Converting a 1971 - 1978 Eldorado into Rear Wheel Drive

[narnone]

Vintage Paul,
I owned a 1972 Eldorado when I was a kid and could never keep front ends under it. Also, they ride nice until you hit a pot hole. When they hit it, there is a nice BANG. Some bang more than others, but there is always a bang to it. If the front end had any wear, it would reflect on the handling big time. As soon as there was any play, the Eldorado would be all over the road.
I would sometimes romanticize about the Eldorado and take one for a test drive. As soon as I hit a bump or the front end was slightly worn, I remembered what I disliked about the car.
They are very front heavy, that's where all the weight is. When I was 17 I bought a 32K mile 1972 Eldorado, white with a maroon interior.  Loaded with every option, including a sunroof. I parked it in the same spot every day. The car has been gone now for over 30 years, but the divots in the driveway are still there.
Some people love them just the way they are. One of my friends is having a heart attack about what I'm doing. It's a personal preference thing I guess. I figure if someone does not like it, there are plenty of Eldorado’s out there that are front wheel drive.
I guess another way to word this is, I love the look of the 1973 Eldorado. It is my favorite Eldorado. I DIPISE the front end. I mean really, really, really, hate it.

The biggest thing I hear from people who don’t like what I am doing is, but their great in the snow. Yep, I’m going to put $50K in the Eldorado and drive it around in the next snow storm, here's your sign!

[The Tassie Devil(le)]

G'day Nick,

Now I see what you are doing, and the only problem I see is that you need to add a great deal of strength to the side rails to stop the car from bending in the middle.

Any convertible frame is built differently to that of a car with a solid roof, as the roof is a structural member.   Look at the convertible and you will most probably notice that the frame material in the centre could be a different thickness than that of the sedan.   Or even a different tensile strength.

I cannot say for sure, but from what Convertibles I have seen, there is an added layer at the bottom of the chassis to stop the flexing, and years ago, they built an "X" Member to control torsional movement.

If you are going to vastly increase the power output of the engine, then you will definitely need to strengthen up the frame, or dare I say it, add a roll cage, but that would be defeating what you are after?

Bruce.

[narnone]

Hello Bruce,
I thought the same thing about the convertible frame. We checked the Fleetwood frame and did not find any difference. 
I have the parts book for the Eldorado and could not find a difference between the convertible and the hard top. I am not saying I am 100% right, but I could not find a difference. I really tried to find a difference. The part number for a frame does not mention convertible or hardtop. It’s one part number for both.
The frame actually has 4 sections. The front and rear sections seem to be the same for all RWD Cadillacs. The two side rails are where the differences come in. It appears they are sized to the Cadillac being built. That side frame used on the Fleetwood is the shape and type on the Eldorado. It seems Cadillac used the same side rails regardless of the body.
The Fleetwood frame has 4 mounting points on each side just like the Eldorado convertible.  Two in the front, one towards the center and one right in front of the rear axle.  The front mounts are part of the front frame while the rear mount in front of the axle is part of the rear frame section. We found the rear mount behind the rear axle to be the exact same distance from the mount in front of the rear axle as the Eldorado.
In fact, the distance between the front mount on the front section to the one towards the center on the rail is the same on both cars.
My understanding is the Deville’s do not have that center mount. I have never checked since I did not have one.

[mario]

wonderful job Nick I really appreciate all the framework you're doing?
Ciao,
Mario

[narnone]

Update:
Steering Column:
I did not know the steering column in an Eldorado was different then a RWD. Live and learn.
We either have to machine a new upper flange, or change out the steering column. My steering column is in mint condition and is red. We are going to machine a new flange and hpe it works.

Front Frame Modifications:
It appears we need to add 3 to 4 inches to the front of the frame. We have gathered all of the parts for the front clip and cut the front horns off an extra Eldorado frame. I hope to have the front clip on in a week or so.  Will post pictures when we are have this part finished.

[INTMD8]

Nice job Nick! That is awesome. I may have missed it but what do you plan on doing for a floor pan? Maybe Riviera would work?

One day I would like to build an AWD Eldo or Toronado.

[narnone]

Here is what we are up against with the tunnel.
The rear has to be changed. It is Cadillac only. There are no gear sets available for it, not even the factory gear sets. So if the rear ever develops an issue, you will have to change it.

We need to drop the rear to 3.53 or 3.73 in order to get accommodate the overdrive transmission. We are looking at a Ford 9” because of the features and how easy it is to service. The Cadillac rear has the input of the driveshaft very low in relation to the center of the rear axle. The ford rear has the input at the center. Off the top of my head, the shaft will be 3” higher at the rear then it is today.  That may mean we need to have a slightly higher tunnel in the rear. However I am not sure.
The other issue is the Transmission.  My tranny guy said he could build a 700R4 to handle the engine. He builds race trannies. . My original thought was to use a 4L80-E. If a 700R4 can be used there are 3 advantages:

1 The front tunnel could be smaller because the 700R4 bell housing is smaller. In fact, the overall size of the tranny is smaller.

