I have done the CV IFS install on my '58 F100 and I couldn't be happier with the improvement in ride quality. I am aware that there is a way (kit) to install a late 80's thunderbird IRS in our trucks. My concern is what would my truck drive like with independent suspension all around. I know it will ride great but I am concerned about how it will perform.

Will the independent suspension hang curves well at high speeds? See, what I am thinking is that with independent suspension all around, the truck will tend to roll and sway easier. In my mind, it seems that going around a curve at a high rate of speed will cause the wheels on the outside to roll under the truck and result in poor handling.

My question is, will the truck perform well at high speeds driving on curvy roads? The ride quality is not a concern of mine because I know it will ride great. Also, will the rear end from this car hold up to the power of a built 351 W? I would hate to try to burn out and end up tearing up the rear end.

Thanks for the input.

 

Go for a rear end out of a supercoupe, thicker sway bar, limited slip and disc breaks. The later 94+? Had disc brakes as well. The cars handle fairly well and weigh pretty much the same so shouldnt handle too bad even with the higher center of gravity.

Thats the conclusion I came to after researching a cv front/tbird rear swap.

Scott

 

I would like to see if I can get a posi independent rear susp. I'm sure I could get that as an upgrade if necessary. Disc brakes are also at the top of my want list.

My goal is to have a good/great handling truck. My long term goal is to have a suspension that would allow a trip or two around a road course track for a time trial just for kicks.

I would like to know if the independent rear susp I've heard of (t-bird, lincoln) has aftermarket parts to upgrade the handling.

Thanks again for the input.

 

the t bird or Lincoln rear end from a v8 car should have limited slip and disk breaks if not limited slip it will be a 8.8 third member gear ratios and aftermarket parts are around everywhere

 

The first thing I would do in your truck for what you are describing is put in a set of drop springs from Eaton Detroit. The lower it sits the better it will handle. That would finish up your IFS.

With the IRS you have a few options. They came with both disc & drum brakes. Mine has drums that I will be converting to disc. The bolt circle is smaller than the CV but that is changed relatively easily. Hubs from a Cobra are bolt in which will give you the matching bolt circle. When you swap to this bolt circle you will want to swap to discs. Using the Cobra discs will require an adapter to mount the calipers as the rotors are larger & the calipers need moved out.

The Lincoln units came with all aluminum housing third members. Some are also bagged. I prefer coils over bags but again that is your choice. If you find a unit out of a Super Coupe it will be posi with gears that are something like 3.27. That is the lowest gears you can get in stock form. The third member is an 8.8 so you can get aftermarket gears in any ratio you desire. Aftermarket anti-sway bars are available beefing up that area. Aftermarket axle shafts are also available beefing up your axle shafts. A simple brace can be fabbed to add additional support for the third member mounting. Aftermarket springs are also available. Aftermarket brakes are available.

The hub to hub is considerably narrower than the CV IFS so ultimately you will need either wheel spacers or a complete custom set of wheels built. I will be going the wheel route. Additional strengthening of the IRS subframe can also be done. Here is a link to an article of how to accomplish that. There is a guy who makes the caliper adapters. Information for them can be found here.

Something I see noted that I totally agree with. Get the IRS unit from a V8 vehicle (unless the Super Coupe). Your logic is backwards when it comes to handling. Ferrari, Porshe, Lamborghini, Pantera, pick any supercar & you will find 4 wheel independent suspension. The years for the IRS are '89-'97.

Strength & torque. An IRS is a handling rear suspension not drag racing. As long as you drive it with that in mind you should be fine. The aftermarket axleshafts are rated for up to 650hp but they do not list torque. My assumption is comparable. I do not imagine you will be seeing numbers like that from a W series engine for street use. I plan on that out of my 385 series but it doesn't take that much to get 600+hp out of a big block. Again it's not the hp anyway it is the torque you will be dumping into it. Normal driving / acceleration should be no problem at all.

 

Okay so it looks like you have answered almost all my questions with one reply. And it looks like I would be able to strengthen the IRS however much I would be willing to pay for. I still have a couple of questions though.

1. Would I be able to use extra wide wheels to make up for the difference in the width of stock axle and IRS. Like 12-15 inch wide wheels or would that rub the frame. The wheels I have on it now sets the tires about 2 inches away from the frame and they are 10 inches wide.

2. Would the IRS hold up fine in stock form to an occasional romp from an est. +/- 400 hp engine that is built to be heavy on torque? Or would I be better off to put in the heavy duty axle shafts right away?

