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Open Roads Forum  >  Travel Trailers  >  General Q&A

 > GM 6.2L 420hp and 10-speed

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APT

SE Michigan

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Posted: 11/13/20 09:26am Link  |  Quote  |  Print  |  Notify Moderator

jfortenbery wrote:

On long hills (or should i say slight upgrades), it would shift (in tow mode) from 6th (2,300 rpm) straight to 4th gear (3,800 rpm) skipping 5th altogether. AND, a GM V-8 just don't sound happy to me at 3,800 rpm. This was a Silverado w/ max towing pkg and 3.42 gearing.



2300rpm sounds like 5th gear to me. That 5.3L can sing all day long at 3800rpm for 300k miles. [emoticon] I have same trans, 3.73 gears though. 5th gear for me is about 2200-2500rpm at 65-72mph. One gear downshift is 2900-3300rpm. So I think your trans is going 5th to 3rd gears. This is very typical of our engines/trailer combos for nearly any hill larger than an overpass. I would recommend locking out 5th and 6th gears for your old combo. Keep it close to 3000rpm the time so it dos not need to downshift as often.

The 6.2L/10-spd with smaller gear spacing would do better. However, if you lose the same amount of speed in the new 8th gear, the trans will still skip a couple gears get that engine up to 3500-3800rpm to hold your desired speed. So you should pay attention to how often the trans shifts even with new truck. Start to limit the top gears. I recommend targeting 2500-3000rpm for flat highway cruising with any naturally aspirated engine. And that 6.2L will also live 300kmiles at 3800rpm.

marpel, The 5.3L and 6.2L both have AFM. I'm not hearing of issues with it in the last 10 years. Look up used 5.3L/6.0/6.2L GM trucks with >200k miles. I bet you find a lot.


A & A parents of DD 2005, DS1 2007, DS2 2009
2011 Suburban 2500 6.0L 3.73 pulling 2011 Heartland North Trail 28BRS
2017 Subaru Outback 3.6R

Grit dog

Black Diamond, WA

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Posted: 11/13/20 10:18am Link  |  Quote  |  Print  |  Notify Moderator

3800 rpms is child’s play for any LS motor.
He!! They don’t make real power until 4000 anyways.

I too have a lot of 4000-5000 rpm hours on LS powered trucks. Not an issue.


"Yes Sir, Oct 10 1888, Those poor school children froze to death in their tracks. They did not even find them until Spring. Especially hard hit were the ones who had to trek uphill to school both ways, with no shoes." -Bert A.

jfortenbery

Cincinnati Area

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Posted: 11/13/20 01:59pm Link  |  Quote  |  Print  |  Notify Moderator

The data tells me it'll be a decent improvement, but data don't always tell the whole story. What I never liked about my 5.3/6speed was mainly the transmission. On long hills (or should i say slight upgrades), it would shift (in tow mode) from 6th (2,300 rpm) straight to 4th gear (3,800 rpm) skipping 5th altogether. AND, a GM V-8 just don't sound happy to me at 3,800 rpm. This was a Silverado w/ max towing pkg and 3.42 gearing.

BTW, I'm pulling a 32ft Outback 280KRS at about 8,000 lbs. I hope this new combo (and 460 ft/lb torque) will ease on down the road - or up the hills - a bit easier.

dakonthemountain

Crestline, California

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Posted: 11/13/20 10:19pm Link  |  Quote  |  Print  |  Notify Moderator

I'll pipe in! My numbers here are general as I don't have my files with me, but it gives you an idea of just what a "half ton" is capable of with the proper equipment. Yes, it was pricey, but I dreamed of a truck like this my entire life, so I was ready for the price with ALL the bells and whistles! As a point of reference, I've been RVing since 1987, with fiftwheels, travel trailers, campers, duallys, etc., and full timed for 9 years in a 30' pull trailer with a single axle one ton truck and then a 36' full wall slider fiver with a GMC extended cab dually.
I purchased my 2018 Sierra Denali, with the Denali Extreme package new in March 0f 2018.It has a 6.2V8 8/4 with 8 speed auto transmission. Empty I average 21.5 MPG. Fully loaded with full tanks and gear, towing, 13MPG. I pull an EVO T2050, dual slide 23' travel trailer (25'11" bumper to hitch) with a max weight of 7,900lbs. I have weighed the rig but I don't remember the exact weight, but it's under the mfg. rating and quite a bit below the trucks tow capacity. The tow rating of my truck is over 9,000 lbs with the extreme package and I can tell you after over 15,000 miles of pulling it I LOVE it! I have never had a truck that so effortlessly pulled a trailer without being a dually (and I've had a number of them!) Never had an issue with power. The magnetic suspension adjusts (supposedly) 1,000 times a second and it's like driving a luxury car, with or without the trailer. Like I wrote, I don't have my paperwork or files with me, but suffice it to say I am Completely happy with it!.... though it WAS more expensive than my first house!
So there you have it. It's not the 10 speed, but I can only say that if it's anything like my 8 speed with the 6.2 you would LOVE it!
Best of luck !
Dak


2018 GMC Denali "Extreme" and 23' EVO 2050T Travel Trailer
Escapee member #224325-Since 1992


jfortenbery

Cincinnati Area

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Posted: 11/16/20 08:14pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks for the encouraging responses. I have a question, though. How do you "lock out" specific gears?

CavemanCharlie

Storden,MN

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Posted: 11/17/20 04:25pm Link  |  Quote  |  Print  |  Notify Moderator

jfortenbery wrote:

Thanks for the encouraging responses. I have a question, though. How do you "lock out" specific gears?


On my F-150 there is a button on the shifter stock with a plus and a minus on it. After putting the truck in gear you can push the minus button and each time you do it will lock out a gear. So if you have a 8 speed and you push it once and the tuck will only use 7 gears. Lights on the dash will turn on to tell you.

jfortenbery

Cincinnati Area

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Posted: 11/17/20 05:12pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks, CavemanCharlie!

APT

SE Michigan

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Posted: 11/17/20 05:47pm Link  |  Quote  |  Print  |  Notify Moderator

GM is similar. USe shifter to pick "Manual" mode. From a stop, it will show '1'. Then use +/- to pick the top gear the transmission will use.

BurbMan

Islip, Long Island

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Posted: 11/17/20 06:25pm Link  |  Quote  |  Print  |  Notify Moderator

dakonthemountain wrote:

The magnetic suspension adjusts (supposedly) 1,000 times a second and it's like driving a luxury car, with or without the trailer.


I had that suspension on the Suburban and you're right, it's the best! Only issue is that the shocks cost $150 each when they need to be replaced at 100k miles.


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