: What speed does your DTS shift into D/OD?



billdaman
04-01-13, 07:24 PM
I just noticed today that my DTS will only shift into D/OD at speeds in excess of 42 MPH. It doesn't matter if I let off the gas or maintain speed. I need to hit / maintain at least 42 before it shifts into D. Once it hits D it will stay there unless I slow dramatically, or accelerate enough to make it downshift.

My other 2 GM vehicles (Avalanche and Envoy) shift into D/OD much sooner, as early as 25 mph if I pull off the throttle.

Anyone else see a different speed to go into D on their DTS?

Superjim
04-01-13, 07:47 PM
Mine USED TO shift at 41....
From what I have read... that is normal for the DTS.

I reset mine to shift into 4th at 36mph AND have the torque converter also lock up at 36.
I like it a lot better that way.

MoistCabbage
04-01-13, 08:01 PM
Shift points are dynamic, there is no 1 speed at which each gear change occurs.

billdaman
04-01-13, 08:16 PM
Shift points are dynamic, there is no 1 speed at which each gear change occurs.

That's what I thought until this weekend, but its not dynamic in my vehicle in "Normal" driving, 40 deg temperatures , car loaded or unloaded it is consistent. I tried at least 20 times and couldn't get it to shift before 42 mph

Superjim
04-01-13, 08:16 PM
The specs in the Transmission Control Module control the MINIMUM SPEED that it will shift...

billdaman
04-01-13, 08:17 PM
Mine USED TO shift at 41....
From what I have read... that is normal for the DTS.

I reset mine to shift into 4th at 36mph AND have the torque converter also lock up at 36.
I like it a lot better that way.

Jim, I need that shift profile in my DTS!

Superjim
04-01-13, 08:22 PM
Jim, I need that shift profile in my DTS!

The TCM can be reprogrammed at any "GOOD" speed shop that uses EFI Live or HP Tuners software.

danog
04-01-13, 09:18 PM
Shift Speed




Hydra-Matic 4T80-E Shift Speed Chart









1–2 Shift@ +/− 3 mph



2–3 Shift @ +/− 4 mph



3–4 Shift@ +/− 5 mph



4-3 Coast Down shift @ +/− 4 mph



3-2 Coast Down shift @ +/− 4 mph



2-1 Coast Down shift @ +/− 4 mph



VCC Apply 4th Gear





% of TPS



10



25



50



10



25



50



10



25



50





Model



Series

















AAN



K



8



18



37



14



34



68



23



55



112



35



16



7



42





MLN



K



7



15



33



12



28



56



18



45



93



35



14



6



36

tightwad
04-02-13, 02:09 PM
mine is the same as bildaman's. shifts into O/D at 42 mph. Letting completely off the throttle at any speed below 42 will not get it to upshift. I think it's programmed that way so it won't lug. Local traffic around here runs about 38 - 40 mph, so it's frustrating to be driving in third all the time. I was hoping Jim would tell us how his tune job affected this. Now I know it can be fixed, I'll just have to pry open my wallet and get it done.

Submariner409
04-02-13, 03:39 PM
O/D is 4th gear - it's about a 0.68:1 ratio. 3rd is the 1.00:1 gear. TCC (Torque Converter Clutch) drops out that last 300 or so of rpm slip above 42 mph or so. TCC/VCC is the fuel mileage - emissions bugaboo that afflicts so many earlier 4T80E transmissions, either through a P 0741 (TCC stuck off) or P 1860 (TCC solenoid or circuit) fault. Two successive start-run-drive cycles during which either code sets and you get a SES light and the car will fail emissions.

Get to a road on which you can easily run at 45 - 50 mph. TCC/VCC engaged. Holding speed with your right foot, lightly touch the brake pedal with your left - TCC should drop out and engine rpm increase by about 300. Take your left foot away from the brake pedal and TCC once again engages. TCC also drops out at some throttle opening that requires more than a tad of power increase. When you have your gas pedal foot stuck through the firewall for max acceleration TCC will NEVER engage.

Superjim
04-02-13, 06:04 PM
mine is the same as bildaman's. shifts into O/D at 42 mph. Letting completely off the throttle at any speed below 42 will not get it to upshift. I think it's programmed that way so it won't lug. Local traffic around here runs about 38 - 40 mph, so it's frustrating to be driving in third all the time. I was hoping Jim would tell us how his tune job affected this. Now I know it can be fixed, I'll just have to pry open my wallet and get it done.

