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Discussion Starter #1
I'm at a crossroads with my rig ('79 FJ40) i've been trying to do some endurance racing in the mod class of the ECORS series but i keep breaking stuff in my axles (built cruiser axles), i'm in the process of putting a 14 bolt in the rear and making plans about the front end. Basically i am dreaming of IFS and wondering if it can be done for anywhere near the same cost as building a D60 to the hilt? My rig is tubed out in the front with the radiator in the back so i believe i have room for the ifs up there. Is there anyone building production ifs parts yet for our sport? Or are there any factory pieces that are strong enough to hold up with mods? I have searched :flipoff2: and all i have found are blingin' one-off ifs buildups that are too badass to even look at...
 

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I've built several a-arm (front and rear) race vehicles (all 2wd). The "one off" components are not that scary as they sound.

My current build sheet for an IFS Ultra4 uses a lot of off the shelf parts.

In terms of off the shelf components that help save a lot of money:
-Knuckles/spindles - Look into 3/4 or 1 ton Chevy front knuckles. Strong. 4 bolt Unit bearings. Adaptable for uniball uppers and lowers. Easily gusseted/braced for strength
-Diff - Chevy 3/4 or 1 ton front AAM 9.25 front differential.
-Shafts - No way around this: they are going to be expensive. Call up RCV and tell them what you want. Lifetime warranty and they are strong. They can make the Inner CV bolt right to the AAM 9.25 diff and the outer stub shaft/cv fit the 3/4 or 1 ton unit bearings.

For the fabricated parts - building a-arms isn't that hard. Design them / mock them up and then build a jig so you can accurately reproduce them. They don't have to be elaborate, just simple and strong.

The actual geometry is more difficult. If you don't have any experience with IFS / IRS geometry modeling, find someone that does or READ, READ, and READ. I spent a couple years learning from the best Pro-2 and Pro-4 short-course drivers in the world and I've barely scratched the surface.

Things to know to have a halfway decent handling rig.
-Roll center
-Roll center migration
-King-pin inclination axis
-Camber curve
-Bump steer minimization
-anti dive / anti squat
-shock travel vs wheel travel
-spring rising rate
-front to rear roll axis

The list goes on and on but nail down the biggest items and its a good place to start.
 

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You may want to look at fullsize 3/4 ton/1 ton chevy IFS parts.

The knuckles are big, 9.25" diff (with pretty much all gear ratios and lockers available).

RCV makes shafts for them, which are probably cheaper than "custom" stuff. Or I'm sure they would make some with longer center shafts if you wanted more travel/differnt track width.

http://www.rcvperformance.com/product-details-axles.aspx?sku=CVJIFS-GM2535



The difference is, will you be happy with 15" of travel? because when you get to more than that, you are pretty much looking at center mounted diff.

Check out Bebe's thread on what they did to her H3.
http://www.pirate4x4.com/forum/showthread.php?t=915987

They started out with a TTB HP44 diff, but ended up cutting up a LP44 and using Ford 9" axle end bearings and custom inner shafts to build a "center section". The inner shafts were D44 Rear axle blanks with the Chevy Inner CV flange bolt pattern cut into them, then cut and splined to lenght.

Then they used 1 ton chevy CV axles and custom A-arms to the stock knuckles. I believe the HP44 center section would have been better, but they needed driveshaft clearance. You could always buy a cheap-ass D60 rear axle or Ford 9" and cut it down using the same method.

That said,


If I were doing it, I'd look at getting a 2500HD long travel kit from Pure Performance, KillerOffroad, or Dixon Bros, and adapting it to my frame with all 2500HD parts (center diff, brakes, unit bearings, etc). That way your maintenance/wear items would be easily sourced/replaced.

http://www.killeroffroadfab.com/products



http://www.pure-performance.biz/?r_intro=1


http://www.dixonbrosracing.com/content/blogcategory/12/5/


^^They all claim 15+" of travel with 4wd.

The downside to using the Chevy diff, at Chevy full width, would be that you will end up with a wide track width ~75" or more... but a custom "narrower" center like they used on Bebe's H3 could solve that.
 

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Discussion Starter #4
what about H1 hummer stuff, like the center section or knuckles? any better than 1 ton chevy or about the same?

and what about steering? can you still just use a form of full hydro or do you have to use the bling $$$ desert truck stuff?
 

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Discussion Starter #5
NIck, i think i have 14" of travel now, so 15" would be cool. i wonder how it would be for trail riding and point and shoot stuff? and damn 75" is WAY to wide for ecors treedodging racing

the rcv's part of the build don't scare me unless they are more than rcv's for a D60 would be?

and there's no way i would use a D44 center section, D60 minimum.

do you have to have a centered chunck or can it be offset?
 

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what about H1 hummer stuff, like the center section or knuckles? any better than 1 ton chevy or about the same?

and what about steering? can you still just use a form of full hydro or do you have to use the bling $$$ desert truck stuff?
I think h1 portal boxes are perfect for a long travel setup. Jimmy's built an ifs car with full hydro, or you could build a relay setup like '86-95 toyotas used and add assist. Check out the threads by mosebuilt; lots of common hard parts with fabrication in between.
 

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Discussion Starter #7
The actual geometry is more difficult. If you don't have any experience with IFS / IRS geometry modeling, find someone that does or READ, READ, and READ. I spent a couple years learning from the best Pro-2 and Pro-4 short-course drivers in the world and I've barely scratched the surface.

Things to know to have a halfway decent handling rig.
-Roll center
-Roll center migration
-King-pin inclination axis
-Camber curve
-Bump steer minimization
-anti dive / anti squat
-shock travel vs wheel travel
-spring rising rate
-front to rear roll axis

The list goes on and on but nail down the biggest items and its a good place to start.
Where's the best place to learn about this stuff? Dezert racing forums? And do you have a build thread?
 

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Desert racing forums are halfway decent if you can wade through all the BS. Google is your friend. There are a couple different websites with info on design IFS for road scenarios (not all that different). SAE Formula has design reports from different universities that have good info about ifs design. Circle track guys spend a lot of time on this as well.

I don't have any build thread with the IFS design info. Most of it is tightly guarded secrets between teams.

http://en.wikipedia.org/wiki/Roll_center


http://www.onedirt.com/tech-stories/suspension/finding-your-center-finding-your-front-and-rear-roll-center/

Google "roll center design" or something similar. Basically you draw the suspension in 2D and calculate/measure the static roll height at all points through the travel. This is the theoretical point in which the suspension will roll about at that given static moment. The idea is to minimize the roll center migration as the point will move as the suspension cycles.

Then you compare it to the rear roll center and COG to determine moment about the roll axis. That can be used to calculate anything from swaybar rates to spring rates.

The height and migration of the front and rear roll centers will affect oversteer, body sway, braking, etc. Even with a well designed IFS/IRS, we still build in a LOT of adjustability to fine tune the suspension to the driver and chassis. Our modeling is pretty close but it never translates 100%, especially when you throw in surface traction, bumps, camber, wheelspin, etc, etc, etc, etc.
 

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mookie said:
Basically i am dreaming of IFS and wondering if it can be done for anywhere near the same cost as building a D60 to the hilt?
First off, what is your definition of a built to the hilt D60? Some people think $6,000 is an expensive D60, some built D60 front get to $10,00 and above.

Unless you build it all yourself, that $6,000 range will be tough to hit. $10,000 is a more realistic price range, but it depends on how much you are going to do yourself and how much you want to buy.

You can build your own if you do your homework. IHCJ9 has some good bullet points to study. As touchy as link suspension can be to improper design, IFS is even touchier. Definitely spend your time designing and researching to come up with a design that will work.

You also need to take a real close look at your rear suspension link set-up, it can affect how the front reacts a lot.

Mirroring the geometry from a stock vehicle but with longer a-arms for more travel is a great way to start out. If you are worried about overall width, just move your inner pivots closer together.

Also google A-arm vs J-arm, the J-arm is def the way to go with a front engine rig, easier to get longer arms, which mean more travel.

CV pivots and plunge is another term you'll need to research and look at. If your pivot points are off from the CV pivots or you have too much plunge, you'll tear stuff up.

14-15" is huge, you'll love the way it works. Getting above 15" can get tough unless you know your design geometry and/or start going wide.


mookie said:
the rcv's part of the build don't scare me unless they are more than rcv's for a D60 would be?
The regular D60 RCV CVs can be used for your outers if you plan using a D60 spindle and hub arrangement, but you also have to have inner CVs, so more money there.

