November 15, 2018, 07:04:55 PM

Author Topic: vibration help needed  (Read 1283 times)

Offline arutha

vibration help needed
« on: October 15, 2016, 05:11:33 PM »
Hello,

I am getting a vibration starting around 70 and increasingly gets worse as I go quicker. Really bad around 100-110 so I back off.

Don't think it is wheels/tires.  Had them re-balanced to help rule that out.

FD with ls1/t56
Setup is Samberg cradle, trans mount and diff mount for stock rear.
rear has no play and was fine when it was the rotary. Very slight play at the trans side.  DSS shaft, re-balanced it any way.  Trans bushing, I have lowered and raised the trans and no difference.  Used tremec angle finder and varied between 2.1 and .6 degrees, never a difference.

Looking for ideas.  I track the car, currently at one and did notice that when I raise the trans, under hard braking the trans/engine must be tilting since my shifter started hitting the cut out I made when going to 3Rd.  Should all of that move?  The braces are sturdy and engine/trans bushing are snug.

thanks

Offline Bowtie7

Re: vibration help needed
« Reply #1 on: October 16, 2016, 09:31:40 AM »
Possibility of the shaft that holds 5th and 6th gear being worn out inside trans. You wont be able to go fast enough to really confirm this but try it in 4th gear and see how it feels.
Mazcare build #10 1988 FC LS2 power now with Ronin Exploder diff setup

Offline arutha

Re: vibration help needed
« Reply #2 on: October 16, 2016, 10:29:42 AM »
it does it in 4th gear as well. 

Offline arutha

Re: vibration help needed
« Reply #3 on: October 17, 2016, 06:47:28 PM »
new update, new tires changed nothing.  one strange thing, it does seem to go away when I push the clutch in, so only under load is it happening.  Both acceleration and deceleration.  Hopefully this points to something.

Offline ZDan

Re: vibration help needed
« Reply #4 on: October 18, 2016, 11:06:11 AM »
Might try clocking driveshaft 180 degrees relative to diff input.  I had a similar vibration to what you describe after I had some diff mount work done once and that cured it.  Maybe worth a shot...
'94 RX-7 / 6.8 LS3 / T56 Magnum
0-184.8 in 5280'  :)  (with the old 6.0...)

Offline IMPULSE.ACTIONS

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Re: vibration help needed
« Reply #5 on: October 18, 2016, 12:26:02 PM »
Might try clocking driveshaft 180 degrees relative to diff input.  I had a similar vibration to what you describe after I had some diff mount work done once and that cured it.  Maybe worth a shot...

I just did this exact same thing at the 1/2 mile over the past weekend.  I was getting a bad vibration from about 40-55 and then again around 105-120.  I was going to swap a different driveshaft in but couldn't find a bastard u-joint that would work so when I put the original DS back in I clocked it 180* and it eliminated the problem.

Offline Nfinitecc

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Re: vibration help needed
« Reply #6 on: October 18, 2016, 09:02:06 PM »
I clocked mine and had a good reduction, feels good up to 110, never gone any faster.
« Last Edit: October 18, 2016, 10:19:04 PM by Nfinitecc »

Offline Negrok20r

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Re: vibration help needed
« Reply #7 on: October 18, 2016, 09:54:10 PM »
How do you clock a ds? I took my down couple times and I never knew anything about degree the ds  :confused:
Lucky me never had a problem with it .
dc2 k20 turbo
93 FD under construction
" If you don't have time to do it right, when will you have time to do it over ? "

Offline arutha

Re: vibration help needed
« Reply #8 on: October 19, 2016, 02:47:25 PM »
I did rotate the DS prior to having it balanced again. I will try it again though, anything else to look at?

Offline Donthitme

Re: vibration help needed
« Reply #9 on: October 19, 2016, 03:25:26 PM »

Offline arutha

Re: vibration help needed
« Reply #10 on: October 20, 2016, 08:01:58 AM »
First time seeing that one, thanks for posting it.  Have others had to do that?  Guess I need to get it on a lift and see what's going on, would rather not alter the diff mount if I can help it.

Offline Sketch_hs

Re: vibration help needed
« Reply #11 on: November 02, 2016, 07:07:26 PM »
My car is smooth up to 150mph with the change to the softer bushing, but there is a little movement in the diff vs the samberg poly mount. I had to take it back out and clearance the mount. The samberg setup comes very close to hitting itself and only doesn't because of the poly mount stiffness

After clearance the mount it's really good. I did notice some minor crack looking marks on the bushing. Not sure if it's just lines or actually starting to fatigue, time will tell.

Very happy with this setup now!

Offline arutha

Re: vibration help needed
« Reply #12 on: October 27, 2018, 08:33:14 PM »
FIXED....

So I used plum-bobs and lasers to get a straight line from harmonic balancer through tail of trans all the way back to the diff.   And then the same thing, using the axles, closest I could get to the diff.  Then a protractor, and the intersection point was 6-7 degrees...    I ended up slotting the trans brace and moved the tail of the trans around 1/2 an inch towards the driver side, problem fixed.  Up to around 155 without issue.

If you want to use a CV joint driveshaft to fix it, the joint needs to be at the diff end.

Online Cobranut

Re: vibration help needed
« Reply #13 on: October 27, 2018, 09:51:08 PM »
I wouldn't think one CV and one U-joint on a shaft would ever work well, unless the U-joint was running at 0 degrees, which is not good for the joint itself.
1995 FD, 7.0 Liter stroked LS3, T56, 8.8, Samberg kit.