# Converting a FWD vehicle to RWD, anyone with experience?



## TX_Dj (Jul 25, 2008)

CRX is unibody, yeah?

If you want to make it RWD, and if it has never (?) been offered as an AWD car, you will need to construct your own replacement chassis in order to bear the loads of and mount the suspension to. Then basically "bolt" the car to its new frame.

Or, you can undertake a huge endeavor to build your own suspension mounts (and driveshaft tunnel) to the existing unibody frame.

If it was of an era where an AWD version (?) was offered, there is a possibility that the mounts for the AWD parts in the back are still there, but not likely. That would simplify things greatly, but as with most "FWD with an AWD option" type setups, the majority of tractive forces are delivered by the FWD, with the rear parts just taking some small percentage of the power. I.E. not rated for moving the whole vehicle, let alone under electric torque...

I think you may be biting off more than you can chew unless you have a whole shop at your disposal and the experience in fabrication to make it happen.


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## paker (Jun 20, 2008)

Jay Lenno did that with a 1966 Olds Toronado. If Lenno did it you know it wasn't cheap.

http://www.seriouswheels.com/cars/top-1966-Oldsmobile-Toronado-Jay-Leno.htm


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## notailpipe (May 25, 2010)

TX_Dj said:


> Or, you can undertake a huge endeavor to build your own suspension mounts (and driveshaft tunnel) to the existing unibody frame.


Well if I do a mid-motor mount then I won't need a driveshaft tunnel, possibly use the differential from a Fiero which is already setup for mid-engine, RWD.

I know it'd be a lot of work, but does anyone know what specs, specifically, need to be known to choose the replacement diff? Like, the width of the wheel to wheel mount has to be the right length, or can it be shortened, etc.?

Thanks.

p.s. Checked out the link. Jay Leno does tons of awesome stuff, spends a ton cause he can. I don't think this necessarily means it has to be an expensive job. He put in a 1000HP prototype engine in and also fully restored it. Interesting though


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## Duncan (Dec 8, 2008)

Hi Notailpipe

A number of RWD cars have a rear subframe that carries the diff (and its reaction loads) and also carries the inboard end of the bottom wishbones
I am using a Subaru diff and rear subframe on my special
You will then have to locate the strut tops - if your car has struts that should be easy - use the existing towers
Finally with the Subaru I have the fore-aft tie rod
In my special I have changed a forwards tie rod to a rearwards one

To TX's point about the strengh for a RWD conversion - I would not worry too much about that - the braking loads are always higher than the tractive loads and your body will be designed for those
The bumping and crashing loads are higher still
You will need to ensure that there is a good load path for the rear subframe mounts and the fore-aft tie rods

On a different subject - which planet are you on? - how are you comunicating with us humans?


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## notailpipe (May 25, 2010)

Duncan said:


> On a different subject - which planet are you on? - how are you comunicating with us humans?


Hahaha, my location is best country on the planet, not best planet in the galaxy!

Please pardon the rabid patriotism.


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## notailpipe (May 25, 2010)

P.S. Thanks for the tips, Duncan. I'll look into this some more and relay the parts I did not understand to my neighbor with the dragster in his garage.


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## Duncan (Dec 8, 2008)

Hi Notailpipe

_*Hahaha, my location is best country on the planet, not best planet in the galaxy!*_

Strange - I didn't know there was a Colorado in Godzown is it somewhere on the west coast?


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## toddshotrods (Feb 10, 2009)

Sometimes these conversations scare me, but I totally dig the creative ideas that come up on this forum. Hot rodding (my thing) started with guys doing things that had never been done, using pure ingenuity to solve problems that had never been encountered - and grew to what it is today. The difference though, is they weren't usually traveling at, or capable of, the speeds we are/have today; and there weren't millions on other vehicles on the roads with them.

Most questions here start off just like yours: open-ended (I know I probably did it as well, when I first got here). You didn't give enough specific information to get answers specific to your situation. A couple that need to be answered:

*What is your budget to convert to RWD?* If you say $200 (purposely exaggerated), you're not going to have a safe conversion. If you say Leno-ish, I can tell you what shop to drop it off at and how awesome it will be.