The diffs are pretty easy to get into. All you need to do is to figure out how wide your CV flange to flange needs to be. The Spidertrax and Currie 9" hsgs both are designed for a 14-1/2" - 14-5/8" flange to flange. You can get a D60 down to that measurement with some machine work and another great one to mess with is the GM 9.25" center; easy to get into the 14" range on the F to F measurement and has a high pinion. Anything narrower is going to be tough to do, especially with a front engine.

Zippy7 on here and I have been working on a design to bring IFS to the price level of a high end D60 price, it is tough, but we think we are on a good start. All the parts and pieces will be available individually so you can build the whole set-up or just use a few of our parts to build your own around.

We're designing ours around the D60 RCV CV outer and the 934 inner CVs, the best price to strength ratio. Though it will also take the monster series 30 CVs for those with deep pockets.
 

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A race worthy fabricated IFS assembly wont likely be as cheap as a dana 60 set up.

the 2500/3500 chevy ifs is as close as it comes
 

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what about H1 hummer stuff, like the center section or knuckles? any better than 1 ton chevy or about the same?

and what about steering? can you still just use a form of full hydro or do you have to use the bling $$$ desert truck stuff?
H1 hummer stuff is portal boxes, really strong, but almost a completely different setup. They are RETARDED WIDE and have a TERRIBLE scrub radius, that is why the Hummer H1 wheels have like 7" back spacing. They also have inboarded brakes on a AMC 20 center section. The portal boxes would take the stress off the CV axles and diff though.




You could run a regular double ended ram just fine.
The high $ desert truck racks are for center mount diffs with LONG a-arms, which need LONG tie rods to not have huge amounts of bumpsteer.

NIck, i think i have 14" of travel now, so 15" would be cool. i wonder how it would be for trail riding and point and shoot stuff? and damn 75" is WAY to wide for ecors treedodging racing

the rcv's part of the build don't scare me unless they are more than rcv's for a D60 would be?

and there's no way i would use a D44 center section, D60 minimum.

do you have to have a centered chunck or can it be offset?
I think it would work good for all around riding, maybe not straight up rock garden crawling, but everywhere else it would be great.

The RCV chevy axles are ~$2500. D60 straight RCVs are ~$2300.

You wouldn't and probably couldn't easily package a centered diff in the front, but you could build one narrower than the Chevy 9.25" factory diff.

Here is one on Ebay. They are cheap and very plentiful.
http://www.ebay.com/itm/2005-Chevy-2500HD-truck-front-differential-complete-Chevrolet-/270928282977



The STOCK wms is 69.5". You could run a tubular upper a-arm with uniball, factory balljoint lower and get ~11" travel.

The long travel kits add 9" of total width to get ~15-16" of travel. This would require longer center shafts in the CV axles.


If you got a cheap (free?) D60 rear axle, you could cut it down, convert it to semi float Ford 9" ends and get the blank axle ends machined to bolt up to a Chevy CV axle (instead of lug studs)

^^ This is essentially what they did on Bebe's H3, but with a D44 and the H3 knuckles.
 

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Also, if you went the IFS Chevy diff/Arms/Etc, you might consider buying a used regular lift kit for a 2500HD.

This would get you a pre-fabbed lower cradle and the taller knuckles (larger balljoint spread will handle the loads better). Just hang the cradle from your frame, fab upper A-arm mounts on the frame.



Then you could buy or fab your own A-Arms.

As far as geometry, I'd just copy the GM geometry for the most part, maybe add some negative camber with the A-arm to help with tire contact patch during hard cornering.

As ihcj9 pointed out, there is A LOT that goes into the HOW and WHY of IFS suspension geometry, but if you copy a decent factory setup, it'll handle like the decent factory setup
 

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Discussion Starter #14
hmmm.....my worktruck is a '99 4x4 chevy 3500, that would be handy to have to look at for comparison and setting up. and i bet you can get that centersection etc for practically free at pull-a-part.

the more i think about it though the stupider it seems to me to put ifs in a freaking land cruiser. i already have a 4-link setup that works good, prolly just gonna do the D60
 

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IF you go with the 2011-up Chevy parts, they are even better, BIGGER EVERYTHING. More travel and a better front diff (not a stupid clamshell style like the one i posted earlier). Of course stuff that "late model" might be hard to come by, but not impossible

Here is a shot of the front suspension with a BDS 4" lift


Here is the front diff. actually has a "real" diff cover



and apparently if you get a uni-ball upper A-arm they will pull 10-11" travel in stock form, Maybe more with coilovers instead of the stock torsion bars?


