: Towing with 02 Deville



jrb03deville
02-13-12, 06:00 AM
Is it ok to tow in overdrive, it doesn't really say in the manual. I have a 800 lbs pop up and a 1700 lbs boat and I don't use either a lot.

00 Deville
02-13-12, 08:03 AM
I would tow with the shifter in 3.

Ranger
02-13-12, 12:19 PM
Not sure, but I would thing OD is OK for flat and level cruising.

Mark D
02-13-12, 02:02 PM
Most manuals do have a section on towing. Most of those recommend not using OD when towing. On the 800 pound load, you would probably be ok. On the 1700 pound load, I'd say, no matter what the manual might or apparently doesn't say, I wouldn't bet on running OD. It's a gamble with the transmission, and that's an expensive repair. Costly enough that it might make you decide to junk the car rather than repair it. Why risk it for a potential slight increase in mpg?
It also depends on how far you tow when you do tow. And on the gradients. The worst are those that appear flat, like a 1 or 2% grade. The car is working much harder, but the driver doesn't notice it. On steeper grades, the driver usually notices and takes the action of using a lower gear.
Yes, I agree with the first reply. Run it in 3. At least with the heavier load. Your car will appreciate your efforts.

One good clue that can tell you when you're car is being overworked is if it is downshifting a lot, or the torque converter isn't staying locked up. If the converter can't lock, or can't stay locked, that's a clue that you're loading it up pretty hard.
Mark D.

maeng9981
02-13-12, 07:56 PM
800 lbs? OD would do fine. That's about 4 heavy passengers. Probably won't need to do this for a 800 lb load, but do shift into 3rd if you face a uphill. Or when you need engine braking assist.

If weight gets greater than that then there is only one answer. Use 3rd.

Mark D
02-14-12, 02:00 PM
One thing to think about when trying to decide what to tow with what vehicle and how to do it is this:

The weight is not the only factor. Putting 700 or 800 pounds in a car puts much less stess on the drive train than towing an 800 pound trailer with tiny wheels.
The trailer itself creates considerable drag, far more than the weight being pulled. The faster you go, the higher the drag.
Little trailer wheels create more drag than big trailer wheels.
There is aerodynamic drag to consider.
There is poor trailer construction to consider - - - Lots of times wheels are way out of tow, and sometimes caster, to create more drag than they otherwise would. Trailers can be most difficult to drag behind a car.
Still, typically the smaller trailer in the original post probably won't be much of an issue. I'd still keep it in 3 if it were my car. It doesn't hurt anything but gas mileage. Unless you're going downhill with a tailwind.
Mark D.

weister42
02-23-12, 04:26 PM
800 lbs? OD would do fine. That's about 4 heavy passengers. Probably won't need to do this for a 800 lb load, but do shift into 3rd if you face a uphill. Or when you need engine braking assist.

If weight gets greater than that then there is only one answer. Use 3rd.



I've packed eight people in my Deville once and my car did not have any problem accelerating to traffic speed, it stopped and turned just fine although you can feel the the extra 1000+ pounds that you're lugging around. I was in D and on level ground.

pcmcalibrators
02-23-12, 05:59 PM
If the trailer is wired correctly the trans will go into Tow/Haul Mode

If the PCM command Tow/Haul mode what would be the issue with using OD?

00 Deville
02-23-12, 06:20 PM
If the trailer is wired correctly the trans will go into Tow/Haul Mode


If the PCM command Tow/Haul mode what would be the issue with using OD?

AJ,
What exactly goes on inside the PCM when the RIM detects a trailer is attached on cars with the V92 (trailer provisions) option. The 2000 Deville schematics call the RIM input "trailer detect" on the 01 and later the same input is called "transmission shift inhibit signal".

Is TCC lockup inhibited?

Below is a thread on the Deville board where a theory was kicked around concerning this input... thoughts from someone that's lives inside the PCM would be helpful. :worship: (http://www.cadillacforums.com/forums/cadillac-deville-1985-2005-including-1985/239593-p0741-possible-workaround-00-05-deville.html)

http://www.cadillacforums.com/forums/cadillac-deville-1985-2005-including-1985/239593-p0741-possible-workaround-00-05-deville.html

jrb03deville
03-16-12, 10:31 PM
So does the 02 Deville automatically shut off the overdrive when you tow. I didn't see that option code.

00 Deville
03-16-12, 11:26 PM
So does the 02 Deville automatically shut off the overdrive when you tow. I didn't see that option code.

I really doubt that the installer of an aftermarket trailer harness tied the wiring into the RIM to enable the "transmission shift inhibit signal" going into the RIM like a Deville that came from the factory with RPO Code V92 (trailer provisions) has.

Submariner409
03-17-12, 10:10 AM
"overdrive" and TCC are two different things in the 4T80E transmission.

Overdrive is 4th gear - at 0.68:1 ratio. (3rd gear is the direct drive, 1.00:1 ratio)

TCC is Torque Converter Clutch control - that extra feature that removes the last 300 or so rpm of slip in the torque converter at steady highway loads at over 43 mph in 4th gear. Any moderate to aggressive gas pedal application (hills, passing, load) drops out TCC.

jrb03deville
03-21-12, 06:35 PM
Ok it looks like the safest thing to do is run in 3rd and I don't have a problem with that but it seems like its really high Rpms on the highway, at 60 that's about 2500 rmps in 3rd is it ok to go 65-70 in 3rd.