Lower Control Arm Bump Stops

[Roy W]

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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[Kennedy]

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.

[Roy W]

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 ??

[Kennedy]

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.

[crashz]

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.

[Roy W]

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 ??

[crashz]

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.

[Roy W]

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.