1992 Dodge, Cummins power, 5 speed D-250. 140,000 miles. Last summer late, my truck would get a bounce in it, scared me the 1st time. let it all cool off and it would be ok. Next hot day after driving then setting a bit, it would start to bounce again. I changed rear shocks and thought all was ok but the weather cooled also. Today 80 degrees, short ride and the bounce is back. This makes no sense to me but never the less it is happening and severly at times. New rear shocks, checked the drive shaft, rear end, transmission and all looks normal. Tires all seem ok good tread etc. I can leave the house, short ride like getting a hair cut and all will be ok. The truck sitting in the sun a while, return to the house and the bounce will start. I t will make you think the rear end is going to bounce into the ditch. Tire pressure doesn't seem to0 matter as I have went up and down on the pressure, rotated the tires. The bounce seems to come from the right rear of the truck but hard to tell for sure. I have no idea what to try next and don't understand what the temp. has to do with it. It will start the bounce at about 30 MPH and doesn't matter if the clutch is in or out. Any ideas anyone?

 

maybe somethig with your brakes, not too sure but sounds like they might be heating up and just grabbing, just an idea, some wiser people will chime in soon.

 

the only other thing would be to check the wheel barrings.

 

When in doubt, check all of it. Spring shackles, spring mounts, engine and trans mounts. U joints etc. Just spend a Sunday afternoon crawling under the truck with a large pair of Channel Lock (slip joint) pliers and a descent pry bar.

 

I had same prob, a buck will get you five its a caliper. Drive it a bit until it starts bouncing and check the rotors, feel of the rim on each side in the front. Be careful they can get very hot. Some of the trucks used a phenalic piston in the caliper, its a type of plastic. Over time it swell and wont realease all the way.

 

Does it happen at the same place, on the same road? Sorry, had to ask.

 

rotrate the tires front to rear. if the problem moves to front you have a tire problem
Clark

 

Thats one thing i love about this site. One question can recieve a bunch of replies, that come from our on experiances. Its just nice to have several ideas to play with, and most times one will be right.

 

Sure beats the heck out of a shop that charges $60+ an hour for diagnostic time, and they wont find a problem with your vehicle. "It's just old and tired, has 190K on it."

DP

 

Had several pickups that bucked like a bronc in heat,,suddenly and no warning. Acted like the thing grew a square wheel, get back down to slow roll,disappear and only reappeared when too flat of road or hitting a bump to set it off. It was bad enough to jar your teeth out. Oncoming eyeballs got REAL big. Check your ball joints and tie rod ends. Think you have to jack her up to get proper picture for this. Maybe warmer temps expands some part that kicks it off. It doesnt take much and seems to travel where its from.

 

I think you have an emergency brake cable that's seized, holding a rear brake partially applied. You drive several miles, then the drum is hot enough to start changing shape. After cooling off, it's round again.

 

That proved to be my issue with intermittent bounce/wobble. Had a front tire wear stupid and was indeed out of round. Now the rear bounces a little when coming to a stop.

 

when mine gets to the wear bars it will give a very fair imitation of death wobble. every time
Clark

 

I posted this the other day and lost it somehow. My 1992 D 350 Cummins Powered 5 speed gets real bouncy as the weather warms up. A new swing bearing and mid point u-joint, rear shocks and tires rotated. taking a short trip parking then returning the rear of the truck will start bouncing so bad I think that it is going into the ditch. All winter the truck was fine, last summer it started this and I did the above mentioned things and thought it was fixed. As the weather has warmed up here (80's) it has started it again. The tires all look good and this is a part time thing. I don't understand the warm up causing this. Anyone have any ideas??

 

Found it and merged 'em for ya.