TECH WEEK Jag XJ6 IFS into F100

And thus we begin the all-intensive front suspension swap to rid my F100 of its poor ride, vague steering, and nose-bleed stance.

You see, this F100 is my daily driver. But it is also an old truck with a host of worn out components that drives with the grace of a tractor. And since I had pretty much decided early on that I planned to drive the wheels off of this thing for years and years to come, some major upcoming modifications became apparent. I wanted to go through the entire truck, build it the way that suited me, and know that it would be a reliable and cool ride that I can hop in at a moment’s notice and drive anywhere in the country.

The first of these major upgrades would be in the chassis department. The beauty of an IFS swap is that it upgrades your suspension, steering, and brakes all in one fell swoop. Sure, the old leaf spring & I-beam axle setup worked okay (and I certainly don’t think you could call it weak or unreliable), but it just didn’t offer the kind of smooth ride and responsive handling that I wanted in a vehicle I might drive coast to coast one day.

Thus I went into this project with a singular attitude in mind:

Do not take any shortcuts. Do it right from start to finish, no matter how much time or effort it took. I also kinda applied this logic to money. Basically, don’t be a cheap ass and skimp on important parts. Do it right the first time. Otherwise, it’s not gonna be worth a shit in the long run.

Upon doing an initial search on IFS swaps, I realized that the perfect solution did not exist merely because everyone has a different idea of what the perfect IFS has to offer. So, I needed to decide what the important points were for me and make some compromises. An early survey suggested several valid candidates. For example, there was the Crown Vic swap, which was very appealing due to its modern aluminum design and the fact that it practically bolts into place under the F100 chassis. There was the Mustang II swap, via an endless supply of bare crossmembers through complete hub-to-hub kits available from your favorite mail order store. There was the Volare swap, a tried and true old school method that got these trucks down where we wanted them. And it goes on and on. Custom kits, subframe grafts, etc. It was all out there. Honestly, I was a bit overwhelmed.

I was led onto the Jaguar front end by our very own ElPolacko here on the HAMB. Actually, I had wished to ask about the Dakota crossmember that he manufactured since those who had used it seemed to really like it. Unfortunately, I soon found out that they were no longer available. I was a few months too late. “I suggest you look into something like the Jag XJ front suspension,” said ElPolacko in short reply. So I did.

I went to Google, punched in my query, and stumbled upon a few gems hidden away in the furthest corners of the Internet. Apparently, the XJ6 front end was a very popular swap down under. Those Australian hot rodder’s had it down to an art, especially with the ’53-56 Effies.

I ultimately decided to go with the XJ6 front end because of its strong, compact design, elegant looks, and modern components (like rack & pinion steering and disc brakes with big 4-piston calipers). It was clearly a nicely engineered front end that would be a big improvement for the F100. Where other IFS options failed, the Jag front end prevailed. Unlike the obscenely wide Crown Vic, the Jag nails the track width to suit the F100 (59.5” compared to the stock 60&#8221. Unlike the under built Mustang II, the Jag is designed for a vehicle in the same weight range, if not a little more, as the F100. Unlike the hassle involved with installing a Volare clip, the Jag’s crossmember easily fits a variety of frames. For example, some of us have recently been watching 53sled’s Jag swap into his ’53 Chevy coupe: http://www.jalopyjournal.com/forum/showthread.php?t=513236
And a while ago we saw zman stuff one under a ’57 Buick: http://www.jalopyjournal.com/forum/showthread.php?t=24785 Hell, he even used the Jag rear suspension while he was at it. Anyways, point being, it will pretty much fit under anything and look good doing so.

For me, it also came down to the little details. For example, the Jag features forged control arms, which are plenty strong and look nicer than stamped arms in my opinion. There are no strut rods to worry about either. Also, the hubs have the same 5x4.75” Chevy bolt pattern, so many wheels will bolt right on. I have heard some people complain about the center of the hub being too big to fit the center bore of some wheels, but my regular smoothies fit without issue.

And now that I’ve exhausted my reasons for why the Jag swap is a serious competitor in the IFS market, it’s time to put one under a ’64 F100.

The first step is to get your ass down to the junkyard and snag the front end out of any ’79 through ’86 XJ6 Series III. The XJ12 cars will also work, but they come with higher rated springs, which may or may not be helpful for your application. The XJ6 springs turned out to be just right for my truck.







