Rear body&frame improvements

Rear body&frame improvements - 03/21/15 01:18 PM

Most of the handling improvements focus on the front and center of the car where most of the action is, but (short of installing a rollbar/cage) I like to see some inputs about improving the body/frame stiffness on the rear of the car.

Partly reason for asking is my own car has some sheetmetal rust-issues at the rear which I'm fixing as time permits, but over time I noticed (duh) how quickly the body structure becomes weaker because of this. Letting me to think even a stock (rustfree) body is just marginally sound to begin with.
Like, when I'm in the process of parking my car over a heavily crowned roadsurface and wheel on a curb, or when slowly avigating a speedbump at a sharp angle, I can sometimes actually hear the body structure 'work' at the rear because of the rearaxle and leafsprings putting more and less strain on the suspension-mountings.

I'm thinking, for instance, just like the beefy lower radiator supportkits available, the rear of the body could use some similar improvements aswell.

What say you?
Or, is my car really just a turd waiting to crumble and fall apart...

Posted By: GoodysGotaCuda

Re: Rear body&frame improvements - 03/21/15 01:27 PM

I was thinking about this the other day and will need to take a look at things. At least on my e-body, things are pretty tight back there with the fuel system wanting to take a bunch of real estate. The shock crossmember is the best thing going back there, perhaps it can be improved upon, boxed, reinforced.

While your rust is reducing it's rigidity, it is a form of active light weighting too.

Posted By: RylisPro

Re: Rear body&frame improvements - 03/21/15 04:40 PM

When I installed my ATL fuel cell I had a fuel cell cage built out of 1x1 inch (25mm x 25mm) square tubing grafted on two 2x2 inch (50mm x 50mm) square tubing running across the frame rails.
It really stiffens things up back there

Posted By: GoodysGotaCuda

Re: Rear body&frame improvements - 03/21/15 04:58 PM

Quote:

When I installed my ATL fuel cell I had a fuel cell cage built out of 1x1 inch (25mm x 25mm) square tubing grafted on two 2x2 inch (50mm x 50mm) square tubing running across the frame rails.
It really stiffens things up back there

Pics? I'm intended to use a modified stock tank, but am curious on how yours was executed.

Posted By: RylisPro

Re: Rear body&frame improvements - 03/21/15 05:07 PM

https://board.moparts.org/ubbthreads/show...page=0&vc=1

Posted By: jcc

Re: Rear body&frame improvements - 03/21/15 05:24 PM

Not sure in daily drivers there is a lot to be gained back there relative to efforts spent at the front, IMO.

Some of what I did can be seen starting at Pic #14
https://board.moparts.org/ubbthreads/show...part=1&vc=1

Posted By: GoodysGotaCuda

Re: Rear body&frame improvements - 03/21/15 05:42 PM

Quote:

Not sure in daily drivers there is a lot to be gained back there relative to efforts spent at the front, IMO.

Some of what I did can be seen starting at Pic #14
https://board.moparts.org/ubbthreads/show...part=1&vc=1

Nice work, did you make the recessed battery tray, or what that a purchased part?

Posted By: jcc

Re: Rear body&frame improvements - 03/21/15 05:52 PM

Thanks, I built three, of different depths, for my different cars, weight lower is always better

Posted By: 68cuda440

Re: Rear body&frame improvements - 03/22/15 05:02 AM

I did some 1x2 structure to support my aftermarket fabricated tank.

Attached picture 8467269-P82A0188.jpg

Posted By: Supercuda

Re: Rear body&frame improvements - 03/22/15 04:09 PM

Quote:

I can sometimes actually hear the body structure 'work' at the rear because of the rearaxle and leafsprings putting more and less strain on the suspension-mountings.

Pretty sure if you are hearing things your problem is elsewhere. I'd go over the rear suspension and make sure nothing is sloppy, wore out, or rubbing at extreme angles.

I'd work on chassis improvement front to rear, what happens if the rear is stiffer than the front?

Bad things.

Posted By: joes68340s

Re: Rear body&frame improvements - 03/22/15 04:32 PM

Ive owned a few E bodies and they have been pretty sound but then I purchased what was supposed to be my last car dream car. AAR Cuda It has every E body flaw known to man the rear upper shock mount has cracks and flexes the lower front frame rails have issues. So anything you can do to repair or replace and reinforce is going to make it a better car.

Posted By: dickdale

Re: Rear body&frame improvements - 03/23/15 10:50 AM

Herman, a while back I found these pictures of reinforcing the rear:

Posted By: BigBlockMopar

Re: Rear body&frame improvements - 03/23/15 11:37 PM

A-bodies are a little different in that area. The rear shackles are much closer to the rear of the car.

I think I will want to beef up the rear crossmember and perhaps add/beef up the crosssection near the upper shockmounts.
And of course fix the rust in the outer sheetmetal.

Posted By: TC@HP2

Re: Rear body&frame improvements - 03/23/15 11:56 PM

With the extra propane(?) tank you're carrying in the rear, I don't doubt you hear some creaking and groaning going on. If I recall, you've added something like 300# to the trunk. What the actually translates to for stresses in your vehicle, I'm not sure, but I bet you could use a few extra gussets here and there. Rear torque boxes at least and maybe a some extra brackets around the shock bracket.