When I had it changed from 42 mph to 36 mph... I liked it SO MUCH better... :)
It made a big difference to the overall feel of the car when you are only going around 40.
If you are using real light throttle, the TCC will also engage after a few seconds.
If you start giving it a little gas the TCC will unlock... if you give it MORE gas it smoothly goes back to 3rd gear... then as soon as you ease up on the gas, it shifts back to 4th and the TCC locks up again.

I have driven loaners when mine was being serviced...
I was always glad to get my car back.
In my opinion, all of them should be set to go to 4th gear at a lower speed than 42.

Jim

Submariner409
04-02-13, 06:50 PM
The kicker is that the Northstar is a little engine that needs RPM to develop power. The TCC engagement speed was developed to be a "happy medium" between RPM drop (fuel savings) and RPM operating range (power band).

Remember - this puppy is a tad smaller than a 1964 Chevy 283 !

stormnn
04-02-13, 07:39 PM
My 06 shifts at 42 under light throttle. what's wrong with it staying in 3rd below that speed? Makes it more responsive.
Norm

Dadillac
04-02-13, 08:19 PM
My '08 Performance shifts into OD, while under very light throttle, at 38 mph.

Don

Superjim
04-02-13, 10:18 PM
The kicker is that the Northstar is a little engine that needs RPM to develop power. The TCC engagement speed was developed to be a "happy medium" between RPM drop (fuel savings) and RPM operating range (power band).

Remember - this puppy is a tad smaller than a 1964 Chevy 283 !

At 36 if I stand on it, it INSTANTLY drops all the way back to 1st gear and is at about 4000 RPM...
Mine doesn't have the PAUSE/HESITATION that most of them have when changing gears.
The pause and accompanying timing retard to make it shift smooth along with the 1/2 second shift times have been eliminated on my car.

I reckon it's just a personal thing... I just like it to shift earlier if I am not in a hurry.
If I AM in a hurry... it doesn't shift from 1st to 2nd till 7000 RPM.
Then I want it to shift FAST, from one gear to the next.

TulsaVic
04-03-13, 10:41 AM
Light load I can get it to upshift at about 39. Otherwise, steady throttle, it does it at 43 - 45.

Submariner409
04-03-13, 01:34 PM
Here are the later "DTS" transmission ratios - 3 is D, 4 is OD. TCC is not a gear - it is a viscous clutch that removes most of the 4th gear slip between the TC stator and rotor.

1 = 2.96
2 = 1.63
3 = 1.00
4 = 0.68 (OD)

You need to find your model/option final drive ratio - most were the economy/cruise 3.11:1. There are speed-rpm tables, TCC engaged above 43 mph, in my albums.

danog
04-03-13, 10:26 PM
Transmission General Specifications (4T80-E)





RPO Codes

MH1



Production Location

Willow Run, Ypsilanti, MI



Vehicle Platform, Engine/Transmission, Usage

H, Ksp



Transmission Drive

Transverse Mounted Front Wheel Drive



1st Gear Ratio

2.960:1



2nd Gear Ratio

1.626:1



3rd Gear Ratio

1.000:1



4th Gear Ratio

0.681:1



Reverse

2.130:1



Torque Converter Size, Diameter of Torque Converter Turbine

265 mm



Pressure Taps

Line Pressure



Transmission Fluid Type

DEXRON® VI



Transmission Fluid Capacity, Approximate

Bottom Pan Removal: 7.0 L (7.4 qts)
Complete Overhaul: 12.0 L (12.6 qts)
Dry: 14.2 L (15.0 qts)



Transmission Type: 4

Four Forward Gears



Transmission Type: T

Transverse Mount



Transmission Type: 80

Product Series



Transmission Type: E

Electronic Controls



Chain Ratios, Designates Number of Teeth on the Drive/Driven Sprockets

39/39



Final Drive Ratios

3.11, 3.71



Position Quadrant

P, R, N, X, 3, 2, 1



Case Material

Die Cast Aluminum



Transmission Weight Dry

121 kg (266.75 lbs)



Transmission Weight Wet

133 kg (293.21 lbs)



Maximum Trailer Towing Capacity

1 361 kg (3,000 lbs)



Maximum Gross Vehicle Weight (GVW)

3 084 kg (6,800 lbs)