Traverse Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
I have had my 2009 Traverse for about 10 months (16k miles). After 3 trips back to my service dept for an engine light....which seems now to be fixed I have noticed a strange up and down of my RPM's.

At any speed above 40 or 45 mph (1600 or 1700 rpm's) if I hit the gas enough to raise my rpm's to about 2500 and then take my foot OFF the gas and in a sense coast, my rpm's will drop all the way down to 800 or 900 while my speed stays the same. The tach will not go back up until I touch the gas.

I can be driving at 65 MPH with my tach under 1000 rpm's in this environment.

Has anyone else had similar issues or has noticed the same?

The strange part in all of this is that if you don't look at the tach you won't feel anything different. Its the visual aspect of going 65 and having the rpm's look as if you you are stopped at a traffic light that tends to be uncomfortable.

Any comments or thoughts will help.
 

·
Registered
Joined
·
80 Posts
jerseyshore said:
I have had my 2009 Traverse for about 10 months (16k miles). After 3 trips back to my service dept for an engine light....which seems now to be fixed I have noticed a strange up and down of my RPM's.

At any speed above 40 or 45 mph (1600 or 1700 rpm's) if I hit the gas enough to raise my rpm's to about 2500 and then take my foot OFF the gas and in a sense coast, my rpm's will drop all the way down to 800 or 900 while my speed stays the same. The tach will not go back up until I touch the gas.

I can be driving at 65 MPH with my tach under 1000 rpm's in this environment.

Has anyone else had similar issues or has noticed the same?

The strange part in all of this is that if you don't look at the tach you won't feel anything different. Its the visual aspect of going 65 and having the rpm's look as if you you are stopped at a traffic light that tends to be uncomfortable.

Any comments or thoughts will help.
Are you saying you can be going 65 w/ your foot on the gas pedal and your tach will read only 1k or do you have to leave your foot off.
 

·
Registered
Joined
·
2 Posts
Discussion Starter #4
Thanks for your question.....

In general after hitting the gas and thus rasing my rpm's to 2500, if I then take my foot off the gas and coast, my rpm's will drop down to below 1000 and stay there until .........I either once again step on the gas or I start to slow down and the vehicle needs to down shift.

On my way into my office this morning, on a slight downgrade I popped the rpm's and then got off the gas. From there I watched the tach drop down to the 900 level and stay there for a good ten seconds while my speed stayed above 60 mph. Once I hit a slight incline and my speed dropped slightly my rpm's bounced back to about 1800 and stayed there as I once again got back on the gas.

Looks strange but the ride and shift feel 100% normal.

Not sure at this point what to do.
 

·
Registered
Joined
·
11,417 Posts
maybe hook up a scanner- and see what the OBD port is showing for RPMs...

Could be a bad stepper motor????

But at 60-- I think the lowest I see is maybe 1500.... ill double check.
 

·
Super Moderator
Joined
·
2,043 Posts
I haven't checked mine, but isn't that normal? The torque converter is unlocked, therefore the rpms drop down to idle levels.

If the torque converter were locked, the rmps would hold.

Maybe I'm missing the question here?
 

·
Registered
Joined
·
994 Posts
Quantum said:
I haven't checked mine, but isn't that normal? The torque converter is unlocked, therefore the rpms drop down to idle levels.
+1?

If I understand the topic of this thread correctly i.e.simply put: foot off gas causes rpm to drop dramatically regardless of the gear it is in then I think I can say that this behaviour is shared by my Traverse.
 

·
Registered
Joined
·
11,417 Posts
I think the problem is that hes going above 65-- and hes under 1000 rpm.....

Ill have to try it at 40-45 and seeing if I can get below 1000.... but hes saying that he can then get up to 65-- and its still under 1000...

I tried 60-65- lowest RPM's I could get was about 1400.... quickly glancing.
 

·
Registered
Joined
·
1,880 Posts
rbarrios said:
I think the problem is that hes going above 65-- and hes under 1000 rpm.....

Ill have to try it at 40-45 and seeing if I can get below 1000.... but hes saying that he can then get up to 65-- and its still under 1000...

I tried 60-65- lowest RPM's I could get was about 1400.... quickly glancing.
Well, I tried it today.

I was going down a slight grade ....enough of a grade to coast. Cruise was off, speed was 60 MPH going down the grade. After coasting for approximately 2000 feet, the RPM settled down to 800 RPM ...in gear, and, as soon as I touched the gas to maintain 60 MPH, tach went back to 1500 /1600 RPM.

Bob
 

·
Super Moderator
Joined
·
2,043 Posts
Yes, I still consider this to be the normal operation of the transmission/torque converter unlocking. My dad's F-350 does this too. If you are driving 60MPH and let off the gas, it holds the rpms as you slow down, but if you tap the brake pedal, the torque converter unlocks and the rpms drop down to 600.

I think the Traverse does the same, minus the brake pedal tap. Probably a fuel mileage thing.
 

·
Super Moderator
Joined
·
2,043 Posts
jerseyshore said:
At any speed above 40 or 45 mph (1600 or 1700 rpm's) if I hit the gas enough to raise my rpm's to about 2500 and then take my foot OFF the gas and in a sense coast, my rpm's will drop all the way down to 800 or 900 while my speed stays the same. The tach will not go back up until I touch the gas.
Ok I tried this tonight on a highway trip. The sentence above that you wrote is the key! At 40-45MPH the torque converter is not locked, so if you let your foot off the gas, the RPM's drop to 800. Mine does this too. The reason you know that the torque converter is not locked is because if you press the gas pedal, the RPM's jump up faster than the vehicle speeds up. Example of converter unlocked: if you are doing 40MPH at 1500RPM, you can step on it, the RPMs will jump up to say 2500 even though you are still doing 40MPH.

At 65MPH if you keep a steady speed, your torque converter is locked. This means if you let off the gas pedal, the RPMs will still be maintained. They will drop SLOWLY as your speed drops. Example, if you are doing 65MPH, your RPMs are around 1700 or so, if you let off the gas, the RPMs drop IN PROPORTION to engine speed. . . so 60MPH 1500, 55MPH 1400 (or whatever I'm just picking numbers), but it won't drop to 800 until the torque converter unlocks.

So long story short, you vehicle is operating correctly.
 

·
Registered
Joined
·
1,880 Posts
On a transmission equipped with a "converter lockup" feature,the lock up would occur and the engine RPM's would DROP, thereby creating an overdrive situation. Lower RPM's=better fuel mileage. When the brake pedal was touched, or if the accelerator was depressed a pre determined amount, the lock up would disengage, the RPM's would then rise. "Overdrive" was then disengaged, so to speak. Only real problem I saw with this arrangement was the lock up solenoid would sometimes fail .... causing the converter to stay in the locked mode, causing the engine to stall out when stopping the vehicle. It could be compared to stopping a stick shift car, without depressing the clutch. It would buck, kick, then stall.

The Traverse has a "new era" 6L80 6 speed transmission, gear ratios for each gear are close to one another, so peak performance can be achieved without excessive RPM's and fuel consumption through the shift pattern. I believe 6th gear has an 0.56 ratio or a number close to it, the modern day "overdrive".

If you a descending a grade, with cruise OFF, and touching the brake, the transmission will downshift to the next lowest suitable gear, to maintain constant vehicle speed, i.e., trans going from 6th to 5th gear.

If the cruise is engaged and you are descending a grade, the transmission will downshift, on its own, to the next lowest suitable gear, to maintain constant vehicle speed ...... thereby not creating a "runaway" situation as you descend a grade, in either scenario.

Bob
 
1 - 12 of 12 Posts
Top