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How to Eliminate Sag in Rear Suspension of 2008 Toyota Highlander Caused By Towing Boat Trailer


We have a 2008 Toyota Highlander Limited AWD with an aftermarket tow hitch. When attaching a boat trailer with a 19foot boat, the back end of the vehicle easily sags several inches. The Highlander has no trouble towing the weight, can pull the boat up hills, and generally seems OK with the load except for the rear suspension. Im rather concerned that Im going to catch something on a bump in the road and yank things loose. Will this or one of your other products help level out the vehicle?


Expert Reply:

The # CSS-1145R Coil Sumo Springs you'd looked at would be an economical solution that would improve the rear end suspension sag you're experiencing, but might not remove all the sag depending on the trailer's tongue weight. Since you state that you don't have any other towing problems, this alternative might suffice for you.

This being said, having the ride height compressed in the back causes a few effects you might not have considered. When the rear suspension is compressed by more than an inch or two, the aim of your headlights is altered so you'll be blinding oncoming traffic and you might not be able to see the road surface at night as well as you should. Also, when the rear suspension is compressed, the front suspension is un-sprung to a degree, which can negatively affect steering and braking response which could lead to problems.

A weight distribution system would use leverage provided by spring bars to transfer a portion of the trailer's tongue weight to the front axle of the Highlander, thus leveling the ride height between the two axles and eliminating the rear squat you spoke of.

A weight distribution system like the Fastway e2, part # FA92-00-0450 would be my first choice. The system is designed for trailers with tongue weights under 450 lbs, which is most likely where your boat trailer would fall. I'll link to an article that explains how to determine the trailer's tongue weight. The trailer ball isn't included, you'll need # 63845 for a 2 inch ball or # 63853 for a 2-5/16 inch ball. You'll also need a pole tongue adapter, part # EQ95-01-5950 to provide an attachment point on the trailer for the spring bars, because boat trailers don't have an A-frame trailer tongue. This system is also compatible with surge couplers which are found on many boat trailers.

Not only will the weight distribution kit I recommended eliminate the sag you mentioned, it'll also help prevent trailer sway caused by oncoming traffic or cross-winds.

I've linked to some product videos for the items mentioned above.

expert reply by:
Mike L

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