Help with towing numbers on a 1500 chassis

[bcbickers]

Greetings All,

We used our travel trailer for the first time this weekend. I spent some time at a CAT scale and would like some advice about my vehicle's setup. Here are the numbers. If it matters, weather was clear and 85* F.

Description	Weight - no trailer	Weight w/ trailer
Steer Axle	3380	2980
Drive Axle	3580	4820
Trailer Axle	-	6280
Gross Weight	6960	14080

The Suburban drove fine with no sway or untowards movements. With the Tru-Cool 40k cooler, transmission temps never got over 160* F. Fuel economy was 9.2 mpg (hand-calc'ed) running about 60 mph in the Texas Hill Country. Several of the hills forced a downshift into 3rd and 3,000ish rpms, but some 4.10s will fix that.

My biggest concern is how much overweight the rear axle was (4,820 lbs. actual vs 4,200 lbs. GAWR). I know part of that is an improper WDH setup, since not enough weight was getting transferred to the front axle. I probably should have moved most of our cargo (clothes, food, cooler) to the trailer as well. I'll bet that was at least 200 lbs. Tongue weight also seemed a little high at 1,240 lbs (~17% of 7,120 lbs. trailer weight). I might need to look at what all is in the front compartment and move things around a bit.

So two questions:
1) If I upgrade to a 14-bolt rear axle, does that also increase my rear GAWR and possibly my GVWR?
2) The front GAWR is 3,600 lbs. and the rear is 4,200 lbs. Added together, I get 7,800 lbs. GVWR, but the door placard says 7,400 lbs. Which is the correct number from a capability and safety perspective, not a legal one? Are any of you over GVWR or GCWR, and if so what is your towing experience?

 

[Big Mama]

just curious. How much did the rear sag? Does your rig have rear auto leveling? I sold my Yukon but was amazed at how well it towed but I was only pulling 5500 pounds. I have a Sierra now but want to follow this thread.

 

[intheburbs]

So two questions:
1) If I upgrade to a 14-bolt rear axle, does that also increase my rear GAWR and possibly my GVWR?
2) The front GAWR is 3,600 lbs. and the rear is 4,200 lbs. Added together, I get 7,800 lbs. GVWR, but the door placard says 7,400 lbs. Which is the correct number from a capability and safety perspective, not a legal one? Are any of you over GVWR or GCWR, and if so what is your towing experience?

Short answers:

1) If you upgrade your rear axle, it upgrades your rear GAWR. Nothing else.

2) The GVWR reflects the weakest link in the "chain" of systems in your truck - axles, engine, transmission, suspension, brakes, etc. So yes, based purely on weight ratings, your axles combined can handle more than 7400 lbs. The limiting factor driving the 7400 lb rating is something else - I'd guess either the brakes or your axle ratio.

Long answer:

Regarding your experience/trip aar: One of the reasons your rig was so stable is because of the high tongue weight. And that illustrates the half-ton conundrum. High tongue weight equals stability, but a low rear axle rating makes that dangerous.

Description	Weight - no trailer	Weight w/ trailer
Steer Axle	3380	2980
Drive Axle	3580	4820
Trailer Axle	-	6280
Gross Weight	6960	14080

You can "almost" make the numbers work with your current weights, if you play around with the WD bars and move some cargo around:

Front - 3693
Rear - 4193
Trailer - 6194
Total - 14080

That gets you 13% hitch weight, which is just about perfect. I don't see any reason to spend the coin to upgrade the rear axle. Instead, spend it on a good WDH like an Eqaulizer, get it dialed in and call it good. If you want to do something to the rear axle, get one of those Mag Hytec diff covers with the cooling fins on it, to help keep the axle temp a little lower.

If you plan long road trips, like hundreds of miles per day for multiple days, I'd buy an IR thermometer so you can check on the rear axle temperature. I did a simple test until I upgraded to the 2500 - whenever we'd stop, I'd put my hand on the rear axle - if I didn't burn myself, it was good. We actually did do some middle-of-the-night driving precisely to help keep the rear axle cool.

Welcome to the wonderful world of towing with a full-sized half-ton SUV. Yes, the rear axle is the most commonly overloaded component, and the primary reason I upgraded to a 2500. My 2001 Suburban is wearing rear axle number 4, precisely because I broke it several times (while on vacation) from towing heavy.

