problems w/GM 6 speed in trailer tow mode
November 9th, 2010, 10:32 AM
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problems w/GM 6 speed in trailer tow mode
Would be interested in knowing if anyone else with a GM 6 speed automatic transmission has had the following problem:
Vehicle is a 2008 Suburban 2500 w/6.0 ltr engine, 4WD, and approximately 36000 miles, although following problem has existed since new.
In trailer tow mode, and pulling a trailer of about 5000 lb wgt, when slowing down on any type terrain, transmission will down shift from 5th or 6th gear all the way down to 3rd or even 2nd. In other words, instead of shifting down sequentially as GM states it should (i.e. from 6th to 5th to 4th, etc.) it will skip several gears. The result of this is over rev of the engine and sudden deceleration, which cannot be good for the engine and driveline.
I have had the vehicle in to the dealer several times (3-4) with this complaint but have not been able to duplicate the problem without the trailer attached. Went there several weeks ago with trailer hooked up and they gave me an "event recorder" that attached under the dash as they could not let a tech be gone for the amount of time to get to a known hilly area where the vehicle would reproduce the problem. I did reproduce the problem four times for the recorder and when I returned the device and they hooked it to the shop computer for read out, they said nothing was recorded, or at least nothing that showed on their computer. At that point they supplied another recorder of a different type, and I again hooked up the trailer and recorded three more of these events. Returned this device to them and after waiting several days for some reply, called them. They again reported that nothing had been recorded on the device, or at least nothing they could pull up on their computer.
It stands to reason if they say nothing was recorded, when the events did occur when using two different devices, two different times, either the recording equipment is faulty, or I am getting the run-a-round. Also if they say nothing was recorded, is also precludes any further investigation on their or GM's part.
Just wondering if anyone else with a Suburban or any other GM vehicle with this transmission with trailer tow mode has had the some problem, and if so what was done to fix it.
Thanks in advance for any help.
Vehicle is a 2008 Suburban 2500 w/6.0 ltr engine, 4WD, and approximately 36000 miles, although following problem has existed since new.
In trailer tow mode, and pulling a trailer of about 5000 lb wgt, when slowing down on any type terrain, transmission will down shift from 5th or 6th gear all the way down to 3rd or even 2nd. In other words, instead of shifting down sequentially as GM states it should (i.e. from 6th to 5th to 4th, etc.) it will skip several gears. The result of this is over rev of the engine and sudden deceleration, which cannot be good for the engine and driveline.
I have had the vehicle in to the dealer several times (3-4) with this complaint but have not been able to duplicate the problem without the trailer attached. Went there several weeks ago with trailer hooked up and they gave me an "event recorder" that attached under the dash as they could not let a tech be gone for the amount of time to get to a known hilly area where the vehicle would reproduce the problem. I did reproduce the problem four times for the recorder and when I returned the device and they hooked it to the shop computer for read out, they said nothing was recorded, or at least nothing that showed on their computer. At that point they supplied another recorder of a different type, and I again hooked up the trailer and recorded three more of these events. Returned this device to them and after waiting several days for some reply, called them. They again reported that nothing had been recorded on the device, or at least nothing they could pull up on their computer.
It stands to reason if they say nothing was recorded, when the events did occur when using two different devices, two different times, either the recording equipment is faulty, or I am getting the run-a-round. Also if they say nothing was recorded, is also precludes any further investigation on their or GM's part.
Just wondering if anyone else with a Suburban or any other GM vehicle with this transmission with trailer tow mode has had the some problem, and if so what was done to fix it.
Thanks in advance for any help.
November 9th, 2010, 1:08 PM
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Does it do it in tow/haul mode without the trailer? The dealer stating that they don't have the time for the tech to ride with you is not a valid excuse. I wouldn't stand for that. I would follow the steps in the GM appeal process as outlined in your service manual. Once you file an appeal you will get their attention. I bet they then find the time.
suggest following Step One first.
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will be resolved by the dealer’s sales or service
departments. Sometimes, however, despite the best
intentions of all concerned, misunderstandings can
occur. If your concern has not been resolved to your
satisfaction, the following steps should be taken:
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Discuss your concern with a member of
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management, it appears your concern cannot be
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When contacting Chevrolet, remember that your concern
will likely be resolved at a dealer’s facility. That is why we
suggest following Step One first.
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Both General Motors
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of Columbia. Eligibility is limited by vehicle age, mileage,
and other factors. General Motors reserves the right to
change eligibility limitations and/or discontinue its
and your dealer are committed to making sure you are
completely satisfied with your new vehicle. However, if
you continue to remain unsatisfied after following the
procedure outlined in Steps One and Two, you can file
with the Better Business Bureau (BBB) Auto Line
Program to enforce your rights.
