Front shock thuds and thunks - suggestions welcomed
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2004-2007 Cadillac CTS-V Performance Mods Discussion, Front shock thuds and thunks - suggestions welcomed in Cadillac CTS-V Series Forum - 2004 - 2007; Well the newly rebuild Penske shocks are on. Thanks Troy. I won't give any feedback yet as I'm having an ...
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    ichpen's Avatar
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    Penske front shock thuds and thunks - suggestions welcomed

    Well the newly rebuild Penske shocks are on. Thanks Troy.

    I won't give any feedback yet as I'm having an issue with the fronts. Big thud/thunk on heavy compression going over bigger bumps at high speed.

    The shocks as you can see in the pic come with their own height adjustable perch and top hat.

    I'm running 560lbs sprint springs, 10" length in front.

    Rears are solid so far.

    Just looking for ideas/suggestions. I shouldn't be bottoming out with this length/stiffness of spring and I was running the same springs on QA1s prior without issue.

    P.S. on a smooth corner when I'm not thunking and thudding this shock combo is quite amazing.

    Pics of front passenger side below to give you an idea:




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    Re: Penske front shock thuds and thunks - suggestions welcomed

    What about the compression setting?

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    Re: Front shock thuds and thunks - suggestions welcomed

    No idea, they were setup at a dyno and adjusting these penskes is no easy feat, have to get a tool down from the top.

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    Re: Front shock thuds and thunks - suggestions welcomed

    Cant really help much just wanted to make sure that brake line isn't rubbing the shock tube. With the whole tube threaded it would take long to eat through the brake line.

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    Re: Front shock thuds and thunks - suggestions welcomed

    Good call on the brake line. I'll tape up that shock to avoid future problems.

    Figured it out and a lesson to those thinking of switching to more exotic shocks. It's the upper control arm bushings that were moving up and down. Because of the design of these the top hat (that retains the top of the spring actually sits below the threaded cap). This is different from QA1s where the top hat sits on top of everything. So basically all that's left is the bushing held down by the top nut and she moves. With QA1s the top hat acts as a stop (as it's wide enough) preventing any up and down movement. Big question is what to stuff up there that's strong enough not to bend with shock movement.

    TroyFlemming suggested I can reuse my stock shock parts for this but I'm trying to get a good pic of what the upper part of a stock shock looks like. I have most bits but I think I'm missing something.

    Anyone got a pic or a service diagram of front shock disassembly?

    Cheers.

    Nik

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    Re: Front shock thuds and thunks - suggestions welcomed

    Good luck finding the fix for those sweet Penskes. BTW, I paypal'ed you payment for your QA1s last night as promised. No hurry on the shipping, but keep me posted and a tracking number would be appreciated. Thanks.

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    Re: Front shock thuds and thunks - suggestions welcomed

    Just for a little info on these Penskes they are one of six sets Penske built as direct bolt-in and valved for the CTS-V with no modifying anything and one off rear shock clevis and yes I sold them extremely cheap, but rather they get used and not sitting on shelf, already have a set aswell.


    Now what caused the issue was switching from QA1's to Penske instead of stock to Penske. With QA1's you discard some stock bushings with install, unlike Penske's that are direct bolt-in and use some stock washers/bushings. Glad ichpen saved his stock bushings/washers since after going back and forth issue is solved with the help of paint.

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    Re: Front shock thuds and thunks - suggestions welcomed

    What kinda picture do you need?

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    Re: Front shock thuds and thunks - suggestions welcomed

    Quote Originally Posted by ichpen View Post
    Figured it out and a lesson to those thinking of switching to more exotic shocks. It's the upper control arm bushings that were moving up and down. Because of the design of these the top hat (that retains the top of the spring actually sits below the threaded cap). This is different from QA1s where the top hat sits on top of everything. So basically all that's left is the bushing held down by the top nut and she moves. With QA1s the top hat acts as a stop (as it's wide enough) preventing any up and down movement. Big question is what to stuff up there that's strong enough not to bend with shock movement.

    TroyFlemming suggested I can reuse my stock shock parts for this but I'm trying to get a good pic of what the upper part of a stock shock looks like. I have most bits but I think I'm missing something.

