Subframe tightening?

[AF.]

Whenever I jack the front end of my car up and then lower it onto the jackstands, the entire front of the car "droops" down a bit more than I think it ought to.

Does everyone's car do this??? Besides subframe connectors (which I'm planning on), is there a trick to stiffening the front end?

Last time I had it aligned, the guy who did it (a real Mopar nut) didn't say anything about the subframe being loose or dangerous, etc etc. I should have asked him about this when it was on the lift.

Searched this forum high and low but found nothing. Thanks in advance.

 

[Davea Lux]

I am assuming that you have checked your C body frame for excessive rust and that the stub frame is solid. There are rubber donuts between the stub frame and the mounts, one set under the bottom of the cowl and one set under the front seat foot well. The donuts tend to get squashed as the car ages and this can cause them to no longer be tight on the mounts. I would start there, Remove the rubber plugs from the foot well and put a socket on the bolt heads, if they turn freely, the rubber mounts are probably smashed and need to be replaced. Also check the bolts at the rear of the stub to be sure they are tight.

Minor adjustments to the ride height can be done by turning the torsion bar tensioning bolts, this will work for about a half inch or so. Any more than that, you may need to replace the torsion bars. Check the short cross member between the torsion bar stubs to be sure that it is tight and not cracked or otherwise failing. Bad lower control arm bushings can also cause the front end to drop so also check those. Check the alignment on the steering column shaft where it goes into the coupling. If the shaft appears cocked all the way to the top, that can be indicative of a collapsed cowl mount. Usually that can happen if the car has been driven hard off road or over center dividers.

Dave

 

[CBODY67]

Howdy and Welcome!

What vehicle do you have? Model year can determine how the front "frame" is attached to the body structure. Why the proposed "connectors"?

CBODY67

 

[AF.]

Dave, that's great info, thanks. Yep, the car & subframe are about as solid as you could ask for. (The quarter panels are a different story, ha ha.) I didn't know there were donuts between the subframe and the mounts; I can almost guarantee they've never been replaced. I'll definitely start there; the checkup procedure is good info as well (didn't know that). It's funny you mention driving over center dividers; I did exactly that once (on accident) in the rain and the car took it on the chin and kept driving normally.

I converted to manual steering (and am going back to power), but the coupler and box lined up just fine, so I don't think anything got blasted too badly in that mishap (or ever, I hope). My alignment guy gave the car his blessing.

Cbody67 - I have a '68 Fury 2DHT. Proposed connectors are so the car doesn't turn into a pretzel when I let go of the transbrake.

 

[GJS]

Dave, that's great info, thanks. Yep, the car & subframe are about as solid as you could ask for. (The quarter panels are a different story, ha ha.) I didn't know there were donuts between the subframe and the mounts; I can almost guarantee they've never been replaced. I'll definitely start there; the checkup procedure is good info as well (didn't know that). It's funny you mention driving over center dividers; I did exactly that once (on accident) in the rain and the car took it on the chin and kept driving normally.

I converted to manual steering (and am going back to power), but the coupler and box lined up just fine, so I don't think anything got blasted too badly in that mishap (or ever, I hope). My alignment guy gave the car his blessing.

Cbody67 - I have a '68 Fury 2DHT. Proposed connectors are so the car doesn't turn into a pretzel when I let go of the transbrake.

I’m pretty sure a 68 Fury would not have rubber isolators at the frame/body connection points.

I think I’m missing something here: you’re saying that the entire front of the car (the stubframe, everything attached to it, suspension, bumper etc) droops the lowered onto jack stands?

 

[CBODY67]

I believe the '65-'69 C-body cars have a solid rubberized/coated insulator under each bolt. Bolts in the horizontal and vertical "planes" of the front body section. Nothing like the '69-'73 cars in that respect.

CBODY67

 

[AF.]

GJS, I put my jackstands here (hard to know exactly where they're placed in this picture) - right on the subframe. (pic stolen from this thread: 1969 - 1971 C body Stub Frame (subframe)). When I unload the jack, the nose sags down by an amount I am not really comfortable with. Hopefully I don't have a collapsed cowl mount as Dave was saying earlier.

I also got lost ogling the Magnum Force subframe - pretty cool stuff, has anyone here tried one?

 

[Davea Lux]

Usually if the cowl mount has significant damage, the will be a wrinkle or bow in it towards the bottom where it mounts to the stub. Also check to see if the mount where it protrudes from the stub has been driven upwards into the vehicle floor. I suspect that if your steering column shaft is still in alignment that the mounts are probably not damaged. When you release the car onto the jack stands, does an abnormal gap open up where the door meets the front fender or does opening or closing the doors become difficult or impossible?

