First time towing with Denali and have a few questions for the forum

mrpep · 07-08-2016, 07:13 PM

I seemed to have towed fairly well I'd D but sometimes the Rpm's would climb up to 4K suddenly, I would drop to 3 gear and no luck , it wasn't until I hit the brake then it would drop. What would cause my rpm to spike from 2500 to 4000 in the blink of an eye??

Sent from my iPhone using Tapatalk

**Mr. Dan** · 07-08-2016, 07:27 PM

Transmission downshifting.

What style of Denali? Sierra, Yukon, Yukon XL, Acadia, Terrain?

mrpep · 07-08-2016, 10:12 PM

Quote:

Originally Posted by Mr. Dan

Transmission downshifting.

What style of Denali? Sierra, Yukon, Yukon XL, Acadia, Terrain?

Yukon , 6.0 v8 , just jumps from 2500 rpm to 4000 rpm Ina blink of an eye .

Sent from my iPhone using Tapatalk

MillerTime · 07-08-2016, 11:09 PM

Quote:

Originally Posted by mrpep

Yukon , 6.0 v8 , just jumps from 2500 rpm to 4000 rpm Ina blink of an eye .

Sent from my iPhone using Tapatalk

What year?
Do you actually notice an increase feel of the rpms reving or do you only see it on the tac?

The mid 2000s GM instrument clusters have stepper motors that wear out. They can have iratic movement and then the needles quit moving eventually.
Hopefully it is this, otherwise you may have a trans or torque convert issue.

asquared · 07-08-2016, 11:23 PM

Was this on flat land, hill or mountain? Did it feel like transmission was slipping or just working harder? How heavy is your trailer?

mrpep · 07-08-2016, 11:52 PM

It was going uphill and it seemed to need to switch gear so the cruise control just went nuts and went full throttle on the RPM's , it was loud and the cluster tac showed 4K.

Sent from my iPhone using Tapatalk

asquared · 07-09-2016, 12:07 AM

Don't use cruise control. The engine will run at higher rpms when going uphill. Do you have a tiw/haul mode button on your Denali? Putting that on while towing will help hold your fears longer before shifting. Depending on the hill grade you will want to downshift for going up and down a hill. Don't be afraid of higher rpms when towing on the hills.

mrpep · 07-09-2016, 12:18 AM

I was using the tow/haul button, so hitting 4K rpm is ok? What about when it seems to hold a high rpm for a while ? And it doesn't seem to switch gear? It feels like that is not normal, sometimes I will switch from D to 3 when I feel this. Sometimes this helps get that gear and sometimes it doesn't. Should I ever use 2??

Sent from my iPhone using Tapatalk

MillerTime · 07-09-2016, 01:06 AM

Quote:

Originally Posted by mrpep

I was using the tow/haul button, so hitting 4K rpm is ok? What about when it seems to hold a high rpm for a while ? And it doesn't seem to switch gear? It feels like that is not normal, sometimes I will switch from D to 3 when I feel this. Sometimes this helps get that gear and sometimes it doesn't. Should I ever use 2??

Sent from my iPhone using Tapatalk

No need to switch to 3rd when its doing that. Its the torque converter working in its lock / lockout mode before dropping a gear.
I will have to look at my escalade tomorrow, but i think those motors are designed to handle 6,000 or so rpms.
If it makes you feel any better my big block boat turns over 4,000 rpms almost the whole time i run it. And many times i am running 4,500-5,000 rpms.
Granted marine engines are designed for that, while vehicle engines are more designed for fuel economy these days.

I dont think I've ever shifted down to 2nd gear, or 3rd even except on the older trucks, like my '88 or '96 chevys i had or an old powerstroke with the tow mode dropping off the OD.

Hearing you explain it, i think your fine. I bought a gas Silverado a month or so ago, and i am really surprised how much it shifts back and forth. My diesels hardly ever downshift.
My Silverado drops down, and revs to 3500-4000+ rpms, empty, not towing, running down the turnpike on rolling hills.

