MikeStang 247 Report post Posted January 13, 2015 Alright gents. I have a pretty good vibration when I put my foot in this beast so I decided to check my pinion angle and here is what I found. With the car on stands and level the drive shafts carried a bit from a .02 degrees to 0 so safe to say it's flat lol...pulled the shafts loose and checked the yolk and it was showing 3.2 degrees Positive. So there's no telling how far it's going out of whack when I foot it hard, maybe this is causing some of my spinning issues also? Anyhow I have 4 wedges each are 2 degree wedges. I don't think there is any way to lower the transmission mounts down so should I just add wedges under the rear or what? I'm running reverse eye springs Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted January 13, 2015 . what a coincidence, i just finished writing this around 1 hour ago for some other people. we need the following: trans angle pinion angle shaft angle up or down from trans shaft angle up or down from pinion did it just start? if so what did you change? your shaft or pinion yoke might be bent or the shaft is out of balance. The optimal angle for any driveshaft to run at is 1/2 degree in opposing directions from the trans and pinion . . this is where many vibrational and frictional problems are non-existent. In order to minimize power loss and vibration in an offset configuration [trans and pinion not in direct line], the pinion centerline and the transmission centerline need to be as parallel as possible under steady throttle/cruise condition. In general, for most typical street applications, the pinion angle should be around 2 degrees lower [nose down] than the trans with the car in a static position and full tank of gas . . under steady throttle/cruise, the pinion nose will rise slightly and continue to stay this slightly elevated position [hopefully becoming close to parallel with the trans angle] until the car decelerates at which point the load will be removed from the suspension.th The angle of the driveshaft should be around 4 degrees down from the trans and up from the pinion. The angle of the driveshaft will decrease as the suspension compresses. At steady throttle, there will be some load/torque on the suspension which will cause the nose of the pinion to rise [the pinion rises less on a 4 link trailing arm suspension than it does on a leaf spring one] . . this will also decrease the angle of the shaft as well as change the centerline angle of the pinion to the trans . . the pinion nose can rise enough to cause the driveshaft to go beyond horizontal to the pinion and trans as seen in the video below of a stock ford lightening truck . . this is not ideal but in a stock, non performance street vehicle it is sometimes accepted as a compromise to keep the suspension/ride “softâ€, and/or reduce production costs. If the centerlines of the trans and pinion are out of parallel, the u-joints travel at uneven operating velocities [cycle from one speed to another every revolution] causing the drive shaft to do the same . . a driveshaft with incorrectly phased yokes will also do the same . . the farther out of parallel the trans and pinion are, the more uneven the shaft and u joints operating velocity will be . . this can be seen in the example videos below . . the faster a vibrating driveshaft turns, the worse the vibration will be. This vibration is hard to distinguish from a bent or unbalanced driveshaft, bent pinion yoke or bad u joints, therefore, if you think you have a driveline vibration, it is best to have theses things checked before making any driveline angle changes. Another problem occurs when a t5 and t5 trans mount will lower the rear of the trans slightly, this combined with lowering the car could cause the driveshaft to run uphill away from the trans . . not great but many do this have some have no problem ir simply don't notice the vibration sand others have big problems with it . . one of the cures for this is to lower the engine but the lowering mounts are hard so they transfer more drivetrain vibration to the body. Ford lightening . . upon acceleration, the driveshaft goes past horizontal which is what you do not want on a high perf car or at high speeds, but at steady throttle the angle is fine. https://www.youtube.com/watch?v=XkkFoThS5Wc Street car at drags . . driveshaft never goes beyond horizontal to the trans. https://www.youtube.com/watch?v=sAfCBwVkyBg drive shaft velocity examples https://www.youtube.com/watch?v=gmV4qwLfOMY this guy is a bit messed up in what he is saying . . what he says does not match the sound of the card he rubs on the gear, but it is still a good example if you only listen to the sound of the card. https://www.youtube.com/watch?v=T4P75ZQvpws . 1 1969_MACH reacted to this Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 13, 2015 Barnett, Thanks for all the info. Here are some details. 