Here's the loading sticker for my 2500:

And the rear axle rating? The limiting factor is actually the rear leaf springs. The axle itself is rated to 8600 lbs, and the two rear tires can handle a little over 6,000 lbs. So I no longer worry about overloading it. And notice the axle weights add up to 9680, even though the GVWR is "only" 8600.

 

[dntnvme]

Greetings All,

We used our travel trailer for the first time this weekend. I spent some time at a CAT scale and would like some advice about my vehicle's setup. Here are the numbers. If it matters, weather was clear and 85* F.

Description	Weight - no trailer	Weight w/ trailer
Steer Axle	3380	2980
Drive Axle	3580	4820
Trailer Axle	-	6280
Gross Weight	6960	14080

The Suburban drove fine with no sway or untowards movements. With the Tru-Cool 40k cooler, transmission temps never got over 160* F. Fuel economy was 9.2 mpg (hand-calc'ed) running about 60 mph in the Texas Hill Country. Several of the hills forced a downshift into 3rd and 3,000ish rpms, but some 4.10s will fix that.

My biggest concern is how much overweight the rear axle was (4,820 lbs. actual vs 4,200 lbs. GAWR). I know part of that is an improper WDH setup, since not enough weight was getting transferred to the front axle Wollongong towing company. I probably should have moved most of our cargo (clothes, food, cooler) to the trailer as well. I'll bet that was at least 200 lbs. Tongue weight also seemed a little high at 1,240 lbs (~17% of 7,120 lbs. trailer weight). I might need to look at what all is in the front compartment and move things around a bit.

So two questions:
1) If I upgrade to a 14-bolt rear axle, does that also increase my rear GAWR and possibly my GVWR?
2) The front GAWR is 3,600 lbs. and the rear is 4,200 lbs. Added together, I get 7,800 lbs. GVWR, but the door placard says 7,400 lbs. Which is the correct number from a capability and safety perspective, not a legal one? Are any of you over GVWR or GCWR, and if so what is your towing experience?

Upgrading to a 14-bolt rear axle can increase your rear GAWR, but it does not automatically increase your GVWR. The GVWR is set by the manufacturer based on the vehicle’s overall design, including suspension and frame limits, so raising it would require more than just an axle upgrade. The door placard GVWR of 7,400 lbs is the official safe maximum weight for your vehicle, not the sum of the front and rear axle ratings. Exceeding the GVWR is not recommended as it can compromise safety and vehicle performance.

 

[bcbickers]

Sorry for the delay, folks. It turns out this tow killed my transmission. I went to run an errand the day after I got back, and the tranny was stuck in second gear with the torque converter locked. Won't shift at all, although reverse works fine. Manual mode is completely inop. I noticed some stuttering on the way home but thought it was some bad gas since we stopped at an out of the way, not-the-best-gas-in-the-world station. Seems it was actually the converter slipping. Neat thing is I now have an excuse to put a built transmission along with the 14-bolt and 4.10s. So she's at Circle D getting a refresh.

just curious. How much did the rear sag? Does your rig have rear auto leveling? I sold my Yukon but was amazed at how well it towed but I was only pulling 5500 pounds. I have a Sierra now but want to follow this thread.

The rear sagged a little, but nothing major. I was actually surprised how little sag there was considering the weight on the rear end. No idea how old the shocks are, but I know they have been replaced at least once because they aren't OEM, front and rear.

Short answers:

1) If you upgrade your rear axle, it upgrades your rear GAWR. Nothing else.

2) The GVWR reflects the weakest link in the "chain" of systems in your truck - axles, engine, transmission, suspension, brakes, etc. So yes, based purely on weight ratings, your axles combined can handle more than 7400 lbs. The limiting factor driving the 7400 lb rating is something else - I'd guess either the brakes or your axle ratio.

Long answer:

Regarding your experience/trip aar: One of the reasons your rig was so stable is because of the high tongue weight. And that illustrates the half-ton conundrum. High tongue weight equals stability, but a low rear axle rating makes that dangerous.

