Driveline Vibrations

[overkill91]

Well i got my Cobra back up and running and im having some driveline vibration issues. I adjusted the pinion angle last week and that helped quite a bit but im still having some issues.
Currently the top of the mainfold is at 3* and the pinion angle is ~3* (i will verify these again this weekend) It is still making a vibration though. It does it the worst when i put the car in neutral while going 50+ MPH. You can feel it when its in gear (mostly 4th and 5th) when you are shifting or at a neutral load.
Any ideas where to look?

Some other things i have on the car...
HPM mega bite Jr lower control arms, HPM solid adjustible upper control arms with alum. bushings, TKO tranny. I also have recently had 4.30s, detroit true track and 31 spline axels installed.

 

[overkill91]

ideas anyone?

 

[duane v]

What driveshaft are you running?
What tranny-mount are you using?
Did you use the PHP tranny cross-member kit, or make a spacer?
Which bell-housing are you now using?

DA SNAKE BOY !!!!

 

[Tabres]

Is your driveshaft making contact with the body anywhere?

I would put a bet on your driveshaft being out of balance? Maybe worn out u-joints? I assume the transmission mount was new with the new transmission?

 

[STAMPEDE3]

What driveshaft are you running?
What tranny-mount are you using?
Did you use the PHP tranny cross-member kit, or make a spacer?
Which bell-housing are you now using?

DA SNAKE BOY !!!!

Wondering the same things.

Had same problem before PHP kit.

 

[overkill91]

What driveshaft are you running?
FMS aluminum DS off of my 91. It looks identical to the stock one as far as length etc. goes.


What tranny-mount are you using?
Using a Poly trans. mount and the stock motor mounts.

Did you use the PHP tranny cross-member kit, or make a spacer?
I moved the cross-member back and put some spacers in to move the back of the tranny up. I wasnt a big fan of the PHP cross-member kit. It seemed like it was sagging and twisting the cross member.


Which bell-housing are you now using?
I have a lakewood bel-housing. It was dialed in at the machine shop when i had my engine re-built.

Thanks everyone for the posts!

 

[STAMPEDE3]

Do you have a D/S spacer. The shaft is a little short.

http://www.steeda.com/store/-catalog/driveshaftspacer.htm


This made a big difference on mine. The length of the TKO is a little shorter than the T45. Tremec recommended this to me when I had issues.

 

[duane v]

Do you have a D/S spacer. The shaft is a little short.




This made a big difference on mine. The length of the TKO is a little shorter than the T45. Tremec recommended this to me when I had issues.

yeppers.....the 91 DS is too short...get a FMS aluminum DS for your year car, and dont use the Tremec supplied yoke, it's too short....the yokes on the 96-98 stock and FMS driveshafts are 31 spline, and work perfectly....IMO, DS spacers are not a good thing....DA snake boy!!!!

 

[STAMPEDE3]

yeppers.....the 91 DS is too short...get a FMS aluminum DS for your year car, and dont use the Tremec supplied yoke, it's too short....the yokes on the 96-98 stock and FMS driveshafts are 31 spline, and work perfectly....IMO, DS spacers are not a good thing....DA snake boy!!!!

Now I'm confused Duane.

When I did my 3550 (As you know the TKO is a upgrade version of the 3550 but cases are the same) I order the FMS D/S for my car. It was the same length as the stocker. I had the vibe thing going and was told by Steeda and Tremec themselves that the 3550 was shorter and to use the spacer. It did solve my problems and for what it's worth I had no issues with it.

And I beat the crap out of it. LOL

Would I rather run without it? Yes but it looked to me like there was no way to get around it without having a custom D/S made.

Of couse If I were running the set up you are I would have had a shaft made.

 

[duane v]

Now I'm confused Duane.

When I did my 3550 (As you know the TKO is a upgrade version of the 3550 but cases are the same) I order the FMS D/S for my car. It was the same length as the stocker. I had the vibe thing going and was told by Steeda and Tremec themselves that the 3550 was shorter and to use the spacer. It did solve my problems and for what it's worth I had no issues with it.