Steve29rlx · 07-09-2016, 01:56 AM

The transmission shifting to a lower gear is what causes the rpm to go up. It is normal for the transmission to down shift when going up a hill while towing. If it stayed in the higher gear it would cause the engine to work harder. Lugging the egine is harder on the truck than 4000 rpm. Engines develop hp at higher rpm. Gas engines develop torgue at higher rpm than diesel.
Go ride a multi gear bicycle on hilly terrain. You will see that in the lower gears you have to pedal faster going up hill to maintain speed, but it takes much less effort than the higher gears. Same thing with you Yukon, rpm might be higher, but it is less strain on your engine.

mrpep · 07-09-2016, 06:38 AM

Got it , thanks guys - just seemed kind of weird cause I didn't get this with my van but then again I am hauling much more weight now Adays.

Sent from my iPhone using Tapatalk

RSchleder · 07-09-2016, 06:49 AM

Your tow vehicle is performing exactly like it should. If it did not shift down to a lower gear which cause's the RPM's to rise, the engine would lug and the transmission would be in the incorrect gear causing excessive heat which is your transmission's worst enemy! Just enjoy and let the electronic "brain" in the transmission do it's thing, it's designed to keep the engine and transmission in sync, don't try to out guess it!

mrpep · 07-09-2016, 07:00 AM

Ok thanks , I actually thought the electronic brain was on drugs when it did this , lol - also, I swear I could see the gas needle drop when it revved that high, lol

Sent from my iPhone using Tapatalk

**Mr. Dan** · 07-09-2016, 07:41 AM

We would still like to know the answer to MillerTime's question: what year is your Yukon Denali?

Those 6.0L engines are known to burn some gas. My son has one in a Yukon Denali. His username on another forum is Gasguzzler!

mrpep · 07-09-2016, 08:45 AM

2003 and when towing I used 7.5 mpg

Sent from my iPhone using Tapatalk

**Mr. Dan** · 07-09-2016, 08:51 AM

Quote:

Originally Posted by mrpep

2003 and when towing I used 7.5 mpg

Sent from my iPhone using Tapatalk

Our son's unit is also a 2003.

MillerTime · 07-09-2016, 09:12 AM

Quote:

Originally Posted by mrpep

2003 and when towing I used 7.5 mpg

Sent from my iPhone using Tapatalk

Quote:

Originally Posted by Mr. Dan

Our son's unit is also a 2003.

I think alot of those Denali's were all-wheel-drive back then. That will contribute to the lessened mpg.

I bought an escalade wrecked a few weeks ago, i think its a 2002 or 2003 with the HO. 6.0. Its Awd and i only drove it around 50 miles home.
The DIC showed it got 14.5 mpg with aftermarket exhaust on it and empty. I did notice it shifting alot, but i thought it was due to reduced back pressure from the aftermarket exhaust . I already have a stock muffler to put back on it to try to regain the back pressure needed to keep it in the torque area a little better w/o shifting all the time.

mrpep · 07-09-2016, 09:42 AM

I get 14.5 in town as well , it's just towing and I just bought this specifically for towing , lol

Sent from my iPhone using Tapatalk

SuicideSaints · 07-09-2016, 11:33 AM

Completely normal! It'll eat gas when it downshifts and holds higher rpms. Seems like it's doing what it's supposed to. Mpgs seem right. Maybe not the best TV but it'll do.

jughrad · 07-09-2016, 02:15 PM

You should actually try to leave it in the high RPM gear the whole time and not let her shift so much. My Denali has a manual shift capability and I leave it in a single gear on hills.

You should have a digital readout of your transmission temperature. You will notice that it stays cooler when you are running higher RPMs.

You need to keep that transmission temperature below 200 degrees. With lower RPMs you are probably not getting a full converter lock on your transmission and the clutch may slip under load.

That 6.0 L engine is designed to operate at 4000 RPM with no problem. Your transmission is not capable of operating above 200 degrees without damage.

You may also like: