Engine/Transmission (1994 - 1998) 1996 2500 Severe Rear Axle Hop

[emailmike]

Help,



I'm having a problem with severe wheel hopping on my '96 3/4t ext cab w/4. 10 limited slip rear end.



Travelling greater than around 40mph, when I hit a bump on the road, i. e. when they're doing asphalt resurfacing and you hit that area where the ground up asphalt meets the uncut asphalt with about a 2 inch height difference, or when I hit railroad tracks, the rear end starts bucking up and down uncontrollably until I slam on the brakes. As I rapidly decelerate, the hopping begins to slow, where it disappears under around 40 mph, then it smooths out and all is fine.



A little background on the truck. I had the Rancho 2" front lift kit, Rancho 9000's all around, and BFG 35x12. 5 AT's installed when new. Never had a problem with wheel hop. A couple of years later I bought a 9. 6 foot Bigfoot slide-in camper and installed a set of Hellwig Standard Helper Overload Springs and a Hellwig anti-sway bar. When the truck is empty it does the "hop" when hitting those bumps as described above.



In trying to identify the problem, I've unhooked the overload springs, but it still happens. I have not unhooked the sway bar, but I can't believe that that would cause the problem. I'm thinking of traction bars but would prefer new springs that will raise the rear 2" and eliminate the factory lift block altogether, but I have not found a spring manufacturer that has a set.



Any ideas?



I have heard of another guy here in Anchorage that had the same problem, and after 3 tries at getting it fixed he traded it in for a Ford. The dealer is clueless and I need to fix it.



Thanks, Mike in Anchorage.

 

[redramnc]

More details needed - is it a long bed or a shortbed? What kind of rims are you running? Have you checked balance on rears? You could be seeing axle-wrap due to loose hardware but that should be obvious to see.



My basically stock 96 2500 2WD auto 3. 55 LSD hops under acceleration to the point that my rear tires wear twice as fast as the fronts. I do not get any hop at speed except when accelerating hard over rough surface. Sounds like something is majorly amiss in the balance department on yours.



Does the rearend make any strange noises when turning tight? I wonder if maybe the LSD is trying to do its job but the tire bounce is causing it to have to adjust and exacerbating the problem to the point of resonance in the system.



I know I ain't much help with this but please post the resolution, if you find one. Good luck.....

 

[fritzbo29]

I know this may sound weird, but that may be the Death Wobble. When I originally had it on my '94 regular cab, I swore it was a problem with the rear end. It turned out it was the Death Wobble, and getting the front trackbar replaced with new shocks completely cured the problem. I swear, when the wobble starts you fear for your life as you have such poor control of the truck.



Hope it fixes easily.

Fritz

 

[emailmike]

More Info on Truck

Here's more info on the truck:



4x4; LWB; Wheels are aluminum American Racing Outlaw II's .



A "DEATH WOBBLE" it is, but it's not wobbling from the front end, only the rear hopping up and down. I replaced the original ball joint on the track bar with the adjustable one from Luke's. I have not purchased the track bar drop bracket from Skyjacker Suspensions yet. The 2" Rancho lift is really only about 1-1/2", so the front end components aren't that far off. I did buy the 2" Pitman Arm drop from Skyjacker to keep things lined up (except the track bar). (Note: even though everyone involved from the Rancho Tech line to the tire dealer guaranteed that 35x12. 5 tires would not rub, both rub the outer fender well in turns, the driver's side the worst. I haven't clipped the fenders preferring to move to a narrower Michelin XZL 9R16 when the time comes).



I had been thinking too that it could be the LSD trying to "kick in" when one wheel gets raised off the pavement more than the other. But I concluded that a problem with the LSD would show itself on a more consistent basis, as you mentioned around corners?



It doesn't appear to be a problem with the rear tires being out of balance. The truck rides smooth as silk with a slight imbalance around 70 mph. This hopping problem only happens when I hit a bump (even a smooth whump) in the road surface. Then it starts hopping a little and QUICKLY starts resonating more and more until I throw the brakes on and get it under 40. To say the least, it's scary when it happens!!



I've pulled my hair out trying to figure it out with the dealer. Fortunately I've had another truck to use to haul stuff around, but I sold it recently. I can still use the Dodge around town as long as I keep it under 35 mph.



I was hoping that there was an easy fix TSB that I could show the dealer, but apparently not ...



I was thinking axle wrap maybe, but does axle wrap exhibit itself this way? I am willing to buy a new set of springs for the rear to raise it 2" and replace the block, but haven't found anyone who makes a set.



I will keep this open until I find a resolution and GREATLY appreciate everyone's input and thoughts!



