Upgrading a 1500 4x4 for travel trailer towing

[bcbickers]

Greetings All,

For those of you towing a travel trailer, I would like some advice. We are in the market for a couple's model and are leaning towards a Grand Design Imagine 23LDE. Specs are as follows:

Dry Weight = 5,597 lbs
Max Weight (trailer GVWR) = 6,995 lbs
Tongue weight (12% of max trailer weight) = 840 lbs
Length = 28'-5"

While I would love to get a 2500, those are rarer than a hen's tooth and cost a fortune when you do find one. And per the wife, it has to be a Suburban. This 2012 is our third Suburban (one GMT-800, two GMT-900s), and she has no interest in driving/owning anything else. So, I need to outfit my 2012 4wd Z71 to tow as best as possible. According to the door sticker, it has a payload of 1,423 lbs. The trailer, the two of us, and a little bit of gear puts me right at that payload. My thoughts are to install 14-bolt axle, 4.10 gears, rear airbags, and upgrade the radiator and trans cooler. Should be less than $5k, which is a far sight from the $15-20k (or more!) a good 2500 would cost. So is it worth spending the money to upgrade my 1500, or should I just bite the bullet and find a 2500?

 

[Marky Dissod]

... need to outfit my 2012 4wd Z71 to tow as best as possible. According to the door sticker, it has a payload of 1,423 lbs.
The trailer, the two of us, and a little bit of gear puts me right at that payload.
My thoughts are to install 14-bolt axle, 4.10 gears, rear airbags, and upgrade the radiator and trans cooler.
Should be less than $5k, which is a far sight from the $15-20k (or more!) a good 2500 would cost.
So is it worth spending the money to upgrade my 1500, or should I just bite the bullet and find a 2500?

14-bolt axle might not be NECESSARY, but it's money well-spent anyway, so do that.
4.10 axles MIGHT be overkill? Depending on how often you DON'T tow / haul, you may be sacrificing unladen highway MpG.
4.10 will improve your city MpG, your towing MpG, and extend the life of your 6L80, once you reprogram / tune the ecm & tcm for purpose.
If unladen highway MpG is a MAJOR concern, 3.73 ought to be acceptable, if not preferred over 4.10.

Did I mention?: Tune the ecm & tcm for purpose, regardless of axle gears. It'll further improve your 6L80's durability / longevity.
Part of the tune improvement comes from improving the powertrain's cooling system performance, so you won't need to upgrade the radiator.
Disabling Engine Half@$$ (under 230F coolant temp) improves the engine and transmissions' durability / longevity as well.
Never hurts to slap an auxiliary fan on the ATF cooler you already have.

You may also want to consider braking upgrades in addition to suspension upgrades (are those 17" or 18" wheels?).

 

[bcbickers]

14-bolt axle might not be NECESSARY, but it's money well-spent anyway, so do that.
4.10 axles MIGHT be overkill? Depending on how often you DON'T tow / haul, you may be sacrificing unladen highway MpG.
4.10 will improve your city MpG, your towing MpG, and extend the life of your 6L80, once you reprogram / tune the ecm & tcm for purpose.
If unladen highway MpG is a MAJOR concern, 3.73 ought to be acceptable, if not preferred over 4.10.

Did I mention?: Tune the ecm & tcm for purpose, regardless of axle gears. It'll further improve your 6L80's durability / longevity.
Part of the tune improvement comes from improving the powertrain's cooling system performance, so you won't need to upgrade the radiator.
Disabling Engine Half@$$ (under 230F coolant temp) improves the engine and transmissions' durability / longevity as well.
Never hurts to slap an auxiliary fan on the ATF cooler you already have.

You may also want to consider braking upgrades in addition to suspension upgrades (are those 17" or 18" wheels?).

Thanks for the quick reply and advice!

We plan to visit my father in northwest Arkansas and it's quite hilly there, so I figure an axle upgrade is worth doing for performance and peace of mind. And who knows where else our adventures will take us, so plan for worst case, right? RE: the gears, our 'burb spends 90% of its time running around town, so that's good news about the increase in city mpg with 4.10s. Sounds like a fair trade off.

For the drivetrain, I had the engine rebuilt over the summer due a collapsed #6 lifter. As part of the rebuild, the AFM was deleted and a CamMotion truck cam installed for a little better low-end. The whole thing is tuned by @BlackBearPerf for 89 octane. I didn't know you could tune the coolant temp though, so I will ask them about it.

And thanks for the brake recommendation. I am running Powerstop rotors and pads and stock 18" wheels with LT275/65R18s Load Range E tires, so I didn't give stopping much thought. I'll look into what upgrades are available.

