Tow Haul??

I have a 2006 GMC z71. I am going out of town from fort worth to Arkansas. Is it ok that I drive with the tow haul on, on the highway??? I have only had this truck for 2 months and boat ramp is only 1 mile from storage. This will be my first long haul.

Britt, What Motor is in your z71? I have a 2006 suburban with the 6.0l and it says in the manual that there is no negative effect to using the tow/haul mode. It also states that it has no advantages to using it when not towing. I have pulled my boat over 1000 miles in a week, and usually never use it. I get better gas mileage with out it. I think your Z71 would be fine!!

There is no down side to using the tow haul as far as reliability is concerned, mpg might take a hit though. If your towing much of anything I've found that you need to at least leave it in 3rd. Don't have to use tow haul on the highway unless you're pulling a lot of grades. Tow haul is usefull before (around town) and entering the highway because it provides higher shift points for better acceleration and higher line pressure when it shifts which will help keep the tranny cool. I also think it locks the torque convertor longer. If you let it pull in OD, it will shift down at any grade, then shift back which will heat up the tranny real quick. Heat is the killer of tranny's.

I've got a tranny temp gauge, with it in 3rd with tow haul on, I rarely get over 160 deg. The only time I've gotten close to 200 is pulling a steep grade with the torque converter unlocked and it reached 210 for about 2 min then cooled off.

It has the tow package so I think it has the trans cooler on it. I hate to drive in 3rd and lose the mpg. BUt then again I would hate my tranny to have damage

Britt you will not hurt your tranny unless it's hunting alot. I would only use the tow/haul mode going up a mountain passes or an incline. If your truck starts hunting for gears make sure you push that tow/haul button.

So should I drive in overdrive or 3rd gear?? I am going to be on the highway going about 70mph

Drive in overdrive, when you hit a steep grade or mountain pass then push the tow/haul button and your set. Driving down the freeway I drive without the tow/haul button.

You won't notice for a long time, but it's actually best to tow in 3rd for long hauls. Yes, you'll pay more for gas, but it will save you tons of wear on your transmission. The hunting problem was stated earlier, but even if it's not hunting (which it will, grades or no grades) you're still towing on a very weak gear. Best to keep it in 3rd, keep your oil pressure high and save the tranny. Then again, if you're trading in your truck every couple years, no need to worry about it Keep tow-haul on, it does not affect MPG on the highway at cruise, and it firms up the shifts as well as changing the RPM points.

(Message edited by tonality on July 02, 2007)

Well actually I dont trade in but every 8 years. My last truck didnt have the tow haul and I towed in overdrive. However I got to where i Had to tow in 3rd because it would hunt. Thanks for all the input guys. I really glad we have this site to discuss these issues.

Britt tow with tow/haul mode on in D. Tow/haul mode decreases the shifting of the trans and is supposed to increase line pressure, to help increase transmission longevity.

Drive in D with tow haul on. On the freeway it will shift into 4th on it's own. It basically just holds shifts to a higher rpm. We do it every time we pull the boat and it's a lot of freeway.

I have a Z71 with a 5.3L / 4L60E with a Transgo shift kit and a couple other upgrades, and it will not stay in 4th unless I am going downhill, have a tailwind, or I'm going over about 75 mph on flat ground. I always tow in 3 except for those conditions.

The band on a 4L60E is weak for heavy loads with the stock servo, and it slips more than it should when it shifts under load. It might not be enough to feel or throw a code, but you really want to avoid hunting between 3 and 4 on that tranny. A shift kit won't really help this, either. You can get a heavy duty servo, but it will make the 1-2 shift too hard for most peoples' taste.

Tow/haul does change shift points and increase line pressure. It makes your tranny shift a little harder, which causes less clutch / band wear, less heat, and thus longer life. It has some, but not all, of the benefits of a good shift kit.

Amen on that crappy tranny. SO glad they're upgrading that thing for the 09 lineup.

Of course, if you blow your sun shell or the entire tranny, you can always just drop an 80e in there :P

(Message edited by tonality on July 03, 2007)

Trace, sorry to hear you have had problems with your trans. I have three different light duty truck/suvs and they have all been good. Also, mine seem to always shift into 4th at or around 60mph.

I blew the sun shell reaction gear on my 02 Z71 with only 28k on the truck. Of course, it was only 750 miles after a transmission flush that the service rep swore would alleviate the problem. He is now working in the cashier's cage.

I had the hard 1-2 shift, aka the 'chevy clunk' since day one. I always used t/h mode and we pulled the boat less than a mile to and from the ramp.

I haven't had any problems with the one in my truck. It has 133k on it now, probably 25% of it towing, and has had the shift kit installed since about 50k. I learned a lot about them when the one in my 95 Impala lost 3 and 4 (due only to an improperly peened orifice plug), and I rebuilt it myself.

Actually, I take that back - a shift solenoid went out at about 80k. I should have just replaced them all when I put in the shift kit.

thats the point of the tow haul mode. Use it!

dhcomp - who are you talking to, or what are you saying the point is of T/H mode?

Speaking for myself, I know exactly how it works and what it does, and it could do nothing to prevent the tranny failures I've had. I think it is a great feature, and it will definitely extend the life of the frictions, but a shift kit and not towing in OD is even better.

Based on Trace's input and general towability I use tow/haul and keep it in 3 in my 5.3L Z71 when I tow. Sure I might lose 1mpg or so but it's waay cheaper than a tranny rebuild.

Figure the truck gets 12mph when towing in O/D and 10mph when towing in D3 (extremes), it costs less than $5/100 miles to save your tranny.

There is some serious 4L60E knowledge in this thread:
http://web.camaross.com/forums/showthread.php?t=420697