Description	Weight - no trailer	Weight w/ trailer
Steer Axle	3380	2980
Drive Axle	3580	4820
Trailer Axle	-	6280
Gross Weight	6960	14080

You can "almost" make the numbers work with your current weights, if you play around with the WD bars and move some cargo around:

Front - 3693
Rear - 4193
Trailer - 6194
Total - 14080

That gets you 13% hitch weight, which is just about perfect. I don't see any reason to spend the coin to upgrade the rear axle. Instead, spend it on a good WDH like an Eqaulizer, get it dialed in and call it good. If you want to do something to the rear axle, get one of those Mag Hytec diff covers with the cooling fins on it, to help keep the axle temp a little lower.

If you plan long road trips, like hundreds of miles per day for multiple days, I'd buy an IR thermometer so you can check on the rear axle temperature. I did a simple test until I upgraded to the 2500 - whenever we'd stop, I'd put my hand on the rear axle - if I didn't burn myself, it was good. We actually did do some middle-of-the-night driving precisely to help keep the rear axle cool.

Welcome to the wonderful world of towing with a full-sized half-ton SUV. Yes, the rear axle is the most commonly overloaded component, and the primary reason I upgraded to a 2500. My 2001 Suburban is wearing rear axle number 4, precisely because I broke it several times (while on vacation) from towing heavy.

Here's the loading sticker for my 2500:
View attachment 456801

And the rear axle rating? The limiting factor is actually the rear leaf springs. The axle itself is rated to 8600 lbs, and the two rear tires can handle a little over 6,000 lbs. So I no longer worry about overloading it. And notice the axle weights add up to 9680, even though the GVWR is "only" 8600.

Upgrading to a 14-bolt rear axle can increase your rear GAWR, but it does not automatically increase your GVWR. The GVWR is set by the manufacturer based on the vehicle’s overall design, including suspension and frame limits, so raising it would require more than just an axle upgrade. The door placard GVWR of 7,400 lbs is the official safe maximum weight for your vehicle, not the sum of the front and rear axle ratings. Exceeding the GVWR is not recommended as it can compromise safety and vehicle performance.

Thanks for the info about the GAWR and GVWR. The rear axle and receiver hitch are my biggest concerns. I was 600 lbs over the axle rating and 200 lbs over the hitch rating. Kinda shocked all that failed was the transmission. GVWR seems ok, as we are right at 14,000 lbs. with the three of us and all of our gear in the Suburban and the trailer. And I can probably get that down a few hundred pounds by being a little more judicious with what I pack instead of just throwing in every little thing for every possible contingency. I'll bet all the tools and the jack I packed in the front compartment are 150 lbs alone. :O

I should just find a 2500 and be done with it, but I really love appearance of the Z71 package, which is half-ton only. And I have already put an engine in her after the #6 lifter gave out. So thanks to everyone for your input and assistance with helping me keep and improve my 'burb.

 

[Marky Dissod]

I should just find a 2500 and be done with it, but I really love the
APPEARANCE
of the Z71 package, which is half-ton only.

There are hundreds if not thousands of Tahoes & Yukons driving around in NY / NJ, that you'd not be able to distinguish from an Escalade without checking the VIN.
What stops you/anyone from adding Z71 makeup to a 2500?

 

[Geotrash]

Sorry for the delay, folks. It turns out this tow killed my transmission. I went to run an errand the day after I got back, and the tranny was stuck in second gear with the torque converter locked. Won't shift at all, although reverse works fine. Manual mode is completely inop. I noticed some stuttering on the way home but thought it was some bad gas since we stopped at an out of the way, not-the-best-gas-in-the-world station. Seems it was actually the converter slipping. Neat thing is I now have an excuse to put a built transmission along with the 14-bolt and 4.10s. So she's at Circle D getting a refresh.



The rear sagged a little, but nothing major. I was actually surprised how little sag there was considering the weight on the rear end. No idea how old the shocks are, but I know they have been replaced at least once because they aren't OEM, front and rear.






Thanks for the info about the GAWR and GVWR. The rear axle and receiver hitch are my biggest concerns. I was 600 lbs over the axle rating and 200 lbs over the hitch rating. Kinda shocked all that failed was the transmission. GVWR seems ok, as we are right at 14,000 lbs. with the three of us and all of our gear in the Suburban and the trailer. And I can probably get that down a few hundred pounds by being a little more judicious with what I pack instead of just throwing in every little thing for every possible contingency. I'll bet all the tools and the jack I packed in the front compartment are 150 lbs alone. :O

I should just find a 2500 and be done with it, but I really love appearance of the Z71 package, which is half-ton only. And I have already put an engine in her after the #6 lifter gave out. So thanks to everyone for your input and assistance with helping me keep and improve my 'burb.