 

[strutaeng]

Sounds like a good plan. You have the 10 bolt axle, right? 14 bolt would be a good upgrade. 4.10 gears for that load. The owner's manual lists a towing capacity of 8,000 lbs with highest ratio available of 3.42 and the K5L HD cooling package (and only 5,500 lbs with the same ratio but no HD cooling package... that's kinda strange?)

I wish there was a way to swap out the rear suspension to a leaf springs on the 1500 SUVs, which is better suited for load, but I don't think it's possible. And would make the vehicle harsher riding empty. Airbags would work.

 

[strutaeng]

8500 lbs for a short wheelbase 2wd SUV?!

That's kinda optimistic, no?

 

[Foggy]

With those upgrades you should be fine for 7000 max weight
Make sure to get a high end weight dist hitch set up.. I have the 4 point
one with sway control built into the head.. It's expensive and takes patience to
set up, but way way better that my old set WD set up with the chains and sway mechanism.
Blackbear will be able to readjust the tune for the gear upgrade when you do that.
They already optimize the cooling fan settings/etc... But make sure you tell them
exactly what you are doing.
IF you didn't want to change the entire axle, you can upgrade the G80 diff
& diff and bearings to better that won't bite the dust.. I have all that stuff but
I also have a 14 bolt here ...neither of which I've done yet !!!
I would look for geotrash posts on trans cooling.. You'll find some great info
there and what many of us have done for a fan forced trans cooler install

Good Luck !!!!

 

[Foggy]

Equalizer is the name band that I used.. I used the 10K version
But you certainly could / should use the 8K version
It's the bomb in my experience
It's spelled funky "equal-i-zer" I think
They are a US based company and actually answer their phones.
I was impressed as I had questions/concerns when setting my system up..
The absolute only drawback is the price, you get what you pay for

 

[bcbickers]

With those upgrades you should be fine for 7000 max weight
Make sure to get a high end weight dist hitch set up.. I have the 4 point
one with sway control built into the head.. It's expensive and takes patience to
set up, but way way better that my old set WD set up with the chains and sway mechanism.
Blackbear will be able to readjust the tune for the gear upgrade when you do that.
They already optimize the cooling fan settings/etc... But make sure you tell them
exactly what you are doing.
IF you didn't want to change the entire axle, you can upgrade the G80 diff
& diff and bearings to better that won't bite the dust.. I have all that stuff but
I also have a 14 bolt here ...neither of which I've done yet !!!
I would look for geotrash posts on trans cooling.. You'll find some great info
there and what many of us have done for a fan forced trans cooler install

Good Luck !!!!

Equalizer is the name band that I used.. I used the 10K version
But you certainly could / should use the 8K version
It's the bomb in my experience
It's spelled funky "equal-i-zer" I think
They are a US based company and actually answer their phones.
I was impressed as I had questions/concerns when setting my system up..
The absolute only drawback is the price, you get what you pay for

We have rented a few smaller trailers in the past, so I bought a Camco Eaz-Lift TR3 1,000 WDH (1,200 lb max tongue weight). It worked pretty good the couple of times I used it, but it wasn't the panacea everyone says. That's probably because I just bolted it on, tightened the sway control a bit, and sent it. Once I upgrade the Suburban and buy a trailer, it sounds like I need to spend some time at my local Cat Scale and a few miles on the freeway getting everything set up.

Thanks again for all of the advice. It is very much appreciated!

 

[bcbickers]

Sounds like a good plan. You have the 10 bolt axle, right? 14 bolt would be a good upgrade. 4.10 gears for that load. The owner's manual lists a towing capacity of 8,000 lbs with highest ratio available of 3.42 and the K5L HD cooling package (and only 5,500 lbs with the same ratio but no HD cooling package... that's kinda strange?)

I wish there was a way to swap out the rear suspension to a leaf springs on the 1500 SUVs, which is better suited for load, but I don't think it's possible. And would make the vehicle harsher riding empty. Airbags would work.

Best I can tell, I have the 8.6" / 10 bolt with 3.42s (RPOs GU6 and G80). She pretty well rigged for light to medium duty towing (KC4, KNP, K5L cooling and JL1 trailer brake controller). The largest trailer we rented was 25' total length and about 6,000 lbs. The tow was fine, but the transmission got up to 210* (ambient temp was mid-to-high 80s) and dropped to third on a few of the hills (maybe an 8-10* incline). I figure with better cooling and some torque multiplication, she can handle a 28' 7,000 lb load.

 

[Marky Dissod]

Get your tune recalibrated for 4.10 and the understanding that you'll be towing heavier.
If it was in 3rd on the inclines, it'll likely be in 4th with 4.10, which indicates towing MpG could improve.
212F is ok for Dexron6 ATF, 4.10 and recalibrating the tune will help keep temps under control too.
As said, adding an auxiliary fan to your ATF cooler is never a bad idea, even if it doesn't quite need it.
An ATF cooler upgrade SEEMS a bit overkill, but feel free to ask someone with better info.