And I beat the crap out of it. LOL

Would I rather run without it? Yes but it looked to me like there was no way to get around it without having a custom D/S made.

Of couse If I were running the set up you are I would have had a shaft made.

I run a TKO plus, and it's a 3550 like yours....I use the aluminum FMS DS for a 96-98, and I have no vibration whatsoever....You may have an issue with the block plate, the welded block plate nut nearest the starter needs to be ground down 1/4", or it hits the head, and if that welded block plate nut is hitting the head, the register bore run-out on the BH will be wayyyy out of spec...

Also, I found that the height of the spacer under the tranny mount needs to be 1.125" to get the optimum tranny angle.....DA snake boy!!!

 

[STAMPEDE3]

Gotcha, thanks. :thumbsup: (Although the new owner has it now.)

But in his case, yes the 91 shaft is too short.

 

[overkill91]

Gotcha, thanks. :thumbsup: (Although the new owner has it now.)

But in his case, yes the 91 shaft is too short.

Well i did some more adjusting this weekend and got the pinion angle under control 100%. Still made the same vibrations so i swapped out the alum. DS with the stocker and the vibration is gone now.
As far as the lengths go though, the drive shaft lengths (joint to joint) and the yoke lengths are exactly the same on my stock one and the aluminum one. Is there anything different between the various years of driveshafts besides length? Im assuming that all driveshafts are 0 balanced correct?

I think im going to to talk to a local driveline company and see if they can custom make one for me or re-balance this one.

Chris

 

[STAMPEDE3]

FMS aluminums should be 0 but a lot of people have had issues with them.

Did you try indexing it or indexing now with the stock one?

The local driveline company should be able to balance it or at least check the balance on both of them.

 

[overkill91]

THe driveshaft was fine on my 91 but it only had 3.55s and didnt have the solid upper adjustable control arms like i have on this car. Can you explain what you mean by indexing?

Thanks,

Chris

 

[duane v]

Removing the four 12 mm DS bolts and rotating the DS in 90 degree incriments and re-tighten the DS bolts....hopefully you dont have to go 270 degree's to get rid of the vibration :-D .....DA snake boy!!!!

 

[overkill91]

Removing the four 12 mm DS bolts and rotating the DS in 90 degree incriments and re-tighten the DS bolts....hopefully you dont have to go 270 degree's to get rid of the vibration :-D .....DA snake boy!!!!

I have heard of people doing this but i dont understand what it does? How does this change the balance of the shaft? Just curious...

 

[STAMPEDE3]

It's weird, but think of it this way.
Your pinion gear and DS mounting flange on the rear could be slightly out of balance, If the DS is slightly out of balance also and both of the heavy sides end up in the same place the vibe is bad.'Now rotate the DS until the heavy side is opposite of the pinion heavy side then they will offset one another.

 

[overkill91]

It's weird, but think of it this way.
Your pinion gear and DS mounting flange on the rear could be slightly out of balance, If the DS is slightly out of balance also and both of the heavy sides end up in the same place the vibe is bad.'Now rotate the DS until the heavy side is opposite of the pinion heavy side then they will offset one another.

Yea, that makes sense. I guess i didnt think about the mounting flange and pinion gear possibly being out of wack. Thanks!

 

[97tntcobra]

well over kill91 i just got my car back running and i have the same set up as u, 31 spline axles, true trac, 411 gears, upr upper and lower fully ajustable control arms i have a after market ds dont no what kind though and a lakewood bell housing,tko 600,ram clutches and flywheel and im having vibrations to i had a 3550 so i just used my cross member my tranny mount is the same one off my 3550 same ds just diffrent yoke i tried to set my pinion angle at -3 but it vibrated worse so its at -1 right now,also my new clutches dont ingage until the pedals all the way up, i have a fire wall ajuster.I have taken it all back apart and checked my pressure plate bolts and all was good so if any of u have any ideas on either one. I think i need a ds spacer hopfully that will fix it

 

[97tntcobra]

also i it jumps when its in revs like its missing teeth on the gears but if u rev it up its ok