    Anyone got a pic or a service diagram of front shock disassembly?

    Cheers.

    Nik
    Nik - Not sure I'm understanding your explanation. The upper control arm bushings are in the two "legs" that protrude from the bottom of the upper strut mount. Nothing you've done should've affected those at all. Here's a picture from my KW install. This shows the pieces of the front top mount, going from left to right. There's nothing else below the top mount other than the big rubber spring isolator and the bumpstop/dust sleeve piece.



    If I understand what you're saying with the Penskes, it sounds like your upper spring perch isn't seated up against the bottom of the upper strut mount. Is that correct? Here's how the KW setup fits together - the upper spring perch adapter fits up against the bottom of the strut top mount:


    Does the shaft of the Penske strut have a shoulder to it, so that the upper strut mount is sandwiched between that shoulder and the top nut? I just went out in the garage and grabbed one of my stock struts to take a quick picture:



    I made it into a crude diagram so you can see how tightening the top nut sandwiches the upper strut mount (aka big-ass aluminum top mount assembly) between that shoulder and the nut. The KW is the same way (the shoulder is actually even bigger, but I don't have a particularly good picture of it):



    If the Penske shaft does not have a shoulder like that, then I could see that under compression there really wouldn't be anything preventing the shaft from pushing up through the top mount. I can't imagine that's how the install is intended to be; there must be something missing. Either that, or (more likely) the top nut hasn't been tightened down all the way to firmly seat the upper strut mount against the shoulder on the shaft.

    Hopefully all that makes sense.
    '05 Stealth Grey CTS-V, Hyper Silver Linea Corse Venetos w/Continental ExtremeContact DWs (summer), black Team Dynamics ProRace 1.2 wheels with 275/35-18 R-compounds (track), Hyperblack Rota Torques (winter), KW Variant3s, V2 front brakes, Hotchkis rear sway bar, EPS cam, TEA-ported 243 heads, FAST92 intake w/LS2 TB, JBA Camaro/G8 1-3/4" shorty headers w/JBA cat pipes, Corsa exhaust, UUC motor and tranny mounts, UUC shifter, MAPerformance trailing arms, Specter cradle bushings, etc...

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    Re: Front shock thuds and thunks - suggestions welcomed

    Is "Big-ass aluminum top mount assembly" a technical term?

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    Re: Front shock thuds and thunks - suggestions welcomed

    OK, kind of hard to explain without pics. The penskes are a little different. When I did my QA1s I ditched the big ass rubber isolator and the dustboot/bumpstop. The QA1 top spring mount/hat goes on top of the thread cap and props up directly against the control arm bushing. The nut goes on top to keep the shock on control arm. So, the spring mount being wide and relatively flat makes full contact with the rubber on the underside of the control arm.

    The Penske's have the top hat 'under' the thread cap (you can kind of make it out in my pic, it's a separate cap from the shock shaft). So we only have the top most threaded bolt protruding pretty tall with only a large jam nut beneath (no hat) then we have the hat (which is a lot pointier, boy this sounds more and more disney) beneath that. So when the shock compresses and travels up the nut is small enough to only make contact with the very center of the control arm bushing hence it pushes the whole bushing up. If I had been smart I'd have seen that and put a big ass washer right above the jam nut.

    Phew... I'll just take some pics tomorrow at the shop to show you the issue. Now if I had retained the stock shock crap (which I thankfully mostly did), I'd reuse that big ass rubber washer (in your pic on the left) and use the metal top on that dust boot (minus the bump stop) to make contact with it. Or just use a very chunky metal washer up there.

    Your design is a bit different looking at the pics.

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    Re: Front shock thuds and thunks - suggestions welcomed

    Quote Originally Posted by tweeter81 View Post
    Good luck finding the fix for those sweet Penskes. BTW, I paypal'ed you payment for your QA1s last night as promised. No hurry on the shipping, but keep me posted and a tracking number would be appreciated. Thanks.
    Got the cash. Thank you sir. I'll ship them out Thursday, they're packed and ready. Just a little tied up as you can see.

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    Re: Front shock thuds and thunks - suggestions welcomed

    Quote Originally Posted by darkman View Post
    Is "Big-ass aluminum top mount assembly" a technical term?
    Very. Hopefully it's not confusing the non-technical types.

