FWD Trans to Midengine conversion

[Hi Tech]

I've been researching the Fiero midengine V8 conversions, and I have a few questions, as I'm considering doing one, myself.

Some guys use a Longitudinal FWD transmission, such as a TH325-4L, from an '83-'85 Riviera, Toronado, El Dorado, or Seville.

What I haven't figured out, is how they use a "steering" axle on the rear, and how it becomes a "fixed" axle when they mount it in the rear of the vehicle.

Has anyone here done this type of conversion, or could someone at least explain how they make it so the rear wheels stay as a "fixed" straight axle?

The reason I ask, is that I'd like to experiment with a Buick 455, this transaxle that we're discussing, and build a midengine '70 Skylark or Chevelle.
If you really want to know why, it's just because I have all the parts to do it, and it will be something unique and different, and I think it would perform much differently, and better, with the engine behind the driver.

Thanks in advance, guys!

[TheSilentChamber]

If the hub is incorperated into the rear suspension, and the rear suspension does not turn, it doesnt matter, same as an independent rear end.

[Black Lotus]

Examine the 84-87 Fieros rear suspension linkage. What you would have to do is something similar, namely attach the tierods from the wheel hubs to a point on the frame (some Corvettes do this too).
Not related to the tierod gig is the fact that this isn't the happiest marriage of engine and chassis, at least from a handling standpoint. The engine sits WAY too high.
Have a look around the web, there are some websites, heres's one guys idea on how to do it--
http://www.fieroaddiction.com/SBCLa.html

[Hi Tech]

TSC,
Please have patience with me, and forgive me for not understanding (yet), but if you take the steering linkage from the front, and move it to the rear, then how do you stop the tires from steering in the rear?

[Hi Tech]

Originally Posted by Black Lotus

Examine the 84-87 Fieros rear suspension linkage. What you would have to do is something similar, namely attach the tierods from the wheel hubs to a point on the frame (some Corvettes do this too).
Not related to the tierod gig is the fact that this isn't the happiest marriage of engine and chassis, at least from a handling standpoint. The engine sits WAY too high.
Have a look around the web, there are some websites, heres's one guys idea on how to do it--
http://www.fieroaddiction.com/SBCLa.html

That's where I found the info that caused me to ask my question.

I'm not looking for criticism or analysis, yet, (I know that's not your intention, Lotus), but I just want to build something different for myself, just because I have the parts sitting around, and I don't want to just throw them away, I'd rather use them for something, and I thought this might be a cool thing!

Have you ever seen a Big Block powered Trike? With this same transmission design, it would also be possible for me to build that, too.

Check out Lightning V8 Trikes, and their Chevy 502 Trike!
It's cool, but it's WAY too long!
118" wheelbase is the same as my car.

By using the FWD transmission that we're discussing, I could shorten the wheelbase by almost 1/2, for better turning radius, among other advantages.

Now, back to my confusion...

[Moppie]

As the lotus driving porcine said, you simple anchor the steering arm to a point on the chassis. i.e. the part of the suspension the steering rack normaly attachs to, simply has a linkage run off it, that is mounted to the chassis in such away that it can move up and down with the suspension, but not allow the strut to turn.
If you use an adjustable linkage then you can also have some radicaly adjustable toe angles to go with it.

[Hi Tech]

Originally Posted by Moppie

As the lotus driving porcine said, you simple anchor the steering arm to a point on the chassis. i.e. the part of the suspension the steering rack normaly attachs to, simply has a linkage run off it, that is mounted to the chassis in such away that it can move up and down with the suspension, but not allow the strut to turn.
If you use an adjustable linkage then you can also have some radicaly adjustable toe angles to go with it.

I understand that much about attaching the moving linkage to a fixed chassis location, but is there a more permanent way, such as just using straight axles, as opposed to CV shafts?

That's why I'm asking, because I don't know what's available, or what's possible for better alternatives.

[UncleBob]

why would you want straight axles? Keep the CV's, keep the independant suspension. Thats a good thing.