The BBB Auto Line Program is an out of court program
administered by the Council of Better Business Bureaus
to settle automotive disputes regarding vehicle repairs or
the interpretation of the New Vehicle Limited Warranty.
Although you may be required to resort to this informal
dispute resolution program prior to filing a court action,
use of the program is free of charge and your case will
generally be heard within 40 days. If you do not agree
with the decision given in your case, you may reject it and
proceed with any other venue for relief available to you.
You may contact the BBB Auto Line Program using the
toll-free telephone number or write them at the following
address:
BBB Auto Line Program
Council of Better Business Bureaus, Inc.
4200 Wilson Boulevard
Suite 800
Arlington, VA 22203-1838
Telephone: 1-800-955-5100
dr.bbb.org/goauto
This program is available in all 50 states and the District
of Columbia. Eligibility is limited by vehicle age, mileage,
and other factors. General Motors reserves the right to
change eligibility limitations and/or discontinue its
participation in this program.
November 9th, 2010, 2:48 PM
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Hoe:
No it does not do it when not towing a trailer. It does operate correctly when in tow mode and not towing a trailer, i.e. shifts become firmer, both up and down, but it does not "skip" gears when downshifting without a trailer hooked up. I have a tendency to think because the problem occurs mostly at a time when I am going down a steep hill, (of which there are a lot in my area) that speed picks up so quickly when you start down a hill with the trailer attached, that whatever causes the transmission to go into the downshift mode sees the speed increasing rapidly and tries to slow the vehicle down before things get out of hand, therefore the downshift to a much lower gear all at once rather than sequentially as it is supposed to do. It very seldom does this on level ground when losing speed or slowing down and I cannot ever remember it shifting like this (skipping gears) unless I was braking fairly hard at the same time.
I may be giving the transmission control too much credit for trying to slow the vehicle down quickly when it see's it (the vehicle) gaining speed rapidly, but I am at a loss to explain it any other way. Also the dealer has told me several times that GM says the transmission CAN'T or is not designed to downshift the way it is doing under the circumstances described. It is only supposed to shift down one gear at a time, NOT skip any gear on the way down.
I am hoping someone else will see this thread and have either experienced the same problem and knows the solution or has some ideas as to what is causing it that I can take back to the dealer.
I understand the procedure for "going up the ladder" if problems are not resolved at the service writer/technician level. However I would like to avoid that for several reasons. Main among them is the guy I have been dealing with at this dealership (bought the vehicle elsewhere) has ALWAYS bent over backward to help and solve any problems I have had to this point with the vehicle. I want to try to maintain that relationship with this dealer and personnel, especially since he is close, and I have 65K miles left on the powertrain warranty. I am sure you get my drift.
No it does not do it when not towing a trailer. It does operate correctly when in tow mode and not towing a trailer, i.e. shifts become firmer, both up and down, but it does not "skip" gears when downshifting without a trailer hooked up. I have a tendency to think because the problem occurs mostly at a time when I am going down a steep hill, (of which there are a lot in my area) that speed picks up so quickly when you start down a hill with the trailer attached, that whatever causes the transmission to go into the downshift mode sees the speed increasing rapidly and tries to slow the vehicle down before things get out of hand, therefore the downshift to a much lower gear all at once rather than sequentially as it is supposed to do. It very seldom does this on level ground when losing speed or slowing down and I cannot ever remember it shifting like this (skipping gears) unless I was braking fairly hard at the same time.
I may be giving the transmission control too much credit for trying to slow the vehicle down quickly when it see's it (the vehicle) gaining speed rapidly, but I am at a loss to explain it any other way. Also the dealer has told me several times that GM says the transmission CAN'T or is not designed to downshift the way it is doing under the circumstances described. It is only supposed to shift down one gear at a time, NOT skip any gear on the way down.
I am hoping someone else will see this thread and have either experienced the same problem and knows the solution or has some ideas as to what is causing it that I can take back to the dealer.
I understand the procedure for "going up the ladder" if problems are not resolved at the service writer/technician level. However I would like to avoid that for several reasons. Main among them is the guy I have been dealing with at this dealership (bought the vehicle elsewhere) has ALWAYS bent over backward to help and solve any problems I have had to this point with the vehicle. I want to try to maintain that relationship with this dealer and personnel, especially since he is close, and I have 65K miles left on the powertrain warranty. I am sure you get my drift.
November 9th, 2010, 7:35 PM
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Shark:
Do you mean the "manual mode" by placing the gear shift lever in "M", and then downshifting manually when slowing down? If that is what you mean, then yes I have done that when in extremely hilly terrain to keep it from shifting down like it does when in "tow mode". It does operate correctly then.
