Project Mini - Front Straight Axle Swap

Project Mini - Front Straight Axle Swap - Part 1

Http://www.4x4wire.com/toyota/tech/mini_frontsusp1

Short Cuts

Author: Jay Kopycinski August 2000

With the rear suspension complete, we turned our attention towards the front end of our truck. The IFS suspension is fairly capable for many types of wheeling. However, for harder rock crawling we prefer a straight front axle setup for improved travel capability and increased durability. To gain these traits, we'll be swapping in a '84 model front axle and converting to leaf springs. As we did on the rear suspension, will be doing some homebrew mods in some places and adding some aftermarket parts too. Follow along as we show you how we did it......

Removing All the IFS Components


Starting the front suspension disassembly	The pile of IFS parts we removed

We started by parking the truck with the front frame rails supported by jack stands placed just behind where we expected our shackle hangers to end up. Next, we unbolted just about everything related to the front IFS suspension and drivetrain. We removed the pitman arm from the steering box, but let the box in place. We removed the front driveshaft and plugged the brake lines to prevent fluid loss.

With everything removed that could be done without cutting, we were ready to proceed with the liquid wrench. We cleared the area of all our tools and parts and took a look. There were quite a few brackets left hanging from the frame. I lit the torch and went to work. About an hour and a half later I had all the remaining IFS hangers removed. Another hour and a half later and we had the frame rails ground smooth and had a clean canvas on which to start our swap.


Here's all the IFS brackets on the frame	Here's all the IFS brackets on the floor	The frame rails are looking cleaner already	Frame rail after being ground smooth

Installing the Front Spring Mounts

Dropped front spring mount we fabricated

Our overall plan for the front suspension was to use dropped front mounts and mount the shackle below the frame rail. We prefer this method over running highly arched springs and it would offer several benefits. It would give us good lift while keeping the springs fairly flat. This method is also a bit stronger, keeps the ride smoother, allows the springs to flex very well, and allows the springs to bend backwards well without fatiguing them rapidly. The only downside is a small loss of approach angle at the front of the frame when compared to higher arched lift springs.

Holding the front mount in place with a jack

We fabricated a front hanger mount that dropped the front spring mounts about 2 1/2" when compared to a normal straight axle truck. More detail on this type of mount can be found on my Front Suspension Tech page.

The front spring hanger was positioned under the front frame crossmember and held in place with a floor jack. We then welded the mount in place. Our mount was positioned such that the center of the spring eye holes were spaced 2 1/8" rearward from the front face of the front frame crossmember (the one with the large holes punched in it).

Springs and Shackle Hangers

We used stock rear shackle hangers up front

We had decided to use our old rear springs as the basis for our front hybrid spring packs. We used just the rear main leaf to mock-up our front spring mounting. We had also decided to use the stock rear shackles (3 1/2" eye-to-eye) up front and mount the shackles under the frame rail using a set of stock rear shackle hangers. This setup will provide us with plenty of shackle movement without any problem of the shackle hitting the frame rail, as is sometimes found with a shackle mount tube sitting in the frame rail. Energy Suspension bushings (kit #8.2103G) were used in the spring packs and shackles. The front spring eye was bolted to our dropped mount using 3/4" hex bolts and nyloc nuts.

Using only the main leaf from one of our stock rear spring packs, we estimated where we wanted our hangers mounted and tack welded one in place. After several tries of articulating the main leaf and shackle combination and moving the hanger, we settled on a final location. We chose a center-to-center distance of 45 1/4" between the front mount hole and the rear shackle hanger hole. We marked this location and removed the tack welded hanger.

A homebrew jig to align the shackle hangers

To ensure we got both hangers located correctly we used a little trick to hold them in place. After inserting the new poly bushings in the hangers, we slipped a piece of ½" electrical conduit through the bushings. With both hangers slid snugly over the conduit, we adjusted the distance between the two hangers to match the mount separation at the front of the truck. With our little jig adjusted, we used a floor jack to lightly hold the assembly under the truck. Final adjustments were made and the hangers were tacked in place. We removed the tube and bushings and final welded the hangers to the frame.


Energy Suspension poly bushings were used	Aligning the rear shackle hangers	Checking the spring movement up front

Mounting the Springs and Axle

We built five leaf packs for our front axle using the following leaf stack:

Main leaf: 0.280" thick, 47" long (original rear leaf)

Second leaf: 0.280" thick, 47" long (original rear mil wrap leaf)

Third leaf: 0.280" thick, 45" long (a Mazda 2WD leaf)

Fourth leaf: 0.280" thick, 40.5" long (original rear third leaf)

Fifth leaf: 0.280" thick, 34" long (misc. 2WD leaf)

We mounted our front spring packs and attached the front axle to the leaf packs using a u-bolt flip kit from All Pro Off Road. Prior to attaching the plates, we welded a homebrew steering stabilizer bracket to the driver side u-bolt plate. This allows us to install a steering stabilizer from this point to a bracket added to the tie rod. I prefer to mount the stabilizer to the tie rod rather than to the draglink so that the stabilizer and both mounting points always travel together. This ensures consistent movement from the stabilizer and makes component clearance easier.

We also positioned the front axle slightly offset from the spring center pin. With our new spring setup, we chose to move the axle backwards 1" on the spring pack. To do so, we drilled two new 5/8" diameter holes in the springs perches, offset 1" from the center of the perch. We also drilled matching holes in the u-bolt flip plates. Also, to beef up the stock perch a bit, we had previously welded a 1/4" steel plate to the top of each perch.


All Pro flip kit...plates and u-bolts	Steering stabilizer mount and new center pin hole	Added perch plate and redrilled center pin hole

Stay tuned because next month we'll add our steering, brake upgrade, shock mounts, and driveshaft to complete the front suspension.

Thanks for reading!