1. Yolk is a Brand new Ford Yolk 2. Driveshaft is a shortnend stock unit...there isnt a single weight on it anywhere, nor was there when i got it. 3. Driveshaft angle from the front about 6" from trans output varies from .02 to 0 degrees....usually stays at 0... its kinda tight under the car with the exhaust and stuff so its damn near flat. 4. The Rear pinion angle is +3 yes its pointing up already lol. 5. I didnt pull my shaft to check the trans output angle. 6. I know the engine is right around -3 as I checked that when I put the motor in. I have had this vibration since I put the car together as far as I can remember...... When Im driving around and get the car into OD and the converter locks up its pretty much smooth all the way to 2200 rpm's as I slowly bring the rpms up the vibration slowly increases. Or I can get it to 2200 RPM's slowly then just stomp the hell out of it and its an instant roller coaster lol the wheel starts vibrating, seats vibrate etc... lol When you do the slow roll past 2200 its like the vibration comes in waves much like the sound of the card in the video its like a Hummmm...Hummmm...Hummmm faster you go faster the Hummm. MAybe I just slip a 2 degree shim in under the rear tonight and see what happens. The car is pretty low lol Quote Share this post Link to post Share on other sites
buening 63 Report post Posted January 13, 2015 Typically the tailshafts of the trans point down, so you may have less of a driveline angle issue as you may think. Pull the driveshaft and put the angle gauge across the vertical flat of the tailshaft (near the seal) Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 13, 2015 yeah gonna do that tonight, But isnt the +3 degree angle on the rear diff a problem? plus I didnt have anyone in the driver seat which will likley give it another degree as the suspension loads...So to get into the negatives I will need a 6 degree shim to get me to Negative 3 degrees. I know the trans and rear should be on a parrallel plane in oppisite directions but there is no was to change the transmission angle...at least not without drilling LOL Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted January 13, 2015 yeah gonna do that tonight, But isnt the +3 degree angle on the rear diff a problem? plus I didnt have anyone in the driver seat which will likley give it another degree as the suspension loads...So to get into the negatives I will need a 6 degree shim to get me to Negative 3 degrees. I know the trans and rear should be on a parrallel plane in oppisite directions but there is no was to change the transmission angle...at least not without drilling LOL you did not post enough info to offer a suggestion. the general info you need is in my post. your trans is the same angle as your engine . . your engine is 3 degrees down so your trans is 3 degrees down. your pinion is 3 degrees up so it is the same as the trans which is not the best scenario unless yoir pinion does not rise during cruise mode.. . this info is in my post. Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 13, 2015 Well the only info I didnt give and we dont know is the shaft angle up or down from the trans. 1. Motor is at -3 so trans is at -3 2. Drive shaft measured at trans is at -.02 3. Driveshaft measured at rear end is 0 4. Pinion flange is +3 So what more is there??? Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 13, 2015 Sounds like the opposing angles are right but they should be backwards...WTF ? Just gonna slip in a few shims and try it out...if it gets better problem solved, if not i keep investigating Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted January 13, 2015 ok your shaft is basically in line with the trans. yoiur driveshaft runs down 3 degrees from the trans. the trans and pinion angle and trans are the same angle. this is kinda impossibles. yes i think simply trying shims is the easiest at this point. as i mentioned, the ideal in a static position is pinion angle around 2 degrees lower than the trans so it is as close to the same as possible in cruise mode and the shaft slightly down from the trans and slightly up from the pinion or vise versa on the shaft angle but the same on the pinion, kinda sorta. Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 14, 2015 Well popped in some 2 degree shims...and looked at the Ujoint caps and joint...there is some damage in the way of scuffing on the Ujoint cross posts where the needles ride, along with discoloration, and these are Spicer joints so no cheap junk. Anyhow bolted in the 2 degree shims and there is no car vibration at WOT BUT I am getting some wawa wawa noise not I didn't have lol...so I think I need more down angle but to do so I need longer bolts for my spring pack...also it doesn't unload the tires when it shifts like it was doing. So I need more shims and new Ujoint lol Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted January 14, 2015 so you lowered or raised the pinion? if the joints are discolored they are junk but those will go well beyond 4 degrees of angle before they bind so something is odd. you are probably fixing one angle on the driveline that reduces vibration but making another angle worse whivh makes the vibration worse so you may just be robbing peter to pay paul now but only more testing will tell/ you can also run a constant velocity joint if you want and that will eliminate the vibration if your pinion and trans angle are close. Quote Share this post Link to post Share on other sites
