Towing, Suspension Sag, Gearing

C

Corry

New member
Sep 15, 2024
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2
Cairns
We're yet to take delivery of our 'Sports Luxury', which is top of the range here in Aus, just wondering for those that tow heavy trailers with it, do they suffer from suspension sag at all in the rear?
On occasion I'll be using it to tow our boat, 2.8t (6000lb), which has a tow ball weight of around 280kg (620lb) and I'm wondering if I need to do anything to the rear to keep it all level. Weight distribution bars aren't really an option with a boat trailer.

Also, when towing with my 79 Series Cruiser Ute, it's recommended not to use 5th gear, only 4th as it is 1:1 ratio and the overdriven 5th gear isn't designed for heavy towing. Wondering if there is anything different that I should be doing when towing heavy trailers with the GX?
 
Thanks for that ColoradoOutdoors, that one dropped around 2". Would be good to know what the tow ball weight is of the trailers.
I guess I'll find out when we get ours delivered.
 
The suspension is designed to sag with tongue weight. Example spring rates are 200 pounds per inch, meaning 600 pounds would compress it 3 inches. I believe the GX springs are stiffer.

Weight Distribution Hitches more importantly shifts weight on to the front (steering) wheels to give better control.

Here is my 5000# trailer with approx 800# tongue weight and another 100# WDH.
1727361501756.png



I'm not sure if the Tow Haul mode locks out overdrive in Auto, which I believe is gears 9 & 10 on the GX. I tend to cut over to Manual shift. Cruising fast on flats, I might use 7 or 8. In the mountains I tend to use 5 or 6, maybe lower in steep sections.
 
That's interesting info nopantz, would be interesting to find out what the sorting rates actually are on the GX. Sagging 3" I'm guessing would have an affect on how the vehicle handles.
I won't really have the option of a weight distribution hitch with the boat due to the amount of reversing it'll do.
I wonder if anyone will end up doing an air bag assist kit or the likes
Thanks for the info, very interesting.
 
Hi you prob already have balanced your boat on the trailer, but keeping the weight center directly on the trailer wheels really helps the hitch weight on the tow. Like stow your cooler etc gear aft of the wheels. your 10SPD is a great option to have. Take some time to feel out the performance in the gear ranges!!
 
Hello. The towing capacity is available on the Lexus website: 9000 and some change depending on trim. I cannot find a mention of the tongue weight limit. Any already-owners willing to check their owners manual and post what it says about tongue weight limit? Thank you in advance.
 
Payload capacity is 1500 and change but mine was derated from options, so about 1500. I assume about 900# TW plus 600# for passengers. I haven’t taken to the scales, but expect I’m close.
 
1000# for the class 4 receiver. Of course you're payload is going to be the biggest number to watch since you'd be hard pressed to properly load a trailer up to 9k and be in spec. I'm sure that number is only attainable with a flat trailer loaded with concrete block. Certainly not a travel trailer.
 
Cablebandit said:
1000# for the class 4 receiver. Of course you're payload is going to be the biggest number to watch since you'd be hard pressed to properly load a trailer up to 9k and be in spec. I'm sure that number is only attainable with a flat trailer loaded with concrete block. Certainly not a travel trailer.
Click to expand...
Thank you. Is the 1000# from the manual? I won’t tow anywhere near 9k. The boat and trailer weigh about 4500lbs. The tongue weight I’m guessing is between 4 and 500. I saw the Defender 130 has a large towing capacity but I think the tongue limit is only 300lbs or so. Which effectively limits towing to around 3000lbs using the rule of thumb of tongue weight about 10%-15% of trailer weight. Just wanted to confirm the GX doesn’t have the same issue: large towing capacity functionally limited by small tongue weight limit.
 
About 4500 pounds total. I am not using a weight distribution hitch and bars. I only tow it twice a year about 18 miles. It does squat more than I thought it would. If i was towing every week I would get the full weight distribution system.....

1729552006450.png
 
nopantz said:
The suspension is designed to sag with tongue weight. Example spring rates are 200 pounds per inch, meaning 600 pounds would compress it 3 inches. I believe the GX springs are stiffer.

Weight Distribution Hitches more importantly shifts weight on to the front (steering) wheels to give better control.

Here is my 5000# trailer with approx 800# tongue weight and another 100# WDH.
View attachment 3707


I'm not sure if the Tow Haul mode locks out overdrive in Auto, which I believe is gears 9 & 10 on the GX. I tend to cut over to Manual shift. Cruising fast on flats, I might use 7 or 8. In the mountains I tend to use 5 or 6, maybe lower in steep sections.
Click to expand...
Super nice looking rig!
 
BENDOU said:
Would like to ask the brand of these airbags and where you got them. I have been looking for some, obviously I didn't do well in my search. Thanks!
Click to expand...
Parts I used. I cut 3 tapered donuts off the taper damper from inside the coil spring which worked out perfect. My GX550 was bottoming out the bump stops when I hit dips on some roads even though I have an Andeson weight distribution hitch. I did not use the side backet on the Tundra Airlift kit. The axle is the same on the 2022 thru 2024 TRD Tundra but the frame shock holder is welded on the frame in a different spot. The bump stop is the same bolt pattern and the Tundra axle to frame is 8 inches vs Gx550 6.25 inches. Coil spring is taller on the Tundra. Side bracket is not needed IMHO as the steel plates are very thick and strong. Ride appears to me like stock with zero air pressure.

https://www.etrailer.com/Vehicle-Su...Cruiser/2017/F4164.html?VehicleID=20171014419




 
Last edited:
The drive train is perfect for towing with a 3.31 axle ratio and 10 speed automatic transmission with:

First gear: 4.92
Second gear: 3.26
Third gear: 2.35
Fourth gear: 1.94
Fifth gear: 1.53
Sixth gear: 1.19
Seventh gear: 1.0
Eighth gear: 0.80
Ninth gear: 0.66
Tenth gear: 0.61
Direct Shift-10AT
You can keep the engine in any rpm range you want without the need to go to lower axle ratios.
 
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