I do not believe, that I can remember, ever trying the lever in manual mode while the trailer tow mode was also engaged. I had a suggestion from another person on another board to just tow in regular mode, but I would prefer to tow in tow mode as it improves the upshift performance of the transmission as well as more aggressive downshifting when accelerating/slowing with a trailer. It also will hold the transmission a little longer in each gear to eliminate the "hunting" back and forth that an automatic will do sometimes when towing. The main problem as stated several times is skipping gears from high speed when downshifting and then over revving the engine, especially under part or no throttle.
All in all I like the idea and the performance of the transmission in most all respects, and the idea behind it. My chief complaint is the downshift sequence problem that GM tells my dealer it is NOT supposed to do when in tow mode. If GM says it is supposed to work a certain way, then I would like it to work that way, much less the extra wear and tear on the engine drive line by the way it downshifts now. When you are coasting at 50-60 MPH at 15-18 hundred RPM, and all of a sudden the transmission downshifts to 2nd and exceeds 5000 RPM, that cannot be good for any part of the driveline, much less passenger confidence if they don't know what is going on.
That plus the two times I was able to satisfy their request to duplicate the problem with the "event recorders" and then they were not able to get any info from their own test equipment, has me frustrated, to say the least.
Thanks for the replys.
Do you mean the "manual mode" by placing the gear shift lever in "M", and then downshifting manually when slowing down? If that is what you mean, then yes I have done that when in extremely hilly terrain to keep it from shifting down like it does when in "tow mode". It does operate correctly then.
I do not believe, that I can remember, ever trying the lever in manual mode while the trailer tow mode was also engaged. I had a suggestion from another person on another board to just tow in regular mode, but I would prefer to tow in tow mode as it improves the upshift performance of the transmission as well as more aggressive downshifting when accelerating/slowing with a trailer. It also will hold the transmission a little longer in each gear to eliminate the "hunting" back and forth that an automatic will do sometimes when towing. The main problem as stated several times is skipping gears from high speed when downshifting and then over revving the engine, especially under part or no throttle.
All in all I like the idea and the performance of the transmission in most all respects, and the idea behind it. My chief complaint is the downshift sequence problem that GM tells my dealer it is NOT supposed to do when in tow mode. If GM says it is supposed to work a certain way, then I would like it to work that way, much less the extra wear and tear on the engine drive line by the way it downshifts now. When you are coasting at 50-60 MPH at 15-18 hundred RPM, and all of a sudden the transmission downshifts to 2nd and exceeds 5000 RPM, that cannot be good for any part of the driveline, much less passenger confidence if they don't know what is going on.
That plus the two times I was able to satisfy their request to duplicate the problem with the "event recorders" and then they were not able to get any info from their own test equipment, has me frustrated, to say the least.
Thanks for the replys.
November 12th, 2010, 12:22 PM
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I would agree with what has been stated by the others here. If you would like I can get you into contact with our Customer Assistance Center to have the issue looked at in this way. They would work with you and your dealer to get a resolution for you. Simply direct message me your contact information and I will set you up with our Assistance Center. I hope this helps you.
Jeff Morris, Chevrolet Customer Service
Jeff Morris, Chevrolet Customer Service
Last edited by Chevrolet Customer Service; November 15th, 2010 at 3:07 PM. Reason: Word misspelled
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November 13th, 2010, 2:22 PM
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Things are moving along, I hope.........
Chevy Customer Service:
Thanks for your reply to my earlier posts..
As previously stated, I DO NOT (at present) have a problem with the dealer I am working with on this problem. The reason as stated for the post on the tow mode problem was to see if anyone else had been experiencing or had experienced the same problem, and what was done to solve it. That being said, I do appreciate the advice given by you. As I also stated on another thread, this same dealer was of good help and did solve another problem, when the technician was able to be shown that the problem I was complaining about actually existed. This was only able to be accomplished by having him with me, as there were no codes being left in the vehicle computer on that problem, or in the case of the tow mode problem I am now trying to get resolved, no codes left, either in the vehicle computer or the two different "event recorders" that I have been furnished with, and even though the vehicle did experience the problem while they (the recorders) were hooked up, would not either record the events, or allow them to be read out on the dealers equipment.
That was the thrust of my posts about both my problems, not that the dealer was not responsive and could not solve it, but the fact that the diagnostic equipment I was being given was not doing it's job, and that because technicians at dealerships today depend so much on modern diagnostics that if it does not show a problem, you do not have one, as far as they are concerned, unless it can be duplicated with a tech in the car at the time the problems appear. As everyone knows, the problem never reproduces itself when you take it to the dealer, so that is a source of aggravation for the vehicle owner, and lost time for the dealership.
I was just contacted late yesterday afternoon by the service writer at the dealership, and he is going to schedule a technician to ride with me next week for as long as it takes to show just exactly what the problem is. I think now that two times with the recorder, and nothing recorded on it or available for read out by them, has also convinced them that in some cases, the tech MUST go with the customer if the problem is going to be solved, no matter the time involved away from the shop. Hopefully I will be able to reproduce the problems with a tech along, and this will have the same happy outcome as the problems with the stabilitrak and traction control lights coming on for no reason, and they can solve this also.