*What are your personal skills in this area/what tools & equipment do you have/what kind of resources (skilled willing-to-help friends, etc)?* If you're in your driveway, with a drill and hacksaw that you've never used before, it's going to be a serious challenge. If you've cut cars into pieces and put them back together, it's going to be a cakewalk (though it's curious that you'd be asking for help ).

Suspension has geometry. Mixing and matching components can be an awesome way to build something unique, but you have to know that the geometry is going to be correct to not throw you into a tree somewhere!  Give some more information and I'll throw out some ideas. It may be a while before I get back to this thread today - I have a l-o-n-g work day ahead of me...

In short, what you're considering has been done many times, and can work very well - if done properly.


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## notailpipe (May 25, 2010)

Hmmmmm.... I have worked with metal before and done some welding, but this is definitely the biggest such project I'd undertake. It'd probably be me, my willing-to-help friend, and his friends Mr. Welder and Mrs. Sawzall. 

I mean, if we strip the rear mounts off a RWD junkyard Fiero and then adapt those to go into my strut mounts, would you still say that < $500 project is necessarily a deathbed on wheels??

My car is a 1990 CRX DX. From a website: "Suspension, front/rear	MacPherson struts, lower lateral arms, torsion bars, tube shocks, anti-roll bar/
beam axle with integral anti-roll bar, trailing arms, Panhard rod, coil springs, tube shocks"

To be honest, that is all the information I have, and I don't know all that much about suspensions. I was hoping to, like most projects I complete successfully, just learn a lot of it along the way and ask lots of questions. But here I don't even know what to ask except:

Can I do this on that much money? 
Will a Fiero work? 
Don't the rear wheels already have a suspension, just free-spinning hubs? Can I somehow connect axles to those hubs and just build a bracket for the differential? 

I am okay with the answer "srsly this is impossible stop" - I just want to know why it's not possible. As we say where I work "unless it breaks the laws of physics, it's possible." <Insert remarks about budget here>


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## Duncan (Dec 8, 2008)

Hi Notailpipe

What do you intend to do?
Where are you putting the motor?

Is your budget for the FWD to RWD conversion or for the motor/batteries/controler?

Does the Fiero have a rear subframe you can unbolt or are the lower suspension arms bolted to the shell?


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## toddshotrods (Feb 10, 2009)

The Fiero rear suspension and powertrain all mount on a steel cradle. That unit can be unbolted from a Fiero and modified to fit under something else. You should also be able to find one in a recycling yard, or on the side of someone's house, pretty cheap.


Some of the issues involved:

It's much wider than the CRX. You either have to narrow it, or flare the CRX body around the wheels - which would probably be really, really, out there! 
Narrowing it brings up the question of what your drive system will be. If you plan to use the Fiero manual transaxle, you may be able to use two short axles (replacing the long one that goes to the right wheel with another left axle) and still fit the motor between the transaxle and the right strut tower - maybe. The other alternative would be to use a mid-80s/early-90s 4WD S10 front diff (the Fiero axles _should_ plug into it - not 100% on that though) and you would need a coupler to hook your motor to the diff (direct drive). There are a decent selection of ratios available for that diff, so you can fine tune your gearing. You would need a bigger, heavier, motor to have enough torque to run direct drive though (as opposed to running a transmission). Adapters are available for the Fiero transaxle if you go that way.
You have to figure out whether you can mate the Fiero struts to the CRX's strut towers and keep the geometry right. MacPherson style struts set the camber and caster of the suspension with the location of their top mount. (That is grossly oversimplified, but should make the point that the location is important.) Worse case scenario, you have to move the CRX towers or build something new. Best case you find a setup that works and everything lines up with proper geometry.
You need to think about where the Fiero cradle's 4 bolts mount to the CRX. Those locations should be propery designed or reinforced to carry the loading it will introduce. To be honest, I always felt GM kind of flubbed this on the front because the points on the car it mounts to look a little weak. You may actually be able to improve on it in your car. I don't remember any reports of them breaking, even with the more serious racers, but it could have been better.
What you're proposing is doable, and I only meant to scare you enough to make you think about what you're doing. A friend with a welder and recip saw is a good resource. What it will take is getting the components you plan to use and measuring everything a kazillion times, drawing, planning, etc. (In the case of the Fiero) How much narrower, what axles, what drive setup, what geometry... It gets frustrating sometimes after the car is all cut up, and you might have to push yourself through to the finish line.


