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Thread: Lower Control Arm Bump Stops

  1. #1
    Join Date
    Jun 2005
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    St. Augustine, FL
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    Default Lower Control Arm Bump Stops

    Since it was new, my 2005 2500 4 X 4 lower control arms have just barely cleared the yellow rubber lower control arm bump stops when level at rest. I checked other new trucks at the dealership at the time and they were all touching the bump stop as well. I don't understand this, as this only leaves a very small amount of lower control arm travel (1/8") before it contacts the stop. This has to affect the harshness of the ride. I realize I could crank the torsion bars up a bit and gain some clearance, but my truck sits level now (ARE topper and 60 gallon auxiliary tank) and I don't want it to be nose high.

    The problem gets worse when I hook up my travel trailer which has 1000 lbs of hitch weight and then install the weight distribution bars, which then distributes the hitch weight equally (500 lbs front, 500lbs rear) and causes the front end to drop even lower and compresses the bump stop against the lower control arm when at rest. I just returned from a 6000 mile trip to Yellowstone and when I got back noticed the bump stops were beat up pretty bad from being bottomed out and pounded to death by potholes on highway bridges. (as well as my back)

    Does anyone else have this problem on a stock height truck ?? I plan on replacing both bump stops. Are there any available on the aftermarket that are better quality than OEM replacements ??
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    2005 Chevy 2500HD, CC, SB, 4X4, Duramax, ARE Topper, 60 gallon RDS toolbox/tank combo, Kennedy Headlight Booster, Isspro pyrometer and boost gauges, EGR Blocker, PCV Kit, Bilsteins, 265 Michelin MS-2, TTS Exhaust, pulling 35' Jayco travel trailer.

  2. #2
    Join Date
    Mar 2000
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    10,795

    Default

    Those are not bump stops they are a cellular air spring of sorts. A functional part of the suspension. I recently replaced the units on my 2002 as they were in pretty rough shape, but that truck runs with the bars cranked down and a lot of compression on these devices.

    Suspension/ride quality is something that needs to be tuned. A set of Air Lift bags will do you wonders. Add the Wireless Air control and it gets even better. You also do not need to crank your weight dist bars super tight. Try adding a link to the tension side once and see how that goes.

    When I carry my 2002 on my car trailer I hate to even think about what the tongue weight is, but it has to be HUGE as most of the cab is ahead of the axle CL. I run bags and bars and it rides decent, but tuning the air psi is critical.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

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  3. #3
    Join Date
    Jun 2005
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    St. Augustine, FL
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    180

    Default Air Lift Bags

    So if I understand you correctly John, you're recommending I add air bags to the rear, then add a little hitch weight to the truck by dropping down another link on the chains, thereby taking weight off the front ??
    2005 Chevy 2500HD, CC, SB, 4X4, Duramax, ARE Topper, 60 gallon RDS toolbox/tank combo, Kennedy Headlight Booster, Isspro pyrometer and boost gauges, EGR Blocker, PCV Kit, Bilsteins, 265 Michelin MS-2, TTS Exhaust, pulling 35' Jayco travel trailer.

  4. #4
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    Mar 2000
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    Default

    Yes, no, maybe...

    Sorry to sound so evasive, but you will have to find what works for you the best. Bags will make a huge difference this I will say for certain. This alone may get what you need as less squat puts less load on the bars.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  5. #5
    Join Date
    May 2009
    Location
    NH & Eastern NY
    Posts
    205

    Default

    John is right, they compress as part of the suspension. Almost all of the 1/2 tons will be partially resting on the stops and the 3/4 and 1 tons appear very close. I tried to adjust my torsion bars so that I had no contact on the stops, but my ride height and Z height were way out.

    I replaced my stops with Timbren load boasters. The Timbrens helped tremedously on carrying the snowplow, but like the stock stops, are a constant and active part of the suspension. I have a few complaints with them as well:
    1) They make the ride a bit more harsh (obviously), but they feely like they are not as linearly compressable, so they stop hard on big potholes.
    2) The additional force of the Timbren seems to cause additional distortion in the A arm bushings, as if the Timbren is harder and more resilent than the bushing. This has made trips to the alignment shop much more frequent.

    At some point I think I'll replace the Timbrens with stock stops as I don't plow much any more. I beleive that there are new air shock / load boosters offered for the GM trucks that mount in the shock locations. This may be an option too.
    2012 Chevy 2500HD ECSB, 6.0L gas, auto, 4x4, LT
    2003 F450, 7.3L PSD, 6 spd stick, 2wd, dump truck
    1983 GMC K2500 pickup - working on a Cummins 5.9L swap
    1987 GMC K3500 Dump, 6.2L diesel, TH400 auto - project plow truck

  6. #6
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    Jun 2005
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    St. Augustine, FL
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    Default

    Thanks guys. I will order a set from gmparts direct, although their exploded view is not very clear. Do you know what GM calls them ??
    2005 Chevy 2500HD, CC, SB, 4X4, Duramax, ARE Topper, 60 gallon RDS toolbox/tank combo, Kennedy Headlight Booster, Isspro pyrometer and boost gauges, EGR Blocker, PCV Kit, Bilsteins, 265 Michelin MS-2, TTS Exhaust, pulling 35' Jayco travel trailer.

  7. #7
    Join Date
    May 2009
    Location
    NH & Eastern NY
    Posts
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    Default

    Also check for proper operation of the shocks and make sure the rubber bushings are sound and there is no play. I replaced my shocks last year, but up until then have had to periodically tighten the upper shock mount. The rubber bushing would compress and harden, causing a slight movement between the shock body & the mount. Keeping them snug keeps the ride smooth.
    2012 Chevy 2500HD ECSB, 6.0L gas, auto, 4x4, LT
    2003 F450, 7.3L PSD, 6 spd stick, 2wd, dump truck
    1983 GMC K2500 pickup - working on a Cummins 5.9L swap
    1987 GMC K3500 Dump, 6.2L diesel, TH400 auto - project plow truck

  8. #8
    Join Date
    Jun 2005
    Location
    St. Augustine, FL
    Posts
    180

    Default Jounce Stops

    Just a followup on my original jounce stop thread. GM now has a new heavy duty pointed yellow jounce stop that appears on the later model Z-71 equipped cars. The part number for the newer type is 15835667. The original round type part number is 15015538. The Z-71 type is available from GM Parts Direct for $42 inc shipping.
    2005 Chevy 2500HD, CC, SB, 4X4, Duramax, ARE Topper, 60 gallon RDS toolbox/tank combo, Kennedy Headlight Booster, Isspro pyrometer and boost gauges, EGR Blocker, PCV Kit, Bilsteins, 265 Michelin MS-2, TTS Exhaust, pulling 35' Jayco travel trailer.

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