buening 63 Report post Posted January 14, 2015 Sounds like the opposing angles are right but they should be backwards...WTF ? Just gonna slip in a few shims and try it out...if it gets better problem solved, if not i keep investigating No they are not backwards. The trans almost always points down, so in order to get opposing angles the pinion should be either level or slightly pointed up. I typically have a degree or two so to allow for pinion wrap. My trans is 2.5° down and pinion is 0° with no driveline vibrations that I can feel. Keep in mind the angle changes constantly depending on WOT, part throttle, cruise, and deceleration. Pick your poison in which you want the vibration. With leaf springs the pinion angle can change drastically during WOT. I'm surprised you can feel driveline vibrations only at WOT, typically its a complaint during cruise and part throttle when things are less noisy. Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 14, 2015 I understang what yall are saying for sure. Buening I know how your saying they are supposed to be buy why does everyone recomend that the Pinion be pointing down if the transmission is pointing down also when they KNOW this is wrong according to the information provided by the manfacturer. I also have my slapper bars set with about 1/4" of space between them and the spring so it is limiting how far the rear will go. On paper my pinion is now at +1 degree.... I would like to get it to -2 ideally to see what happens lol... car is pretty smooth now with the exception of the thrumming sound and slight vibration, its definatley cyclical so its in a rotating part LOL. The U-Joints were not damaged to the point where I could feel the scarring or snag it with a fingernail but I could see the discoloration and printing on the shaft from the needles, so I know there is an issue, plus the grease was looking burnt and they dont have buy about 4000 miles on them. Where could I get a CV joint driveshaft? Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted January 14, 2015 mike stang . . did you watch all the videos i posted for you? thIs is exactly what you want when you are cruising down the road . . at a stop the pinion nose will be slightly lower because there is no load on it . . this is why you set the pinion slightly down from the trans . .. this is 100% correct and the best case scenario . . this being said, there are occasions where you need to run it just the opposite like buening is which is not ideal and would never ever happen in a drag race car alyhough there are other types of race cars that use his set up. . . Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 14, 2015 Yes I get that but if the transmission is -3 degrees than that means in order for the rear end to be parrallel the rear end needs to be a +3 degrees correct? Which if my rear was at +3 already it should be good to go but it aint LOL. If trans is down rear end should be up if the trans is up rear should be down ? I totally understand the concept and the effect of the rear end rising to 0 plane when force is applied. I need to get my car on a 4 post lift and have a look and see if there is any way to modify the transmission mount if needed. Now I gotta try to find a center pin bolt with a taller head on it to fit through the damn shims and still go into the spring perches deep enough to locate the rear end :P Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted January 14, 2015 . it sounds like you did not watch the driveshaft velocity videos i posted . . these will likely show you exactly what your problem is. i basically posated all the pertinent info there is in the world about driveshat and pinion and trans angles . . i don't know anything new to tell you . . if you can;t do it like the drawing or like buenings set up you will probably always have some vibration unless you install a cv joint on at least one end . . call a driveline place to ask about this. . Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 14, 2015 I watched all the videos, learned a bit also lol. I may end up having to get a driveshaft with a CV on one end to correct the problem. If a single CV will correct problems like this why dont they just put CV's instead of U-Joints? Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted January 14, 2015 I watched all the videos, learned a bit also lol. I may end up having to get a driveshaft with a CV on one end to correct the problem. If a single CV will correct problems like this why dont they just put CV's instead of U-Joints? some cars with conventional drivreshafts do have a type of cv but these are typically on cars or trucks with extreme driviline angles but in general they do not use things that are not necessary . . cv joints are expensive and can't handle as much power as a srd u joint . . the cars do not vibrate from the factory so they do not need cv joints . . changing things from stock like lowering the car or installing 5 speed trannies etc, changes the driviline angles and voids the warranty, lol. of you do not want it to vibrate, you can put it back to stock. Quote Share this post Link to post Share on other sites
