Author Topic: 80 mph vibration.... puzzling (Read 4572 times)

Robb_Scottsdale · « **on:** August 13, 2003 - 11:16:06 AM »

Maybe someone can offer suggestions here...

70' challenger with 383 and 727

right at 80mph the car starts vibrating. Significantly, but not violently. You can hear the car humm, feel it in the seat, and the rearview Mirror goes wacky.

It is much more pronounced if I dont have my foot on the accelerator. When it starts doing it, If I let off the gas and coast, the vibration becomes most noticeable and is there until the car gets down to 77mph or so....

Giving it gas / accelerating seems to tame the vibration in half. But the vibration is still there. Untill I come down to 77mph

The vibration is worst when the car is coasting.

Last night I put on a different set of rims and tires and took it out on the highway. The vibration was still there at 80mph but not as pronounced as with the other tires.
Ride quality was different all around though with the different tires. 70/14"s

Otherwise the car rides and drives fine, steering is straight, and no other issues at other speeds.

Whatya spose it is

heminut · « **Reply #1 on:** August 13, 2003 - 12:37:42 PM »

Rob, have you checked your U-joints?

Robb_Scottsdale · « **Reply #2 on:** August 13, 2003 - 12:53:22 PM »

Nope, not yet.... seems reasonable

I was going to replace the rear one when I throw my new pumpkin in.... Ill do both U joints though.

theres been no bad clunks or squeaky-squeaky noises that I have heard with other bad U joints in previous projects.... so hadnt thouhgt of it.

oldvamoparfan · « **Reply #3 on:** August 20, 2003 - 10:17:58 PM »

If U-joints are ok, then check for any play at rear trans bushing/yoke area. Another common cause of drive line vibration is it could have a small dent in the drive shaft itself. Any dent at all will really mess it up. Also, most shafts have a small balance weight on them somewhere. Check to see if you have a weld spot somewhere that a weight may have come off. Since you are changing the hogs head, that could fix it, because play in the pinion bearing could also cause vibration.

Robb_Scottsdale · « **Reply #4 on:** August 21, 2003 - 01:04:42 PM »

I havent actually done any work yet, but I did get the rear off the ground to investigate a little.

There appears to be some play in the rear U-joint. Not much, but I can feel a little slop with my finger tip on one of the Ujoint arms to cup arear when I rotate the tire "forward to reverse to forward to reverse" (independent of the gearing itself slack itself)

Driveshaft looked good, no dents and the weld-on weight was there, but Im probably going to take it in to a Driveline shop anyway while the rear gears is apart, just so I can eliminate the variable for the future.

Ill update with results this weekend probably, thanks guys !!!!

lemonboy69 · « **Reply #5 on:** August 21, 2003 - 01:39:17 PM »

Have the shop check the straightness and trueness of your driveshaft...

LB

Robb_Scottsdale · « **Reply #6 on:** August 22, 2003 - 02:23:44 PM »

Quote from: lemonboy69 on August 21, 2003 - 01:39:17 PM

Have the shop check the straightness and trueness of your driveshaft...

LB

Quote

Driveshaft looked good, no dents and the weld-on weight was there, but Im probably going to take it in to a Driveline shop anyway while the rear gears is apart, just so I can eliminate the variable for the future.
Robb

that was the point in taking it to the shop actually, but even still......

I really dont think its the driveshaft itself. We didnt get any vibrations at all from Seattle to PHX (1300 miles ?) and that was ~80mph the whole way. Nothing has happened to the car since then either.

UPDATE---------------------------

Turns out I had 3.23 gears in there originally, peg-leg of course.

Replaced the both Ujoints, and had the driveshaft dynamically balanced. You can see where the old weights were removed and where they welded on some pieces of flat washer. 1 inch to the left of where the old weights were located.

Waiting on a new yoke to get here (7290, 29 spline), wont be until end of next week though.

