Severe shake downtrack, cause?
- Thread starter gregsdart
- Start date
-
I had the same issue with a different rims and tires both front and back. Not sure if the shake is there after the 1/2 shift, too focused on the run? I hope the culprit is the driveshaft, the shop should get to it monday or tuesday.
This same issue was there when i shifted at 7200, 600 rpm lower.
I had the same issue with another set of wheels and tires on all four corners. But i appreciate all comments; helps me sort out the possibilities.
dusterbing the peace
FABO pyrite member
Was it right after the shift like it is in your current setup? Would be neat to compare against an old graph to see differences in the anomaly.
Yup. Tire balancer rpm isn't enough to detect this. One tire manufacturer (Mickey Thompson?) had a batch that did exactly as you described.
9secRR
Well-Known Member
yes it was Mickey Thompson that had the problem. We experienced it with the dragster, bad slicks. Got a new pair and problem solved.
Woody500
Well-Known Member
Sounds scary, and another reason no Heims on the street. At least opt for Johnny Joints. They come from offroad & have a lot more Range of Motion. Not sure how they last on the street, but they are heftier, rebuildable, have boots to keep dirt out & zerks to flush dirt/water out.
Steve Strope used them for a Challenger he built a couple years ago. You got a glimpse of the rear suspension in a Hot Rod Mag Strope article, not long before they went to the 'Coffee Table Book' they now publish.
Your problem may either be a Heim that is too small so threads pulled or maybe a softer steel as used in cheaper joints.
Dartswinger70
Well-Known Member
Bad U joint / U joint bolts tight?
Joints seem fine, being checked again though.
Dartswinger70
Well-Known Member
If you can take it to test and tune and put it in neutral when it happens see if it changes with the trans out of it etc. we used to do that just to isolate if it was drivetrain or rolling parts and chassis etc. with the car in neutral it is coasting no power being applied etc. I had a recent experience in my Fox body mustang if I was on the gas I had a driveline shudder at coast it backed off turned out the driveshaft u joint yoke bolts were loose at the rear. I locktite blued them and tightened them down its common on those cars that they need locktite. OP you had also mentioned a "new motor" can you pinpoint he RPM? is it consistent? could i t be the engine? a balance issue? I had a pressure lplate throw a weight once on a 4 speed car actually it was on my Mopar A 833 ,th eshake was very bad but i could get the car to do it in neutral sitting still so that eliminated any rolling or moving chassis parts etc. Just troubleshoot with a process of elimination that will pinpoint it . Its a bit of work but putting the old motor back in may pinpoint to the new motor if that is it. I had pulled my 4 speed a half a dozen times till i figured out it was the pressure plate and even then it was a guess...
Last edited:
Well, looks like I may have found the problem. The driveshaft had a slight bend in it, and needed a fair amount of weight added to balance it out. About 50 grams on one end and 25 on the other, both within 30 degrees of each other. The slight bow in the shaft was on the heavy side, opposite where they had to add weight. They were able to straighten it with a little heat. So,,,,, lets hope this is it .
dusterbing the peace
FABO pyrite member
Glad to hear you found it! Maybe Santa will put a new one under the tree?
furrystump
Well-Known Member
- Joined
- Nov 13, 2004
- Messages
- 2,611
- Reaction score
- 2,343
I got 7 lbs out by going from a mild steel shaft to aluminum, both from PST out of FL. Very happy with both.
Vibration not felt anymore, but there is still some harmonics showing up in the acceleration graph from about 6800 to 7200, so keeping an eye on everything. I found a good tight tailshaft bushing, and the shaft was balanced as i said earlier. So far, happy with the outcome. Car went 8.589, 158 mph at BIR
-
Similar threads
- Locked