Gotta say, I've never seen a car tear up the shackle area, so not sure how much of an improvement those would yield.

Quote:

Herman, a while back I found these pictures of reinforcing the rear:

Posted By: jcc

Re: Rear body&frame improvements - 03/24/15 12:07 AM

My thinking, any past rear shackles is only for impact protection.

Posted By: BigBlockMopar

Re: Rear body&frame improvements - 03/24/15 12:22 AM

The rearcross member, to me, has about the same function as the lower radiator support; Keeping the frame rails located in one plane.
Especially when one springpack is pushing harder on the body then the other side, like when cornering.

Posted By: jcc

Re: Rear body&frame improvements - 03/24/15 06:04 PM

Yes we agree, however the rear bumper for example also to some degree does the same thing, the point is, if its past the rear shackles, it does a poorer job of stiffening and a better job of impact resistance, relative to its distance from the shackles.

Posted By: Dan@Hotchkis

Re: Rear body&frame improvements - 03/24/15 08:08 PM

We've had our fair share of issues with the rear cross brace.

And we've R&D'd a pretty good solution....

We've done initial testing on 68-72 B Bodies and E Bodies. Works great so far.

Posted By: joes68340s

Re: Rear body&frame improvements - 03/24/15 08:43 PM

Dan any time frame when that will be available.

Posted By: mopardude318

Re: Rear body&frame improvements - 03/24/15 08:51 PM

Quote:

We've had our fair share of issues with the rear cross brace.

And we've R&D'd a pretty good solution....

We've done initial testing on 68-72 B Bodies and E Bodies. Works great so far.

PLEASE make one for an A-body! I'd buy one! And please don't say an A-body is not worthy! Then We are our own worst enemy

Posted By: Dan@Hotchkis

Re: Rear body&frame improvements - 03/24/15 09:11 PM

Quote:

Dan any time frame when that will be available.

Right now we will try to have one installed on E Max and on display at Carlisle.

Posted By: Dan@Hotchkis

Re: Rear body&frame improvements - 03/24/15 09:14 PM

Quote:

PLEASE make one for an A-body! I'd buy one! And please don't say an A-body is not worthy! Then We are our own worst enemy

We can always do a one off and if there is enough excitement about the B&E, the boss will have me prototype stuff for the A's. I think that the construction for the A bodies may be a bit tougher as the pin-style upper mounts would be tricky.
I've had to repair one of those that blew out from air shocks once. Super not-fun.

Posted By: lilcuda

Re: Rear body&frame improvements - 03/24/15 09:25 PM

Do you have subframe connectors on the car? If not, I would start there.

Posted By: BigBlockMopar

Re: Rear body&frame improvements - 03/24/15 10:56 PM

Yes, frame connectors are present. Welded front and rear, but plan to weld them to the floors as well.

Posted By: dangina

Re: Rear body&frame improvements - 03/25/15 03:21 AM

Quote:

Yes, frame connectors are present. Welded front and rear, but plan to weld them to the floors as well.

before you do, check the rules of the track you wanna run at, some classes don't allow you to weld to the floor plan, or you get bumped to a class you probably don't want to be in.

Posted By: GoodysGotaCuda

Re: Rear body&frame improvements - 03/25/15 04:28 AM

Quote:

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We've done initial testing on 68-72 B Bodies and E Bodies. Works great so far.

Probably a stupid question, but what are the large circles for near the ends? Modular frame mounts of some sort?

Posted By: Dan@Hotchkis

Re: Rear body&frame improvements - 03/25/15 05:05 AM

Quote:

Probably a stupid question, but what are the large circles for near the ends? Modular frame mounts of some sort?

Current design allows a full TTI 3" system on all platforms.

Posted By: BigBlockMopar

Re: Rear body&frame improvements - 06/28/15 01:09 PM

Topic update;

I've tackled the rust issues on the drivers side of the car, welded the rear floorboards to the frame connectors on both sides, and repaired and beefed up a rusted section of the rearmost crossmember.

Also noticed at the front, a connecting panel between framerail, firewall and inner fender wasn't spotwelded at all about 3" from the edge at the factory, so I rewelded this and added more welds along the edges.

Still have to fix the rust issues on the pass. rear sheetmetal but these aren't as severe as the left side of the car.

The car already feels way more solid while driving, which is no surpise of course seeing the extend of the rust it had;

In the last pic you can see I still need to straighten and clean up the lines of the wheelopening edge a bit better.

Posted By: CKessel

Re: Rear body&frame improvements - 06/28/15 04:34 PM

Looks like typical old car stuff. As you do your repairs, are you putting in any anti rust treatments to the new and old exposed areas? Body cavity wax etc? Would be a good idea.

Posted By: BigBlockMopar

Re: Rear body&frame improvements - 06/28/15 10:39 PM

Now the outside is fixed I will work on rustprevention from the inside.
I've got a high quality liquid rubber that will be applied on the inside panel overlaps and welds. Then all this will be covered with regular body undercoating.

The car has gained a lot of structural strength again.
Before the rustrepairs, whenever I say, parallel parked on a crowned road, I could hear the car's rear body structure work.

But also when just driving around everything feels way more solid. I've even adjusted the rear shock absorbers one click looser.

Posted By: brads70

Re: Rear body&frame improvements - 07/06/15 04:46 AM

Dan that design, will it require a shorter shock?