I have a 1981 Bonnie, a recent problem has shown up suddenly. It seams like after driving for about 10-15+ min each time i stop and then accelerate the rear end tends to jump(or shake) side to side in pullses. Does anyone have any idea what might cause this the rear drums are just fine and the bearings are also fine too. Thanks

It'* possible that one,or both of your rear tires are out of round due to the belt slipping. Another possiblity might be the rear shocks are shot.

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Its not an up and down movement, but a side to side movement that occurs at low speeds. its like the *** end is movin sided to side, this also produses a kind of loud klunk sound when accelerating and dedelerating. can you think of anythign that could cause that?







Thanks ill tell the buddy about your welcome.

Bent rim?

Does this car have posi-traction( a limited slip rear differential)?
If not have you looked to see if everything is tight? Shocks, Springs, Worn Bushings? How many miles on this beast?

Its a 1981 bonnie with a 307 5.0 v-8 its got 138000 on it, rear drum breaks, with limited slip differential. i know for sure its not a bent rim cause this only happens after i have drivin for more than 10-15 min and only at low speeds, nothing is affected after about 30 mph. If you look at if from the out side it almost looks like a bent rim, cause there is a sway side to side in a pattern


Thanks to all for givin your input

My moms old van did the exact same thing.. it was a transmission problem I believe.. :(
the banging/thud sound anyways...

307.. thats crazy thatd theyd switch engines on us. I never figured out if I had a 305 or a 307 but the headers fit OK so....
I'm still a little confused though.
Is there any way to be absolutely sure?

My guess is that there is something funky happening inside that differential. Has anyone checked the oil level in that differential recently. Since it'* limited slip, it needs a special lubricant(I can't remember what it is at this time though) to make it perform properly. I'm guessing something is binding in there causing the wheel hop and/or that side-to-side movement. You might want to get that checked out. Otherwise, I don't have anymore clues for you. Keep us posted on what you find.

That 307 was a good engine from Oldsmobile. The 305(5.0 liter) was built by Chevy.

thanks ill check the diff fluid and the planitary gears also hopfully that is what it is. This is the only real problem i have at the moment and just want to get this fixed. I pick up the car at a great price 100 bucks for the thing the body has never seen an accident and only has a few spots of surface rust, only thing i had to replace so far is the rear break cylinders. So fixin this is would be great thanks for the input. Also the 305 307 i found in the owners manual. the manual says that the 1981 came in a 3.8 liter 231 v-6(buick), 4.3 liter v-8 265 (pontiac), and 5.0 liter 307 v-8 4 barrel carb (oldsmobile), and the 5.7 liter 350 V-8 diesel (oldsmobile). I got the vin codes if needed, if ya need any info from the manual just ask i can hit that up for ya. Thanks agian and ill check out the diff fluid, keep comin with the ideas of the problem if ya think it could be somthing else.

Just a heads up on what has been happening, checked the diff fluid that is all in order and does not seam to be the problem, but as i had the car jacked up i noticed that the left wheel would spin faster and sooner than the right one, so possibly this is the problem. so i am gonna redo the breaks and see if i can get this fixed, only other thing i can think of is that the spider gears are screwed or the pinion is loose causing some wheel play. thanks agian for all your help ill keep ya posted