Need someone with a early 720 to help me out.

[jvb5577]

I am interested in trying to swap the compete steering column, box, ect. from a early 720 to my 79 620.

I just need to know the frame rails distance apart at the box mount and the idler arm.  Want to know if it is the same on the '79 frame.  I haven't had the time to go to a junkyard and take some measurements so hoping someone here will help me out.

 

I already have early D21 spindles and I think most of the geometry is the same from '79 - early 80's.  So I hope this will work as an option to give me more room.

[supererogator]

If you are running 2wd, I have an 80, and am happy to measure for ya.  I have been under my hood too much in the last bit.  A small distraction would probably be a good thing for me.  Can you tell me exactly what you need measured, and/or give me pics?

[datzenmike]

You may have noticed the 620 box and idler are mounted on the insides of the two frame rails while the 720s are on the outside. I believe the frame rails are more or less the same distance apart as I have put a 620 cab on a 720 frame and it's a perfect fit.

[jvb5577]

Thanks super it is a 2wd but I think Mike has it for me so no need to measure.

 

That is why I wanted to switch to the 720 steering to get the box and idler out from the inside.  I figured they were since they pretty much have the same upper and lower arms and spindles.  Mike do you think this is a good choice to go with the 720?

[datzenmike]

I guess it's ok. The column and box is, (more or less) in the center of the frame rail and the sector shaft down the inside on the 620 and down the outside on the 720 frames. I've run both on my '78. This will give you a U joint and a collapsible spline as well as a rag joint on the column. This will be good if raising the body and the collapsible part in an accident.

 

There is the hole in the floor to cover up. I think the 720 column will take the 620 turn signal/high beam switches, maybe even the ignition switch so the 620 clam shell will fit. I didn't have that problem as I kept the 720 turn signal/headlamp switch assy on left and the stalk on the right side for the wiper controls as well as the steering lock ignition and clam shell.

[wayno]

The issue will be the mounting of the steering gear and idler arm, you have to beef up the frame, otherwise the side pressures will destroy the frame, I put a steering gear on the outside of my 521 work truck, eventually it screwed it up, and the steering was very spongy for a long time, till I finally did it right.

The front idler arm bolt was shared by both the idler arm and steering gear, it was to much for the frame.

 

 

[jvb5577]

Wayno are you sure you didn't have a rust issue before that helped cause this?

[wayno]

Wayno are you sure you didn't have a rust issue before that helped cause this?

 

No, that frame got ripped apart because of the power steering, but I did not know what I was doing back then, it was all trial and error with a lot of error.

This was all before Ratsun existed, I put 620 disc brakes on my 521 first, and dealt with all the issues till I finally figured everything out over a year later, and had it driving like it should, then I added power steering, which puts a lot of side pressures on the steering gear itself, which twists the frame mount area.

I tried to beef it up a little as time went by, mostly I kept tightening the mount bolts till it got to the point that I actually started to break them, it was a distinctive sound when one of the hardened bolts let loose, no matter how much I tightened them bolts, the steering gear would move in this top to bottom twisting motion, I tried a lot of things to try and stop it, this brace I made that mounted to the horn mount holes that went around one of the power steering gear metal lines worked good for a while, but in the end I had to add some fresh metal.

I actually cut up a 720 frame a while back and kept the power steering gear mount area section, if this last fix did not work, I was going to cut the 521 section out, and weld the 720 section in.

 

Going that route would have made me have to figure out the idler arm mount, but that is just another hurdle to overcome.

To understand exactly what I did, you really have to know the whole story, I figured out that the 521 idler arm is reversible, so it can be used on the driverside, so I removed the steering column/gear, and put an idler arm in it's place, now I have a steering system with no way to steer it, then I had a custom centerlink made that had a tierod connection on the pass. side near that idler arm, I put the 720 steering gear on the outside of the 521 frame as far forward as I could get it, then I used the stock centerlink to make the system complete.

The custom centerlink.

The pass. side centerlink tierod connection.

Driverside idler arm.

You can see the 720 pitman arm here and how close it is to the driverside idler arm.

Here is the 720 steering gear mounted to the outside of the 521 frame, the back mount bolt is shared with the idler arm mount.

In the photo below you can see an upper mount bolt, I welded a piece of angled metal to the frame to try and stiffen the steering gear, I originally did not have this mount bolt, you have to do everything possible to make the mount solid, otherwise it will destroy the frame.

[datzenmike]

I can tell you from adding power steering to my 620 that this puts massive strain on the frame. I had no problems, but with the flick of the wheel you could be in the other lane so fast your head would spin. This adds a measure of safety as you could, with practice, avoid a sudden problem in front of you. My truck last weighed 3,500 pounds without me! or 1,000 pounds over stock.

[jvb5577]

Ahh this is power steering.  I wasn't interested in getting the power steering.  I was more after having the arms on the outside of the frame for more engine clearance.  :thumbup:

 

I will read threw your build thread.  Thanks guys