    Quote Originally Posted by ichpen View Post
    OK, kind of hard to explain without pics. The penskes are a little different. When I did my QA1s I ditched the big ass rubber isolator and the dustboot/bumpstop. The QA1 top spring mount/hat goes on top of the thread cap and props up directly against the control arm bushing.
    OK, I'm not sure what a thread cap is, and again, you're not touching the control arm bushings.



    Quote Originally Posted by ichpen View Post
    The Penske's have the top hat 'under' the thread cap (you can kind of make it out in my pic, it's a separate cap from the shock shaft). So we only have the top most threaded bolt protruding pretty tall with only a large jam nut beneath (no hat) then we have the hat (which is a lot pointier, boy this sounds more and more disney) beneath that.
    This is where I lose you. I'm just not sure what you mean by a "thread cap". Hopefully you can take some pictures that make it more clear. To go back to my previous question - does the shaft of the Penske strut have a shoulder on it?

    Quote Originally Posted by ichpen View Post
    So when the shock compresses and travels up the nut is small enough to only make contact with the very center of the strut top mount bushing hence it pushes the whole bushing up.
    You definitely don't want the spring riding on the rubber bushing. You want the spring riding on the big-ass aluminum piece, as it did with the stock setup. Borrowing a picture of the bottom of the big-ass aluminum piece from the FAQ, you can see the marks left by the stock rubber spring insulator on the metal.



    Looking forward to your pics tomorrow.

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    Re: Front shock thuds and thunks - suggestions welcomed

    Quote Originally Posted by AAIIIC View Post
    Nik - Not sure I'm understanding your explanation. The upper control arm bushings are in the two "legs" that protrude from the bottom of the upper strut mount. Nothing you've done should've affected those at all. Here's a picture from my KW install. This shows the pieces of the front top mount, going from left to right. There's nothing else below the top mount other than the big rubber spring isolator and the bumpstop/dust sleeve piece.



    If I understand what you're saying with the Penskes, it sounds like your upper spring perch isn't seated up against the bottom of the upper strut mount. Is that correct? Here's how the KW setup fits together - the upper spring perch adapter fits up against the bottom of the strut top mount:


    Does the shaft of the Penske strut have a shoulder to it, so that the upper strut mount is sandwiched between that shoulder and the top nut? I just went out in the garage and grabbed one of my stock struts to take a quick picture:

    Hopefully all that makes sense.
    Those KW's are just like stock with a threaded cap/sleeve body and these Penske's can be run that way, however they can also be run in a true coilover design with upper quick change spring retainers.

    Now what was causing ichpen issue was instead of having upper mount stop washer, Penske's were mounted straight into the rubber bushing and then through the aluminum mount which is incorrect. He now has the stop washer and it will seat Penske upper cap directly against the aluminum like shown your KW do.

    The benefits of this design of Penske are there for sure ride quality anybody that has used them knows. Now the benefit of running with quick change spring retainers is true coilover and ability to remove shocks in future without having to rip the whole front-end apart. If you need to remove a KW you would need to remove upper aluminum mount. With Penske's after install, you can now undo one upper jam nut and two bolts on lower control arm and pull shock out with spring still retained.


    Majority of V owners could careless about this benefit since they are daily drivers, but unlike KW that are not user rebuildable and the limited lifetime warranty covers little to nothing I have heard, Penske's can be rebuilt over and over for under $100 at home or send them in for $60 a shock.

    When you get down to it the FG2 are by far best bang for buck if you just add coilover sleeve, but in long run Penske's trump them all in every single category rebuildability,ride quality,performance. Only thing is price, although I sold them dirt cheap helping a forum member out, when purchased from Penske on this same design you are easily at $3500 in no time. I have said it before and will again the older these cars get the more Penske's make sense. FG2 are going to get harder and harder to find. Used ones will get more and more miles on them at used part places.

    I am sure ICHPEN will post more shots of shocks after issue is fixed, the rear shocks are the best part.

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    Re: Front shock thuds and thunks - suggestions welcomed

    What Troy said.... Best advice is don't throw your old washer/shock parts away as you never know when you'll need them. Pics coming today after hopefully getting this fixed up.

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