Buick Park Avenue Rear Subframe swap and bushings due to rotted subframe.

[Crazyc]

This discussion covers Buick lesabre / park avenue / Lucerne / bonneville / Cadillac DTS

Rear subframe rotting rusting or bad bushings.

The rear cradle I’m using for my 2002 buick park Ave is out of a 2011 Lucerne. The park Ave rear cradle clamshell design has rusted and failed due to it holding water, an oversight GM apparently realized 5 years into this platform and made necessary adjustments.

The newer (06+) tubular design in Lucerne allows for water mitigation. Noted differences are braking system, calipers and E-brakes backing plates and the leveling system has been moved from the rear sub frame to the unibody. I’m planning on cutting that bracket off and welding to the newer frame. I may have to bend it or modify it to sit properly but bending it until the car sits at the proper height shouldn’t be a big issue. I haven’t verified if the unibody has the mounting location for newer style on the older car. I’m assuming not.

At minimum, I found that the bushings in the newer style subframe are the same (superseded) bushings. Although also no longer available, plenty of these newer 2006-2011 cars in the junk yards to pull subframes or bushing out of that aren’t annihilated. You can remove cradle and pull these bushing out, and assuming your cradle comes out in one piece, you can reinstall these bushings into your cradle.

See pics attached to see the older and newer frame style.

 

[Crazyc]

Rained today. So no working on it today. Ordered the rear upper mount bushings yesterday and they should be here by tomorrow. These are also going extinct. As you see fit up to 2011. Funny, the park Ave body style I’m working on started in 1997. And says fits up to 2011. Which is the year of subframe I’m swapping in. This gives me hope that these all fit the same cars. Great little side note.

 

[Crazyc]

Subframe out of the 2011 Lucerne

 

[Crazyc]

Rotted subframe

 

[Crazyc]

View attachment 47902

More pics of rotted rear subframe

 

[Crazyc]

Here is the load leveling sensor and harness. You have to disconnect the sensor from harness and fit it through this small opening between tank and subframe.

 

[Crazyc]

Braking system was different between the 2002 & 2011. Had to swap out the backing plates, calipers and caliper brackets. I’m swapping wheel bearings as well, as I’m not sure they are the same either .

 

[Crazyc]

Had to cut and remove exhaust as it was in the way for removal. Cut the pipe in an area where it will be most accessible for rewelding about 5” in front of the exhaust hangers.

 

[Ultra Ego]

Thank you for documenting this and providing the photos.

 

[Crazyc]

The bolts (3) on the front bushing plates are the scariest to remove. The car in the junkyard the bolts stripped out in the frame and the unibody just broke off and ripped out and bolts never came apart. Had to cut them off. To remove these, we soaked the bolt nipples for three days with liquid breaker. We then used an oxygen / acetylene torch and heated the unibody around the bolts to expand the metal and carefully worked the bolts in and out SLOWLY. We kept alternating heat and lube on the bolts (in hopes to “shock shrink” the bolts) and they did eventually come out. Took 2-3 hours for six bolts. Got them all out successfully without frame damage. Had to wrap the fuel lines and other sensitive items underneath so as not to burn them. This is fun. lol

 

[Crazyc]

Thank you for documenting this and providing the photos.

I’ve done this before with a same year / same make car several years ago. Haven’t attempted the 1995-2005/2006-2011 swap.

Seems like it’s going fairly smoothly. Although noted my rear spring perches are rotted. Put a halt in moving forward. Ordered new perches today they will be here tomorrow. My welder will be here at 7am. I’ve already removed a spring perch from passenger side. (No pics) will have tomorrow. I’ll also probably start another thread on those.

Part numbers: 25710008 & 25710009

Rear Driver Side Spring Seat - Certified - ACDelco (25710009)​

Rear Passenger Side Spring Seat - Certified - ACDelco (25710008)​

https://s3.amazonaws.com/rp-part-images/assets/ad35e76da3c473902be5953be868d97b.webp

Frame perch

 

[Crazyc]

Frames out.

Took the front two large 19mm bolts in the middle of the bushing plates out first. (Learned taking them out last at junkyard was a spring loaded disaster) then let the frame hang on the air shocks (4x10mm bolts) and the rear subframe mount bushings . (2x 19mm bolts)

secondly unscrewed the two rear subframe bushing bolts one at a time and left one side hanging up to wiggle the springs out. After that, the last bolt was unscrewed, frame was lowered down resting centered on a jack stand while we undid the 4x 10mm lower shock bolts.

Frame was down at that point Minus a few e brake cables and one harness that crossed the rear subframe to the two wheel bearing ABS sensors. (See pics)

 

[Crazyc]

Rear subframe bushings. Mine are actually better than the 2011 Lucerne and the park Ave at the junkyard. I ordered two new ones, (extremely rare parts) so they will be going in (remove 2x 13mm bolts per bushing plate) and I will keep these for someone else on the forums doing this swap.

Part number listed further up on this thread.
GM number : 10397249

 

[DrivenDaily]

Gotta give you kudos for taking the time during a hard project like this to take pictures and then write it up!

 

[HotZ28]

Is the car really worth all the effort & expense? Where else is the rust damage?

 

[Crazyc]

Is the car really worth all the effort & expense? Where else is the rust damage?

Value is determined by the eye of the beholder

 

[silverbullet04]

Value is determined by the eye of the beholder

Indeed. If the car has some sort of sentimental value, then this job is worth it.

 

[Crazyc]

Indeed. If the car has some sort of sentimental value, then this job is worth it.

It’s not that much work. 3-4 days to save a super clean car.

 

[Crazyc]

Spring perches and rust

 

[silverbullet04]

It’s not that much work. 3-4 days to save a super clean car.

Body looks clean. I have a very clean 04 lesabre, but I'd love to have a park avenue. It's nice that you're saving her.