Thanks again, Mike in Anchorage...

 

[kchristopher]

Does the wobble disappear when you put it in neutral instead of hitting the brakes?



Do you have to slam on the brakes or will gradual application cure it?

 

[LSMITH]

Are you sure the shocks are good? I would also try to duplicate it with the tires at max pressure, you may be getting a bouncing ball effect from the tires if you are running them soft. I would also make sure the U-bolts are torqued properly. Traction bars will help tremendously with problems you are having, but there is likely something wrong to cause it to be so severe in your case.

 

[MidwestMotorman]

Mike



Did you tighten up the sway bar bushing bolts with the wheels on the ground and the truck completely off of the jack? If not, you have preloaded the sway bar one way or both ways.



One of the major contributors in the front end death wobble was the caster of the front end. If by chance you changed the pitch of the rear with one of the modifications, you may have caused an aggravated imbalance in the rear.



Rams are know for hopping on overloads, but not to the condition you describe. I would have your rear tires balanced. Do you have weights on both sides of your rims or just the backs? If not, I would give them a true neutral balance and see if that helps.



If you think that the LSD is the problem, drive a dozen circles each way on pavement in a parking lot and see if that helps. Your rear end may need more lubrication or the additive.



I guess time, luck, and the TDR may help. Good luck.

 

[MidwestMotorman]

chirping

One quick note, if you are sure it is the rear end try this. Next time the truck bounces, FLOOR IT. If you do not hear the rear tires chirping or laying black marks, your rear end is not bouncing. If your rear end is bouncing that bad, the rebound will lift the tires from the surface enough to spin them.



I have one stretch of local road that does make the back bounce bad. And getting in it at over 30 mph will chirp the rear tires.



EDIT: If it is just the bed bouncing, then you shocks or bushings are culprit. The bouncing would have stopped if it was the overloads, because you disconnected them.



For those of us that have experienced the Death Wobble, we will NEVER forget what that is like and will recognize it by feel.

 

[Extreme1]

Check the rear shock mounts. I just welded the left upper back in place last weekend. I bounced pretty bad when it was loose.



Also, have someone drive next to your truck and video it so you can see it or show them how to drive it like this and you drive next to it and look. Sometimes this makes the problem really obvious.

 

[emailmike]

Thank you to all who've responded. Answers to questions posed:



... Does the wobble disappear when you put it in neutral instead of hitting the brakes? No, I did try this on a lonely stretch over a R. R. crossing thinking it may be the driveshaft warping under load somehow, but the rear still bounced when I hit the tracks.



... Do you have to slam on the brakes or will gradual application cure it? Reply: When this thing hits, you have to slam on the brakes to slow and quiet it down as fast as possible. If you wait, the bounce feeds off itself and increases rapidly until the whole truck is bouncing up and down; then when you slam on the brakes it keeps bouncing hard until I get it under 40; whereas when you slam on the brakes immediately after sensing it's starting, then I can sometimes get it to stop (as I rapidly slow)before it starts bouncing really badly.



Are you sure the shocks are good? I haven't pulled the shocks off to check, but the truck has 37k miles on it. I will do this to verify.



... duplicate it with the tires at max pressure... Will do.



I would also make sure the U-bolts are torqued properly... Will do.



Did you tighten up the sway bar bushing bolts with the wheels on the ground and the truck completely off of the jack? Reply: I am going to go ahead and reinstall one side with the truck unloaded and on the ground to verify I didn't unintentionally pre-load the bar.



... Next time the truck bounces, FLOOR IT. Reply: I will try this after the above adjustments and check, though your first instinct is to hit the brakes as you hold on for dear life.



I did read through the archives and the DEATH WOBBLE sounds too similar to what is happening for me to ignore that possiblity (though I'd swear at this point that it's the rear end). In addition to the above I am going to verify that the track bar is tight at the Luke Link. I plan on doing these checks after work this week and test drive the truck out on the Glenn Hwy next weekend. (That's a warning for anyone from Anchorage reading this).



One last point: this does not happen when I have the 9. 6' Bigfoot camper slide in in the bed. Maybe it tries to, but I can't tell from the drivers seat. Would the DEATH WOBBLE still happen regardless if the bed was heavily loaded or not?



Thanks again to all, Mike...

 

[Shovelhead]

Sounds like shocks to me

 

[MidwestMotorman]

lots of good advice

There is lots of good advice coming into this thread. As far as the problem not occurring with the camper installed, any amount of weight displacement affects alignment and steering characteristics. It also affects the shock loads. So, changing something just a little can have a big effect. I maybe would try a drive with the Ranchos set at max stiffness.



