Ride height difference

i have a '99 toyota 4runner which significantly sags in the rear whenever i haul luggage. my mechanic inspected it and suggested i change the rear springs to a set one step above the set he saw. i complied, only to find the rear quite elevated than the front, with very visible difference in the front and rear ride heights. please what are the disadvantages of unequal ride heights? thanks.

Your mechanic used the wrong springs. He should have used stiffer springs but with a lower unloaded height, or springs with a more progressive rate.

I’m just guessing but he probably used springs that had the same unloaded height but a higher spring rate. When installed, they would not compress as much so the rear would sit higher. The springs he used should have been stiffer, but a little shorter so that when compressed with the weight of the vehicle, they would end up at the same height as the original springs.

Did you buy this vehicle new or used? If new, did it “signifincantly sag” as much when loaded with luggage when it was new? (How much does your luggage weigh?)

If not, then the problem was that the existing springs were probably “tired.” They were 16 years old, after all, and they DO weat out with time and use.

I’m thinking that standard, but new, spring would have been adequate. As it is, with the rear end up in the air, I’ve got to believe the steering characteristics have been changed, and not in a good way.

I agree with what Dr Rocket said as well, it could be due to worn springs. It could also be due to worn shocks as well. Most vehicles today use gas charged shocks, if they loose their gas charge, it puts more load on the springs. You would have noticed a slight sag (about a half inch) in the rear even without luggage though.

One more thing, have you checked the ride height of other 4 runners to see how they look. It is possible that the mechanic has restored the original factory ride height, but it looks odd to you because you got used to seeing it in a sagging position. We cannot see your vehicle so we cannot judge that.

No experience w/this myself, but I’ve heard of cars that have sagging springs, having the springs re-tempered. The springs are put through some kind of heat treatment, supposedly returns them to their original springy-ness when they were new. I expect you have coil springs, and the times I heard of this done, it was leaf springs that got re-tempered. So uncertain if it would apply in your case. But it might be an option.

This one doesn’t use air shocks. Attached is a link to the rear suspension on this vehicle.

I’m going to bet that Keith’s last post is right. You were used to seeing it too low.
Stop by the local Toyota dealer parts window and ask the to pull up the correct ride heights for your vehicle, as well as the procedure that tells you how to measure them. Be sure the OEM sized tires are on it and try measuring. You may even find that the front springs are tired too.

I wonder if the spring change to “one step above the set he saw” has anything to do with this?

One step above meaning longer than stock length or what?

thanks guys, esp keith and dr. Rocket. not air shocks. previously, i.e prior to the spring change, no sag without luggage but a load as little as 200kg caused a significant sag. vehicle was bought used. i will ask the mechanic to revert to springs similar to the ones he replaced. thanks all.

Air shocks and gas charged shocks are two different animals. Almost all, if not all new vehicles use gas charged shocks. Even my 86 Toyota Tercel 4WD wagon has gas charged shocks and struts. The gas charge allows for a stiffer shock that still delivers a smooth ride.

George, the process you refer to is to anneal (bring to soft) the spring steel and heat treat it all over again to return its spring characteristics, a multi-step heat treat process. Shops don’t have the ovens and metallurgy knowledge to do this. It has to be “subbed out”. Most places just replace the springs. It’s always an option, but not a cost-effective one. I’d guess that the reason you hear of it being done with leaf springs is because it’s usually done by shops restoring old cars, where replacement springs aren’t available and having the original parts has value in and of itself.

I knew someone years sgo that had all 4 spring retempered on his 64 Pontiac, he wound up with a car that was a different height at all 4 corners.

The springs are just worn out, why put in a stiffer spring than was installed at the factory. Then it will be a stiffer ride.
I could see if you wanted to haul a heavy load all the time and get stiffer springs, but just some luggage should not effect the ride height much.

I had a client that had me do the same thing. He insisted that the front of his pickup truck sat lower than when he bought it used a year earlier.
He ordered the springs and I installed them with the understanding that if it was too stiff a ride, it was at his cost with no warranty on the parts or labor.

A week after the new springs were installed he was back with a new set of stock springs.