 

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Depends on your view of race worthy.




How so?
so whats race worthy? subjective. lets make a list:

1. 35" tires or bigger
2. 12+ inches travel
3. lockable
4. And most important: able to take a geniune thrashing repeatably

to do that you need expensive cv's and expensive diffs. as of yet, neither exist. just the cvs alone for the front end are $3000.
 

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The STOCK wms is 69.5". You could run a tubular upper a-arm with uniball, factory balljoint lower and get ~11" travel.

The long travel kits add 9" of total width to get ~15-16" of travel. This would require longer center shafts in the CV axles.


If you got a cheap (free?) D60 rear axle, you could cut it down, convert it to semi float Ford 9" ends and get the blank axle ends machined to bolt up to a Chevy CV axle (instead of lug studs)

^^ This is essentially what they did on Bebe's H3, but with a D44 and the H3 knuckles.
On this note how bad of an idea would it be to use one of these kits and narrow the center section and mounting points 9"-10" to achieve the longer travel with a stock WMS? Obviously on a custom fab front end, but it seem like it would be fairly "easy" to go to a junk yard cut a front end off a frame to have all the mounting hardware you would need and geometry dimensions and just mount it all narrower at the frame end.
 

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wouldn't the IRS Ford 8.8's from Thunder birds or the 9.25" in the rear of an expedition work well for a really long travel center mount setup?

I am not sure how they compare in strength to their strait axle counterparts but the strait axles are quite strong in both sizes and both have good aftermarket for gears and lockers.

for a front engine, especially a heavy engine I would aim for the 9.25 expedition diff as it already handle v8 power and a heavy 6000 lb ish truck.
 

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so whats race worthy? subjective. lets make a list:

1. 35" tires or bigger
2. 12+ inches travel
3. lockable
4. And most important: able to take a geniune thrashing repeatably

to do that you need expensive cv's and expensive diffs. as of yet, neither exist. just the cvs alone for the front end are $3000.

Dustin,

My 1986 4Runner Toyota has:
1) 35" tires
2) 11" travel... don't tell me one more will make a big difference.
3) ARB's front and rear
4) I beat it like a redheaded step child.

The RCV CVs for my Toyota IFS ran $2000.00.

So again, clarification is needed in so many aspects, not only what type of racing you do, but also how much work you can do yourself and how much you think a fully built Dana 60 is.

Now if your list read:
1) 40"+ Tires
2) 18"+ travel
3) 500+ Horsepower
4) Racing at the Ultra 4 level

AND you are comparing it all to a $8,000 D60, then you'd be a lot closer in your statement.

Trying to compare building a fully built D60 to a race ready D60 is hard, too many variables; it would be better to talk pricing. $15K is doable for a race ready IFS and the price will continue to drop. These desert companies that are getting $25,000K + a kit are overcharging depending on what comes in the kit.
 

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Dustin,

My 1986 4Runner Toyota has:
1) 35" tires
2) 11" travel... don't tell me one more will make a big difference.
3) ARB's front and rear
4) I beat it like a redheaded step child.

The RCV CVs for my Toyota IFS ran $2000.00.

So again, clarification is needed in so many aspects, not only what type of racing you do, but also how much work you can do yourself and how much you think a fully built Dana 60 is.

Now if your list read:
1) 40"+ Tires
2) 18"+ travel
3) 500+ Horsepower
4) Racing at the Ultra 4 level

AND you are comparing it all to a $8,000 D60, then you'd be a lot closer in your statement.

Trying to compare building a fully built D60 to a race ready D60 is hard, too many variables; it would be better to talk pricing. $15K is doable for a race ready IFS and the price will continue to drop. These desert companies that are getting $25,000K + a kit are overcharging depending on what comes in the kit.
Good points. all the ifs cars out there on pirate right now are so pricey that its hard to visualize a cheaper solution. if you used stockish parts and your only real bling parts were the outer cvs, then the costs would be more approachable. if you kept the car under 3000lbs that would sure help too.

Several years ago i ran Prichet Canyon in Moab with a 65 year old guy who took his fj cruiser on 35" iroks up every line except knocker rocker and he outwheeled all the minitrucks that day. And i have a beat-up 93 H1 i wheel hard with 37's and it can do amazing things and take repeated abuse. only has broken 1 cv. the h1 stuff can be upgraded to 35 spline for cheap
 
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