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#1
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Vibration on deceleration
So I've finally got rid of the high speed 130mph full throttle I was getting,but now at that speed when letting of the throttle I'm getting a driveshaft vib that will knock ur loose dentures out it goes away about 110mph.Your thoughts?
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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119 |
#2
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If the driveshaft is a stocker then it’s likely giving you notice that it’s going to rip apart on you.
Is the trans mount new?
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#3
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Possible that the pinion angel is off? What did you do to solve the acceleration vibration?
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62' Lemans, Nostalgia Super Stock, 541 CI, IA2 block, billet 4.5" crank, Ross, Wide port Edelbrocks, Gustram intake, 2 4150 style BLP carbs, 2.10 Turbo 400, 9" w/4:30 gears, 8.76 @153, 3100lbs |
#4
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Have you checked the pinion angle and condition of the U-joints? Might be time for a new aftermarket driveshaft.
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1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule. |
#5
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New 1350 shaft,pinion flange ,th400 output shaft and balanced.Shimmed pinion up 2° very bad vibration that would begin at 110mph,no vibe on let off.Shimmed pinion down 2 no vib up to 135 but bad vibration off throttle.Put it back no shim no vib up to 135 ,bad vibe off throttle .I'm right back where I started trying to solve this issue.Shaft had to be balanced 2x to solve vibe at load up to 135.My output shaft bushing does have up and down movement and gear back lash seems excessive.
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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119 |
#6
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On a side note my shaft is not centered in relation to body tunnel,its off to the right.Is this typical with 2nd gen f bodies ?
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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119 |
#7
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So I watch you big dogs from afar but this question is very interesting to me because I am looking into a new rear to replace my 8.2 10 bolt. I've learned the GM 12 bolt is 1/2 inch off center and the 9" is 15/16 off and an inch or so lower than GM's. I've wondered the potential impacts of these deltas. Obviously there isn't a problem as so many run 9" and I'm not far enough along to ask Quick Performance or others about this. I am curious which rear end you have?
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#8
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I would take the TH400 tail off and get the bushing replaced and retry, there should be no play. I use a pinion angle of 4 degrees down on my Caltrac suspension with split mono leafs and don't have any vibration crossing the line at 134 mph. I doubt the backlash is contributing to the issue. What is your pinion angle?
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1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule. |
#9
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It's a 10 bolt 8.5 no full throttle vibration anywhere in the rpm range ,its just on deceleration from 135 mph( the fastest this car will go)down to about 110mph with just engine braking.When feathering throttling the vibe will come and go at high speed.Ill recheck pinion angle and post results.I have noticed slight gear wind when just cruising at constant speed the noise goes away with adding slight throttle or engine braking.
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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119 |
The Following User Says Thank You to joes455 For This Useful Post: | ||
#10
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Quote:
Eric
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"Everybody has a plan until they get punched in the mouth" noted philosopher Mike Tyson Life begins at the end of your comfort zone. “The mind, once stretched by a new idea, never returns to its original dimensions.” |
#11
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Reading this with interest. My son has a 2000 T/A which had a vibration issue on decel after going to a STRANGE S60, new driveshaft, etc. AFter much work at a local "go-to" shop, symptoms changed but never cured. I was helping to diagnose the existing problem and noticed there was about 1-3/4" clearance on the driveshaft-to-output shaft. This really should be about 5/8" from what I understand. I firmly believe this was the original cause of his vibe during decel, caused by the front of the drivesaft not being constrained correctly when back driven during coast.
Sounds like yours with excessive bushing clearance. My 2cents. George
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"...out to my ol'55, I pulled away slowly, feeling so holy, god knows i was feeling alive"....written by Tom Wait from the Eagles' Live From The Forum |
The Following User Says Thank You to george kujanski For This Useful Post: | ||
#12
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Stupid question: is the pinion nut tight? I had one loosen off on an old truck many years ago, and had similar symptoms. Under acceleration, the pinion is pushed out against the bearings, but under decel, it will fall into the ring gear and all hell breaks loose.
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The Following User Says Thank You to wolf For This Useful Post: | ||
#13
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Yes nut tight and indexed to check movement, pre load 20" lbs.No question is stupid, I've once had it go loose well backoff
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76 T/A 455, cnc chamber E heads,OF hyd roller ,yella terra shaft rockers 11.47 119 |
#14
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Recheck your ring and pinion and clearances.
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#15
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Quote:
GT |
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