With the cases of Death Wobble I have experienced, you will see one corner of the front end rise and then the front body will rock/roll back and forth. You sometimes can really feel it in the steering wheel. I really have not heard of any bucking/bouncing with the rear.



The comment to have someone look at your rig while in motion is a good idea. Everyone has different perceptions of what is happening. If you see what is going on, you will know for sure if it is the front end or back.

 

[jtadysak]

samething..

nathanbush. . Boy am I interested in this. . I had the same problem. but it only did it once. . I have a 95 lifted 5" with 35x12. 5x16. 5 with skyjacker nitros. . I've checked it all too and found nothing. . I've attributed it to the big tires and the lift. . Now as I said it's only happened once... and it sure felt like the rear end was bopuncing up and down... I've had a truck with the death wobble and it was different than this. . your right the only reaction is to hit the breaks and slow it down... Somebody once mentioned that the nitro shocks were to stiff and caused the big tires to bounce when they've hit a stretch of road like we did. . they suggested putting on a set of hydraulic shocks and try that. . Well I have'nt tried this yet. . The road your talking about was the same as the one I hit. . the only problem is it's 150 miles away from where I live so duplicating it is a problem for me. . If it does it agian I'll probably get off my but and do it... . PLEASE if you do find the problem. . post it and I also will do like wise if I find the problem... Thanks and good luck...

 

[JTBMC]

Does anyone know what the Torque specs are for the 9/16 inch rear axel U-Bolts. Mine were all loose and I really pulled them down the evening.

Thanks, TJ

 

[B.G. Smith]

Spring clamp nuts.

TJ, the torque is 110 ft. pounds. bg

 

[JTBMC]

Thanks, BG

I loosened them and torqued them properly this morning.

TJ

 

[emailmike]

Update...Still Working At It

This past weekend I finished up the easy things recommended by your input earlier:



The shocks are RS9000's. I found one on the rear that wouldn't allow me to change the setting. It is stuck on 2. I know this is a problem with these and I will have to get that dial replaced asap. Other than that, the shocks were good.



My tires (BFG AT 35x12. 5x16. 5 w/ARE Outlaw II's) are getting ready for replacement. I have about 1/4" tread left (after 35000 miles). I tried locating some Michelin XZL's that Earthroamer was using, to no avail. It looks like either the Rickson's ($$$) or a new set of BFG AT 33x12. 5's soon. I know that worn out tires appear to contribute to the front end DEATH WOBBLE, so I haven't ruled this out as a cause.



The U-bolts were torqued properly.



I reinstalled the sway bar ends with the truck unloaded and on the ground. Interestingly, one side of the sway bar needed to be jacked up about 1/2" for the link bolts at the sway bar ends to line up (this is particular to the Hellwig design, which is unlike the OEM links connecting the ends to the frame). This may be pre-loading the bar slightly. I need to drive around with one end unconnected to verify that this isn't causing the bucking. But I'm doing things one at a time to try and find the cause by elimination.



I retorqued the Lukes Link and greased the front end, but it did not appear to be loose.



Then I took it out and tried to get it to play Bronco Billy. Unfortunately I coudn't find a whump in the road to cause it to start bucking on me (the only place that it consistantly happens is halfway between here and Fairbanks across a RR track that is skewed slightly to the road). I am going to keep driving it over some bad parts and see if it still does it. The hopping has always started when I'm least expecting it, so I think I have a better chance of getting it to act up when I'm not TRYING to get it to act up



I will keep this posted until I find the cause (or buy the new model). In the meantime I will ask that this thread be put into the regular forum to keep the 911 airwaves cleared.



Thanks again to all, Mike...

 

[emailmike]

Update #2 May 31 2002

... Still working on it...



I've found a a 4 mile stretch of nasty ashalt road south of town and have been able to duplicate the truck's DEATH WOBBLE on a regular basis. I am now convinced that it is not the rear end hopping up and down like I thought, but the front end doing the "wobbling". Amazingly, I don't get a lot of feedback through the steering wheel that would normally lead one to suspect it's the front end. But after reading all the posts about the DEATH WOBBLE and applying what is happening to me, I'm pretty well convinced. The trick to identifying this is being able to concentrate on the problem instead of freaking out when it happens. After a couple of wobble incidents I've pretty much eliminated the rear end cause the rear does not appear "hopping".



I have systematically readjusted the Hellwig rear sway bar links so that one side wasn't preloaded. I then went to the front end and retorqued the Luke's Link to it's tightest setting. Next was checking that the BFG AT's are at 50 psi all around. Little if any change in wobble.