Axles came out real easy with minimal brake disassembly, hopefully Ill remember how to do it by then.

73cuda383 · « **Reply #7 on:** October 21, 2003 - 01:01:45 PM »

I have the same problem with 80 mph vibration. Its great to have this checklist info

I will reply when I figure out what my problem is.

cuda · « **Reply #8 on:** October 31, 2003 - 08:10:58 PM »

I also had some vibration at 80 mph, but it went away at 130

73cuda383 · « **Reply #9 on:** November 03, 2003 - 08:58:15 AM »

I'm to scared to reach that speed right now in fear something may explode

Robb_Scottsdale · « **Reply #10 on:** November 20, 2003 - 10:28:56 AM »

New Ujoints, Driveshaft rebalanced, new pumkin too...

$:-\$

My 80mph vibration is still there too.... but not as much, but still when not on the pedal, if I have the pedal down I dont get the shuddering.

Oh well, Something will break eventually I guess. Till then it keeps me speed honest and ticket free. haha

Chryco Psycho · « **Reply #11 on:** November 20, 2003 - 12:54:42 PM »

probably tires

Robb_Scottsdale · « **Reply #12 on:** November 20, 2003 - 06:20:57 PM »

I thought that too, hoping that maybe the balance was off I put on the other set of 4 rims and tires one night and went for a cruise, and while the vibration wasnt as pronounced, was still significantly there. I probably have compound issues, that would be my luck.

Was re-reading this post and saw mention of the trans driveshaft bushing possibly having play/slop. Seemed OK last time I was under it but will re-check that too.

always something......

74CUDA360 · « **Reply #13 on:** December 04, 2003 - 09:39:48 PM »

Vibrations always a pain,start from the top,is the steering box tight? If not adjust it,Are the tires balanced corrrectly,are they worn and the belts are gone bad, atire shop can diagnois this. Ball joints bad ? Jack car and use a crow bar to check. While car is jacked check tie rod ends,should be no play. Take drive shaft to a shop,have it balanced and u joints replaced,check wheel bearings with car jacked ,should be no play.Yes even worn or loose shocks can cause a vibration. Motor mounts,tight,loose ,worn?Sometimes you can isolate a vibration,steering wheel= front end. Seat vibration= rear end. Grab the shifter if major vibration=drive train.Not an exact science,been through it,can drive you crazy. Good luck.

Robb_Scottsdale · « **Reply #14 on:** March 09, 2004 - 11:02:50 AM »

VIBRATION PROBLEM SOLVED.

The Idler arm was broken at the Steering linkage. Specifically, the shaft of the idler arm that goes down into the center link and you put the castle nut and cotter pin on to.

It allowed the linkage assembly to move freely up and down about an Inch, but not left and right. Never felt it in the steering wheel, but it made the whole friggin car shake if I wasnt accelerating and I was doing over 70mph.

Mystery solved.

Author Topic: 80 mph vibration.... puzzling (Read 4572 times)

Robb_Scottsdale

80 mph vibration.... puzzling

heminut

Re:80 mph vibration.... puzzling

Robb_Scottsdale

Re:80 mph vibration.... puzzling

oldvamoparfan

Re:80 mph vibration.... puzzling

Robb_Scottsdale

Re:80 mph vibration.... puzzling

lemonboy69

Re:80 mph vibration.... puzzling

Robb_Scottsdale

Re:80 mph vibration.... puzzling

73cuda383

Re:80 mph vibration.... puzzling

cuda

Re:80 mph vibration.... puzzling

73cuda383

Re:80 mph vibration.... puzzling

Robb_Scottsdale

Re:80 mph vibration.... puzzling

Chryco Psycho

Re:80 mph vibration.... puzzling

Robb_Scottsdale

Re:80 mph vibration.... puzzling

74CUDA360

Re:80 mph vibration.... puzzling

Robb_Scottsdale

Re:80 mph vibration.... puzzling