I have a buddy that just picked up a 55 F100 project that someone started and lost interest in. The front end of the frame has been properly c notched and boxed in with the axle flipped on top of the leafs. The previous owner also installed a rack and pinion steering unit, this truck has never been on the road and driving, so I wanted to ask if this set up is safe to use. All of the work performed on this truck like the 4" chop, suicide doors, frenched antenna, shaved everything,front flipping clip etc, was all done with an extreme amount of care and skill and the frame work is of the same quality. I know rack and pinion isn't recommended for a dropped axle pick up but does it make any difference when you have the axle flipped on top of the leafs? You guys are the experts on this sort of custom work, so I thought I'd ask here first
You start off by saying "properly c-notched" .... and then you ask if its safe .... lol. Probably best to post up some detailed pics and get some expert opinions but definatly don't put it in the road if your not sure .... for the "other guy's" sake.
CAN...it be safe, yea, if done somewhat/mostly correctly. But without detailed pictures, it's very difficult to tell if your buddys truck is even close to safe. Mike
I'll have to see if he can send me some. I was at his place yesterday but didn't have a camera with me.
Is the r&p mounted to the frame or axle? If frame, is it mounted at the correct height to minimize bump steer? If axle mounted, how is the movement isolated from the steering shaft? I thought about doing this one time, but didn't see a clear solution to the various problems one would encounter.
There is a reason you dont see some things regularly. The engineering to make it work has never been done because its just a bad idea. Rack and pinion on a straight axle is one of those things. Can it be done? Sure. Is it a good idea? One needs to ask, "why"? Other methods have been used for about a hundred years now, and it works. Have you ever seen a production car with a straight axle and rack and pinion? I would follow here, not lead.
Other than being non-traditional, why doesn't it work? As I stated earlier, I thought about it, but realized I had a more proven way to go, with parts I had on hand. I was working on a COE truck, so the lower end of the steering column was way ahead of the axle. My thoughts were to use a front steer rack mounted to the axle, (zero bump steer) with the steering shaft pointed straight ahead. At the bottom of the steering column a small 90 degree gear box with U-joints on input and output shafts would get steering wheel input to the rack. With this arrangement the rack could move vertically and the u-joints would absorb the travel with very little axial movement of the steering shaft. This was a p***ing thought, but I think it would have worked quite well, if I could have found a rack heavy enough to handle the stresses of a heavily loaded pick-up axle. As for the OP, I would have to see how things were hooked up, (shafts, U-jounts, etc before I could p*** judgement.
A rack mounted on the axle would need more the just u-joints to handle the bumps, there would have to be some type of slip yoke (like a drive shaft has) as the leanth would change as it moves up and down. Never seen one I felt would work. Saw one that someone just let a GM 3/4 DD shaft slide up and down inside the column. I wondered how long it wold last before it wore out and failed. Problem with mounting a rack to the frame is your tie rods are short (maybe a foot) and the pivot point of a straight axle is not (3,maybe 4'), leads to bump steer since the arc during travel is so different. The Unisteer racks they sell now work better but the tie rod is long, going from the left rail all the way to the right spindle, much closer to the pivot leanth of the axle.
Down here we use a RHD GM R&P mounted under ch***is rails with a beam axle. R&P is mirror of a LHD Cadillac Cimarron (J car). Steering arms are longer and pivot in middle via large plate attached to rack housing. Engineered with good geometry, minimal bump steer with no adverse handling as suspension travels through equal arcs. NEVER mount a R&P to the axle. A recipe for disaster.
http://midfifty.com/item.php?INV_ID=5874 RACK & PINION STEERING KIT FOR STOCK AXLE Fits: 1953-56 Ford F-100 trucks Part #:4610 Price: $699.00KIT Qty:<INPUT style="WIDTH: 40px" id=QTY cl***=rght value=1> Each truck takes: 1 ADD TO CART + Wish List Kit comes with power rack & pinion, rack to axle mounting plate and hardware. Custom made steering arms, tie rod ends, lower u-joint and steering shaft, and all mounting hardware. ALERT: See instructions when installing, improper installation voids warranty. This is a nice kit, but be aware the axle moves up and down, so a slip shaft style shaft is included. All kits include new steering arms to correct accerman, and reduce bump-steer. More exhaust clearance than a stock box. Works with any height springs & axles. You can use a stock or aftermarket steering column. A power steering pump is required. Includes: **Power Rack & Pinion, ** Tie Rod Ends** Rack & Pinion Mount Kit, ** Steering Arms ** u-joint for Rack & Pinion ** All necessary hardware ****KIT WILL NOT WORK WITH STOCK 3 SPEED COLUMN SHIFT as there is not enough room for shift linkage. if instructions are not followed carefully on install, wrong plumbing order can cause blown top seal. If leak detected on install is usually blown seal caused by improper application of pressure internally due to improper plumbing. Sy prefers the "toyota style" or power ***ist to this set-up. Keep in mind if using Disc brakes the caliper needs to be in the FRONT, if in the rear may cause clearance problems, most brake kits are front caliper, but if yours is rear you can flip the brackets most of the time. If the slip shaft is too short it will bottom out, follow the directions when cutting it. do not use with shifter as it takes up too much room and you want as much distance between the U-joints as you can get. If using original column you will need 4625 centering bushing
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