Engine/Transmission (1998.5 - 2002) 65 MPH Bounce

[DNiccoli]

99 2500 QC 5-Speed 4x4

I have only owned the truck for about 3 months, but I have noticed that while on a cement highway and traveling around 65mph the truck starts to bounce. It is not a wheel out of balance but feels more like something in the rear suspension. It had air bags to Begin with but after trying a bunch of different air settings with no change I removed them. I have tried lowering and raising tire pressure with also no affect. I am thinking that maybe the original shocks have worn out.

Any other Idea's on the cause? Also what kind of shocks have worked best? I usually drive the truck empty with an occasional trip with a 12 foot slide in camper.

 

[PZicha]

I am dealing with the same problem and come to the conclution that it is the shocks also , all 6 tires are new and have been balanced twice . I have just replaced the front shocks with Gabriel VST shocks and have noticed a change to the better and am going to do the rears on monday . I believe we are both on the same track . If you do all your shocks before monday please post your results... ... Peter

 

[WDPhillips]

I have a similar problem with a 97 3500. Mine started with some issues in the front end which I have now corrected with new steering stabilizers, front end alignment, front brakes, all 6 tires balanced, and new KY heavy duty shocks all around. My front end is now solid as a rock now but I still have this rear end "bounce".



I did have loose tailgate latches, replaced those. Believe it or not this did help the rear end "bounce". But something is still there. I was going to proceed with tire pressure, I am running around 70psi, with Michelin MXs, but it looks like this did not help for you. I also want to make sure the spare tire is tight and the pickup bed is tight. If the tailgate could make a difference they also might be a source.



I certainly will be interested in what you all find.



Regards, wd

 

[PZicha]

My rear shocks will be installed on tuesday , I realy hope more peaple post this has to be a common problem

 

[WDPhillips]

Tire Pressure

Wow, what a difference tire pressure makes! I went to a local truck stop and weighed my front and back axel, 4080 lbs and 3020 lbs respectively. The using the method of calculating tire pressure discussed in this forum, I found that my Michelin LTX L235/85 R16 tires needed 55 psi in the front and 45 psi in back duals. Not the 65-70 psi the garage that rotated and balance my tires had set them all at!



My ride is very smooth now and I do not have the rear end bounce! I hope this helps someone else.



Regards, wd

 

[dan_gilson]

I have about 5 miles of highway that does this to me to. It does not matter what tire pressure. I did go to softer shocks and it helped but not much.



DNiccoli touched on this. It is a cement highway and it just happens to have the expansion joints at the same length as my wheel base. From 59-71Mpg it is just bad. At 65 I am off the pavement as much as I am on. Which is not good for braking and steering.



So, my suggestion is check you equipment and when you know it is good try different speeds. It may be the key to your smooth ride.

 

[PLaFrombois]

I had the same type of problem. Even after replacing all shocks and balancing the tires it still felt that the truck was bouncing all over. No matter what pressure I changed to it was still prevalent. I went back to where I had the tires balanced because I thought I dropped a weight or the tires were starting to separate. It turns out that I have two wheels that are noticeably bent and another one is slightly out of round. These are the original chromed steel wheels. Unfortunately, I can't prove that they did anything wrong when they mounted my tires. Just an excuse to buy after market. Any suggestions as to which ones I should look at purchasing?

Thanks

Paul

 

[dan_gilson]

Good point. So, a good question to ask is whether you get the bounce all the time or only on specific sections of highway.

 

[PZicha]

My bounce was not always there and got much more pronounced once the speed exceeded 65mph before the front shock change. ( still waiting for rears to come in ) After I put them in I took the truck up to 75mph and got a very smooth ride with the exception of the rears still bouncing a bit

 

[BarryG]

As someone mentioned on the cement freeways with the expansion joints I believe it has to do with harmonics. The expansion joints coincide with the wheelbase somehow and it makes them more pronounced. I think the best you will be able to do is lessen it some by adjusting shocks, air pressure etc. Which will change the frequency somewhat and that will change the harmonics. Surely there is an engineer type out there that can better explain it than me. I drive a stretch everyday and throttle plays apart in my drive. Accelerating it is not as bad or slowing not as bad constant speed is the worst going up the grade I feel it quite a bit but going home and down the grade I don't feel it at all.

 

[WDPhillips]

PZicha:



Any change in the rear end bounce with your new shocks?



wd

 

[PZicha]

Yes that smoothened it right out , two of the old shocks had no resistance left . the ride is very nice on the highway now but very firm on the bumps , I read on other posts many members use bilstein shocks , I used gabriel VST's

 

[RADdodge]

Adjustables give you more options...

I found the adjustable Rancho shocks to help a lot. Especially when carrying a slid-in camper. When the truck was new, the truck would bounce like crazy. Taking the truck home from the dealer, I HAD to get off the road when I hit the freeway section that was concrete (I should have stopped at a fast food restaurant first!). When we used the camper, the truck would start bouncing like a rocking horse at some speeds. That was completely solved by the adjustable shocks, making it firmer in the rear that in the front. Just the opposite when the truck is unloaded – i. e. firmer in the front than the back. Hope that helps some.

 

[MD500E]

Has anyone thought about our quad cabs having something to do with it. I would think the newer trucks equiped with quad cabs would have a slightly less stiff chassis than the older extended cabs without the door. More flex, more bounce



Just a thought.

 

[dan_gilson]

For me and my drive it is a wheel base length thing. Both '96 extended cab and the '98 quad cab have the same bounce over the same stretch of freeway. The quad cab does have more flex than the extended cab. I notice that if I start pushing hard in the corners or 4 wheeling.

 

[Kyle]

I think it's axle wrap

I've tried several things and have come to the conclusion it's axle wrap. This problem seems to be more pronounced on the 4x4 versions because of the taller blocks on the rear axle. (taller blocks = more leverage on the springs and more axle wrap).



A few have gotten rid of the bounce with new spring packs that eliminate the blocks or with traction bars that eliminate the axle wrap. Both solutions are about $500.

 

[andrewkoperdak]

DN,

Maybe I don't understand what you are talking about, maybe I do. My 2X4 bounces really good on certain cement highways. I have found that putting several hundred pounds in the bed, over the rear axle, smooths the ride nicely.

I bought serveral bags of rocks from Home Depot ( 80 lbs each) and leave them in my bed. This also lowers my rearend so my truck and 5th wheel don't hit anymore.

My 2 cents

Andy

 

[RichB59]

I have the same problem

at exactly 65mph I get a slight bounce on some roads. I think I'll change the O. E. M shocks . I guess Rancho 9000's are good???? I haul a light travel trailer so maybe even air shocks of some kind to help support the tongue wieght would be good. Just wanted to add myself to the evidently long list of bouncers.



LOL RichB:{ :{ :{

 

[Dr.Kayak]

I have the same problem. Have Rancho 9000s set on 1 (soft). and reduced my rear pressure to 50 lbs with no help. The bounce goes away at 80mph. Does not bounce at all with my camper on. I think adding weight to the rear is the only answer. Or get the government to fix the roads.

 

[jwdeeming]

Dr. Kayak,



Running empty, I have all four Ranchos set on 3. This was a huge improvement on the bounce / oscillation problem. Try that and experiment with different tire pressures. I think setting your rears to level 1 may be too soft to help.



JimD