1999 Tahoe Towing

[pedub]

Thanks for all the reply's, I feel Better about towing now, if it goes in and out of OD I will run in 3rd, this boat and trailer don't weigh much, just wanted to see what you Guys thought. Thanks again

 

[Marky Dissod]

... feel better about towing now.
If it goes in and out of OD I will run in 3rd, this boat and trailer don't weigh much ...

Is your axle gear 4.10, 3.73, or 3.42 (or even less)?

4.10, if the engine RpM in 4th is kept OVER 1250RpM, may be okay to be in 4th.
3.73, if the engine RpM in 4th is kept OVER 1500RpM, may be okay to be in 4th.
3.42, if the engine RpM in 4th is kept OVER 1750RpM, may be okay to be in 4th.

 

[drakon543]

ya my 97 towed an 04 f150 (heavier version) for quite a distance with no real problems except for the larger hills.

 

[Larryjb]

It does neither of those things.
Only way to prevent 4th is to use the shifter to do so.

Tow / Haul mode will not use 4th anywhere near as readily or as often as Normal mode, but it will use 4th.
Tow / Haul mode will not lock the TCC as often as Normal mode, but it will lock it - more likely in 3rd than 4th.

When Normal mode prefers 4th, Tow / Haul mode will more likely use 3rd.
When Normal mode prefers 3rd, Tow / Haul mode will more likely use 2nd.

Normal shift mode prioritizes MpGs over drivetrain durability under heavy load, assuming a very light load.
Tow / Haul mode sacrifices MpGs to protect the transmission, assuming a heavy load.

I tried the Tow/Haul mode today, without any load in the back (trailer or cargo). It didn't upshift to 3rd until I was at 60 km/h (that's 40 mph for you guys south of the 49th), and the torque converter did lock up, bringing the rpms to about 1500. Once I got up to 70 km/h (about 40 mph), I couldn't get the torque converter to lock up, and I remained in 3rd. I wasn't on the freeway, so I didn't want to take it up to 80 km/h (50 mph) today. I do recall that it will go into 4th without any load (trailer or weight in the back) at higher speeds.

Overall when using Tow/Haul, it seems to prefer upshifts at around 3000 rpm. On our next camping trip, I'll see how long it prefers to stay in 3rd, whether it will upshift to 4th at 3000 rpm or not. My guess is that as long as you don't exceed 60 mph, the transmission will normally stay in 3rd.

That said, it's probably a good idea to keep the shift lever in 3rd while towing anyway.

 

[Mean_Green]

OK, while we're on this, I have a small tractor, referred to as a SCUT. Bare weight is around 1800 pounds with the filled tires. I do not have a trailer, so would have to rent a U-Haul 5 x 10 or so, maybe a 6 x 12.

I will not have to haul very often, only if it needs to go to the dealer about 80 miles away over mostly flat rural roads, with a few low rolling hills.

Do I have anything to be concerned about?

 

[Marky Dissod]

... anything to be concerned about?

Depends on your axle gear, and how steep the uphills are.
Unless your axle is 4.10 or greater, probably a good idea to keep it out of 4th going uphill.