I then changed out the Rancho 9000 hydraulic shocks with Monroe Sensamatic Gas shocks. That helped control the wobbling, but it is not the cause of it nor the cure for it. After 39k miles the Ranchos have a lot of play in the first 1/2 inch of movement. I assume since this is where the shocks work most of their time it's worn the insides there.



I will next take the truck in again and get it aligned. I have noticed that the front end is a little more sloppy (which you normally don't notice over time). I checked the tie rod ends and they are still ok, though I'd like them tighter. The ball joints may be suspect and I'm going to check those with the front end raised and the wheels on the car. I suspect they're going bad since they're "permanently" lubricated with no zirk fittings.



I also plan to bite the bullet and go with the 19. 5" steel wheel option. I can get Goodyear G124 265/70R19. 5's that are the same diameter of my BFG 35x12. 5x16. 5's, but they are 2 inches narrower (10. 3 vs 12. 5). That will eliminate the slight rub I have since new on the inside of the fender wells. This is an expensive option, but I can at least take the tires with me if I buy a new truck and replacement tires are available here in Anchorage. But the tire/wheels are 2 months out (waiting on Rickson to get their wheels in).



One step at a time. I find comfort in knowing that it all worked great when I bought it, and it's only a matter a time and money until I get it back working normally again.

 

[Extreme1]

Thanks for the update.



Go to Dave Fritz's website and get the alignment specs there. That will halp with the wandering you may end up with using stock specs.

 

[Todd T]

not sure who the author of this was but i cut and saved this a while back about the same thing and how to correctly align ou trucks.





here goes. .



In a previous posting written by ???? (don't remember), they were complaining about a shimmy in their Ram 4x4 after striking bumps in the road.

I suggested that the front end alignment has either too little or too much caster, thus causing a caster shimmy. He did not like my response and changed his concern from a "shimmy" to a "bounce" (big difference), and insisted it was the shocks. Maybe it is, I haven't driven it. He also said the alignment "checked out". Here's the problem:

Alignment programs (and service manuals I believe), give a wide acceptable range for front caster on the 4x4 Rams. I believe the range is 2 degrees to 5 degrees (if that's not correct, it's pretty close). The problem occurs when the alignment tech (independent or dealer) tells you that the measurements "checked out fine", just because they were in this broad range of acceptance.

Caster readings that fall on either end of the scale are subject to caster shimmy, even though they are "acceptable". I had to align some 30 trucks and attend a 9 hour "Dodge Ram Chassis Dynamics Diagnostics" training session (fancy name, ehh?), before finding out that 3 degrees to 4 degrees is the optimal caster setting for 4x4 Rams that eliminates caster shimmy.

Below I will post what specifications I set Ram trucks to. First I want to give a little more info on correct Ram alignments so you can see if you had a job well done,

The eccentrics on the lower control arms ARE NOT for individual wheel caster adjustments (even though our alignment machine says they are). The eccentric sleeves in the upper ball joints are for adjusting individual camber and total cross caster (difference in caster between two front wheels). This is why replacement eccentrics are position able in eight different ways.

Once camber and cross caster are attained with the eccentrics, the lower control arm eccentrics are then used to swing the caster readings into specifications. The two eccentrics must be swung in the SAME direction in EQUAL amounts. If they are not, it will create a setback condition (one front wheel further forward than the other).

FYI - Comparing between the two front wheels, caster will cause a pull to the smaller value and camber will cause a pull to the larger value. A truck set up with caster pulling in one direction and camber pulling in the other direction, can lead to a wandering truck; even though it is "in specifications"!!!!!!

If the eccentrics on the lower control arms of your truck are not pointing the same direction, the alignment was done incorrectly and the axle was "twisted" or "forced" into position to attain the acceptable values (seen them from the factory this way, go figure).

A correct alignment will set the truck up with a slight negative cross caster (truck has slight pull to left) to compensate for right hand road crown. Camber will be equal side to side slightly on the negative side. This will help maintain acceptable camber when hauling heavy loads, as the truck tends to lift in the front when towing. Camber will then fall slightly positive when towing.

Just because the alignment shop says "it's in specifications", that does not mean it is set up for proper performance and handling!!!!!!!!!



Specifications (my personal settings for every Ram I align): all specs below are in degrees.



Left Wheel Right Wheel

-------------- ----------------

Caster 3. 2 3. 5

Cross Caster -. 3



Camber -. 10 -. 10

Cross Camber 0. 0



Toe - standard specs, (maybe a little out if you tow a lot, they will pull in as the front end lifts up).



Brent

ASE Certified

Gold Certified Chrysler tech







hope this helps you out

Todd