One note I would like to make about the Jag crossmember is that regardless of what you put it under, it can be made as easy or as difficult to mount to the frame as any other swap. However, there are two main ways to do it. The first way is to simply fab up a couple forward and rear frame brackets, and then bolt the crossmember right up, retaining all of the original rubber bushings, for an ultra plush ride. The benefit of this method is that the crossmember remains untouched, making it easily replaceable, and that the whole front end can be unbolted from just four points.



If you go this way, you will have to use the original Jag Z-joint in your steering hook up to make up for the movement in the rubber mounts.



I suppose there are also fancy telescoping shafts you can buy from Borgeson and the likes that will work just as well, but make sure you’re buckled up before looking at the price tag.

The second way is to cut off all the extremities and fabricate some perches to mount it up sleek & solid to your chassis. You can either weld or bolt it in at this point. The advantages here are a more responsive road feel and you can get the vehicle an inch or so lower at the same time because it attaches directly to the frame. Now, here’s the thing- If you choose to go with bolting it in, you have the benefit of still being able to drop out the whole shebang by unbolting it, but you keep the tighter suspension feel. This is my idea of a winning compromise.

Off to the junkyard we go.

The ’82 Jag I pulled my front end out of had been crushed down in the mud under another car for who knows how long. It was at least 90 degrees out that day, and conveniently the car was black. I nearly passed out wrestling the front end out from under the car. It took a good 4 or 5 hours working at it alone. But alas, it came out. I forked over $150 for it and dragged it home in the truck it would soon be married to. Upon disassembly, I discovered that it had a broken spring (not surprisingly- probably from having another car dropped on it).



I was off to a rough start. On the plus side, nothing irreplaceable was broken or bent. But man, the whole thing was a disgusting caked-on greasy mess. I scraped ¼” thick layers of grime off it while asking myself if I should just cut out this hot-rodding hobby nonsense.

The next step was to rip out the old suspension. The truck decided to fight me all the way too. It took all of a weekend for me to cut out a few rivets and extract some frozen bolts. I could tell from how my project was going so far that this was going to get a hell of a lot more fun.



At that point, I needed to sit down and stare at the Jag IFS for a while, and figure out how I was going to mate it to the F100. After sufficient time spent listening to oldies and looking at all the stuff strewn about the garage, I realized that the most important measurement to get was the axle centerline.

F100s sitting at stock height look just dandy. But as soon as you lower them, as many of you have discovered before, the wheels tend to appear pushed back in the fender opening. It’s a subtle visual thing, but since we’re doing a whole front end swap anyway, why not make it look right while we’re at it? All we need to do is nudge that centerline forward an inch or two, and then the truck will look rad.

Once the axle centerline was determined (1.25” forward of the original), the next step is in figuring out how to physically marry the crossmember to the frame. I am no pro fabricator, nor do I have any specialty tools. Just a Hobart flux core machine and a couple hammers formed my basic tool palette. In fact, I had never done anything like this before, and since the truck is my daily driver, I also couldn’t afford to have it off the road for too long. That meant leaving the 292 and front sheetmetal all in place, and working at the swap from underneath. Fortunately, I convinced my parents to let me takeover their garage for the duration of the project, which proved to be a huge help. What a sad SOB I am…

In the meantime, I began stripping the various parts, and painting them with KBS RustSeal. I am very impressed with the quality of KBS products. They are a lot like POR15, but a tad cheaper and a tad better.











I also began ordering stuff to rebuild the suspension. I called up Andrew over at Jaguar Specialties and he walked me through the process. There are a few idiosyncrasies with the Jag IFS that you should be aware of when rebuilding them. I can write more about these for anyone who is interested. I treated myself to an upgraded 1” solid swaybar with poly bushings and end links. I decided to stay with rubber for the control arm bushings though, since I was hard-mounting the IFS anyway. I didn’t want the ride to be jarring. New Lemforder balljoints, Brembo rotors, etc. etc. completed the package. Of course, all of this can be gotten for less from places like RockAuto or even your local parts store. But whatever.



Since I wanted to solid mount the IFS, I cut off the awkward crossmember mounts and cleaned it all up with the grinder. I also trimmed any extraneous parts that didn’t need to be there.







With the old suspension removed from the truck, it was easy to tell where the crossmember naturally wants to bolt up to. The original shock mount bolt holes are the perfect template to work from.

