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| vibration on decel | Login/Join |
DRR Trophy |
I've been chasing a vibration on decel all summer. I've checked everything I could think of and no luck. I changed transmissions over last winter and had a wishbone installed in the car. I can't honestly say that it was there from the 1st hit of the season but definitely most of the season. Ring and pinion gave up with 1 week left in my season, the ring gear bolts actually fell out. I was thinking that was the issue I had been chasing. New center section installed and vibration is still there. It happens right when I let out and only lasts a split second but can be pretty aggressive. I've checked driveshaft/u-joints, 4 link, and I can't find it. Driveshaft pulls out 5/8" from fully pushed in the trans. Any ideas on what could cause this? | ||
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DRR Sportsman |
What's your pinon angle? Joe Without data, you’re just another guy with an opinion. | |||
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| DRR Trophy |
-1.25-1.5* Well, at least that's where I had set it. I did have new 4 link hardware installed when they build the wishbone. I assumed they didn't change anything but never thought to check I guess. I actually may have checked it because I had to re-set the preload but not sure if I checked it or not, but good place to look.This message has been edited. Last edited by: inferno camaro, | |||
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DRR Pro |
Take your shaft to Patterson Driveline & Machine and see what's up. Did you disassemble the u-joints to check them?? "Despite the high cost of living, it remains popular." Dave Cook N375 | |||
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| DRR Pro |
Some good stuff here... https://www.slideserve.com/bina/driveshaft-assemblies I suspect you might have a joint Brinnelling, (slide 37) or have changed the operating angle (slides 16-18) or possible the tube has twisted enough to cause a phase problem. ?? "Despite the high cost of living, it remains popular." Dave Cook N375 | |||
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| DRR Pro |
I have experienced a vibration sorta like you describe 3 times...twice when the crankshaft broke, and once while a rod exited the pan....  "Despite the high cost of living, it remains popular." Dave Cook N375 | |||
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| DRR Trophy |
No I didn't take the joints out to check them. I just remover the driveshaft and looked at them. I have lost a crankshaft before and this feels nothing like that did thankfully  | |||
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| DRR Sportsman |
Had this problem on a dragster, usually don't feel it during acceleration but in the shutdown area it comes really bad. My case i've seen the same cause, wheels out of balance. Front runners were out of balance the first time didn't take much weight to correct, second time i had 1 rear tire that took a bunch of weight to balance, when i installed them I didn't balance at all and they were bead locks so it was a relatively easy test. I figured i'd give not balancing a shot. Well that didn't work. Removed and checked the rears, found one tire way out of balance. De-mounted the tire spun it a quarter turn and re-mounted, all it did was move the location of where the 8 or so ounces needed to be on the wheel. Vibration went away after that balancing. I was pretty concerned with all that weight but things are much smoother now. All of my balancing is done on a bubble balancer, old school version that uses oil as the damper, much better than the el cheapo version from harbor freight, i threw that one away. | |||
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| DRR Trophy |
Hmm, I did put new tires on in June and not sure if it was doing it before that or not honestly. If I don't find anything this winter I'll throw my spares on and try it. I will also check my balance but normally if it's off my car shakes like crazy going down track.
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DRR Pro |
I experienced a similar situation but it was not only on deceleration. Vibration that kept getting worse. I almost dropped out of a race because I thought something was going to break. I decided to put the rear up on stands and run the wheel speed up. The vibration was there. Next I took the wheels off one at the time and tested again. With both wheels off there was no vibration. Root cause was the tires turning on the rims. I run radials without screws. This was an easy test. Probably a little dangerous, but easy and it helped me find the problem quickly. Matt Ward | |||
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| DRR Sportsman |
Usually if things are going well during a run, we are accelerating through critical vibration speeds really quickly when we are under power. If you feel a vibration caused by a tire out of balance during acceleration, it usually comes and goes within a second or less. In the shutdown and the car is decelerating, we can hang out at those critical speeds for longer periods of time. For me it seemed about mid-way through the shutdown, if i had to guess 80 ish mph, racing 1/8 mile at 150 MPH trap speed, LONG shutdown area at this particular track, and coast past 1/4 mile stripe, then ease onto the brakes and I'd get the vibration. My vote is tires out of balance. | |||
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| DRR Trophy |
I really hope that is the issue. A nice easy fix is what I like.
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DRR Sportsman |
Always ran Goodyear. Never a problem. The derision was to run a tire called a high growth D2A compound. At about 102 runs it shook on decel. Come to find out, the sidewalls gave up the ghost. Put on another set no shake till 100 runs. Went to a stiff sidewall i believe 2052. Great tire. Stiff sidewall too. not one problem. | |||
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| DRR Trophy |
Thanks for all the responses, here is to hoping it's a tire issue. | |||
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DRR Sportsman |
Check the bushing in the trans tail shaft. Mark Yeager | |||
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| DRR Trophy |
It's a roller tail shaft, it feels the same as my other trans but I didn't pull the tail and actually look at it. Should I?
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| DRR Sportsman |
I'd check it just in case. I knocked a standard bearing out of mine and it would vibrate. Not sure on rollers. Good Luck! Mark Yeager | |||
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| DRR Trophy |
Thanks for the input, I'll pull the tail just to be sure. Driveshaft is already out checking other things so easy to pop it off. The wishbone has a very slight amount of play in it, chassis guy doesn't think that would do it but redoing it just to be sure.
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| DRR Top Comp |
On my dragster it was the front tires. I wanted new front wheels so I bit the bullet and just replaced them both and the vibration was gone. Clowns to the left of me, Jokers to the right. Here I am....... | |||
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| DRR Trophy |
I put new fronts on this season so yet another place to look. | |||
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