1999 Tahoe Towing

[pedub]

Hi Guys, I'm wondering about towing my small 14 ft alum boat, should I leave the truck in over drive or not? I hear its not good for the tranny but this boat don't weigh much. thanks

 

[Trey Hardy]

Little stuff like that I usually leave mine in drive. Anything with any weight like the dump trailer or car trailer I either put it in tow haul or leave it in third if I’m around town. You’ll know if you need to do it or not because it’ll shift back and fourth trying to keep up to speed and you’ll see your transmission temps raising.

 

[Marky Dissod]

Don't know how much a small 14ft aluminum boat weighs, bet its trailer outweighs the boat by a hell of a lot.
(Would it be more aerodynamically advantageous to your Tahoe to turn the boat around? Nevermind ...)

Think of the 4L60E as a 'light-duty' transmission. No matter how it's rebuilt, its weakest gear will ALWAYS be 4th.
And because GM programmed those shifts to favor MpGs over the 4L60E's longevity ...

Long story short, pretty much what Trey Hardy said. Avoid 4th (especially 4th-unlocked).
If you do not have an ATF gauge, you at least have a coolant temp gauge.
By now, you should know where it normally sits.
If it runs any hotter than normal, you can bet the ATF is also running hot - use Tow / Haul mode or 3rd or both.

Considerably better results would be achieved by reprogramming your shift tables and TCC tables.

 

[Hoesgottaeat2]

I'll be using my '99 Hoe to tow our boat this weekend as well. It's a 17' Starcraft aluminum. The transmission always operates normally without me having to adjust by shifting to a lower gear. As @Trey Hardy alluded to above, a boat that size is really of no cause for concern here.
I've had (3) rigs over the years with the 4L60 transmission and hauled fire wood on our 5x10 trailer. Those loads far outweighed our boat. Never an issue nor did I ever need to compensate by shifting to a lower gear. And the bodies of those rigs rotted off here in NY, but the transmission never failed me one bit.
I do appreciate your concern though. I am the same way. Keeps me out of trouble...most of the time lol.

 

[Larryjb]

The only issue I've ever had with the 4L60 series was a broken sunshell gear (I think it was the sunshell gear anyway). It happened when we switched from D to R without making sure the vehicle came to a complete stop. Now, I ALWAYS make sure the vehicle is completely stopped when changing from D to R and visa versa.

Apart from that, simply to protect the transmission, I always use Tow/Haul anytime I am hooked up to a trailer. I'll use Tow/Haul on long hills even if I am not towing. This also protects the torque converter because it prevents it from locking up.

You can correct me if I am wrong, but I believe Tow/Haul prevents the use of overdrive and the lockup feature of the torque converter.

 

[Fless]

The only issue I've ever had with the 4L60 series was a broken sunshell gear (I think it was the sunshell gear anyway). It happened when we switched from D to R without making sure the vehicle came to a complete stop. Now, I ALWAYS make sure the vehicle is completely stopped when changing from D to R and visa versa.

Apart from that, simply to protect the transmission, I always use Tow/Haul anytime I am hooked up to a trailer. I'll use Tow/Haul on long hills even if I am not towing. This also protects the torque converter because it prevents it from locking up.

You can correct me if I am wrong, but I believe Tow/Haul prevents the use of overdrive and the lockup feature of the torque converter.

Nothing to hurt by using Tow/Haul. In my '04, using T/H DOES NOT prevent 4th gear from engaging, so when towing I drive in 3rd. I enjoy hunting but my tranny doesn't. YMMV

 

[Hoesgottaeat2]

The tow/haul feature isn't/wasn't on any on '99 or older rigs I've owned. Was it even an option in the 90's?

 

[Hoesgottaeat2]

The only issue I've ever had with the 4L60 series was a broken sunshell gear (I think it was the sunshell gear anyway). It happened when we switched from D to R without making sure the vehicle came to a complete stop. Now, I ALWAYS make sure the vehicle is completely stopped when changing from D to R and visa versa...

When I say the same thing happened to us, I mean the SAME EXACT THING happened to us. It happened when my son was still in his "learning curve" stage at 16 after he first got his license. Sunshell gear is what it was called IIRC.

 

[Marky Dissod]

You can correct me if I am wrong, but I believe Tow / Haul prevents the use of overdrive and the lockup feature of the torque converter.

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.

 

[drakon543]

unless the trailer is built like a tank or the truck isn't running very well leaving it in overdrive will be fine. if you find its struggling on hills you can always give it some help when a hills coming up and take it out lf od at that point.

 

[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.