When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Setup is 94z 4.8/th400/10bolt spohn tunnel tq arm/spohn solid motor mounts/spohn th400/t56 trans mount/ strange built driveshaft and midwest 10" converter.
Before I put the 9" and turbo setup in i wanted to make sure i got rid of the gremlins. In all the fbodies i have owned im stumped w this one. I have the pinion set at -2 in attached pic with two different angle gauges confirming it. Im getting a lot of clunking making me feel like the tq arm is loose somewhere but have not been able to isolate yet. At about 45mph i get a massive car shaking vibration that sounds like the car wants to throw the driveshaft through the floor.
Any thoughts on what else i can check? I have new tires coming in this week sobit i doubt this is tire derived, but i could be wrong.
It needs to be a -2 difference in relation to the angle of the engine/drivetrain. Your angle currently could be completely off right now even though the pinion is sitting at -2 like your gauge shows. If that makes sense.
Ex: If your drivetrain is at 0 your pinion is at -2 then you would be good. -2-0= -2. You need to measure the drivetrain to actually see what your pinion should be set at.
Pinion minus drivetrain angle.
Hopefully my math is correct. Haha
Last edited by Badazz 97 TA; 06-06-2017 at 11:57 PM.
This is correct, the back angle means **** without the front number. Also, I dont care what anyone says, I dont trust the torque arm mount for an accurate measurement. I go straight to the u joint.
You'll want to measure angle a and angle b in this pic.
This is correct, the back angle means **** without the front number. Also, I dont care what anyone says, I dont trust the torque arm mount for an accurate measurement. I go straight to the u joint.
You'll want to measure angle a and angle b in this pic.
I'll have to pull the driveshaft this weekend. Thanks for sharing this picture I saw it in another thread you helped the chevelle guy out, it helped me a lot to have it to think through this. Overall, I know it's not just the back angle. I checked the angle off the harmonic balancer and the vertical side of the torque arm and it is roughly 2 degrees. Even the tremec app says I'm close. What I don't get is the MASSIVE shudder and shake of the entire car at 45-50 mph. I can't drive past that speed without feeling like the car will break in half. It's that bad.
measure the angle of your driveshaft and compare to the rearend. THAT is the most important angle. Looks like your driveshaft is going up and the rear is going down, I bet you have a -10 degree pinion angle
measure the angle of your driveshaft and compare to the rearend. THAT is the most important angle. Looks like your driveshaft is going up and the rear is going down, I bet you have a -10 degree pinion angle
The negative you see on my digital protractor is that measurement (it has that feature that you can press a button and will give you the difference automatically). I put it on the driveshaft first, then on the bottom of the tq arm and adjusted until the offset was -2. then i confirmed it with the harnmonic balance to vertical side of tq arm and then the tremec app. I'll pull the driveshaft this weekend and see what it is on pinion to pinion as recommended above.
I'm going to swap the springs too and put back in my SLP SS springs vs this Eibach lowering springs as well this weekend.
measure the angle of your driveshaft and compare to the rearend. THAT is the most important angle. Looks like your driveshaft is going up and the rear is going down, I bet you have a -10 degree pinion angle
Stop giving advice sir, you dont have the slightest understanding of pinion angles.
I will check this. Is there a measurement anyone knows of how much?
You'll have to check with the rear suspension loaded, but you want to have 3/4" to 1" between the tailshaft housing and the bottom of the pinion yoke for travel over rough bumps.
You'll have to check with the rear suspension loaded, but you want to have 3/4" to 1" between the tailshaft housing and the bottom of the pinion yoke for travel over rough bumps.
Hope that makes sense.
yup crystal clear, will check the slip and if it is excessive. I have my race ramps for all four corners, so I can keep it fully loaded, no issue.
This is correct, the back angle means **** without the front number. Also, I dont care what anyone says, I dont trust the torque arm mount for an accurate measurement. I go straight to the u joint.
You'll want to measure angle a and angle b in this pic.
Everything you need to know is in this post. Rotate DS so the u joints are vertical - the caps on the yoke side are straight down. Use a socket for a spacer to get actruecreasing in your angle gauge.
Make the two angles match. That's the best starting point. Sometimes it makes sense to run a slight negative pinion angle - I run -4 degrees on the trans yoke cap and -3.5 degrees on the rear diff yoke cap for best all around results. This scenario is a "-0.5" pinion angle. YMMV. For heavy track use some guys run -1.5 to -2.