3. If my goal was to do an occasional autocross type of race, would this be an effective way to get there? I realize I would have to beef up the IFS along with the IRS but would this be a good way to get closer to that goal? I think I read in your buildup thread that you wanted to do some autocross with your truck as well. I just want to be able to drive it competitively at some amateur autocross competition, while maintaining the option of driving it on the weekends or sunny days.

And as far as going lower with it, I am fine with taking her down a inch or two. The lower the better in the world of handling.

Thanks for the input by the way. It really helps when guys like me need some answers.

 

How hard are Supercoupes to find? and are you saying look for a Thunderbird Supercoupe? The name alone makes me think it would be hard to find, and I know nothing about it. But if I could find it, that sounds like a pretty good way to go.

 

I have yet to see a Super Coupe in either of the Pik A Part or Pull A Part yards here in Indianapolis. Yes it is a Thunderbird. On to your other questions.

1. No idea as I do not have a truck like yours but imagine it is similar to mine as far as wheel well area. I had 10" wheels on mine before. I plan on 10" unless I can get 12" wheels in there. If 12" I would imagine it would be tight.

2. If the IRS came from a V8 car I would think it should be able to handle the 400hp. You didn't say if you were stomping into it from a dead stop or rolling. I would think rolling would be no problem. Dead stop I think I would be looking at the heavier axle shafts. Better safe than sorry

3. The truck will still have everyday driving ability. You really won't notice the changes you make until you get into a heavy stress situation. Example heavier anti-sway bar. Never notice it during normal driving. When you really start to push it in corners you will notice a difference over stock.

I had a feeling after you drove it a bit you would want to go lower. I remember when you first put the IFS in you were all good with ride height. Now it looks like it sits high doesn't it? It's because you are so accustom to looking at it.

 

Okay... yeah lower isn't a bad thing, and as it sits right now doesn't look bad to me but lower would look even better .

One more question I can think of right away. What is the measurement from hub to hub of the IRS? And how much does that differ from the CV IFS width? That could be a factor of how much I want to do this swap.

Also how much will the rear drop compared to stock truck ride height in the rear? Cause I think I still want a rake from front to rear of about 1.5 to 2.5 inches. That will maintain the "truck" look and I think it gives it an old school muscle car look as well.

Thanks again. Now it's time for work to make a few bucks.

 

The hub to hub on the IRS is 63 1/4". That is in my thread.

I have 1 1/2" drop springs up front. I also cut 1/2 coil out of the MN12 IRS. With that I have a difference between front & rear of 1 3/4". Now that I have swapped in the 460 the nose dropped another 1/2" so the difference is 2 1/4".

 

Okay so there would be a natural rake in the truck after the IRS install. I am seriously considering biting the bullet and getting the kit from the people that make it. I figure that by the time I figure out the mounting and fabricate it, I could have already been driving it if I would have used their system. Plus my time is worth something as well.

But first I need to get the rear end. I think I may go scope out the local Pick-n-pull tomorrow. Their online inventory says they have five or so Thunderbirds. Might pick one up tomorrow, who knows. I think rear ends are listed for $125 or so. That seems like a good deal to me.

 

If you can get an IRS for $125 I would ****** it. That's what I paid for mine. Normal pricing in this area is $350. I personally think the $400 for the kit is worth every penny. Like you said by the time you get it all figured out. The rear is easy to do with the kit. They say & I agree that once you have everything stripped out you will have the IRS mounted in 2 hrs. I would say you can do the entire thing in a day. A weekend at the max.

 

Well the price list online says a rear end with drums is $100, with discs $150. So I am assuming that if I jerk out the rear suspension and take it to the front they will look at it and say it's a rear end. I would hate for them to individualize each part and run the price up.

I also think that the $400 kit is worth it... it's just hard to ever spend the money initially I guess. I wonder how quickly they ship? If I get the rear susp. tomorrow I wonder if I could be working on it by Memorial Day weekend? Hmmmmmmm...

 

Dave sent mine out as soon as he got the money order. I don't remember if he does plastic or not. He is just in FL so it won't take long to see it on your doorstep.

 

I think I will check out the junk yard tomorrow and see what they have. If they have what I need, I may get it sometime this summer.

I have to ask, where did your user name come from? It seems like several random letters strung together to me. I figure there is either a story behind it or you just raked your finger across the keyboard when signing up to this forum.