck into a very driveable machine. The TSB had to do with "drive-line noise", but it moved the OD engagement to around 54-56mph. Its beautiful. It lets the torque convert do its thing around town. I noticed no impact on MPG.
The same issue/solution exists for 2000, 2001 (not sure for 03,04) trucks. I have a 2001 Suburban same drive-train. Unfortunately no TSB for Burbs. Its even heavier and with 40mph OD engagement at 1000rpm, its a real dog around town. I wish GM would move the OD engagement setting for Highway operation and let the converter work around town.
Have you thought about getting a a superchips type tuner that can move shift points? Might be able to up your od point to where you want it. Plus you could use it to add a little extra power and things.
When I stated OD in post 848 I meant to indicate when the torque converter locks up (not when it shifts to Overdrive). The issue was that the converter locks up at 40mph and the tranny is already in OD so the engine is virtually lugging, not enough rpms to produce any power...
With the truck TSB fix the converter does not lockup until 54-56mph which is fine.
No running around in 3rd is not the same as moving the torque converter lockup to a higher mph. I do agree with you that it helps the performance, but it does hurt the mpg around town. Having said that, the way I wrote the original post it would be the same as running in 3rd. But that is not what I meant....
The transmission shifts to overdrive and then the converter locks up. It used to lockup at around 40mph, after the TSB it does not lockup until 54-56mph. The TSB did not seem to change the shift points 2-3, 3-OD only when the converter locks up. With the converter unlocked around town it makes the truck much more responsive in city/rural driving when speeds are under 50mph and under 1400rpm (my truck has 3.73 gears).
The truck still goes into OD just like it did before, the TSB lets the converter work around town instead of locking it out.
For those that don't know what a converter does. The converter can almost instantly change the effective gear ration when more power is generated by the engine (its a variable gear). So when the converter is locked at 40MPH the motor is only running at around 1150rpm, its not generating much HP. SO when you moderatley (not enough to force a downshift) step on the gas the motor rpm is fixed at 1150 rpm, speed increases slower. With the converter unlocked, the rpms will jump up to 1400-1600 rpm when cruising at 40mph, thus more power is generated by the engine and more acceleration or extra power to go up a hill. The truck is just more responsive with the converter unlocked under 50mph.
Try it out on your truck. Cruise at around 35-37mph, rpms will be just above 1000, step on the gas moderately you will see the RPMs go up and down almost instantly. When you let off the gas it will go to the least rpm (most efficient when no power is requested or cruising). Now go above 40 after the converter locks up, and try it again. You will see the rpms stay fixed and you get less power.
The TSB again allows the converter to work at low rpm so you get more power when you need it around town. If you are cruising with it unlocked you are still at the lower rpms so very little is wasted with regard to MPG. AS I said I did not see any changes in my average MPG.
I don't mean to agrue the point. I think most people would like this little know TSB, if not have gm back it out.
It doesn't change the shift point. GM would've had a problem with their epa mileage rating if they were to have done that. What it does do is allow for a quicker downshift when the pedal is depressed rather than holding it in OD.
I had questioned the tech at the time when the tsb had been performed on my truck. He had the TechII unit hooked up which could change the shift points. However, when the unit was removed, the factory settings would be enabled thus removing whatever programming he had done to change the shift points.
after he performed the tsb for the lugging. Said GM didn't allow for them to reprogram the shift points. Only temporarily for troubleshooting purposes with the TechII hooked up.
I'm sure if GM wanted the shift points changed the tech would be able to with his/her TechII unit.
I've thought it would be fun to have one but never really seen a very comprehensive explanation of all their capabilities. I speculate that in the end their use may be limited what with GM's stinginess with data.
While we're on shift points I wonder how much throttle pressure others find necessary to downshift out of O/D. I seem to have to practically bury it to the floor, at least 3/4. It wasn't like that when new. Relevant to this, in my view a good improvement for GM engineers to consider would be to put the Tow/Haul switch on the dash, given it's limited use, and replace it with a manual downshift override. Back in the 70's I had a '55' Chev 1/2 ton with 3 speed, O/D. I removed the kick down switch from underneath the throttle and placed it within easy reach. The transformation was remarkable, much more versatile. Sorry, I'm drifting off thread.
The TechII costs the DEALERS about 20grand a peice. If you dont work for GM at a GM dealer you can not even get your hands on one at all. I used to work for GM which is the only reason i know that info.
How do you know that without a scanner on line. >>The transmission shifts to overdrive and then the converter locks up.<< They both cause an rpm drop.
I just feel/listen to the transmission shifting, then verify what I am hearing by moving the shift lever from OD to 3rd. If I think it shifted to OD, then I pull it back to 3rd and see if it downshifts, if it doesn't then I am still in 3rd and it must of been the converter locking.
