Drive line vibration

**Goldcuffs** · 03-07-2009, 03:49 PM

What's up guys. I have a vibration that I believe is in the drive line, specifically the drive shaft or the rear end. I have put a new clutch, flywheel, slave,pilot bearing and new u-joints to correct this problem but it didn't work. I just put on a urethane trans-mount and torque arm mount and that made it way more noticeable. I know the urethane will increase drive line vibrations but this was already a problem before. It's bad enough to almost shake the change out of the ash tray at 75mph. I even tried re-clocking the yolk on the drive shaft. I know it's not wheels and tires because I force balanced them my self. I also seems more noticeable on hard acceleration too. Any ideas?

**Y2KPewterSS** · 03-07-2009, 04:04 PM

Maybe the driveshaft itself needs to be balanced.

**Goldcuffs** · 03-07-2009, 04:21 PM

I've been reading a little on pinion angle. Is that much of a problem with these cars?

**ntimid8r7** · 03-10-2009, 04:02 PM

does it have a whine under load?

**Goldcuffs** · 03-10-2009, 04:41 PM

Not that I can hear. It is very rapid and "short" if that makes sense. I was driving today about 80mph and let off the gas and it was worse on decel. I can shut the engine off while driving and it makes no difference.

**Goldcuffs** · 03-10-2009, 04:44 PM

It also seems to be speed related not RPM. To me that would be from the trans back right?

**mroth2008** · 03-10-2009, 05:41 PM

Check u-joint angles. Is the vibration felt through the shifter?. Engine bushing mounts?. Check pinion bearings if thier wore out, and transmission output shaft support bearing. Most likely an improperly phased driveline, or bent drive shaft.

**camarojunky74** · 03-10-2009, 10:24 PM

does the car have an aftermaket torque arm, and yes measuere your pinion angle car loaded, should be 0 or in the +'s

**ntimid8r7** · 03-11-2009, 03:23 AM

If you had it bad at decel then you need a rebuild of that rear. I went thru the exact same thing to a T with my Blazer. When I popped the cover there were 6 teeth gone from the ring and 3 from the pinion. I used it to pull a trailer for work and really over used it for its purpose and just wore it out. Bangin gears or hard braking can cause it to happen and you will never know it.

**Goldcuffs** · 03-11-2009, 09:15 AM

Originally Posted by camarojunky74

does the car have an aftermaket torque arm, and yes measuere your pinion angle car loaded, should be 0 or in the +'s

Stock torque arm. The trans is 0 and the rear is 0.

**Goldcuffs** · 03-11-2009, 09:16 AM

Originally Posted by ntimid8r7

If you had it bad at decel then you need a rebuild of that rear. I went thru the exact same thing to a T with my Blazer. When I popped the cover there were 6 teeth gone from the ring and 3 from the pinion. I used it to pull a trailer for work and really over used it for its purpose and just wore it out. Bangin gears or hard braking can cause it to happen and you will never know it.

Thanks man, I'll pop the cover and check it out.

**camarojunky74** · 03-12-2009, 08:16 AM

Originally Posted by Goldcuffs

Stock torque arm. The trans is 0 and the rear is 0.

well there is your vibration, they both cant be 0, the trans should be -3 or so and then the rear end could be 0 or +3,

there is your vibration right there. a driveshaft cannot operate at a straight angle it needs an offset. but a adj torque arm, and set it to +3 i bet your problem will go away

**Goldcuffs** · 03-12-2009, 01:03 PM

Originally Posted by camarojunky74

well there is your vibration, they both cant be 0, the trans should be -3 or so and then the rear end could be 0 or +3,

there is your vibration right there. a driveshaft cannot operate at a straight angle it needs an offset. but a adj torque arm, and set it to +3 i bet your problem will go away

Seems like a straight angle would be the least stressful on the u-joints. I read something about trans and rear end angles but I wasn't sure if that would give me a problem at cruise or just under power. What do you mean when you say set it at +3? I want the rear end angled down 3 degrees so under a load it's at 0 right?

**Goldcuffs** · 03-12-2009, 01:04 PM

Originally Posted by ntimid8r7

If you had it bad at decel then you need a rebuild of that rear. I went thru the exact same thing to a T with my Blazer. When I popped the cover there were 6 teeth gone from the ring and 3 from the pinion. I used it to pull a trailer for work and really over used it for its purpose and just wore it out. Bangin gears or hard braking can cause it to happen and you will never know it.

Took off the cover and everything was intact. Re-filled with Mobile 1 75-90.

**ntimid8r** · 03-12-2009, 01:25 PM

Just an outside thought but when you replaced the u-joint did you notice any excessive play on the snap ring side where it mounts to the driveshaft? Sometimes the groove that the snap ring rests in can get widened out or sloppy. So when you're at speed down the highway it creates vibration. If you grab the driveshaft and shake it...there shouldn't be any play in the u-joint area.

**Goldcuffs** · 03-12-2009, 03:12 PM

Originally Posted by ntimid8r

Just an outside thought but when you replaced the u-joint did you notice any excessive play on the snap ring side where it mounts to the driveshaft? Sometimes the groove that the snap ring rests in can get widened out or sloppy. So when you're at speed down the highway it creates vibration. If you grab the driveshaft and shake it...there shouldn't be any play in the u-joint area.

No there was not any play. They pressed in nice and tight and I made sure they moved with out any binding before I reinstalled the shaft.

**camarojunky74** · 03-13-2009, 09:46 AM

Originally Posted by Goldcuffs

Seems like a straight angle would be the least stressful on the u-joints. I read something about trans and rear end angles but I wasn't sure if that would give me a problem at cruise or just under power. What do you mean when you say set it at +3? I want the rear end angled down 3 degrees so under a load it's at 0 right?

yeah your right, im just giving off my own preference, but i just remembered my car is lowered. i think your sharp enough and headed down the right track you will find your problem just keep eliminating stuff

**Goldcuffs** · 03-13-2009, 03:02 PM

Originally Posted by camarojunky74

yeah your right, im just giving off my own preference, but i just remembered my car is lowered. i think your sharp enough and headed down the right track you will find your problem just keep eliminating stuff

Thanks, I'll keep you guy's posted. I think I'm going to go after the drive shaft first.

**Goldcuffs** · 04-12-2009, 09:36 AM

Well, I put 2 new u-joints in (again) and it took care of about 90% of the vibration. The first 2 were from Advance Auto, it was there brute strength line. The second 2 were Precision u-joints from an independent vendor. I don't know if they were ground off center or what, but that was it. I'm still going to get the shaft balanced just to get it out of my mind. Thanks for the input guys.

**thearborbarber** · 04-12-2009, 03:47 PM

From denny's driveshaft's website faq area;

How much driveline angle is right for my application?

Thats a loaded question. The best answer is....the least amount of driveline or u-joint angle is the best amount of angle. Try to achieve the least amount of u-joint angle but don't make it less than 1 degree. A little known fact about u-joints is that they require about 1 degree of operating angle to get the needle bearings rotating. If they do not rotate they will fail. Too much angle will also cause them to fail. The type of rear suspension also plays a big part in setting the angles as well as the engine/transmission angle. Leaf spring cars have a need for more downward pinion angle due to spring wrap-up while coil spring cars control the situation better. Hard acceleration as in the case of a drag race car requires a different setting than a street driven car. Traction bars, ladder bars, 4 links, independent rears all have special needs and requirements.