... per the wife, it has to be a Suburban.

You lucky bastaducci. All my exes, even the good ones, were all "A Caprice is a lil big, no?"
"Only when looking for parking in Manhattan" was the best answer I could muster without growling.

 

[swathdiver]

You'll tow that just fine. Now, being that she's 13 years old now, the 22840115/21648 radiator for the 6.2s is a good upgrade as is the 14-bolt axle for durability.

If yours has K5L, she has 700 watt cooling fans.

But, don't forget the springs and shocks. Mine started to sag with a 5K trailer right before we overhauled the suspension with all GM OE parts.

I took a vacation out west and when we left weighed the truck, she came in at 7,320 pounds (steer axle was 3700!) and probably weighed a little more after we got back from all the shopping the girls did. Truck didn't care.

I recently installed a 14-bolt and changed the gears to 3.73s. You can feel the difference in performance and our city mileage has increased. I have not been able to quantify the gains at the drag strip yet or highway mileage though some basic testing suggests no degradation in fuel economy on the highway. Anyhow, 4.10s would be fun but wouldn't want to spin the motor that high all the time even though the load on the engine is less.

The 2500 Suburbans and NHT pickups all run 3.73s, that's good enough for me.

Love the looks of those Z71 Suburbans!

 

[Marky Dissod]

... recently installed a 14-bolt and changed gears to 3.73. You can feel the difference in performance and our city mileage has increased.
I have not been able to quantify the gains at the drag strip yet or highway mileage though some basic testing suggests no degradation in fuel economy on the highway.
Anyhow, 4.10 would be fun, but wouldn't want to spin the motor that high all the time, even though the load on the engine is less.
2500 Suburbans and NHT pickups all run 3.73, that's good enough for me.

Forgot if it was 2500 or 3500 Sielvierrados (with 6L90s) that could've come with 3.73 or 4.10?

May I differ regarding 'spinning the motor that high all the time'?
With 4.10, bcbickers may very well find that he'll spend MORE time in 4th 5th and especially 6th, especially unladen. Same goes for his spouse.
Plus as said, he'll spend more time in 4th instead of 3rd when towing up steep hills, and more time in 4th & 5th when towing generally.
Up to his driving and his tuner how much time he spends in 6th when towing.

I'll go so far as to say that, if he spends more on gas, it'll be worth the durability/longevity improvement for the engine and transmission.

(Context for my suggesting 4.10 over 3.73:
Long ago I owned a 94 Caprice wagon with LT1 4L60E & 2.56 (still miss it, always will. Long story short, even though 3.42 made it SO MUCH MORE FUN,
my riders asked what happened that made my driving more tame. Since they wouldn't get it, I just took credit for growing as a person ...
Truth is it was ALL 3.42. With 2.56, I tried and failed to drive like a cabbie on meth, to the point that I tuned it to avoid 4th entirely til 3.42 came along.)

 

[swathdiver]

Forgot if it was 2500 or 3500 Sielvierrados (with 6L90s) that could've come with 3.73 or 4.10?

May I differ regarding 'spinning the motor that high all the time'?
With 4.10, bcbickers may very well find that he'll spend MORE time in 4th 5th and especially 6th, especially unladen. Same goes for his spouse.
Plus as said, he'll spend more time in 4th instead of 3rd when towing up steep hills, and more time in 4th & 5th when towing generally.
Up to his driving and his tuner how much time he spends in 6th when towing.

I'll go so far as to say that, if he spends more on gas, it'll be worth the durability/longevity improvement for the engine and transmission.

(Context for my suggesting 4.10 over 3.73:
Long ago I owned a 94 Caprice wagon with LT1 4L60E & 2.56 (still miss it, always will. Long story short, even though 3.42 made it SO MUCH MORE FUN,
my riders asked what happened that made my driving more tame. Since they wouldn't get it, I just took credit for growing as a person ...
Truth is it was ALL 3.42. With 2.56, I tried and failed to drive like a cabbie on meth, to the point that I tuned it to avoid 4th entirely til 3.42 came along.)

The gas 2500 and 3500 Silverados and Sierras could have 4.10s too. They were the only ones with a 6-speed to get those steep gears.

If one tows all the time, the 4.10s might make more sense. In my case, we only tow a time or two or three a year but spend quite a bit of time at highway speeds. At present the difference between the old (3.42) and new (3.73) at 70 mph is 159 rpms.

