Make it handle

[slow4dr]

Originally Posted by Walkersan

Something else I had rattling around in my head recently about IRS. With the huge reduction in un-sprung weight on a IRS, is it the overall weight that is keeping more people from using this type of setup? Complexity maybe?

Cost & Complexity would be my #1 & #2 reasons

[Scot_Douglas]

Originally Posted by Walkersan

Something else I had rattling around in my head recently about IRS. With the huge reduction in un-sprung weight on a IRS, is it the overall weight that is keeping more people from using this type of setup? Complexity maybe?

Originally Posted by slow4dr

Cost & Complexity would be my #1 & #2 reasons

I didn't weigh things when I changed the rearend out, but the Tbird IRS didn't seem to weight a whole lot more than the 12 bolt and trailing arms and associated parts.

Complexity? What? Instead of two pivot bushings to replace in the old trailing arm suspension, I have (I think) 14 or 15 total in this bird rear end. Totally overlooked that one when shopping around. I planned on shortening my wheelbase 5" and going with a 4-link solid axle. When I looked at DOM tubing, rod end and other associated prices - the $150 for this IRS unit seemed like a steal! Not to mention it came with disc brakes.

Of course, I checked the bushing prices AFTER I started the install. Live and learn.

I am excited to see how the truck rides and handles with the mods I've made - I didn't start out to build a truck for the track - but the more I read here and see what can be done with what we have, the more excited I am to try an autocross or two with it.

[slow4dr]

Luckily, the trucks track width and frame rails are wide enough to house many of the factory takeouts available. I tried to use a C4 Vette IRS in an early Nova. I had two options here, expensive wheels with huge backspacing or cut everything down(halfshafts, batwing, control arms, tie rods etc) to shorten the track width to make it fit in the car. When it was all said and done I would have had to do both to make it fit and work properly. At the end of the day even the more expensive and rare Dana 44 option still wasn't capable of holding very much HP when abused(which I had full intentions of doing). I ended up buying a 9" and made a custom 3-link with a watts link for the price I sold the C4 vette IRS for. If I had to do the same thing today I would use the GTO or G8 IRS.

[Scot_Douglas]

Originally Posted by slow4dr

Luckily, the trucks track width and frame rails are wide enough to house many of the factory takeouts available. I tried to use a C4 Vette IRS in an early Nova. I had two options here, expensive wheels with huge backspacing or cut everything down(halfshafts, batwing, control arms, tie rods etc) to shorten the track width to make it fit in the car. When it was all said and done I would have had to do both to make it fit and work properly. At the end of the day even the more expensive and rare Dana 44 option still wasn't capable of holding very much HP when abused(which I had full intentions of doing). I ended up buying a 9" and made a custom 3-link with a watts link for the price I sold the C4 vette IRS for. If I had to do the same thing today I would use the GTO or G8 IRS.

Well, with my application - and I am not discounting my ignorance / lack of experience - I couldn't keep the rear frame rails because they got in the way of upward travel. I think the 6"-7" drop in the rear is the culprit there though. :LOL: truckirs.com uses the same rearend under an old ford and durned near make it a bolt-in affair.

The wms-to-wms of the bird IRS is 63.5"; I'm using 1" adapter plates / spacers on each side for a 7.5" wide wheel with a 38mm negative offset (2010 Camaro).

[slow4dr]

LOL, I ended up moving my rails as well.

[robnolimit]

We have built a few trucks with the Crown Vic IRS, using the factory cage. I have to say that they ride great. We use a 9000 style bag, or a 325 lb spring, as the iRS will naturally want a big more rate that a solid axle. The rails do need to be moved, C'd, or re-shaped to clear the upper arms, but do that after the cage is welded in and its pretty easy.

[Scot_Douglas]

Originally Posted by robnolimit

We have built a few trucks with the Crown Vic IRS, using the factory cage. I have to say that they ride great. We use a 9000 style bag, or a 325 lb spring, as the iRS will naturally want a big more rate that a solid axle. The rails do need to be moved, C'd, or re-shaped to clear the upper arms, but do that after the cage is welded in and its pretty easy.

I've been making it up as I go along.



Also, I attribute this thread and YOU, ROB, for making me really want to get this truck to handle! (thank you!)

[robnolimit]

Thanks, your progress looks good. When the truck is finished at ride hieght, try to set the spring hieght so that the half-shaft is level. Keep building.

[killerpickup]

Have you guys heard of team 321 in Florida, they seem to have their s--t together on the independant rear install. Reach them at Truck IRS.com. killerpickup

[Barney Rubble]

wow, amazing thread, just spent the morning go over it, understood a fair bit.
robnolimit - appreciate a vendor being open to questioning, and responding thoughtfully.

