Lots of TV Downshifting

[KYCAMPER]

Just took out our new 27DSRL and towing with 2012 Silverado 1500 5.3l w/3.42 rear end. TT weight as delivered was about 6000 lb. Towing down a fairly level hwy with some slight hills at 60mph in tow/haul the TV seems to downshift a lot. I have never towed before except for an 1800lb pop up. Downshifting is annoying. TV is rated to tow 9700lbs. Anyone else with similar TV & TT notice the same? DW thinks I need a bigger TV (I find it hard to argue that!)

[Crabman]

Have you tried shifting out of overdrive? With my 4 speed transmission I just switch to 3rd gear if the transmission is hunting for the right gear against a stiff headwind or in hills.

[Rustic Eagle]

Unfortunately the 3.42 gear isn't helping under towing conditions, the 3.42 gear is great for the highways under a no-load condition. I think you will find that most folks prefer the 3.73 gear with the 5.3L for towing.

If you find the transmission hunting for a lower gear often, then like "Crabman" mentioned you need to be in a lower gear otherwise you will find your transmission heating up.

If you get a chance, a visit to a CAT scale will tell you how you stand with your weights, and confirm that your WDH is adjusted correctly. If you find that your at your TV's weight limits (GVWR), this will also factor in to how the transmission behaves.

CAT scale how to: http://www.jaycoowners.com/forums/showthread.php?t=3871

Bob

[vboyd]

Originally Posted by rustic eagle

unfortunately the 3.42 gear isn't helping under towing conditions, the 3.42 gear is great for the highways under a no-load condition. I think you will find that most folks prefer the 3.73 gear with the 5.3l for towing.

x 2.

[owenssailor]

We have the same truck and our trailer weighs 6600 lb loaded. We had no issues towing - last winter went from ON to CA. There were some good grades. Most of the time the truck was in 5th at around 200 RPM. On long grades it would shift down and the engine would rev up to 3500 or very occasionally higher. You could certainly hear the engine then but those RPM's are not a problem for the motor. We did not experience the transmission hunting for gears.

The engine braking worked as it was supposed to on long steep down grades. The transmission will shift down to hold the speed.

I never used the Manual function for the tranny - just tow/haul.

The trucks with the 3.42 6 spd have a better selection of ratios the the older 3.73 4 spd (had one of those).

No question a 2500 D/A would run at lower RPM's and shift down less. If your wife wants one go for it but what you have should work fine based on our experience.

[Flyrotor]

Honestly I had a 23 foot trailer and a Chevy suburban with a similar setup as yours and frankly it didn't pull good at all, just as you are describing, I finally gave up on the half ton chassis and bought a diesel. Of course then it was like riding in a parade so I had to upgrade the trailer too...

[clutch]

As mentioned, keep it out of OD and start shopping. You may not need a diesel but a 3/4 ton with a bigger engine and different differential gears will make towing a lot easier.

[gudde1251]

Are you using the tow/haul mode? Another option is to give Blackbear Performance a call. Justin can customize your shift points for your vehicle and adjust the engine/transmission to work together more efficiently. Cheaper than a new truck. But hey, If the wife says you should buy a new truck, who can argue with that? Gotta keep her happy!

[Camper_bob]

Yeah, if DW is greenlighting a new truck, that's where I would go. I LOVE my truck, but for what I want to do in the long-run, I need a bit more. For my setup, it's JUST enough truck, I don't have much margin.

I have the same truck as you (Sierra) and I tow a 28BHBE that weighs about 7500 lbs loaded for a trip. On flat even terrain, I can just drop it into drive, hit the T/H button and I'm good to go. It'll chug along 60 MPH in 5th gear at about 2K RPM.

HOWEVER, when I get into rolling terrain, it likes to shift down to 4 at the slightest hint of a grade, and sometimes 3 on the steeper grades. This past weekend I was towing and fiddling with things and discovered that I can drop the tranny into M4 with T/H engaged and tow at about 60-65 MPH and 3K on the Tac. The motor makes a bit of noise, but like you said, those revs won't hurt anything with this motor, and the transmission hardly shifted after that. The truck and transmission seemed to do REALLY well at this speed in M4. I just pushed the pedal a little to pick up some speed in the down hill to compensate for the bleed-off in the uphill.

Good luck with whatever you decide!

[Plowtoy]

The BIL tows a 24 foot Terry Expo ('98) with a Durango with a 4.7L and 3.42's. He always tows in OD (although I advise against it, he says it hardly ever gets into OD). He says on steeper grades, it downshifts into 2nd.
What I have found works for me with the Tahoe and 31 footer (or really any RV I have towed with it) is put trans in manual 3, tow/haul on (except in city traffic) and cruise control off. If I keep my foot on the gas, I can control when I want it to downshift. I normally just allow the truck to slow while climbing a grade, rather than have the trans downshift. If I get below 40-45mph, I will let it downshift to get me back up to speed, I just hate raising the RPM's over 3000 for any length of time with a high milage engine.