I didn't know that GM ran such a high gear behind the 4-speed back then. Right before the turbocharged Buicks got the 4-speed, they went from 2.29 to 2.73 to 3.08 and then 3.23 gears. With the introduction of the 200R4, they went to the 3.42 gear. So in 4th, their high gear ratio was 2.29, same as most 3-speed cars of the period. The Monte Carlo SSs with the 4-speed got 3.73s.

 

[j91z28d1]

why is it better to gear so it tows up the hill in 4th gear over 3rd?

unless the tranny has a known weak gear to stay away from. what's the point? you got 6 gears, use them all?

 

[swathdiver]

why is it better to gear so it tows up the hill in 4th gear over 3rd?

unless the tranny has a known weak gear to stay away from. what's the point? you got 6 gears, use them all?

Fewer RPMs? GM recommends towing in 4th for maximum cooling efficiency.

The goal is to keep the engine as close to its powerband as possible at a given speed/gear when towing, right?

I made calculators showing how many newton meters of force makes it to the ground at a certain speed and engine rpm depending on the tires and gearing used. 4.30s are awesome but I don't want a motor turning that many rpms while cruising down the highway at 70 mph.

 

[Marky Dissod]

why is it better to gear so it tows up the hill in 4th gear over 3rd?
unless the tranny has a known weak gear to stay away from. what's the point? you got 6 gears, use them all?

If the rear tires canNOT put enough engine power to the ground, any transmission will eventually upshift, unless you fail to give it enough gopedal.
3.08 axle, 32" tires, 70MpH, 6th gear = 1515RpM . . . 5th gear = 1925RpM . . . 4th = 2605RpM
3.42 axle, 32" tires, 70MpH, 6th gear = 1680RpM . . . 5th gear = 2140RpM . . . 4th = 2890RpM
3.73 axle, 32" tires, 70MpH, 6th gear = 1835RpM . . . 5th gear = 2330RpM . . . 4th = 3155RpM
4.10 axle, 32" tires, 70MpH, 6th gear = 2015RpM . . . 5th gear = 2565RpM . . . 4th = 3465RpM

4.30 is awesome, but I don't want a motor turning that many RpM while cruising down the highway at 70MpH.

4.30 axle, 32" tires, 70MpH, 6th gear = 2115RpM (Is this really that bad? Think about how much LESS time you'd spend in 5th & 4th & 3rd ...)

 

[j91z28d1]

Fewer RPMs? GM recommends towing in 4th for maximum cooling efficiency.

The goal is to keep the engine as close to its powerband as possible at a given speed/gear when towing, right?

I made calculators showing how many newton meters of force makes it to the ground at a certain speed and engine rpm depending on the tires and gearing used. 4.30s are awesome but I don't want a motor turning that many rpms while cruising down the highway at 70 mph.

see that makes sense to me, if gm says 4th gear is the best gear to tow in, which makes since cause they used to say tow in 1:1 not over drive.

so you'd want to gear to what makes it happy in 4th gear on the kinda roads you're normally on.

so using his examples. 3.08 at 70 at 2600rpm seems about right? why would you want to run a 4.10 and tow around in 6th gear? when you can just use 4th?

 

[Marky Dissod]

when you can just use 4th?

He WANTS to make more use of 4th, and less use of 3rd, which means he needs MORE axle gear than the 3.42 GM gave him.

 

[swathdiver]

Here's an example of the differences between 3.42 and 3.73 gears with the 6-speed transmission at different speeds and gear selections:

The difference between ratios here is considered small and not worthwhile. It's made a difference, one that can be felt and for the better. More torque makes it to the wheels and allows one to run 5 mph faster or 5 mph slower at roughly the same engine rpms.

 

[swathdiver]

If the rear tires canNOT put enough engine power to the ground, any transmission will eventually upshift, unless you fail to give it enough gopedal.
3.08 axle, 32" tires, 70MpH, 6th gear = 1515RpM . . . 5th gear = 1925RpM . . . 4th = 2605RpM
3.42 axle, 32" tires, 70MpH, 6th gear = 1680RpM . . . 5th gear = 2140RpM . . . 4th = 2890RpM
3.73 axle, 32" tires, 70MpH, 6th gear = 1835RpM . . . 5th gear = 2330RpM . . . 4th = 3155RpM
4.10 axle, 32" tires, 70MpH, 6th gear = 2015RpM . . . 5th gear = 2565RpM . . . 4th = 3465RpM

4.30 axle, 32" tires, 70MpH, 6th gear = 2115RpM (Is this really that bad? Think about how much LESS time you'd spend in 5th & 4th & 3rd ...)

Well, I started out with 3.42s and cruising at around 1,750 rpms and now just over 1,900. So 4.30s would be 300 rpms more at the same speed. Going to hear those extra rpms through the cab. If I were a kid street racing, maybe, but not now.

Use my calculator, it's more accurate!