Will keep this thread updated as to what happens on that test.
Thanks for your reply to my earlier posts..
As previously stated, I DO NOT (at present) have a problem with the dealer I am working with on this problem. The reason as stated for the post on the tow mode problem was to see if anyone else had been experiencing or had experienced the same problem, and what was done to solve it. That being said, I do appreciate the advice given by you. As I also stated on another thread, this same dealer was of good help and did solve another problem, when the technician was able to be shown that the problem I was complaining about actually existed. This was only able to be accomplished by having him with me, as there were no codes being left in the vehicle computer on that problem, or in the case of the tow mode problem I am now trying to get resolved, no codes left, either in the vehicle computer or the two different "event recorders" that I have been furnished with, and even though the vehicle did experience the problem while they (the recorders) were hooked up, would not either record the events, or allow them to be read out on the dealers equipment.
That was the thrust of my posts about both my problems, not that the dealer was not responsive and could not solve it, but the fact that the diagnostic equipment I was being given was not doing it's job, and that because technicians at dealerships today depend so much on modern diagnostics that if it does not show a problem, you do not have one, as far as they are concerned, unless it can be duplicated with a tech in the car at the time the problems appear. As everyone knows, the problem never reproduces itself when you take it to the dealer, so that is a source of aggravation for the vehicle owner, and lost time for the dealership.
I was just contacted late yesterday afternoon by the service writer at the dealership, and he is going to schedule a technician to ride with me next week for as long as it takes to show just exactly what the problem is. I think now that two times with the recorder, and nothing recorded on it or available for read out by them, has also convinced them that in some cases, the tech MUST go with the customer if the problem is going to be solved, no matter the time involved away from the shop. Hopefully I will be able to reproduce the problems with a tech along, and this will have the same happy outcome as the problems with the stabilitrak and traction control lights coming on for no reason, and they can solve this also.
Will keep this thread updated as to what happens on that test.
November 25th, 2010, 11:13 PM
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The service writer at the aforementioned dealership has been keeping in touch regards a test drive with a tech. Because of the distance from the dealer to the hilly area where this problem can be shown to occur, he (the tech) will need to be gone from the dealership for probably an hour and a half, at least.
Since the boating season is now over with till next spring, and the urgency of solving the problem is not now as pressing as it was when the boating season was still in full swing, I am trying to work with them so as to have the tech gone from the dealership at a time most convenient for them, so as to be able to have him in the vehicle for a period of time that will allow me to get to that location and spend some time there to make sure he is able to experience the vehicle doing what it does when pulling the trailer in tow mode, as earlier described in this thread. The vehicle is now past the 36K mileage figure regards warranty, but I do not feel that should be a problem as there were several reports made regards the problem as early as 20K on the vehicle.
If the problem will manifest itself now with the tech in the vehicle, I would fully expect GM to take care of the problem. If they would not take care of it now because of past 36K, then the problem will get much bigger, quickly, especially as I have documented this problem quite fully, and I do not consider it my problem when their diagnostic equipment failed to record the events twice, with two different recorders, when it occurred.
The service writer contacted me yesterday and we have a tentative arrangement to do this next week, although I need dry pavement to demonstrate the problem, and we have had rain, snow and some ice the last 24 hours. Hopefully the weather will clear up and allow the test drive next week.
I will update this thread as soon as possible, regards reproducing the problem with the tech, and also what action GM takes to resolve it.
Since the boating season is now over with till next spring, and the urgency of solving the problem is not now as pressing as it was when the boating season was still in full swing, I am trying to work with them so as to have the tech gone from the dealership at a time most convenient for them, so as to be able to have him in the vehicle for a period of time that will allow me to get to that location and spend some time there to make sure he is able to experience the vehicle doing what it does when pulling the trailer in tow mode, as earlier described in this thread. The vehicle is now past the 36K mileage figure regards warranty, but I do not feel that should be a problem as there were several reports made regards the problem as early as 20K on the vehicle.
If the problem will manifest itself now with the tech in the vehicle, I would fully expect GM to take care of the problem. If they would not take care of it now because of past 36K, then the problem will get much bigger, quickly, especially as I have documented this problem quite fully, and I do not consider it my problem when their diagnostic equipment failed to record the events twice, with two different recorders, when it occurred.
The service writer contacted me yesterday and we have a tentative arrangement to do this next week, although I need dry pavement to demonstrate the problem, and we have had rain, snow and some ice the last 24 hours. Hopefully the weather will clear up and allow the test drive next week.
I will update this thread as soon as possible, regards reproducing the problem with the tech, and also what action GM takes to resolve it.