6TH Gear OK?

[RStiles]

I own a 2008 quad cab, 4X4, SRW, 6. 7, 6 speed automatic with 4. 10 gears. I plan to replace my 35' 5TH wheel toy hauler with a bigger one with 3 slide outs that weighs about 16,500 pounds loaded and ready to go. Should I refrain form using 6TH gear? The truck has about 12,500 miles on it and about 11,500 miles hauling my current toy hauler. It tows this camper just fine in 6TH at 65 mph. Should I not be using 6TH? Thanks Rick

 

[Jumbo Jet]

I have 3. 73 gears and had a combined load of 17,000 lbs. yesterday. At 65 MPH in 6th, I was at 1600 RPM. Truck pulls much better at 70 MPH in 6th. In 5th, I am at 2100 RPM and it takes a real hill to slow me down.

One other thing I watch are my gauges. In 6th EGT's and boost are higher - which typically means I am burning more fuel.

What are your RPMs in 5th and 6th at 65 mph?

 

[DGamelin]

Listen to your trans if it starts growling, down shift. You know what I mean that sound that says hay lazy bones shift me. I just had to rebuild my NV5600 because I had a S. J. in it and it had the power to hold 6th. Your trans is geared better then mine for towing and 410s help's. I use 6th all the time just shift when you have to. When you run out of places to go, hall that toy box to the U. P. of MI so we can play with too. Great trails up here.



______________________

93 250 2wd 354 auto 267k

04. 5 3500 4wd cc dully 373 6speed 90k

 

[Hoefler]

If it is not hunting gears, ( shifting in and out of 6th) run it. I have 3. 73s and pull a 39' fifth wheel weighing around 16K, average 9. 4 mpg over 3300 miles. A good portion on interstate running 75 mph.

 

[RStiles]

At 65 MPH the tach is indicating approximately 1800 RPM. So it is running about 200 RPM more than the 3. 73, I was wondering what the difference was. I find that I click it down to 5TH before the computer does it because of the feel. Using 5TH at 65 MPH feels like the engine is screaming but it is using very little throtel. I'll be towing in a couple weeks and I'll check the RPM in 5TH. My fuel mileage towing runs from 9 to 11 MPG. In case you didn't know, here in Wyoming, what ever direction you plan to go it will give you a head wind. Thanks for the input. Rick

 

[Hoefler]

Here in the Ozarks, every where is up hill. I tow a loaded 16' enclosed trailer 95% of the time for work, I run 5th all the time. I don't even try 6th until I get above 60mph or on flat ground. With my 5th wheel, I don't us 6th until I am on the interstate over 65mph.

 

[6speed]

I don't know what the automatics are running for temp, but I have a 6sp with a temp gauge and if I try to run 6th with the 16ft I had, it gets extremely hot 220-240. I now pull a 46 ft gooseneck and only pull in 5th, but I also have a Gear Vendors, which helps tremendously. Now even in the hottest of days here in Ga, it only runs about 180-190. I weigh in about 27 plus. Nut when I am not towing the Gear Vendors has given me about 24. 5 to the gallon and thats hand calculated. I prefer not to tow in 6th just because of the heat it generates.

 

[Hoefler]

Cruising the interstate at 75 mph, my temps run around 190*

 

[Simplysmn]

I have never had a problem pulling load's in 6th gear biggest so far has been 25,500 and it came up the mountain passes with ease . I would say watch or listen to engine and if it's luggin down shift but if not leave it alone . Mine is also 410's

 

[imaybail]

I don't know if you are running any type of EGT gauge or not, but you will find that the EGT's run quite a bit hotter with lower rpms and more throttle than with higher rpms and less throttle. That is an important consideration as well as the load on the transmission.

 

[FPettijohn]

Hey everybody, remember these are DIESELS that means they like to be lugged! Unlike a gas motor the hotter they run (within reason) the better the fuel burns and the better the mileage plus the cleaner the dpf is. My truck with 16,000 toyhauler behind is about 5mph slow on the down shift in tow/haul on steep grades. I set the cruise on 67 because of the Goodyear g rated are only good for 70mph at 120psi. She never shifts down on anything under 3% and usually only loses 2mph. I see 1000 to 1100 egt. s on a really hot day and the trans will go from 150 to 170, all numbers I consider safe.

Fred