You can manually cause the converter to unlock by pressing slightly on the brake. Anytime the brake is pressed the converter unlocks.
With some experience, by listening and confirming what you hear and feel by moving the shifter and brake pedal you can determine what the driveline is doing without a scanner.
My brother works at a Dealership and has been able to "show" me what they are capable of.
It is nothing short of amazing. There was soo much I am not able to remember half of the stuff. All of the parameters were editable while in the TechII. Some of the parameters would revert to calibration upon removal of the techII and a restart. Start and stop the a/c, shutdown individual injectors and or coils for testing. Change fuel curves, timing curves. Control torque converter lockup. You name it.
Some of the modifications we want i.e. larger tires. Require a calibration change. That is controlled by GM if we want full G.M. Support. I read an article on jsut this recently and how it is handled by GM. I will try to located the article and post a link here.
I took delivery of my 2004 Sierra 1500 with automatic transmission in December. It was built in August 2003. I wonder if my new truck has one of the problem transmissions mentioned in this article:
I was checking the oil today in my 1997 GMC Sierra 4x4 (126,000 mi with the 5.7L) when I noticed there was almost no coolant in the reservior. Sure enough, underneath the truck there was some orange coolant fluid. Does anyone know if the intake manifold gasket problem that has been reported with the 3.1/3.4L V6's also affects the 5.7L V8? I haven't had time to read through previous postings.
It does. Doesn't necessarily mean that the intake gaskets are leaking, though. Have it pressure tested. Could be the water pump, block heater O-ring, a rad hose, heater hose........
Thanks for the input on Techll. I still can't help but think there's a "way", legal that is; Or, maybe a back engineered knock-off device that has the same capabilities. BTW, speaking of knock-off devices, I had the intermediate steering shaft on my truck greased under warranty to correct the rattle about eighteen months ago. And it's back. No longer being under warranty I bought the kit, but there's an apparently essential tool not included, a # J42640. The service manual shows it as pin-like do-dad that fits into a hole beneath the steering column to prevent the wheel from turning once the shaft is removed. You think Chevrolet would sell me one? Just the kit, not the tool. Does anyone know where these 'J' series specialty tools or the knock-offs can be had. Thanks a lot.
Comments
I can tell you this, if the condition exists it is easily reproduceable. I can make it happen every time and the tech saw it right away.
As an aside, I am sure GM would like to know how this happened too so they can apply this technology of powerful acceleration to the Cavalier. ;-) My sick humor. Sorry.
Incorrect. Always means that there are no variables in which it would never happen. The engine can and has over come the braking of vehicles. Especially the braking designs of todays vehicles.
The idle air controller has been the culprit of a few surges in rpm like that or the TPS signal malfunction can create problems like that.
It is one reason that alot of training and manuals state specifically that after repairs, mechanics should avoid standing directly in front of the vehicle on initial start up.
"It is one reason that alot of training and manuals state specifically that after repairs, mechanics should avoid standing directly in front of the vehicle on initial start up."
That was a killer, I mean hoot ! LOL
Merry Christmas !
Ray T.
Ray T.
2K Sierra, Short Bed, Regular Cab
After the new regulator was installed, the window seemed to open more slowly than I thought it should. When I took it back, the dealer lubricated the window tracks with silicone spray. That made a big improvement. The regulator is a very frail design so a little silicone spray could save others from the same problem & expense.
Also I have made a point to look at the lights of other GM truck when sitting at lights. I have observed the same problem with them. Everyone that I see does the same thing.
Please let me know if you all observe the same thing.
PS It was late Summer when I got the Bonneville,sorry for the late post.
5.3 ltr Ext. Cab
Passenger door will not open, electronics check good, window rolls down, door unlocks, any ideas before we see Mr. Goodwrench???.
Bob
Ray T.
You state that your 1999 Z71 OD engages at around 40mph and that your motor sounds dead.
As you know it is dead, turning around 1000rpm with the OD engaged is silly, I wish GM would wake up.
I have a 1999 Z71 Silverado 5.3, 4x4 XC. I ran across a GM TSB that fixes this. It absolutely turns the truck into a very driveable machine. The TSB had to do with "drive-line noise", but it moved the OD engagement to around 54-56mph. Its beautiful. It lets the torque convert do its thing around town. I noticed no impact on MPG.
The same issue/solution exists for 2000, 2001 (not sure for 03,04) trucks. I have a 2001 Suburban same drive-train. Unfortunately no TSB for Burbs. Its even heavier and with 40mph OD engagement at 1000rpm, its a real dog around town. I wish GM would move the OD engagement setting for Highway operation and let the converter work around town.
