Rear STS subframe swap

[8-Track]

So talking to my extremely knowledgeable friend, and he found that the 93 Allante had rear coil springs, and everything lines up to bolt in from the STS or Allante

Anybody swap the rear subframe into a Reatta?

[handmedownreatta]

there was a guy that bought that and was going to try.thats all i remember.

[Ronnie]

20 hours ago, 8-Track said:

... everything lines up to bolt in from the STS or Allante

If it was that simple everyone would be doing it instead of spending $500 on discontinued rear struts. 

[8-Track]

1 hour ago, Ronnie said:

If it was that simple everyone would be doing it instead of spending $500 on discontinued rear struts. 

That's the big reason I wanna try

Like more power to him for being able to sell those

But I can't afford that, and swapping the whole rear end and buying regular struts would still be more affordability 

[handmedownreatta]

On 3/23/2024 at 6:31 PM, 8-Track said:

That's the big reason I wanna try

Like more power to him for being able to sell those

But I can't afford that, and swapping the whole rear end and buying regular struts would still be more affordability 

and easier to lower.

 

[8-Track]

5 hours ago, handmedownreatta said:

and easier to lower.

 

ABSOLUTELY 

Like 1.5-2 inches lower and they'd look absolutely perfect for what they are

[Barney Eaton]

I thought the Cadillac used the flat composition spring like the Reatta. 

I don't understand how they are different and what makes them easier to lower. 

I have a Eldorado/Seville parts book but I am not home to look into the parts numbers  

Edited March 26 by Barney Eaton (see edit history)

[EmTee]

My wife's '93 Allante' has coil springs in the rear suspension.

[Barney Eaton]

Do the Allante rear struts look like the Reatta with a spring around them?   

If the Allante uses the same sub frame things like the rear sway bar should mount the same

with a little cutting the Allante rear struts might be a easy replacement on the Reatta..... if they are still available. 

[EmTee]

23 hours ago, Barney Eaton said:

Do the Allante rear struts look like the Reatta with a spring around them? 

No, the coil springs and shocks are separate.  In fact, the suspension on the Allante' is so different looking that I'm amazed it could be possible to bolt it onto a Reatta!

 

I'll try to get some pictures to post here later...

[Y-JobFan]

[Y-JobFan]

[Y-JobFan]

[Y-JobFan]

[Y-JobFan]

[Y-JobFan]

[Y-JobFan]

[EmTee]

Great pictures @Y-JobFan  !  I took a couple also.  My understanding is that the Allante' was built on a shortened Eldorado chassis.  When I had mine on the lift I could see the seam where the floorpan was sectioned just ahead of the fuel tank IIRC...

 

 

 

 

[Barney Eaton]

Good pictures......... 

The Allente sub frame is nothing like the Reatta, Eldorado etc 

The bottom "A" arms are cast and look like they could be used on a truck....extra heavy duty.

[2seater]

It sure is a busy rear assembly, especially compared to the Reatta. I wonder if weight capacity has anything to do with it? The Reatta is a pretty heavy car, despite its size, but about 65% of that is up front. Maybe it's an illusion but the unsprung weight looks like a lot more.

[EmTee]

23 hours ago, Barney Eaton said:

The bottom "A" arms are cast and look like they could be used on a truck....extra heavy duty.

Yup, the lower A-arms appear to be cast iron.  The uppers look like cast aluminum.  Maybe the iron is used to help add some rear weight bias to counter the heavy front-drive architecture?  The tube shocks are located ahead of the springs -- I wonder what else (if anything) those might be used on...

[wufibug]

(f I read this correctly, it is fair to conclude that the Allante and Reatta rear suspensions are not a reasonable exchange.  Can we also conclude STS rear suspension is an equally problematic swap into our Reattas?

[2seater]

1 hour ago, wufibug said:

(f I read this correctly, it is fair to conclude that the Allante and Reatta rear suspensions are not a reasonable exchange.  Can we also conclude STS rear suspension is an equally problematic swap into our Reattas?

I don't know the results of any actual swap that has been done, so I don't think there is a known conclusion? The comments, at least from my point of view, was that there are substantial differences but the overall form factor looks feasible. I am not up on the various Cadillac types, but doesn't the Allante have many similarities to the Reatta, where the STS is a four door sedan? It is certainly a more sophisticated suspension. If it indeed will swap in, it is pretty much just four bolts plus parking and service brake lines/cables to try it. I have aged out trying things of that scale.

[Barney Eaton]

I just looked up the specs and both cars have the same 60.3 in rear track but that does not mean the Allente sub frame will install in a Reatta without modification 

to either the body,  sub frame or both. 

[EmTee]

56 minutes ago, Barney Eaton said:

I just looked up the specs and both cars have the same 60.3 in rear track...

Hmmmm, that's surprising to me because the Allante' just looks so much wider to me.  I will say, however, that I've never seen an Allante' parked directly next to a Reatta.  That would be interesting to see...

[2seater]

2 hours ago, EmTee said:

Hmmmm, that's surprising to me because the Allante' just looks so much wider to me.  I will say, however, that I've never seen an Allante' parked directly next to a Reatta.  That would be interesting to see...

I think it is the squared style of the Allante that makes it look wider. The specs say the two cars are almost identical width, height, legroom but a shorter wheelbase for Reatta even though overall length is greater.