Write-Up: Subframe/Cradle Mount Insulators & Bushings

So Matthew, you are only changing the rear upper bushing at the moment correct? Did you have to support the motor for a partial swap?

BMD wrote:

So Matthew, you are only changing the rear upper bushing at the moment correct? Did you have to support the motor for a partial swap?

yes i am only replacing the upper inner bushing. I will probably do it Sunday afternoon and i will post my results. I am really hoping i can just lower the rear corners a little and slide in the bushing.

you should be able too...pretty much what I did. Loosen the outers (bolt out of the inner) and side it in. Do you have access to a lift, or are you jacking the car up?

I also heard that when you mess around with the cradle, you might want to check the alignment at some point.

no lift access. I will have ramps, stands and 2 jacks at my disposal.

7901mark wrote:

you should be able too...pretty much what I did. Loosen the outers (bolt out of the inner) and side it in.

I am probably wrong on this, but does that mean that if you do symmetrical bushing replacements in pairs that you don't necessarily need to support the motor and trans?

You will have to lower the cradle down a little to get the uppers in (so there will be movement down)
and you MIGHT be able to get it done without support....BUT I personally wouldn't do it without some type of "safety net" or brace helping to hold the cradle, just in case. A block of wood might help if your doing this on the ground.

That is basically what I did though. I did one at a time, loosened the bolts as to aquire enough room to get the uppers in. I never had all 4 bolts out at once, but I also did this on a lift and used a tranny jack/support holding the actual cradle itself as it was moved down. You could probably get away with it by doing one at a time, but to get the upper insulators in, the cradle needs to move down slightly.

I theory, if you are only doing the insulators, and nothing goes wrong, yes you could do two at a time. I found most of the lower insulators (they have metal interior sleeves) rusted to the cradle itself, so they could not be simply removed or tapped out. I had to use a chisel and hammer to cut out the fused bushing pieces and then use a die grinder to clean out the cradle holes. Having extra room to work made this a lot easier.

Also you must lower the cradle to do the rear mount, so it's as good a time as any!

AA wrote:

I found most of the lower insulators (they have metal interior sleeves) rusted to the cradle itself, so they could not be simply removed or tapped out. I had to use a chisel and hammer to cut out the fused bushing pieces and then use a die grinder to clean out the cradle holes.

Same here, as I did one at a time and noticed these were rusted into the cradle, I was using a big pry bar to pry out the rusted metal sleeve that welded themselves to the cradle. LOTS of movement....so it was critical that I did this one at a time with proper support.

Thanks guys, great info!

Hey guys. I've been stumped on this one for a while. I have a 95 riviera SC and whenever I take a right or left hand turn at slow speeds (10-25mph) I can hear a series of popping sounds coming from my driver side wheel area. I replaced the CV joints twice and still heard it. Then I swapped the tires around, the popping went away but now it makes a creaking sound instead of a pop. I've also noticed the frequency of noise increases with higher tier pressure. I replaced the outer tie rod ends, ball joints, and a-arm rubber gaskets. The only things I haven't replaced on the front end are the macpherson, the bearings, and the inner tie rod end. Can anyone help me? I was certain it was the CV but definitely not. Could it have something to do with my wheels/tires? Or maybe the parts I haven't replaced?

It's either your struts, motor mounts, control arm bushings, or your cradle mounts. The OEM struts are junk anyway, so might as well replace with something firmer like KYB GR2s. The control arms can be inspected from below. It's not a hard job. The cradle mounts and motor mounts (I think one or both of these is your problem) are a big job, but it can be done for not a lot of money. We have write-ups for. Most of the procedures on he site.

I did the control arm bushings so those are out. I'll have to get the car up to inspect the cradle mounts. From what I remember, they were all intact. I'm guessing if they have rotted out, that would be a good sign of them being the culprit. I'm a little confused on why you think the cradle mounts or the engine mounts would be making that noise. Wouldn't it be something more directly related to the steering components? I did not find the write up on the cradle mounts, rather a lengthy thread that did not say anything about popping or creaking: https://rivperformance.editboard.com/t1897-faq-cradle-mount-bushings?highlight=cradle+mount. What would be popping / creaking on the strut?

I am considering taking turns at 10-25 mph to mean fairly hard cornering maneuvers. Slow, but taking a corner at those speeds is really testing the suspension.

When you make a hard turn, the mass of the engine transfers to the cradle through the motor mounts. If the motor mounts are bad, you have metal/metal contact, which sounds like a knocking/popping or scraping/creaking noise. The cradle itself will shift on its mounts if they are deteriorated, making metal/metal contact with the under-body. A similar noise can result.