New to pickups first post new truck
I want to improve the handling, but not for track (I have a car for that), but just so she drives better. Don't like bouncing along our rough roads. She has leaf/shocks, PS, Power drums; 17" rims with a 6 bolt pattern; SB327.
I have been looking at the Mustang IFS kits...... with power rack; and I am impressed by the No Limit chassis package.
I don't really want her riding any lower, no plans to carry loads either.
The fuel tank will be shifted to the rear also.
Living in Australia is a consideration with shipping costs from the USA, but still with that, it seems to be much cheaper to buy from stateside.
Any thoughts?

[robnolimit]

welcome Barney. Thanks for the props. - what year truck are you working on? Also, we can build the IFS for rhd, we've done a few for aussieland and europe.

[Scot_Douglas]

Originally Posted by robnolimit

Thanks, your progress looks good. When the truck is finished at ride hieght, try to set the spring hieght so that the half-shaft is level. Keep building.

Thanks! Means a lot coming from someone that does it for a living.





I wasn't sure about where to set the IRS, but guessed the same starting point that you mention - I'm close.

Originally Posted by killerpickup

Have you guys heard of team 321 in Florida, they seem to have their s--t together on the independant rear install. Reach them at Truck IRS.com. killerpickup

A few posts back I mentioned them - they have great info and a pretty good method for getting the bird IRS into older trucks. Problem for me is that my rails get in the way - which is less trouble on a skinnier leaf-sprung frame like the Ford they show a buildup on. Also, and this is just my personal opinion, I didn't like how the end product looked on the front of the subframe. To be specific - the outriggers they made to allow it to be a near bolt-in affair - just doesn't "flow".

No matter - I spent lots of time reading and re-reading their site. They offer a pretty good way to go with IRS on the cheap.

[Barney Rubble]

Originally Posted by robnolimit

welcome Barney. Thanks for the props. - what year truck are you working on? Also, we can build the IFS for rhd, we've done a few for aussieland and europe.

I left all that info out of my post coz I thought you might click the link!
She's a 59, and left hand drive!

[M5-]

Originally Posted by robnolimit

We have built a few trucks with the Crown Vic IRS, using the factory cage. I have to say that they ride great. We use a 9000 style bag, or a 325 lb spring, as the iRS will naturally want a big more rate that a solid axle. The rails do need to be moved, C'd, or re-shaped to clear the upper arms, but do that after the cage is welded in and its pretty easy.

Sledding season is almost over so its time for me to dig the 65 out of the snowbank and do some more work on it. I know I read this on here somewhere but what years of Crown Vic are we talking and if I remember they use the 8 3/4" rear end? Will that have a posi in it?

Thx M5

[killerpickup]

M5, Most of my info was on the t-bird 89-97, and the lincoln mark VIII,93-98. Ive been trying to chase down info on the big fords but local wrecking yards seem to be clueless. Iam hoping with my set back and an independant rear Ill have a good chance of taking down some of the local talent. Its turning out to be and extensive build, but Iam really have fun, what with all the professional help its even easier.

[Scot_Douglas]

Originally Posted by M5-

Sledding season is almost over so its time for me to dig the 65 out of the snowbank and do some more work on it. I know I read this on here somewhere but what years of Crown Vic are we talking and if I remember they use the 8 3/4" rear end? Will that have a posi in it?

Thx M5

Originally Posted by killerpickup

M5, Most of my info was on the t-bird 89-97, and the lincoln mark VIII,93-98. Ive been trying to chase down info on the big fords but local wrecking yards seem to be clueless. Iam hoping with my set back and an independant rear Ill have a good chance of taking down some of the local talent. Its turning out to be and extensive build, but Iam really have fun, what with all the professional help its even easier.

The bird/mk VIII units are 8.8 diffs - lots and lots of limited slip / posi / locker choices.
As for finding a rear end - just keep your eye open for t-birds of that vintage in craigslist. You can find them cheap ($500 for a whole car) - if you have the means, you can take the rear end out of it and take the rest to the scrapyard. You can probably part out the engine and trans too - that, along with scrap prices, the IRS will be close to free.

[jayman68]

According to the local Ford shop the 98-03 Lincoln Town Car has IRS, on some models. I have not found one yet and the wrecking yards don't know the info.