buening 63 Report post Posted January 14, 2015 You don't need a CV jointed driveshaft. I've never seen a mustang with those, as they are typically 4x4 oriented. From what you've said your shimmed your pinion so that it is +1° and your trans is -°3, resulting in a driveline angle of 2°. During WOT the pinion will increase to the point where your slapper bars restrict any further wrapping. If the constant vibration is gone then I'd leave your driveline angle alone. Also keep in mind things like driveshaft can be out of balance, axles slightly bent, worn out axle bearings, etc can all contribute to driveline vibrations. There was a thread on the VMF where I was involve (it was a 70 mach) where the guy was having driveline vibrations and I think it ended up being his axles. He went through the entire drivetrain and was testing everything by removing piece by piece and running the car on stands to see if the vibration was still there. Below are two links that you can read through: http://forums.vintage-mustang.com/vintage-mustang-forum/781625-another-pinion-angle-question.html http://forums.vintage-mustang.com/vintage-mustang-forum/773705-pinion-angle-help-70-mach.html Quote Share this post Link to post Share on other sites
buening 63 Report post Posted January 14, 2015 thIs is exactly what you want when you are cruising down the road . . at a stop the pinion nose will be slightly lower because there is no load on it . . this is why you set the pinion slightly down from the trans . .. this is 100% correct and the best case scenario . . this being said, there are occasions where you need to run it just the opposite like buening is which is not ideal and would never ever happen in a drag race car alyhough there are other types of race cars that use his set up. . . Its my experience that all mustangs even from the factory had the transmission pointing down a degree or two, so having the pinion pointing down only further worsens driveline vibrations. I wouldn't say mine is opposite of conventional, more like mine is commonplace among mustangs (again, based on my experience) Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted January 15, 2015 you might also want to sit in the car and rev it to around 2000 rpm for 10 seconds then around 2500 for 10 seconds . . if it vibrates, it is your engine or torque converter etc . . if you have urethane engine mounts, any vibrations will be magnified. you can also put the rear on jack stands and block the wheels then spin it to around 60 mph and see how it vibrates then apply brakes very slowly, then remove the wheels, install all the lug nuts on the brake drums to secure and keep them in balance then do the same thing . . if it vibrates less, it is your wheels. Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted January 15, 2015 Have you ruled out something wrong with the driveshaft itself? Out of balance, yokes not positioned correctly when it was shortened? I haven't seen a balanced driveshaft without any weights on it, but that's just my experience. Quote Share this post Link to post Share on other sites
DocWok 30 Report post Posted January 15, 2015 I had a cyclical vibration once that I was sure was driveline related, in the end it turned out to be the engine cooling fan that was out of balance. Took the fan off and went for a short drive, the car ran smooth as silk. Go figure eh? Quote Share this post Link to post Share on other sites
MikeStang 247 Report post Posted January 15, 2015 Yeah I have seen that happen Doc. Barnett... I have all rubber mounts everywhere.... My engine runs very smooth but I am going to do some testing with the car on stands this weekend, and probably order me a new driveshaft anyhow since this is a Factory unit that was shorten and probably needs to be balanced anyhow. Plus I would like something a bit stronger so I will just upgrade. I Do have a rear wheel seal leaking on the rear end that I need to address, and at that time I may go ahead and upgrade to new aftermarket axles also, which should eliminate the bent axle scenario. Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted January 16, 2015 Was the driveline balance when it was shortened?. I did not add this thumbnail! Why is it here? Its not even one of my pictures. When I try to delete it I get an "Action Failed" error message. Quote Share this post Link to post Share on other sites