 

I jacked the crossmember up to the chassis, only to discover that the corners of the crossmember foul the frame rails by less than an inch on either side. Its an easy little section to cut out. By the way, the F100 frame is 34” wide- so I wouldn’t try using the Jag IFS on anything wider.







The crossmember hugs the chassis nicely and we are now getting into the thick of the action. I got myself a 10 inch by 6 foot piece of 1/8” cold rolled steel to form the mounting cradles out of.



Then I measured twice, cut once, measured again, and bent once. I had to make a ghetto bender since, you know, I don’t have any real tools. So pathetic.



In reality, it’s a GOOD thing that I couldn’t force the bend into a tighter radius. I ended up with two pieces that fit the profile of the frame rails very well. So I was happy. Onto step #386: welding the cradles to the crossmember. Because the pieces are 1/8” wide, I shaved another 1/8” off each corner of the crossmember where it contacts the frame.



In a careful balancing act, I jacked the crossmember up to the frame with the cradles slipped in place. The measuring tape and a couple taps with the hammer got everything locked into place. Shit, I thought to myself, this is actually going according to plan!

Now it becomes a game of measuring and marking, measuring and marking. Here’s an important note for all of you who do this swap: The crossmember should sit flatly against the bottom of the frame rails. Not only is it convenient for mounting purposes, but it will also give you good caster settings down the road (pun… intended?)

The thing to do now is to locate all your bolt holes, drill them, and keep trial fitting the whole assembly until it fits just right. I didn’t want any chance of the crossmember fatiguing over time from any twisting or stress, so I kinda went overboard with the bolt in procedure, adding four vertical studs to lock it all in solid.





The ‘studs’ are really just grade 8 bolts that I pushed through the backside and welded in place.



Like we said earlier, the shock mount holes make perfect bolt in points, along with two more in the back for additional support.



Finally, it was time to make the design a bit more permanent. The crossmember went back under the truck with the cradles in place. Once everything lined up correctly, and the butterflies in my stomach settled, a few tacks here and there assured that the pieces wouldn’t move on me when I pulled it out to weld it all together.

I gingerly lowered it and moved over to the bench. I was really new to welding (this was my first time ) so I practiced laying a few beads on other pieces first, then dived right into the finish welds on the crossmember.



I added gussets where it looked necessary, and went wild with the welder, hoping it would all be okay.



When the smoke dissipated, I was looking at this:



Not too bad if I do say so myself!





I test fit the new crossmember to the frame. To my relief, it slipped in place like a dream. Onward we go! On to the million other things that need to be done.

 

Shock mounts. Hmm… From what I had seen online, people had done it in nearly every way imaginable. I took a step back and went with the most logical approach. This is what I came up with:







It works fine, looks fine, and it even keeps the front suspension all self contained (meaning you wouldn’t have to unbolt the shocks to drop out the whole thing). I like little details like that.

Sweet! It looks like we’re done with the crossmember. Let’s lather it up in paint and install it!



Ten bolts per side with some loctite does the job.



Okay, so now what? Steering. Well this was kind of a puzzle. I wanted to keep the original column but obviously had to hook it up to a rack & pinion. F100s have an integral shaft and gear box, so the first thing to do is cut it off leaving as much of the shaft available as possible. But now the shaft is just flopping around at the bottom of the column? No problem. We’ll buy a bearing from McMaster Carr, get a friend (TORR here on the board) to turn down a collar to press the bearing into, and then slip it into the end of the tube.



At this point, my parents kicked me out of the garage under the reasoning that their precious Toyota Camry and Highlander take precedence over an old truck.



That’s cool. Challenge accepted.

I shaved the automatic lever stub from the column and called it good. Up to my Dad’s shop we went for a little home powdercoating. The column just barely fit diagonally in the oven. Semi-gloss black does the trick. I am a believer in powdercoat.



TORR was cool enough to give me a 15” Grant wheel to run instead of the 17” monster. Don’t get me wrong- I love the stock wheel, but I’m kinda following a vision here, ya know?



Oh boy. It’s time. Time to begin the final assembly! From here on out should be a lot of fun. On go the control arms, on go the spindles, on go the hub & rotors, the calipers, the steering rack, the springs, the shocks, the swaybar. Isn’t it grand when it all comes together?











Well aware of all the comments regarding Wheel Vintiques here on the HAMB, I went ahead and bought a pair of their 15x7” bare smoothies from Summit. Can’t beat the shipping… The wheels showed up and I had to throw em on the truck for a peak.