Dave

 

[GJS]

GJS, I put my jackstands here (hard to know exactly where they're placed in this picture) - right on the subframe. (pic stolen from this thread: 1969 - 1971 C body Stub Frame (subframe)). When I unload the jack, the nose sags down by an amount I am not really comfortable with. Hopefully I don't have a collapsed cowl mount as Dave was saying earlier.

I also got lost ogling the Magnum Force subframe - pretty cool stuff, has anyone here tried one?

View attachment 220602

That’s weird: If you’re supporting it Like this photo, the jackstands are inside the frontmost mounting “tabs” which is exactly where I put mine... To be sure, it’s a rare occasion when I’ve had both sides of my car on jackstands and the times I have, I’ve maintained the support of the jack on the crossmember after the stands were in place. I’ve never seen a car bow that way unless something was really not right.... wish I could be of more help!

 

[AF.]

Dave - exactly. The passenger door (which had an alignment problem when I bought the car) 'butts" into the fender with the car jacked up, but acts perfectly normal with the car on the ground. I will look harder for creases around the firewall, thanks!

 

[saforwardlook]

I believe what some folks might miss is that when the subframe is supported in the manner as in the above photo, when the jack is lowered and removed from supporting anything, there is also load removed from the rear leaf springs, such that when the jack is removed from the front of the subframe, the rear of the car comes up when the subframe touches the jackstands and the front accordingly lowers a bit as the car rises in the rear. People mistakenly believe that the subframe is sagging when it is really just the lowering of the front as the rear of the car pivots upward around the jackstands. (And I am assuming the engine is still in your car when you see the front end drooping, whereas in the photo that is not yours, it is not).

If when the jack is lowered and removed, you can't open and close the doors without a lot of rubbing of the door latch mechanism on the striker, then you might want to look things over more carefully. Some additional load on the striker is normal (and the door gap will increase slightly too).

This happens of course whether you have "torsion quiet ride" rubber isolaters or not. And the further rearward you place the jackstands on the subframe, the more the effect as the engine weight in the front pulls the car downward in the front and the rear end pivots higher as the jackstands serve as the pivot point. It is safest to have the jackstands as far forward as is reasonable where the subframe is still fairly flat rather than rising.

So you are probably OK if your subframe is nice and clean and there is nothing more than some surface rust and your doors open and close reasonably well still when supported as in your photo.

 

[rags]

where the jack stands are placed in the photo is where the pads for a lift would be placed. i leave my '65 300 coupe up on a lift all winter with no deflection. scrapped a frame rotten '69 new yorker many years ago. stripped the nose off first, left the drive train in place. started putting it up on the lift, found out the hard way that it's the fenders/nose hooked to the firewall like trusses that make the sub frame rigid.

 

[CBODY67]

(Screeechhhh!!!) There's a terminology issue here, which I got hammered for a while back.

The '65-'68 C-body cars (and probably some prior to that model year break) have a "stubframe", not a "subframe". The "subframe" cars have frame rails which attach to the floorpan in the front floor footwell and front seat area, with INSULATORS, between the rails and the body and between the attaching bolts and the rail on the bottom. Those insulators CAN collapse and deteriorate over time, by observation, just as the bolts can "coke bottle" from rust, by observation. These insulator pairs can also have a metal tube to help locate the halves of them, too. It's the "subframe" that's on the '69 C-bodies and the '70+ Torsion-Quiet Ride C-body cars.

"Subframe" cars, think first and second gen Camaros/Firebirds, have famously used subframe connectors to keep their bodies from twisting from drag race situations. Cracking at the top of the door windows, at the "coach joint" between the quarter panel C-pillar and the roof panel. A friend terms them "flex body" as their GM platform is the F-body. Their construction is similar to the '69-'73 C-body Chryslers. FWIW.

Continue . . .

CBODY67

 

[rags]

sorry. mechanic. not terminology geek. i had to build SUB frame connectors for my '69 newport convertible, which was so rotten that i couldn't open it's doors when it was on a two post lift. had to always put it on a drive on. have compared the SUB frames in my '69 and '65 and i''m pretty sure they're the same and attach the same way.

 

[saforwardlook]

(Screeechhhh!!!) There's a terminology issue here, which I got hammered for a while back.

The '65-'68 C-body cars (and probably some prior to that model year break) have a "stubframe", not a "subframe". The "subframe" cars have frame rails which attach to the floorpan in the front floor footwell and front seat area, with INSULATORS, between the rails and the body and between the attaching bolts and the rail on the bottom. Those insulators CAN collapse and deteriorate over time, by observation, just as the bolts can "coke bottle" from rust, by observation. These insulator pairs can also have a metal tube to help locate the halves of them, too. It's the "subframe" that's on the '69 C-bodies and the '70+ Torsion-Quiet Ride C-body cars.