Mine started out cornering at higher speeds (35-40 mph), then got progressively worse, until it was happening virtually every time I made a turn, even a slow one. It also would happen over uneven surfaces when the car would get shaken around. If I did a slalom type maneuver (left, right, left, right in quick fashion) to induce body roll, and I could hear noise without actually turning the wheel much at all. That told me it wasn't a steering rack issue.

If in your case the problem is occurring at very low speeds, especially if you're not rolling, it is almost certainly the struts. Try putting the front wheels on soft ground, shift into P, then turn the wheels back and forth. Bad strut mount bearings will make a "bump, bump, bump" sound, and possibly a grinding if they are worse.

Not disagreeing with Aaron here, but check the stabilizer links aswell. If they are very rusty it could be the metal sleeve has "welded" itself to the shaft. Mine made a popping sound at low speeds too, so I changed the links and the noise is gone.

Good idea - I didn't think about that. A simple check on a common failure part!

It will still pop and creak at the speeds you were corning at 35 - 40. But above that, it won't. I'll take a look at the mounts and see if I seen anything fishy. Remember, the noise changed from pop to creak when I rotated the tires. The struts do not make any funny noises when parked and I crank the wheel back and forth on hard ground. I will try on soft. Also, I replaced the links with everything else so no problem there. As you can see I've done everything but the strut and steering knuckle. I'll try to eliminate engine mount and cradle mount tomorrow. Other than that, I'm still scratching my head. So strut, bearing, or mounts. I'm running out of things to eliminate. No one thinks it could be inner tie-rod end? Or better yet something with the wheels or tires?? I'm running el cheapos from town fair. I'm upgrading once I figure this problem out.

I've got 230k on my orig inner tie rod ends, and I do some crazy stuff with the steering wheel. Yours would be the first Riviera I've heard of to have them go bad. The inners don't wear nearly as fast as the outers do. Also, I'd think the steering would feel sloppy of they were so bad to be making noise.

A simple look under a lift can spot any bad engine cradle mounts. It took my mechanic all of 10 mins to figure it out.

Did you replace the lower ball joints with the control arm bushings?

Yes I did replace them. What a joy that was. You're probably right about the inner tie rod. No sloppy steering. The noise is not symptomatic for struts or bearings though.... I'll take a look at these mounts and report back.

My subframe bushings have gotten pretty worn. I'm noticing a slight "thunk" in turns when the weight shifts to the left side of the car. I've replaced control arm bushings and engine mounts so at this point I figure the subframe bushing are next. The problem I've run into is that it's nearly impossible to find them. My dad is a GM tech and even he has problems finding them and says that he'll order them when he sees them in nearby inventory but for the most part I'm kinda SOL in my local area. Where can I get good subframe bushings? Polyurethane ones would be nice too

Gmpartsdirect.com - My GM parts desk has them, too. You'll need the nuts, bolts, and spacers, too. Part numbers are above. There is a write-up thread for reference when you install.

We had the sway bar bushings break the frame piece they were mounted to. But this was with an Addco bar and poly bushings. I doubt you did that with a stock sway bar, but it's worth looking at. Our symptoms were very similar to yours.

I'd lean towards Strut Bearings/mounts. That part alone usually creaks/pops when they go bad....moreso than any other suspension component. Ball joints usually don't make the popping sound until they load up, and usually only happens once during a turn, or they squeak going over bumps.

The OP claims the noise only happens at speed. If the strut bearings were bad, wouldn't they make the noise when turning the wheels at a stand still?

Drew - how many miles are on your car?

Hey guys. I'm almost positive it's strut bearings/mounts. 155k miles on the car. It creaks and pops on slow turns / backing out of the driveway in the morning. What stinks is that I'm almost $500 in the hole already rebuilding the front end ugh. That was before I found this forum though . Good people. I just ordered some new KYB-GR2s. Now I just need to get the strut mounts/bearings. Does anyone know if I just pick up the autozone duralast ones if they will be compatable with the KYB-GR2s? I don't see why they wouldn't since the duralast mounts are suppose to be an OEM replacement part.

Order the mounts from Summit Racing: (KYB-SM5276), $51.39 each when I bought mine (need two). PS - mine's a '98, so check compatibility.

I hope that solves your issue, but at 155k you needed new struts anyways, and the KYBs imo are one of the best handling mods you can do for the front end. If the noise doesn't go away, you know what you need to do!