Lowered trailing arm trucks...and shims

[Rich69shortfleet]

The truck was bone stock when I got it. I've lowered it. All I did to the control arms was to add poly bushings and I put in some lowering springs and a rear sway bar. There are no shims in it. I did replace the u-bolts when I installed a set of G60 rear helper springs and had to get the half-leaf touch plates into the axle/control arms/spring plates/shock mounts sandwich but nothing in that mix changed the control arm to axle angle.

However, now that I think about it, the rear axle is not original to the truck. I got it from Manes years ago as it is an original truck 12-bolt posi. It was easier to just swap rear ends than swap the guts into my existing housing. Maybe this axle had a different angle built into it's control arm mounts for whatever reason. Do coil spring and leaf spring axles interchange? If so, do leaf spring rears have a different mount angle than coil spring rears?

[68 TT]

Originally Posted by Rich69shortfleet

..... Do coil spring and leaf spring axles interchange? If so, do leaf spring rears have a different mount angle than coil spring rears?

I know really old thread but nobody answered so I figured maybe it would help someone out if I did.

Trailing arm housings the mounts are on the bottom side of the axle tubes and at a 15-degree angle to the center line. The trailing arms align at a 30-degree angle. They also have mount holes in them for the 3-1/2" x 3/4" U-bolts to pass through to keep them captive. This will make the mounts easily identifiable from the more common car axles with bottom mounted leaf spring perches as the leaf spring perches do not have holes in the outboard sides, only the 1/2" to 5/8" hole in the middle for the leaf spring alignment pin.

Truck leaf spring housings for 67-72 and 73-87(91) have the leaf spring perches on the top side of the axle tubes as the housing is on the under side of the leaf springs. This is unless someone has done a flip kit equivalent and cut off the perches and installed new perches on the bottom side to flip the housing to the top of the springs to lower the truck in the same fashion as a flip kit. Leaf spring perches are installed onto the housing perpendicular to the axle center line.

Different perches being installed is also commonly done to housings from different model years to make them fit our trucks too so you may have to identify the housing type and model year by width and ring gear size and axle spline count.

I used a square body 4x4 housing in my 69 stepside and just installed a set of trailing arm mounts and panhard bar mount onto it, so just seeing the trailing arm mounts on a housing doesn't mean it is a 67-72 part. I also found a set of 2wd square body 5-lug axles and brakes for mine too so counting the wheel studs isn't always a model year giveaway either.

The square body 2wd and 4x4 axles are the same width so my truck can be either 6-lug or 5-lug in just a couple hours of work. I wasn't sure what wheels I wanted to run so the flexibility was a nice option and not having custom axles to get there was nice too. A little extra width but I like how it evens out the front to rear fender lip clearance a little compared to the stock housing.

The 88-98 body style 4x4 housing width fits nicely and evens out the wheel offset front to rear relative to the fender lip even more than the square body housing does so it is a fairly common swap. The perches are in the wrong place to just bolt in though. It requires new perches to be installed for it to work. In the 88-98 body style they went to a different housing width for 2wd that is narrower than the 4x4 housing so there are variations in width to watch out for.