Many cars these days have "tie rods" on the rear wheels. they are simply fixed to the chasis. It makes alignment adjustments easy. Its a good system. You can buy a large array of heim joints to suit your needs for this.

[Hi Tech]

Originally Posted by UncleBob

why would you want straight axles? Keep the CV's, keep the independant suspension. Thats a good thing.

Many cars these days have "tie rods" on the rear wheels. they are simply fixed to the chasis. It makes alignment adjustments easy. Its a good system. You can buy a large array of heim joints to suit your needs for this.

It's not so much that I "want' straight axles, I'm completely open to suggestions, but I'm just thinking that since the engine would be in the rear, and the transmission would be in the rear, all of that torque would be applied pretty harshly to those drive axles, and I wouldn't want one of those rear axles to suddenly make a turn, when it should be a straight drive wheel, especially as I would be driving it!

Thanks, all of you, for your input so far, and I think I'm getting some good ideas, already!

[UncleBob]

you can get heim joints as big as you want. You can make them bigger than the CV shafts if you like. huge overkill, but you can do it if you want.

You should look at F1 cars. Check out the spindly little bars they have holding that 1500HP and more traction than you'll ever see. Not saying you should go with tiny shafts, but this isn't a big issue, its just a matter of how much safety you wish to design into the system. You can make the "tie rods" the toughest thing in the car if you feel like it.

[Moppie]

When Toyota designed the MK1 MR2 (upon which much of the Ferio suspensin design is based, GM copied Toyota after they supposdly copied Lotus, which if you know the suspension on a MK1 MR2 it is pretty clear they didn't) toyota simply took the front subframe out of a Corrolla and stuck it in the back of a wedge shaped chassis.
All the struts, axles, linkages etc, look just like they fell out of the front end of a Corrolla, but instead of a steering rack them simply ran a short 20mm shaft back to a hard mount on the subframe.
(Note, I don't believe the actual parts used in the MR2 and Corrolla are exactly the same, but they are close enough in design its pretty clear they came from the same place).

[TheSilentChamber]

You dont move the steering setup to the back. what happens is that hub is basically turned into a trailing arm, it moves up and down, but there is no way for it to steer. If you do a good enough job designing it you can attach a bar where the tie rods attach and put them at angles where you create a passive rear stearing where it will change the toe in or out a few degrees while corning to make the car incredably agile.

[Hi Tech]

Upon further investigation, it seems that I won't be the first to do this, as I've been told of a guy that has a '70 Chevelle, with 2 455's and 2 transaxles!

I'm still planning to build the midengine 455 and transaxle in my own, though, anyway.

I'm just going to go buy the donor car that I'll need the transmission from, then I can cut out the parts that I'll need for the suspension and conversion to the full frame car. That will probably be the easiest way.

Uncle Bob, another reason that I was thinking of changing the axles, that I just realized, was that I'd like to use the '70 Buick wheels (now available in Billet Aluminum 16, 17, and 18". I was thinking 18" rear, 16" front, for classic profile).
With the smaller '80s FWD lug pattern, the hubs won't fit the older '70s wheel lug pattern.

That's what I was thinking, I just forgot to mention it.

[Black Lotus]

Originally Posted by Moppie

As the lotus driving porcine said, you simple anchor the steering arm to a point on the chassis. i.e. the part of the suspension the steering rack normaly attachs to, simply has a linkage run off it, that is mounted to the chassis in such away that it can move up and down with the suspension, but not allow the strut to turn.
If you use an adjustable linkage then you can also have some radicaly adjustable toe angles to go with it.

Oink!
That's the ticket!
Oink Oink!

[UncleBob]

there is an obvious problem with straight axles on a FWD tranny....what are you going to use for suspension? IE, WHAT suspension?

You'd have to make the entire drive train unsprung weight.....it wouldn't work.

There isn't much unique anymore when it comes to vehicles and V8's. I knew a guy that shoved a SBC into a kawasaki jet ski once.....Crazy stuff.