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## Duncan (Dec 8, 2008)

Hi Todd

" Its much wider" - how much?
I have been surprised how little difference there is in vehicle tracks
could be easier to compensate using wheels with more insett

Strut top location
On the rear its not too sensitive - 
Fore-Aft = Castor does not apply (unless 4 wheel steer)
Right-Left = Camber can normally be tuned where the strut bolts to the upright 
Up-Down - can be compensated for by springs - make sure that nothing fouls on full droop or bump

Moving a long way Right-Left will effect the suspension's ability to keep the wheel vertical when the vehicle rolls in a corner 

Basically struts are very tolerant it takes inches out of position to make a real difference

This is not true for double wishbone - mm are inportant then


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## toddshotrods (Feb 10, 2009)

Duncan said:


> ..." Its much wider" - how much?
> I have been surprised how little difference there is in vehicle tracks
> could be easier to compensate using wheels with more insett...


I'm too sleepy to look up the CRX track right now but the Fiero's (wheel mounting surface to wheel mounting surface) is 61" I believe. Fieros are pretty wide for such a little car. The Del Sol is kind of wide, but the CRX - not so much so. It's so wide that even with the FWD rims that have a more positive offset the Inhaler (Fiero front susp) is wider than I had anticipated. I have a 6-inch deep dish rim on the back, with a 295 section width tire and that's just enough to give the back a proper "fat" look compared to the wide front. Fieros came with FWD style positive offset rims, and I am already using a larger postive offset (pushing the tire inboard more). You're not going to gain much there with rims.





Duncan said:


> ...Strut top location
> On the rear its not too sensitive -
> Fore-Aft = Castor does not apply (unless 4 wheel steer)
> Right-Left = Camber can normally be tuned where the strut bolts to the upright
> ...


I hear you an all that, but I try to get people to think and not just throw stuff together. My point was never that it can't be done, but that there is more to it than just slapping some parts together and going for a joy ride. That's the kind of approach that often results in a vehicles that is just not much fun, even if it's not blatantly dangerous.

There's not a huge amount of camber adjustment, but there is a little. Two bolts hold the strut and upright (spindle,knuckle, etc) together and one of the holes in the upright is slotted. Speaking of caster and 4WS, if you go with an 84-87 Fiero rear cradle the tie rods that adjust this are crap. Not the tie rods themselves, but the inner mounts. They have a ton of bump steer, and it was an awful design from the factory. A little more engineering work would have easily solved this. There are aftermarket bump steer correction kits, and it's not really rocket science to fab one up. Basically the inner pivot point just needs to be brought inline with the lower control arm inner pivot, to provide matching arcs. 88 Fieros came with revised suspension that corrected this.

Once again we are debating safety and need/no-need for precision in certain areas without knowing the full plan or intent. If it's going to be a few steps over an NEV and barely ever go over 40-45mph, the suspension geometry isn't as critical. If it's going for spirited drives down twisty mountain roads, or some type of serious racing, it could be.

Good night.


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## notailpipe (May 25, 2010)

I think I will hold off on this idea for now. I know your intention was not to scare me away from trying this, but I am willing to accept that this might be over my head/budget/time-constraints for now. 

Thanks for all the information and support, I'll re-open this if I decide maybe it's not so bad after all.


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## HighTech (Nov 12, 2008)

notailpipe said:


> Whelp, finally got my donor car, a 1990 Honda CRX
> 
> For various reasons, toying with the idea of converting it to RWD while also converting to electric. Any gearheads here with any experience doing differential/rear-end upgrades?
> 
> ...