When I stated OD in post 848 I meant to indicate when the torque converter locks up (not when it shifts to Overdrive). The issue was that the converter locks up at 40mph and the tranny is already in OD so the engine is virtually lugging, not enough rpms to produce any power...
With the truck TSB fix the converter does not lockup until 54-56mph which is fine.
No running around in 3rd is not the same as moving the torque converter lockup to a higher mph. I do agree with you that it helps the performance, but it does hurt the mpg around town. Having said that, the way I wrote the original post it would be the same as running in 3rd. But that is not what I meant....
The truck still goes into OD just like it did before, the TSB lets the converter work around town instead of locking it out.
For those that don't know what a converter does. The converter can almost instantly change the effective gear ration when more power is generated by the engine (its a variable gear). So when the converter is locked at 40MPH the motor is only running at around 1150rpm, its not generating much HP. SO when you moderatley (not enough to force a downshift) step on the gas the motor rpm is fixed at 1150 rpm, speed increases slower. With the converter unlocked, the rpms will jump up to 1400-1600 rpm when cruising at 40mph, thus more power is generated by the engine and more acceleration or extra power to go up a hill. The truck is just more responsive with the converter unlocked under 50mph.
Try it out on your truck. Cruise at around 35-37mph, rpms will be just above 1000, step on the gas moderately you will see the RPMs go up and down almost instantly. When you let off the gas it will go to the least rpm (most efficient when no power is requested or cruising). Now go above 40 after the converter locks up, and try it again. You will see the rpms stay fixed and you get less power.
The TSB again allows the converter to work at low rpm so you get more power when you need it around town. If you are cruising with it unlocked you are still at the lower rpms so very little is wasted with regard to MPG. AS I said I did not see any changes in my average MPG.
I don't mean to agrue the point. I think most people would like this little know TSB, if not have gm back it out.
>>The transmission shifts to overdrive and then the converter locks up.<<
They both cause an rpm drop.
I had questioned the tech at the time when the tsb had been performed on my truck. He had the TechII unit hooked up which could change the shift points. However, when the unit was removed, the factory settings would be enabled thus removing whatever programming he had done to change the shift points.
-David
I'm sure if GM wanted the shift points changed the tech would be able to with his/her TechII unit.
While we're on shift points I wonder how much throttle pressure others find necessary to downshift out of O/D. I seem to have to practically bury it to the floor, at least 3/4. It wasn't like that when new.
Relevant to this, in my view a good improvement for GM engineers to consider would be to put the Tow/Haul switch on the dash, given it's limited use, and replace it with a manual downshift override. Back in the 70's I had a '55' Chev 1/2 ton with 3 speed, O/D. I removed the kick down switch from underneath the throttle and placed it within easy reach. The transformation was remarkable, much more versatile. Sorry, I'm drifting off thread.
-David
>>The transmission shifts to overdrive and then the converter locks up.<<
They both cause an rpm drop.
I just feel/listen to the transmission shifting, then verify what I am hearing by moving the shift lever from OD to 3rd. If I think it shifted to OD, then I pull it back to 3rd and see if it downshifts, if it doesn't then I am still in 3rd and it must of been the converter locking.
You can manually cause the converter to unlock by pressing slightly on the brake. Anytime the brake is pressed the converter unlocks.
With some experience, by listening and confirming what you hear and feel by moving the shifter and brake pedal you can determine what the driveline is doing without a scanner.
It is nothing short of amazing. There was soo much I am not able to remember half of the stuff.
All of the parameters were editable while in the TechII. Some of the parameters would revert to calibration upon removal of the techII and a restart.
Start and stop the a/c, shutdown individual injectors and or coils for testing. Change fuel curves, timing curves. Control torque converter lockup. You name it.
Some of the modifications we want i.e. larger tires. Require a calibration change. That is controlled by GM if we want full G.M. Support.
I read an article on jsut this recently and how it is handled by GM. I will try to located the article and post a link here.
http://www.detnews.com/2004/autosinsider/0403/14/c12-90918.htm
BTW, speaking of knock-off devices, I had the intermediate steering shaft on my truck greased under warranty to correct the rattle about eighteen months ago. And it's back. No longer being under warranty I bought the kit, but there's an apparently essential tool not included, a # J42640. The service manual shows it as pin-like do-dad that fits into a hole beneath the steering column to prevent the wheel from turning once the shaft is removed. You think Chevrolet would sell me one? Just the kit, not the tool. Does anyone know where these 'J' series specialty tools or the knock-offs can be had. Thanks a lot.
-David
gator, I'd like to read that article.