2 The second is the electronics. If I go with a 700R4 there are no electronics where a 4L80-E needs a computer which adds about $1,000 to the cost.

3 Ratios. The 700R4 has a wide range of gears. First gear is lower at 3.06 where it’s 2.48 in the 4L80E, which is the same in the 400. The overdrive in the 700R4 is a little taller than the 4L80-E. The 700R4’s overdrive is 0.70 while the 4L80-E has a final drive ratio is 0.75. So in town, starting out will be easier and at highway speeds, the right RPM can be achieved with lower gears. If we use 3.73, the Eldorado will start out with ease and at highway speeds, the RPM will still be within the power range.

["Cadillac Kid" Greg Surfas 15364]

Nick,
With all due respect I was just wondering what the goal of this project was.  Something tangible or just something different?
Greg Surfas

[narnone]

Greg,
If you read what I wrote Vintage Paul at the top of page 2. You will get an idea of why I am doing this.  I have always loved Cadillac’s. My favorites are the 1968 Eldorado and the 1973 Eldorado.  The early Eldorado’s should never have been FWD. At least in my opinion. They are way too heavy in the front end.  When they where new, the dealers where told never lift the car from the center frame, but from under the front drive wheels. Today, if you place one on t two post lift, you can watch the door seam open as you lift it.
As for ride, Eldorado’s don’t ride well. They ride nice until you hit a pothole. Usually there’s a bang as you hit it. Any wear in the front end is exaggerated because of the weight. So even a little wear tends to really effect the Eldorado’s handling.
As far as even keeping a front end under them tends to be difficult. The bearing setup tends to wear fast. Again, due to weight.
Performance is another reason.  There is almost nothing you can do to enhance the Eldorado.  The Eldorado has a shorter wheel base then a De Ville.  Let’s see if we can improve the handling and performance.  A lower rear is going into the chassis along with a lower first gear. The Eldorado should fly off the start with a EFI 500 worked a little. Because of the lower rear, 3.73 or 3.53 compared to a 2.73, we can also take advantage of an overdrive.
I did want to keep the Eldorado all Cadillac. That was important to me to get Cadillac RWD ride.
I have seen people try to put overdrives in their70’s Cadillac’s without changing the rear. It will not work. If you do the math, you will be around  90 to 100 mph to take advantage of  4th gear. You get nothing out of it, in fact, you actually hurt performance because the trans is going into overdrive and the rpm’s of the 500 drop so low, you’re out of the power band.
By keeping the Eldorado FWD, no real modifications can be made.  This is an experiment. I realize the Eldorado will still be a 5000 lbs monster.  But so is my truck.  And it performs nicely.
I know there are people who will disagree with me. And that’s good. The world would be boring if everyone agreed on the same things.  Most people love the Eldorado’s just the way they are, and that's great.  I believe if the Eldorado’s from 1967 through 1978 where RWD, their value would be much higher.  With today’s technology you could get them to handle, perform and get much better mileage.

[35-709]

This one seems to do well    ---

https://www.youtube.com/watch?v=qVcW-OG7tiI&list=LL-v-xtvsXHUS795jZL3Ln8Q

[The Tassie Devil(le)]

Highlights the need for an LSD for the Eldo.   Wish I had one for mine, at a reasonable price that is.

Maybe my cars' lack of power is the reason why mine spins both wheels, as the same amount of smoke curls up over the hood, and then continues over the windscreen when the vehicle starts to move.

Bruce. 

["Cadillac Kid" Greg Surfas 15364]

Nick,
I am looking forward to seeing the results of your body swap.  Your "facts" about the FWD Eldo's performance, handling, and "un balanced weight" are really not substantiated in facts, as most of those who have had them would attest.  They were (and still are if maintained properly) just about bullet proof since they and the Toronado were the GM test beds for the upcoming and still in production next couple of generations of front wheel drive vehicles.
The vehicle (full scale) model was presented to Cadillac Engineering with the instructions to make it the Luxury sports car without any compromises, and many of us feel they did just that.
Again, I look forward to seeing your finished project and hearing about the performance as well as the appearance. 
Greg Surfas

[76eldo]

I love all of the Eldorado's ever made in their stock form.
I especially like the ride and feel of my 76 Eldo convertible except that I always wished for two things.

1.  A 4th or overdrive gear to reduce revs at highway speed.

2.  More power.  By 76, the 500 inch motor was really choked down by the lower compression and smog junk.

What Nick is doing, although startling to some, is really a very cool undertaking.
These cars are not super rare like an Eldorado Brougham or a 53 Eldorado, so he is re-engineering the car in a manner that will end up like something Cadillac might have tried as an experiment.