Thank god everything fit. No clearance issues with the hub or caliper. Off to the shop for powdercoating.





Everyone says to not skimp on steering components, so I didn’t. Flaming River stainless u-joints and a ¾” DD shaft connected the column to the rack. Be sure to order the special joint to fit the Jag end. It’s 48-spline.



With the wheels back in black, I got some good ol BFG Radials mounted on them. 275/60/15 and 245/60/15. I think they will look nice. Don’t you love the smell of new tires?

 

We’re almost done! Oh but wait. We’re missing brakes. This is actually a fairly confusing subject since everyone has something to say about master cylinders and yadda ya. After extensive research, I opted for a 1974 Maverick 15/16” manual master cylinder. I don’t like power brakes, but I wanted to make the most out of the nice Jag brakes. This cylinder bolted right up, but I had to extend the pushrod by about an inch to appropriately actuate the cylinder. It got a coat of the KBS paint too.



For hydraulics, I ran a 10psi residual pressure valve through a proportioning valve to the rear circuit, The purpose of the RPV is to keep ever-so-slight line pressure on the rear drum wheel cylinders so they don’t retract too far in when off the pedal. You would have excessive play otherwise. Disc brakes are a lot more effective in maintaining consistant feedback once settled in, so the front circuit was simply run through the proportioning valve and split into left and right lines.



After buttoning up various loose ends, the project was done.







Now there is only one step left. DRIVE. And what better way to do so than on a crisp Fall day in western Taxachusetts?





Godspeed.

 

That is a good summary of the job. Nice pics and descriptions. The Jag is a nice (almost) self contained piece, except the shock mounts. Going to do a Jag swap front and rear into a 53 GMC soon as I get the 86 Jag donor taken apart.

I may section my frame a bit to move the crossmember up into it a bit to get lower, I need to measure and determine where everything will sit before getting too serious with the sawzall and welder.

 

Excellent thread, excellent work on the swap, well done.

Just one quibble.

Please build a mount for that proportioning valve.

Having it hanging out in the void like that, support by nothing but those brake lines is making my teeth itch.

Brake line will fatigue crack if you ask too much of it, and I'm afraid that supporting a weight like that, cantilevered out like it is, in such a high vibration environment is just asking too much.

No big disaster though, as a mount bracket back to the firewall shouldn't be much trouble to build. It doesn't have to be anything very large (or hulk like), just enough to carry the weight of the valve, so the line doesn't have to.

Other than that though, it's a very well executed build that was very well documented.

And honestly, I'm always impressed by a guy turning out good work with no tools.

If you've got a shop full of fabrication equipment, folks really ought to expect you to do good work. Tools don't alleviate the need for skill, obviously, but if you've got good tools, you've got no excuse for turning out bad work (except, I guess, for being a hack ).

Turning out something like this with just a hammer, a grinder, and a half-assed hot metal pump (AKA a flux core wire welder) is yeoman's work, IMO.

 

Nice work....

 

Good post................................Looking at the right front shock.......................Is there a bolt, in the lower hole????

 

wow.... terrific job! now when are you going to fix the front bumper and body?

 

nice work you made this look really easy , bet the old truck drives nice now

 

Very common conversion down under due to availability, price and ride quality of Jag IFS. Big improvement over OEM suspension and better braking. Jag parts are readily available and common. Donor cars are around pretty cheap as other (US) IFS kits are way too expensive so we improvise and use what we can get our hands on. I have a few friends who have done this swap in a few different bodies and have never looked back.

 

Nice tech post.

I just thought I would add this, because someone will ask. These are the Jags to look for as donors.
They are called "XJ". XJ6, XJ12, XJS, XJ4.2, XJ5.3 (where 4.2 and 5.3 indicate engine size in litres) Just stay clear of XJ40 series from ~1987 up.

This is a Series 1. These ran from 1968 to 1973. The front end is good, but the 6 cylinder version has solid disks and 3 piston callipers. The V12 version is "the same" as series 2. If the front panels are gone look at the dash, series 1 cars had the small gauges in the middle of the car.