[RANDOMIZM]

Rob,
I have a 68 suburban that I have Dominator 2600 bags for, and am looking to eventually lay out. However, I'd like to have fun with it whenever possible. Especially after getting to ride along with one of the cars at Del Mar this past weekend. I'm not looking to be able to set fast times, just want a set up that will be fun if I ever took it out to Adams Motorsports Park.
After reading this thread (and taking lots of notes) I have an idea of where I need to go, but also knowing the weight/distribution is different, I'm not entirely sure where exactly I need to go. What would you suggest I do front and rear (i'm on a college budget, but am not afraid to fab stuff up).

Thanks.
BTW- Love the work you guys do.

[robnolimit]

RACE REPORT Another win for the No Limit 55 Bullit. We had a great time Del-Mar, and there was some good competition. Our fast lap was a 34.144 sec. Mary Posi drove it and ran a 34,637, and said she thought it would run a mid 32 as is. That makes me happy. Rob McEwen and the Dueces-Wild shop ran a 35.153 for 2nd, and our J.T. ran 36.647 for 3rd. Rob Phillips ran a quick 34.557 lap in his Hotchkis 69 C-10, for 5th in the vendor class. A great showing for trucks, as even the JT was faster than half of the entries.

[Walkersan]

Originally Posted by 76kcfdeng

Thanks Rob, I hope to have it driving in a few months. Depends on how much body work I want to do before I put it together, LOL. I may paint the firewall and prime the rest so I can drive it for a while and continue the body work. I thought about the spring pockets not lining up but came to the conclusion it would not be an issue. Still working on cross bracing the frame, have to make sure everything will fit.

Any updates on this setup? Really interested in this to increase caster on my 72 since I already bought and installed everything on the front end.

Would this change have a negative affect on bump steer? I am trying to mentally picture the change, and it seems the outer rod ends would raise slightly with this mod, so this would make bump steer worse on a lowered truck... similar to relocating the lower ball joints like Rob did.

Nice job on your run at Del-Mar Rob. Got a video of JT in action there?

Walker

[TrueChevyTech]

been keeping up on this thread for awhile now, I'm interested in a cost effective air ride solution that handles, I have 1 mile of gravel to get over so static will really tear the truck up. front dropmember is very appealing so far. and another thing, if it's vendor bias PM me please! love makes trucks !!

[robnolimit]

Walker - Thanks, had a great time in Del Mar. I should get some video up today. A 'stock' truck has bumpsteer, and the inner pivit is too high (or the outer is too low) In fact, the Hotchkis TVS kit comes with a fabbed centerlink for the steering to lower, and widen, the inner pivits. When you tip the spindle back, the outer pivit rises, and helps to cut down the bumpsteer. So, it can be more help than hurt.
Truechevytech Although I understand the politicaly correct crowd, I'm quite willing to call it as I see it, and let our shop reputation ride it out. That being said, the one thing you need to keep in mind is quality. You can use mostly stock parts, and upgrade to bags, like using Ride-Tech 'cool ride' kits. Shocks will be important, and the longer the better. Try Porters upper mount for the front, and our new rear kit. When it comes to controls, this is where you need to spend some coin. While you can use two dual needle guages, and four switches, use a TOP QUALITY valve block, RideTech, or AccuAir. Yes, you can use their digital diplays/controls if you want too, but that will push up the $$. A large air reserve is more important than multiple pumps. One ViAir 400 or 440 compressor, and a 5 gal tank (or two 2 or 3 gal) will be all you need. 1/4" inch line is fine, but I like 3/8" for a bit more speed on the 'up' stroke. Stay away from anything bigger, as it is tough to tune in to ride height.

[Conundrum]

Originally Posted by robnolimit

Walker - Thanks, had a great time in Del Mar. I should get some video up today. A 'stock' truck has bumpsteer, and the inner pivit is too high (or the outer is too low) In fact, the Hotchkis TVS kit comes with a fabbed centerlink for the steering to lower, and widen, the inner pivits. When you tip the spindle back, the outer pivit rises, and helps to cut down the bumpsteer. So, it can be more help than hurt.

Hey Rob, how much will chopping the crossmember 1.5" affect this same issue?

[Walkersan]

Thanks for clarifying the bumpsteer question. I am definitely in for moving the lower A arm rod forward an inch to increase my caster.

Walker

[Crashjunkie]

This thread is full of useful info. Glad I found it!
I have two questions specific to my 69 Gmc build...
1. Am I wasting my time with leaf springs? I flipped my axle above the springs and am running a set of traction bars from Brothers Trucks that are supposed to act like I moved the IC forward. I haven't gotten the setup on the road yet, so I don't know if it works.
2. Should I spend the time/money on converting to a shortbox, solely from a handling perspective....?
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