[jenoble99]

The 5.3 power band is a bit higher in the rpm range. It is just getting where it wants to be. It is annoying at first but you get used to it. Any gas engine will do the same when towing, be it a half ton or 1 ton. I just turn the radio up.

[clutch]

Originally Posted by jenoble99

The 5.3 power band is a bit higher in the rpm range. It is just getting where it wants to be. It is annoying at first but you get used to it. Any gas engine will do the same when towing, be it a half ton or 1 ton. I just turn the radio up.

I agree. The torque curve on a gas engine is somewhere above 3k rpm. Look up a dyno chart for small block GM's and see where the power is made.

[etex211]

All of that downshifting generates lots of heat, which we all know is the enemy of automatic transmissions. Most half ton trucks aren't equipped to deal with that excessive heat.

I learned my lesson 20 years ago. I burnt up a 700R4 in my '92 Chevy half ton truck because of all of the gear shifting towing a trailer on the highway. Luckily for me, the dealer replaced the transmission under warranty.

Anytime I tow any trailer with a half ton truck now, I take it out of overdrive and put it into whichever gear is 1:1. That's third gear for most any four speed automatic.

[DocBrown]

Yes, its rated for 9700#. A 9700# boat or flatbed trailer. You are towing a brick and are probably at the upper most limit for a travel trailer and that truck. 6000# delivered is more like 7000+ when loaded. In theory you should be fine, but obviously it's shifting more than is good...

You have the 6 speed. I believe t/h mode locks out 5th and 6th. But just for grins, put it into 4 when towing. You are using t/h mode, right?

Originally Posted by Rustic Eagle

Unfortunately the 3.42 gear isn't helping under towing conditions, the 3.42 gear is great for the highways under a no-load condition. I think you will find that most folks prefer the 3.73 gear with the 5.3L for towing.

I just looked at the 2012 manual. The 3:73 were not offered with the 5.3 in 2012. Only 3:08 and 3:42. The 3:73 were only available with the 6.0. I think this was a move to improve CAFE numbers for the truck fleet. This was also done after they added the 6 speed. My '08 has 3:73 gears, but only the 4 speed 4L60E. It doesn't break a sweat but then I'm towing just under 5k lbs.

[Camper_bob]

Originally Posted by DocBrown

You have the 6 speed. I believe t/h mode locks out 5th and 6th. But just for grins, put it into 4 when towing. You are using t/h mode, right?

t/h only locks out 6th. If you drop the lever to D with the t/h activated, it will go to 5th and spin at about 2K at about 60 mph on flat terrain or with a tail wind. But the slightest grade or breath of headwind, and it drops to 4th. 4th is where it's really happiest at 60-65 mph if there is any terrain or a headwind. In M4 with t/h activated, it takes a pretty good grade to get it to downshift to 3rd. I usually will just lean into the pedal a little before a hill I know will cause a downshift, build up a little speed and let it bleed off going up the grade, (or I'll cancel CC and let it drop to 45 mph and 3rd gear if it's a really long or steep grade). That usually keeps it from shifting at all. If you drop it to M4 and activate t/h, that's where it's happiest when towing this much load.

Then when I get back into the coastal plains where hills are nothing but a distant memory, I pull it back up into D and let it chug along in 5th at around 60 mph and 2K on the tac.

I watch the tranny temp pretty closely; last trip out it peaked at 196. After I dropped to M4, the temp dropped 20 degrees in pretty short order.

[DocBrown]

Originally Posted by Camper_bob

t/h only locks out 6th. If you drop the lever to D with the t/h activated, it will go to 5th and spin at about 2K at about 60 mph on flat terrain or with a tail wind. But the slightest grade or breath of headwind, and it drops to 4th. 4th is where it's really happiest at 60-65 mph if there is any terrain or a headwind. In M4 with t/h activated, it takes a pretty good grade to get it to downshift to 3rd. I usually will just lean into the pedal a little before a hill I know will cause a downshift, build up a little speed and let it bleed off going up the grade, (or I'll cancel CC and let it drop to 45 mph and 3rd gear if it's a really long or steep grade). That usually keeps it from shifting at all. If you drop it to M4 and activate t/h, that's where it's happiest when towing this much load.

Then when I get back into the coastal plains where hills are nothing but a distant memory, I pull it back up into D and let it chug along in 5th at around 60 mph and 2K on the tac.

I watch the tranny temp pretty closely; last trip out it peaked at 196. After I dropped to M4, the temp dropped 20 degrees in pretty short order.

Good to know Bob! I follow a similar procedure with the 4 speeds I've owned. Hopefully the OP can get back to us and let us know how he's towing.

[JeepGuy]

If you really like your truck and dont want to get a differnt one you could always look into changeing axle gear ratio, i know for my jeep it was around $1100 installed for gears, master install kit and labor, you rtruck would prob be more due to more labor of its ifs front end but its always a option