Spring under vs spring over

When I first started getting into trucks in the late 90’s, I remember the Jeep guys were all doing spring overs on their yj and cjs. Now I see people are doing spring unders on their Tacomas.

What has changed? Or why on a pickup but not a Jeep?

 

People who want a cheap lift on a Jeep do a SOA as its a free 3" or so. It's terrible. SUA is always better

 

Why is that?

 

SOA requires more work than its worth unless you don't care about the ride or quality, with that it opens up more issues that must be taken into consideration.

The vast majority of people converting to SOA are doing it because its cheap and they are doing the bulk of the welding/labor themselves. A true SOA done right will be expensive and at that point you might as well do a coil conversion.

Some people like it, some people don't. You'll get a plethora of opinions on google.

 

Most people that change to SUA on Tacomas are doing it to use the greater arch to gain rear articulation. When Jeep dudes were doing SOA conversions in the '90s they were doing it to get easy lift.

 

Thanks for the quick response Joe but I have another question. I have no intention of doing this but just trying to learn things. So... how does it affect the ride? I assume that axel wrap and driveline angles could be a problem, but are there other issues?

 

SUA results in less axle wrap and wheel hop because the lateral force transmitted from the axle to the spring counteracts the torsional force transmitted to the spring. Why Toyota decided to go with SOA is beyond me....Axle wrap is noticeable.

 

Axle wrap and driveline angles are an issue. If you are using stock leafs then axle wrap is more prone to happen but offer a better ride. Most people add a stiffer spring to combat axle wrap but sacrifice ride quality and comfort. Older Jeeps used a solid shaft with a slip yoke, the cheap method would have a transfer case drop bracket that lowers the entire driveline. People who do it right convert to a double cardan CV drive shaft and install a slip yoke eliminator.

Our trucks use a SOA and a very flat spring, even with lifts its a low arch spring which offers decent ride comfort but is also prone to some axle wrap. Spring under offers greater droop if built correctly and better stability

 

Thanks to all. I think I learned something, though it does seem to be one of those things that can become a bit controversial with pluses and minuses on either side.