This is a series 2. These ran from 1973 to 1979. Note that the front bumper is higher, US models have rubber bits on the bumpers too. If the front panels are gone look at the dash, series 2 cars had the small gauges in front of the driver. All front ends are good. Vented disks and 4 piston callipers.
( If you happen to find a 2 door version of this series don't cut it up, restorers will pay $$$ for them )


This is a series 3. These ran from 1979 to 1987 as a 6 cylinder car and up to 1992 as a V12. Actually a very different car to a series 2, but looks very similar. Easiest way to tell them apart is by the lack of a front quarter window. All front ends are good, "same as" series 2.


This is an XJS. They ran from 1976 to 1997. All front ends are good. "Same as" series 2 or 3.


This is an XJ40. They ran from 1987 to 1994. Totally different front end. To me they look like they would work, but I've never seen it done.There is very little information available on swapping them compared with the earlier stuff. Best left alone.


Note: where I write "same" I mean functionally close enough, there are numerous detail differences that really don't matter to a hotrodder.

 

Not only is the information golden but your presentation and composition made the post very easy to follow. I am wondering how long did the project take from disassembling the truck to back on the road? Good job!

 

Fan friggn tastic post and job! I had a '62 uni back in the back in the, and I ended up selling it because I hated the ride, couldnt take it anymore as a daily. I have been thinking about picking up another one, and happen to have an '86 XJ6 front setup sitting in my parts pile, complete from rotor to rotor. I think with how this looks going together, that's going to be what I do. Just have to yank out the Y block and put a Chebby in there.

 

Nice !!

 

Well written. Thanks for sharing.

 

Nicely done... only thing i can add is the shock mounts. I'm thinking there may be some reinforcement in their future. But then maybe I just drive mine to hard.

 

well illustrated, and great end result, now just lower the rear

Job well done.

Cheers,

Drewfus

 

Very Nice Job!! Well written, well documented.

.

 

very well written, i can tell you did your tech research before you started. i was under the impression that the brake lines of the jag were 10mm and your truck must be 3/16 or 1/4", did you buy adaptors for this issue or have i been led astray about the 10mm brake lines. i did look them up at rockauto and it stated they were 10mm, what did you find? glad to see somebody can take a clear picture doing a tech article.

 

Fine job, Now buy yourself a Beer

 

Wow, fantastic work - not only the labor, but the photography & writing too. This will be THE go-to thread for F100 guys for years to come.

Do you have a pic of how you joined the stock column to the new DD shaft?

 

55 dude, Jags from the late seventies and up use metric threads on the brakes. The 10mm is the thread diameter, not the line diameter. You can easily make up lines to suit using the Jag fitting on one end and your own imperial fitting on the other

 

toddc i guess if your redoing all the brake lines you could just use the jaguar mc and hard lines from it also. the master he is using is SAE so fitting need some type of adaptor to connect jaguar lines to rest of system.

 

Thank you all for the positive feedback. The article did take me three days to write.

I planned to from the beginning. But I was running out of steam and time towards the end of the project, so I put it on the backburner. Thanks for reminding me to get back to it.

Yes there is. The lighting plays games.

It took about a month working afternoons and weekends.

I've already put over 5000 miles on it and there haven't been any signs of failure. But you may be right.

You haven't been mislead. You'll have to get an adapter or two to make it work.

I carefully ground down the end of the stock 3/4" shaft so there were two flats on each side, effectively making it a DD shaft. It's not hard but I didn't get pics of that step.

 

and I might be crazy. I don't know how many miles it was before I redid mine. But I did end up having to do them over. But sometimes I drive like a lunatic. Especially through the mountains, I love the twisties. I think I probably have close to 50k on mine now...

I'm actually going back over a bunch of stuff right now trying to get her ready to go to the Roundup.

 

zman, do you have any pics of how you did your shock mounts?

 

lol, not sure if I do or not, I'll see if I can get some though... I had a problem with them flexing when the car was driven hard.

 

Nice Job Matt...especially with limitations on room & tools... I really like the cradles you made to bolt-in the x-member and appreciate the line of thought for considering the different units and related compromises.

I've never messed with a Jag IFS or IRS, but this takes a lot of the mystery out of it. Looks like theres some room to section the x-member into the stock rails for those wanting to go lower. What are the clearances like to the oil pan & headers in your F-100?

Again, great job, and thanks for the thorough narrative. This one will go into the archives.

 

One other question...what was the pricing like for all the rebuild parts to make the front end "new" again? I would assume the cost would trend higher than the American IFS options, but as I said...never messed with a Jag before...