I spoke to Nick on the phone the other night and hope to go up to his shop which is less than 2 hours away to check out what he is doing. When I first read his post I will admit it sounded crazy and like it would end up as a butchered unfinished lump somewhere.  After talking to Nick I discovered that he really knows his Cadillacs and already has tackled the tough part of this project.

I might take an 85 Eldo convertible and do the same thing.
That's one way to rid the car of the HT4100 completely.
I have thought about finding a GM frame with the same wheelbase in a RWD configuration but acording to Nicks post the wheel base is a non issue as you can change that in the side rails.

There are lots of ways to enjoy this hobby of ours. I'm
betting this car will be really interesting.

Brian

[narnone]

Update:
We put the doors and front end on. We have jacks and wood holding everything in place. We are going to tack a couple of angle irons in place so we can start aligning everything.  Once we have everything aligned. We will start doing the final modifications to the frame.
See the attached pictures.
We replaced the steering wheel with a 1973 De Ville to help align to the steering box.
I am not saying we are out of the woods yet, but we can see the light at the end of the tunnel in determining if this will work. I am hopping the light we see is not an oncoming train.
I will hope to have a better idea if this idea is going to work by the end of week.
Once we have the frame modified and the front ended bolted correctly, we are going to put a 500 engine in it to see how it sits. There will be no tranny as we have not modified the Eldorado body yet and don’t expect to until I am 100% sure this is going to work.

[The Tassie Devil(le)]

You will probably find that you can relocate the engine at least 6 inches further back than it was in the Eldorado engine bay.

This will give you more rear weight balance in the process.

Plus, in moving the engine rearward, you can do away with the engine-powered cooling fan, and run a pair of electric fans which will allow you to remove the fan shroud as well.

Bruce.

[Mike Josephic CLC #3877]

Absolutely impossible. You could never convert a FWD Eldorado to a RWD design, but you could take an Eldo body and put it on something else.

The only way to do it is to remove the body from the Eldorado chassis and remove the entire floorpan from the lower firewall back.  Then as Bruce said, drop it on a Deville or Fleetwood chassis.  You would have to do some complex measurements and might be able to reuse most of the Deville floor.

Check out Jay Leno's Custom 1200 HP 1966 Rear Wheel Drive Olds Toronado.

http://www.jaylenosgarage.com/cars/oldsmobile/1966-oldsmobile-toronado/#item=84738

He spent way over 100 Grand on this car if not more and it has a custom fabricated chassis and floor.  He has the resources and on-staff designer's/restorer's/customizer's and a complete machine shop and it taxed all of their abilities and took months.

The end result is spectacular, but for an average guy even with a high skill level, it's a tough project.

Brian

Over $100K? -- I'll bet this was a $300K+ proposition given the amount of custom fabrication,
engineering and labor that went into it.  Hey, Jay made about $15 million a year when he was working so what's a few hundred grand more or less. The labor alone at about $75 per hour and 3,000 hours
would be almost that much.

[narnone]

Bruce,
You are correct about the placement of the engine.  It will be back by the firewall. Which is a good thing for balance.

As for the fan. I have two choices. I can manufacture a system much like the one used in 1969 â€" 1972 Grand Prix or put a dual fan system in. If you go on eBay and look at a Grand Prix, you will see GM  built a tunnel to allow the engine fan to cool the radiator. I was talking to my guys about this yesterday. Since the Eldorado will never win a show, I am not overly concerned about using a dual fan system.  Just so it looks good and cools the engine.  An electric fan system would really clean up the engine compartment.

[The Tassie Devil(le)]

G'day Nick,

Personally, I would be going for the electric fans, as installing such a long snouted shroud would require too much clearance for the fan when the engine flexes on the mounts, thus letting too much side-spill of air past the fan blades.

Bruce.

[narnone]

There are several advantages for using electric fans. That being one of them. I expect to be using electric fans.

[narnone]

Update:
We have the body and front fender just about placed.
We have determined we increased the wheelbase by 1 3/8"
This all occurred in the front. So the front wheels are 1 3/8" more forward then they were on the original frame.
This seems to be fine; there is plenty of within the front fenders to accommodate this change. In fact, it looks better than the original placement of the wheel.
At this point, we will be aligning the rest of the front end. Once we have everything aligned, we will be welding the support under the radiator support. The supports for the front bumper has to manufacturered. It appears the frame has to have an additional 3" added to accomidate the longer Eldorado front end.
After these steps are accomplished, we will place a 500 cid engine in the engine compartment to see how the Eldorado sits and insuring the front wheels have enough room for turning.