"Subframe" cars, think first and second gen Camaros/Firebirds, have famously used subframe connectors to keep their bodies from twisting from drag race situations. Cracking at the top of the door windows, at the "coach joint" between the quarter panel C-pillar and the roof panel. A friend terms them "flex body" as their GM platform is the F-body. Their construction is similar to the '69-'73 C-body Chryslers. FWIW.

Continue . . .

CBODY67

I am not sure who decides which terminology is correct, but at least Chrysler itself describes in the 1971 Chrysler body service manual that the front of the frame is a "stubframe". And all the 1971 Chrysler models have torsion quiet ride with the rubber isolators. I used the term subframe in my above explanation because AF.'s car is a 1968 Plymouth Fury, where I believe Chrysler did not really call the front frame section out with a specific name (at least I could not find either word in the 1965 service manual - maybe a parts manual would shed further light - IDK).

I think Chrysler used at least the "stubframe" term in fuselage models because fuselage Imperials had a separate subframe within its "stubframe" to further cushion the engine so the driver would feel even less vibration in the cabin than other models with Torsion Quiet Ride (and it actually worked pretty well, but also added some weight and complexity to the front frame). So maybe that is why the use of the term "stubframe" was (maybe) added for the fuselage models or maybe "stubframe" was used in the non-rubber isolated cars too.

Maybe your current understanding is reversed from what was discussed previously or maybe that is the conclusion reached previously _ IDK. In either case, maybe rags approach is the best and we should just give slack to whichever term is used.

As you said, this comes up frequently.

 

[Ross Wooldridge]

My 66 Monaco did not have any rubber isolators between the s(t)ubframe and the body, nor has any other 65 or 66 that I've seen.

 

[HWYCRZR]

For ‘68 there are no bushings, washers or spacers between the stub frame (or whatever you want to call it)and the unibody. Support the car as if it was on the ground. Wheels or suspension loaded. Check the torque of the nuts and bolts. 75 foot-pounds. If they are tight you may have other issues. If they are loose then the torque wrench will do its magic.

Pictures from a ‘68 Polara. Should be the same as yours.

If the nut on the bolt going through the floor is loose you will need to peel back your carpet to hold it.

These are at the end of your stub on left and right sides.

These are the pair that go up to the firewall/ cowl area. L and R sides.

Also check your transmission cross member bolts as they add side to side rigidity.

 

[Davea Lux]

I was curious, so I checked the '68 parts book and I was wrong, there are no rubber isolators for '68, so that is not the OP's problem. Hope something has just worked loose or there is probably a major structural problem.

Dave

 

[CBODY67]

For ‘68 there are no bushings, washers or spacers between the stub frame (or whatever you want to call it)and the unibody. Support the car as if it was on the ground. Wheels or suspension loaded. Check the torque of the nuts and bolts. 75 foot-pounds. If they are tight you may have other issues. If they are loose then the torque wrench will do its magic.

Pictures from a ‘68 Polara. Should be the same as yours.

If the nut on the bolt going through the floor is loose you will need to peel back your carpet to hold it.

These are at the end of your stub on left and right sides.
View attachment 220653

These are the pair that go up to the firewall/ cowl area. L and R sides.
View attachment 220654

Also check your transmission cross member bolts as they add side to side rigidity.
View attachment 220655

THANKS for these pictures! The lower attachments are in "two planes" and have no rubber isolators or rail extensions into the floorpan under-seat area. I believe the FSM terms those larger black "washers" as "isolators" of sorts, for road noise control? From what I've determined, that whole engine support structure (by any name) makes a very stiff and solid contribution to an already stiff and strong UniBody structure. Aided by the upper "trusses" of the fenders and core support, as mentioned earlier.

The reason I term the Camaro-style front frame section "sub-frame" is that is what GM and others term that style of structure which runs from the front bumper support to under the front seat floorpan area, with two-piece NVH isolation. My apologies if that doesn't jive with Chrysler's terminology. Any "connectors" run from the rearward mount to the front of the rear leaf spring eyelet "pocket", which bolts to the body structure.

With no rearward rails on the '65-'68 C-body cars, which are bolt-on to the floorpan area, I might be curious just how the front frame structure can be connected to the rear body section as such? Which is what got me interested in this thread in the first place.

Respectfully,
CBODY67

 

[polarus]

I was told that a sub-frame is welded to the body, a stub-frame is bolted. Just my two cents. I'd ask DMT about reproducing the isolators but they need an nos one to work from.