The ONLY way you could do the conversion from Fwd to Rwd is to cut the under body to fit a drive line and then you need a different rear end to fit as well. A lot of work for just trying to get Rear wheel drive. That is up to you though. Which may require some different structural bracing and changing a few wire harnesses, brake lines, etc in the process. Why didn't you just want Front wheel drive? Or if you don't want front wheel drive, trade that one for a rear wheel drive straight across at a junk yard or with someone that wants to convert a Front wheel drive. Just makes life a whole lot simpler. Up to you what you want to do.


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## notailpipe (May 25, 2010)

Well, the only reason I'd bother with this work was I was talking to someone who said they might be able to get me a system out of a Tesla, but I can't say who - that was part of the deal. Looks like that's not going to work out anyway, it fell through.

But anyway, that was the only reason I would go through so much work. I know the Roadster is RWD, though I'm not totally sure I couldn't just ditch the transmission it comes with (single gear design) and just hook the motor up to my CRX transmission for FWD anyway.

Anyway, hence the ambitiousness. But yeah, it'd totally be easier to sell my CRX and buy a Z or something instead (but I love the CRX!!!  )

Thx


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## Pete0097 (Apr 12, 2012)

I converted a Plymouth TC-3 to RWD. The car has a 360 police interceptor engine, Tremec TKO 5 speed, and Dodge 8 3/4 rear. The car really was designed to be RWD, but politics changed that. They left the rear subframe as pretty hefty, so I just tied into it. I used a Mustang front end as the width was spot on. In your case, you may need something a little narrower like a Pinto or Vega type front end. The rear is hung with ladderbars and stock coil over shocks


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## lazzer408 (May 18, 2008)

Miata rear subframe.

Small, light, easy to attach to, double wishbone, coilover, disc brakes, small driveshaft, aftermarket parts available.

Maybe you could use another car's front spindles on it and use your CRX struts. Otherwise make bracket to mount Miata coilovers to the CRX hat mounts.


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## mizlplix (May 1, 2011)

My prediction is that you would tear into it like a chainsaw into a wedding cake. Then slowly bog down to an eventual stop.

Been there, done it.

A FWD, 1989 Taurus SHO, Yahama 3.0L 4 cam hotrod, that a guy wanted turned to RWD. Did my part, he didnt have the funds to complete. Sold it off in parts. Lost his A^^.

I even still have the motor.









Miz


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## tinkeringgreg (Mar 27, 2008)

Hi Guys For what its worth I was working at a pontiac dealer when the fiero came out and it was basically a test platform for new body materials so they used existing suspension as much as possible. The front is from a T1000 and the rear is from a 6000. and I think that's why the dont handle that well. I have a friend who put a chevy 350 and an olds toranado transaxle in an 84 fiero. It runs great but handling is another story altogether.

Greg


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## lazzer408 (May 18, 2008)

mizlplix - That intake manifold is a horrible design. Cheap and easy though.

tinkeringgreg - Those cars are aweful. I think GM wanted to compete with Porsche and Toyota (MR2) but like any other american car, it's not cost effective to do it right. I wonder how hard it would be to stick a boxer engine up front but keep the car rwd.


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## mizlplix (May 1, 2011)

The intake manifold is an old style called a log ram. It was used here to look old. It was an exercise to make a late motor look old. The motor ran fine. It maybe lost 50 hp. Off of the original set up though.

Miz


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## lazzer408 (May 18, 2008)

mizlplix said:


> The intake manifold is an old style called a log ram. It was used here to look old. It was an exercise to make a late motor look old. The motor ran fine. It maybe lost 50 hp. Off of the original set up though.
> 
> Miz


Got it. -50hp is actually worse then I thought. What transmission was used? Bolt-on or adapted?


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## mizlplix (May 1, 2011)

It has a handmade bellhousing. Cut off of a transaxle. Plate welded and machined. It had a T-5, turbo coupe clutch and aluminum flywheel. A stand alone timing computer made it run with the d.i.s.
(Maybe not quite 50hp-but a little bottom end torque loss)

Miz


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