One more thing - if you start with the angles matching, pay attention to when it vibrates. If it vibrates under acceleration, you probably need a more negative pinion angle. If it vibrates more under deceleration in gear, then you probably need your pinion angle less negative or maybe even slightly positive.
I check it at ride height with the weight on the tires. Usually I'll use four tire ramps to set the car on so I can get my fat *** under the car to measure.
I jack the rear up, and slide under the back. It doesn't upset the suspension. You want it loaded, at least the rear. Just remember when you tilt the car it will change the trans angle but that doesn't matter, you are comparing them to each other. If you tilt the car 10 degrees, then the trans will be at 10, and if you match the angle on the rear you are at zero. Both at 10 equals zero pinion angle. It's not about the pitch of the car, it's the comparison of the two angles to each other.
Rotate DS so the u joints are vertical - the caps on the yoke side are straight down. Use a socket for a spacer to get actruecreasing in your angle gauge.
Make the two angles match. That's the best starting point.
good tip so i don't have to remove the driveshaft. however at this point I think i have to. I'm going to remove it though so I can measure the slip as well, I hope my driveshaft is not too short at this point. I measured it exactly how Strange said to measure it. I took the drawing with my measurements in the office (they are close to me) and handed it to the tech when they built this driveshaft. Will have to see how things come together this weekend.
I just went through all of this with a new S60 install. I checked the balancer to get drivetrain angle and compared that to pinion angle to get them to zero out, shook like crazy. I took the driveshaft out and measured the tailshaft angle and it was close to the balancer but I made the adjustment to zero the pinion and tailshaft and it shook like crazy. It's like everything else. In theory and in lab conditions, a pinion angle that zeros out the drivetrain angle is the optimum. It just doesn't always work that way when you leave the lab. My driveshaft is lower at the tranny than it is at the pinion. It runs uphill to the rear of the car. It shouldn't matter in theory, but there is some factor in the mechanics of my car that doesn't jibe with the zero angle theory or the -2 result compared to the drivetrain. In the end, I measured the driveshaft angle and put the pinion at -2.5* compared to the driveshaft and it got a whole lot better. It still isn't where I want it, but it's getting there. I may end up at -4 to the driveshaft. If that's where it wants to be, so be it.
Now, I don't claim to be and expert, and I didn't even stay in a Holiday in Express last night, but I have read everything I could find regarding the theory of setting pinion angle and my engineering background and my experience with theory and practical application made me go with a starting point and method that isn't consistent with theory, but worked in my application.
The bottom line is that you have to do what works - for your setup, no matter how wrong it may be relative to a theoretical ideal. That's why the car manufacturers have mules that they drive in actual road and weather conditions and make adjustments that vary from theoretical absolutes but work in the real world.
a better and more accurate term is phase angle between the front and rear u joints. ideally you want this phase angle to be 0.000° all the time under all operating conditions. the more it deviates from zero = more vibration.
i can somewhat understand on the oem torque arm rubber bushing flexing, and seeing 1/2 to 1° of rotation of the axle under constant heavy load such as w.o.t. down 1/4 mile so then set a phase angle to -1° (axle pointing down) to compensate so there's no vibe at 100mph. What i don't understand is using an aftermarket torque arm with a 3/8" steel mounting plate and poly bushing that doesn't flex then you guys go setting phase angle to -2° or more.... first i don't see the logic expecting a new beefier torque expected to flex that much. and on normal highway driving at constant 70mph takes around 30 hp give or take, point being there's little load on the torque arm, and setting phase angle more than 1° away from zero is bad. never drive your car on the street, only at the track under wide open throttle, but wait then you have to stop so from 100mph on decel you then have a -2° phase angle and wicked vibe. Maybe we should use a torque arm that keeps phase angle at what it was set to with less than 0.5° of change?
and what farmington said is regarding u joint operating angle, the angle between the two pieces the u joint connects (drive shaft and yoke). And it is somewhat important, more so on things like lifted trucks not so much these cars. You also want minimum operating angle but not 0.000° because then the roller bearings in the u joint won't move and lubricate themselves. but the higher the operating angle of the u joints, then the more accurate you need to get phase angle to zero for no vibes. Or higher operating angles are less tolerant of phase angle not being 0.000°.
06-06-2017, 07:50 PM
Pinion angle? Massive vibration 45mph 
