BMR - Help / Advice
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2004-2007 Cadillac CTS-V General Discussion Discussion, BMR - Help / Advice in Cadillac CTS-V Series Forum - 2004 - 2007; I'm starting to hear the dreaded "thunk" more and more from the rear of the V. Even letting the clutch ...
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    CVP33's Avatar
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    BMR - Help / Advice

    I'm starting to hear the dreaded "thunk" more and more from the rear of the V. Even letting the clutch out at low rpm's in 6th the "thud" is noticeable. Here's the question. Has anyone installed the Pinion Support Brace and does it eliminate this condition?

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    CVP33's Avatar
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    Re: BMR - Help / Advice

    Anyone know?

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    Dreamin is offline Cadillac Owners Connoisseur
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    Re: BMR - Help / Advice


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    CVP33's Avatar
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    Re: BMR - Help / Advice

    Dreamin - Thanks. I read that too, but was hoping for some real world experience. I still see posts that the BMR kit doesn't stop wheel hop but does improve it. Would like to find out the same info' on their PSB.

    Thanks

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    wildwhl's Avatar
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    Re: BMR - Help / Advice

    CVP33 -

    Should have mine installed tomorrow - as tomorrow is "V" day for me. I now have the trailing arms, toe rods, AWH kit, and non run flat tires aboard. NO WHEEL HOP yet - but also - NO REAL HARD LAUNCHES YET.

    I'll let you know my results this weekend.

    Wildwhl

  7. #6
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    riverrat is offline Cadillac Owners Fanatic
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    Re: BMR - Help / Advice

    FWIW have you retightened everything after the initiall instalation? It took 3 times for mine to "stay" tight and the clunk is now not such an issue. I beleive everything needs to reseat it's self after having the rear end droped then as others have said in other posts the car just gets better over time, sort of a break in period.

    BTW I have oredered the pinion support but don't have it yet. Not because of the thump as I said it isn't the issue it was, but for the other sloppiness of the drivetrain.

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    wildwhl's Avatar
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    Re: BMR - Help / Advice

    OK - UPDATE

    This morning I spent a couple of hours installing the pinion support (simple, 20 minutes once the car is up, no brainer), certifying that the toe rods and trailing arms were installed correctly and rechecking that everything was tight, and checking again all of the cradle bolts to be certain they were tight. I borrowed a friend's monster torque wrench (heavy equipment mechanic) that has about a 36" handle and achieving the 140/185 ft lbs was a piece of cake. It appears the front cradle bolts had backed off/or weren't tight enough at the last install by me to about 130 ft lbs and the rear's were right about 110 or so. They are all FOR CERTAIN torqued to proper specs now - for clarity 185 ft lbs on the front 24mm bolts and 140 ftlbs on the rear 21mm bolts. I will recheck these Tuesday morning after driving for the weekend to see if they change. I also turned the front trailing arm bolts upside down - so that they install from the bottom with the nylon locknut on top of the front cradle mounts. I did this so that I could remove and reinstall trailing arms without dropping the cradle should I desire. Please note that this ONLY works in my application because I have the B&B exhaust and the CORRESPONDING SPACERS for the BMR AWH KIT which will stop the ends of the bolts from hitting the underside of the car. I also installed the B&B exhaust with dynatech cones...but will post those results in a different thread.

    Results - the back of the car is totally solid and very planted. Turn-in is certainly quicker/nicer. Overall handling is if anything improved - but nothing noticable. Noise is minimal - but I do hear the sound of the rearend (read=whine) quite easily now. Not sure is that is a result of the pinion support (doubt it) or just the fact that the cradle/toe-rod/trailing arm bolts are tight, tight, tight now. I also managed to tame the B&B exhaust which may be letting me hear more - but since the stock one was on for the last week I don't think so.

    CVP33 - I can't answer your "thunk" question directly other than to say I have only one noise coming from the rear (two if you count the whine) and it is not a thunk/clunk/bang/pop - but instead what I believe to be one of the toerods rattling at the spherical rod end. I've checked and rechecked this - and everything looks great - but the sound is exactly like what I would imagine that to sound like. Will have to invest more time in the future. See my post on BMR Toe Rods elsewhere for more information.

    All, and I do mean ALL, of the other bangs and pops are gone. I attribute this solely to getting the cradle bolts to the proper torque. You know what they say - "Don't force that son, get a bigger hammer!" It is amazing how little effort even 185 ft lbs of torque is when you have that much leverage!

    Off to drive for a while and enjoy this beautiful 75 degree day WITHOUT WHEEL HOP - oh yeah, did I forget to tell you? NO WHEEL HOP. I TRIED DEARLY. JUST BIG BLACK PATCHES OF PAVEMENT on two launches and my two favorite 2nd gear turns are as easy to hang the ass end out as far as you like and keep em drifting without ANY NOTED WHEEL HOP. Remember, I have GSD3's now too...


    Hmmmm....running out of mods. Where's the Mag I/C thingy majig?

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    Rich H's Avatar
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    Re: BMR - Help / Advice

    Wildwhl - Are you saying that you could have eliminated most of the thunk/clunk/whatever noises from the rear differential simply by tightening the cradle bolts to the factory torque specs? This seems to be what BMR Fab has said in another post on the carbon driveshaft thread. Sounds like the pinion support might be a band-aid we don't need.

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    wildwhl's Avatar
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    Re: BMR - Help / Advice

    Rich H -

    Well, yes and no. We are talking about several different noises here. I'm poor at explaining the differences. The pinion support is there to help reduce the flexing of the pinion area of the rear diff and driveshaft. When the drive train loads up and unloads there are a few noises and this seems to take care of one of them, just as BMR has suggested. It also seems to have taken most of the spongy feel out of the drivetrain (the dreaded low speed 1st and 2nd gear double clunk rattle from the dual mass flywheel or whatever still exists though it seems to occur less often).

    You are correct in assuming that properly tightening the cradle bolts after the BMR antiwheelhop bar/kit is installed takes care of the banging that can be associated with that install. These are noises that aren't there without the kit in my experience.

    I'm not entirely certain the pinion support is necessary or of the exact benefits while driving yet (haven't driven that much). What I can say is that as a whole, it all feels quite good now.

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    bryce3 is offline BAD EMAIL ADDRESS
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    Re: BMR - Help / Advice

    That sounds great that you don't have any wheelhop yet , but what are you launching at???? I have the AWHK and I still have a significant amount of hop. I have tried dropping the clutch anywhere from 1700 to 2200. A BMR tech guy sent me an email saying that they have launched there car at about 2800 with out any hop. I would really just like to lay a sick ass burn out down once and then I can move to the next mod.
    -Sean

  12. #11
    wildwhl's Avatar
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    Re: BMR - Help / Advice

    bryce3 -

    Around 3,000 rpm or so. Also note that I'm no longer running runflats...GSD3's now...and they seem to hook up and I'm gone. However, even before the new tires, wheelhop was virtually non-existent with these parts on board.

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