hey guys new here and need some help before i shoot this car haha. i have a 70 challenger 360 727 auto had recently had a new 8 3/4 third member put in from mancini racing also a new drive shaft from them. over 60 mph the car get a bad vibration almost unbarable to drive and on decelaration i slight grind noise. ive tried almost everything and lost now. i had the tires rebalanced, shimmed the rear end and nothing has helped ive ran the car up to 60 mph on jack stands and see no vibration on the driveshaft but feel it in the rear when i put my had on the axle housing itself ive taken the wheels of and run it up and its still tthere so i think i have solved that its not the tires any help or guide would be appreciated thanks guys james
Welcome to the Mopar bunch.,.Have you checked the axle bearings and universals.Try this, go for a run with your car but make sure you don't use your brakes too much, cuz this heats things up.,.Go home, jack the car up and start feeling for hot spots, not warm, but HOT.When bearings give out they get piping hot.,. put your thumb and index finger on the universals.,. next check rear end housing at backing plates, then pinion on rear end.Bet you find your problem.
When The Flag Drops.,. The Bull ***t Stops.,. P. Engineer, Engine Builder
welcome, 360 and 1970 and challenger is all good. big question- was the rear and driveshaft the only things changed and no vibes before? cuz if so why check the tires ? unless she sat for a while and the tires got flatspotted? checkin for heat is a good idea, but mostly for bad bearings, vibes with a 360 makes me question flywheel/flexplate balance- if you rev it up in neutral does it vibrate?
ok guys sorry had to make a new account since i couldnt log in for some reason with my other one i pulled the drive shaft out sent it to my shop had it rebalanced got it back and there was no vibs at all, on my way to work i got on it at a stop sign ran it the all the gears then all of a sudden it just came back what the hell could cause this?ps this is 360challenger70
if what u say is correct, ask the driveshaft shop if the shaft was way off? did they add weights? I doubt a new shaft from mancini would be almost unbearable to drive? but if she was good after rebalance, "no vibes at all" then u got on it and vibes came back, a guess is it was bolted to the rear on center then after getting on it she moved off center. how can this happen? well the 8.75" rear has a small 7260 u joint and small hold down straps, or a larger 7290 u joint and straps. do u have the small u joints with the larger straps, and the driveshaft slips offcenter?
More a question then statement but it sounds like maybe there could be a problem in the pinion gear. front bearing maybe, somehow got put in place taking drive shaft out and putting it back in and when he got on it, it got back out of line. I had to put this in here because i had a problem relating to this on a 67 Charger and that was my problem, it got bad enough that it snapped the u-bolt, one bolt flush off and had to drill/tap to fix that part of it. Just my pennies worth.
did have the drive shop here take a look at the shaft they told me the rear u-joint was the incorrect one and one of the weights was in the wrong position and the run out was bad kinda pissed at mancini's guy they picked for a drive shaft Marco im sure im using the right u joint retainers it doesnt seem to be moving at all in there, and ron my 8.75 is brand new do we really think it could have gone bad with only 125 miles on it?
Shouldn't, But even new sometimes things happen. New drive shaft also. interesting to us maybe to know what it is, relief to you im sure. I cant believe im the only one who has bought new parts to find they were bad. It sounds like a problem i had so i felt I should mention it. i wish you luck, Im going thru some of these strange happenings here so i do know how frustrating it can be and you with new, thats a tuff one. Ron..
almost anything is possible . disconnect the driveshaft and grab and try and shake the pinion yoke. while u are at it and it is disconnected rotate the shaft 180 degrees for the rebolt up. people have told me this has eliminated vibes for them.
Simple to diagnose an out of balance driveshaft yourself. Get three metal hose clamps large enough to be clamped around the drive shaft. Clamp them all three on with the worm gear in the same spot. Mark the drive shaft with four equidistant marks with a magic marker beginning at the worms. Drive the car. Note any changes in vibration. If it is worse (it very likely will be) come back and loosen the clamps and choose a direction and turn them all to the next mark and retighten them. Drive the car. Keep doing this until the vibration lessens. Then, at that point, mark ANOTHER four marks (use plus signs for these to distinguish from the first set) in equidistants from where the worms are now. Moving in the same direction, loosen the clamps and now move to the next plus mark. Drive the car. See where I'm going here? Once you get it completely vibration free using this method, you can mark where the worms are, take it to the shop and get them to weld an approximate sized weight to the shaft where the worms were located.
____________________I can put a square peg in a round hole. Gimmie that hammer.
Im taking a chance hear but want to ask, Is this the reason for all the new? If it did not do it before and you have original drive shaft, same size/type, try putting it in and see if its as bad or may-be stops, IF this isint the reason for new. you may be able to eliminate the drive shaft theory quicker. just a thought.
I know this is an old post, but I think I know what the problem is and I'll bet it happens more often than you think. I chased the same problem after I had a new driveling built by a very reputable place here in Boise. I had a massive vibration around 2500-3000 rpm on the driveshaft and up. Took it back, they rebalanced it, same issue but a little different. So I swapped the pumpkin for a stocker high ratio rear end I had laying around to see if it was my pinion or something. Putting it together I noticed the issue. I had not seen it on my 3.55 pumpkin as the ujoints sat very snug in the pinion yoke. On this one it was looser and could move it back and forth. The 7260 clips that they used to retain the needle bearing caps in the yoke side are too thin. This allows the u-joint to move about 15 thousandths side to side from center ran the car up (on stands) to the range and if I manually center it (roughly) before tightening the straps down it goes away. If I shift It to one side, it comes back with a vengeance. It makes sense if your driveline moves off center, all that mass moves with it. Crimany, now I need to swap the pumpkin back. Maybe switch to the other type of yoke first, I just never liked the clips anyway. My 71 Challenger 340 is no numbers matching show car anyway, nothings stock. Hope this helps someone.