[Tubablake]

Hi, New Here,

I have a 1997 5.7 K1500 and I'm going to be towing a 5500lbs trailer every weekend for 2.5 months each year.

What does everyone think of towing in OD?
Some say it doesn't allow the clutch? To lockup.
I mostly drive manuals so I'm not too familiar with how a torque converter works.

Help would awesome, Thanks!

 

[99'HEARTBEAT]

This is topic where you will receive a Lot of Opinions, on weather you should Tow in OD or Not.....

For My Truck, When Towing my Boat, I Never Towed in OD......I Always when Towing would be in 3rd Gear.....and the Reason I Tow in 3rd is to Reduce the Surfing and Hunting the Transmission Does when in OD......Its this Surfing and Hunting that Causes Heat, and Heat is the Single Biggest Killer of Auto Transmissions....

 

[Tubablake]

The surfing, could that be a cause of the clutch not locking up?

 

[RayVoy]

I think the clutch will lock up. The surfing (also called hunting) refers to the transmission constantly shifting down, then up, then down again.
The clutch will lock up, but the constant shifting causes it to unlock and relock. This action causes it to overheat.
Most of us use 3rd and even manually downshift to 2nd when the hills are steep.

 

[poncho62]

Like said, tow in 3rd i towing that much weight....I tow a 6000# 5th wheel with mine and use 3rd. I also have an external trans cooler and a temp gauge to keep an eye on things.....Your torque converter will still lock up in 3rd.

 

[Tubablake]

Sounds good to me.
If you were towing in OD on flat and in wasn't hunting would that mean that the clutch is locked up?

 

[RayVoy]

If your rmps are staying around 2000 in OD, the clutch is locked up.

Why do you think you are having problems with your clutch?

 

[Tubablake]

I don't think I am having trouble, I am just worried that towing in OD I screwed the clutch. It runs fine, some of the mountain passes with the trailer I would downshift. I just down want to be climbing down under to replace a torque converter.

 

[RayVoy]

The TQ provides a fluid coupling between the engine and the transmission, the lockup clutch turns that fluid coupling into a mechanical coupling.

The clutch does two things, by removing the fluid coupling, the transmission temps are reduced; and, the engine revs now match the turning rear wheel, improving gas mileage.

The TQ is not usually the part that fails when a transmission overheats.

 

[Tubablake]

Okay, I thought it was all like together in the torque converter. So an automatic still has a clutch plate connecting the tranny and the engine with the pressure plate?

 

[poncho62]

No...a torque converter replaces what a clutch does in a standard transmission....At low RPM, it allows the engine to turn and the trans stay still....as the engine builds speed, the fluid in it causes more resistance so that the trans engages. Once up to speed, there is an electric locking on some transmissions to lock the converter. These transmissions have that...If its switching in and out of lock a lot, that builds heat....If the trans is downshifting gears a lot, that also builds heat.

 

[RayVoy]

No @Tubablake, it is not the same.

Edit: @poncho62 has the answer

 

[Aquila99Sub]

No...a torque converter replaces what a clutch does in a standard transmission....At low RPM, it allows the engine to turn and the trans stay still....as the engine builds speed, the fluid in it causes more resistance so that the trans engages. Once up to speed, there is an electric locking on some transmissions to lock the converter. These transmissions have that...If its switching in and out of lock a lot, that builds heat....If the trans is downshifting gears a lot, that also builds heat.

Very informative - thanks!

 

[Tubablake]

I know we have sort of answered this question, but I'm still a little confused.

If towing in overdrive with the switch on that forces the torque converter to stay locked up, would the transmission be fine? Would heat still build causing a problem?

 

[RayVoy]

To sum it up, if you are going up a hill, downshift to 3rd, real steep,hill, you may need 2nd.
If the road is level, or downhill, use 4th gear. The tq will lock in 3rd, or in 4th.

 

[Tubablake]

Thanks, That's the solid answer I need.

 

[Aquila99Sub]

Trying to understand Black a lil more. Does your Suburban have one of those buttons on the end of the gear stalk that you push to engage or disengage Over Drive? Or any other button that does that? Mine doesn't have that - 1999 K2500.

If it does, then when you disengage the OD, it is my understand that the last, tallest of 5th gear doesn't get used to keep the truck or vehicle in higher RPM ranges which would be ideal for towing - but you should still do what RayVoy stated for hill climbing and such.

 

[99'HEARTBEAT]

The First Year of the Tow/Haul Button"Feature" that is on the Column Shifter was in 1999" ....it Came on the 99" Silverado's and Sierra's 1500 1/2 Ton GMT-800 Platform/Model Trucks......

 

[Tubablake]

Yes I do not believe I can disengage overdrive.

 

[99'HEARTBEAT]

The following Information is on the Working of the Tow/Haul Mode(Button)....Its from the 1999" Silverado Owners Manual Section 4....Page 55

Tow/Haul Mode (If Equipped)
Tow/haul is a feature on automatic transmission equipped vehicles that assists when pulling a heavy trailer or a large or heavy load.

The purpose of the tow/haul mode is to:
....Reduce the frequency and improve the predictability of transmission shifts when pulling a heavy trailer or a large or heavy load.
....Provide the same solid shift feel when pulling a heavy trailer or a large or heavy load as when the vehicle is unloaded.
....Improve control of vehicle speed while requiring less throttle pedal activity when pulling a heavy trailer or a large or heavy load.

Automatic transmission equipped vehicles are provided with a button at the end of the shift lever which when pressed enables tow/haul. When the button is pressed, a light on the instrument panel will illuminate to indicate that tow/haul has been selected.
...Tow/haul may be turned off by pressing the button again, at which time the indicator light on the instrument panel will turn off.
....Tow/haul is designed to be most effective when the vehicle and trailer combined weight is at least 75% of the vehicle’s Gross Combined Weight Rating (GCWR).

Tow/haul is most useful under the following driving conditions:
....When pulling a heavy trailer or a large or heavy load through rolling terrain.
....When pulling a heavy trailer or a large or heavy load in stop and go traffic.
....When pulling a heavy trailer or a large or heavy load in busy parking lots where improved low speed control of the vehicle is desired.

Operating the vehicle in tow/haul when lightly loaded or with no trailer at all will not cause damage. However, there is no benefit to the selection of tow/haul when the vehicle is unloaded. Such a selection when unloaded may result in unpleasant engine and transmission driving characteristics and reduced fuel economy.

Tow/haul is recommended only when pulling a heavy trailer or a large or heavy load.