Or… you could do what some of us did and upgrade to a K2xx (2018, in my case) Suburban 3500 HD. It has the iron block L96 (no AFM), 6L90 transmission, Suburban 2500 frame but with 1-ton pickup suspension bits and running gear.

But that truck did get you home so it deserves to be brought back to health, for sure!

 

[Bigburb3500]

Or… you could do what some of us did and upgrade to a K2xx (2018, in my case) Suburban 3500 HD. It has the iron block L96 (no AFM), 6L90 transmission, Suburban 2500 frame but with 1-ton pickup suspension bits and running gear.

But that truck did get you home so it deserves to be brought back to health, for sure!

I maintain my opinion that the right answer to any towing question is K2xx Suburban 3500. End of discussion lol.

But going to OPs comment about “only the transmission failing” is an interesting one because it does show the weakest link does break when pushed. I think @intheburbs has noted that the rear axle is a weak point and it’s well known the 6l80s are not the best.

Glad the OP got home safe and is able to “rationalize” the upgrades!

 

[bobsburban]

I maintain my opinion that the right answer to any towing question is K2xx Suburban 3500. End of discussion lol.

But going to OPs comment about “only the transmission failing” is an interesting one because it does show the weakest link does break when pushed. I think @intheburbs has noted that the rear axle is a weak point and it’s well known the 6l80s are not the best.

Glad the OP got home safe and is able to “rationalize” the upgrades!

Yes, glad you got home okay. I didn't when our 1500 Suburban's 6L80 failed up in Kentucky on a business trip/vacation. Luckily a friend could tow our trailer home and I could wait at the state park lodge until a tow service could get the truck back to Chattanooga for repairs. I'm now towing with a 2500 Suburban as we're about to leave for 7 weeks in the US and Canadian Rockies. I'm a fan.

A couple of comments:

1) The difference between a 2500/6.0 and a 1500/5.3 is far larger than I suspected. I pulled our trailer up to a campground near where I was competing in a long-range rifle match with the 1500. A two-mile, 6% grade on the way had me twisting the engine to 5000 rpm in second gear to maintain 45 mph up the grade (3.42 gears). When I got the 2500 with 3.73s, I tried the exercise again, as that hill is not far from home. I keep the trailer fully packed and ready to go, so there was little if any weight difference. This time, 3000-3300 rpm in third gear and holding 60 mph easily.

2) If I'm not mistaken, a set of Bilstein 5100s, the skidplate and a decal will turn a 2500 into better than Z-71. I can't see that the Z-71 package has anything else that really contributes to the capability of the vehicle. As I'm looking for cooling capability, a different plastic bumper cover makes no difference to me.

3) Don't know if you have the air shocks on your setup but if you don't want air shocks and their maintenance issues but want more spring capacity, I can highly recommend this mod: https://baselineoverland.com/produc...2007-on-with-660-880-lb-constant-load-c09-037. These rear coils made all the difference in maintaining proper ride height with the trailer on the hitch. The Z-71 rear coils sagged same as stock - just not enough spring rate.

Hope this helps.

 

[Geotrash]

I maintain my opinion that the right answer to any towing question is K2xx Suburban 3500. End of discussion lol.

But going to OPs comment about “only the transmission failing” is an interesting one because it does show the weakest link does break when pushed. I think @intheburbs has noted that the rear axle is a weak point and it’s well known the 6l80s are not the best.

Glad the OP got home safe and is able to “rationalize” the upgrades!

I agree on all points, and I'll add that the weak link of the 6L80 for towing is the torque converter (TC). So a person can go a long way toward increasing the reliability and durability of them by simply upgrading the TC to one that has a billet cover, stronger lockup clutch, and maybe a flanged hub, as many of them do now. We have enough years and miles on the 6L80 fleet out there for rebuilders and converter manufacturers to know where the weak spots are, and engineer viable solutions. Figure maybe $1500 or a little more, out the door, for a new or rebuilt and revised TC, including R&R and a new rear main seal while they're in there.