dizzle Posted September 14, 2009 Share Posted September 14, 2009 I have a rb25det in my 73' z, and the mckinney mount kit. The mckinney mounts came with the solid poly mounts and were way too stiff. So I decided to swap over to the jag mounts that people use for the 2jz swap. I did some basic measurements before I re-built the X member. And welded in new mounting points. Everything worked great and no problems. Then I swapped over to an R200 and I noticed some rather bad driveline vibration at higher speeds. I searched hybridZ and found that I probably have a pinon angle problem. I pulled the top washers of the mustache bar bushings, found some info that said that should help a little. It did, but it is still not gone. So I started to look at how the engine is sitting in there and I think it is crooked and up too high in the front. I am assuming that this is causing too much angle on the trans output shaft. So I am going to try and lower the front of the motor, but this means I have to modify the engine mounts. So what is the best way to go about this? I am assuming that I have to level the car on stands, and then level the engine? But where do i reference level on the rb? The oilpan? timing cover? the valve covers look croocked all the time I think. Does anyone experience doing this? Quote Link to comment Share on other sites More sharing options...
trwebb26 Posted September 15, 2009 Share Posted September 15, 2009 The key is to make the angle at each of the U-Joints equal. If you have a large angle at the joint from the engine to the driveshaft - and the joint from the driveshaft to the diff is perfectly straight... you will see a rotational acceleration in the output into the diff (the vibration). If the angles are equal and "in plane" - the equal U-joint angles will cancel each other out and you will not have rotational acceleration (vibration). Clear? Quote Link to comment Share on other sites More sharing options...
Careless Posted September 16, 2009 Share Posted September 16, 2009 so what you're saying- if i got this right, trwebb26- is that you want the angles of the driveshaft u-joints to be parallel, so if a line was drawn from the two u-joints pointing in the direction of their angles, they would never cross? moreover, I've read that a 3 degree drive-line angle is the max that should be used and is actually better than a straight drive for two reasons.. 1) impact resistance. the driveshaft will move before the entire rear subframe does if there is a head-on collision, resulting in less overall damage. 2) bearing loading. the driveshaft cocked at a 3 degree angle will force the rotation of the entire bearing so that each ball bearing wears out evenly as it spins at all times, rather than the driveshaft sitting in the dead-middle of the bearing and sometimes free-spinning. Not sure which is true or not, but those were two schools of thought I've been told by various people. Quote Link to comment Share on other sites More sharing options...
240zdan Posted September 16, 2009 Share Posted September 16, 2009 Getting it at 3 degrees is tough since the driveshaft is so short. I guess installing a shortnose diff will help with the situation a bit. Since your vibrations started when you swapped in the r200, I would start by checking the condition of the diff. See if there is any play in the pinion bearing. My current r200 is so worn that it makes my car sound like it has straight cut gears. I get some pretty nasty high speed vibrations and vibrations under acceleration/deceleration. I am certain its incorrect pinion/ring gear mesh and excessive pinion bearing slop (just as bad as a worn u joint) causing these problems. The problem only gets worse as the diff heats up. My driveline angles are parallel but my u joint angle is set at 5 degress. Im hoping with a shortnose and more tinkering with mounts i can get it under 3 degrees. Im almost certain the main problem lies in the condition of the diff. Vibrations from incorrect driveline angles are more of a rumble, I get a fast solid vibration coming directley from the rear end of the car. Quote Link to comment Share on other sites More sharing options...
dizzle Posted September 16, 2009 Author Share Posted September 16, 2009 The vibration i am getting is definately from the rear. But it is at any speed over 50 and is fairly constant weather I am accel/decel or not. It comes on at about 50 (lightly) and is dramatic by 70 (or that is what the speedo says anyway). From what i read it sounded like a pinion angle problem, but this is making me kind of second guess. When the old r180 was in there it made noise, but did not shake the rear of the car like it is now. The rear does feel kind of sloppy when i mash the gas, reminds me of when the front diff mount was shot, But much lighter. i am going to try and lower the mounts first. But if not, should i take that r200 to a shop and get it rebuilt or try another one? I thought these things were indestructible? I have a spare r200 that I got for the input flange and stub axles, maybe i could try that one. But just so I get this straight... You are saying a excess of backlash (which I am assuming is the play from when the input shaft starts to turn, untill the out shafts start to turn right?) Can cause this kind of vibration? The diff makes no groans or whines when driving and the oil was very clean when I drained it. I am familiar with bad diff bearing noise from destroying the old r180. And if not: Do I measure the pinion angle with the driveshaft removed, perpendicular to the tail of the trans, and off of the pinion flange on the diff? Or off of the u joints themselves? This is just starting to make me feel stupid Quote Link to comment Share on other sites More sharing options...
240zdan Posted September 17, 2009 Share Posted September 17, 2009 The backlash in the diff shouldnt be an issue as slack is taken up as the right foot goes down. Would just cause an annoying thud. Could also be the indication of a worn diff. My diff howls, creaks, grinds, whines and makes every worst possible noise imaginable. At low speeds it sounds like a train, at high speeds it sounds like my car has straight cut gears. I have slop in the input flange (where the tailshaft connects to). I am assuming that this is causing misalignment of the pinion with the crown, causing a notchy vibration thats felt throughout the whole rear end of the car. (think bearings that have been preloaded too tight, that notchy gritty feeling). Since my problems occur at any speeds, they are most noticable at higher speeds since I cant really feel much in 1st and 2nd as the revs come up quick (tires let loose). I am not saying this is your problem, but since this started happening when you swapped in the r200, maybe its worth checking out. Check out the driveline angles first, obviously. Maybe the mounting of the r200 screwed them up somehow. You cant really do this by guessing, you need to measure the angles. Google driveline angles and youll find tons of sites explaining how. If you have an iphone you can download a sweet digital angle program for free of itunes, works great and is very accurate. If your angles check out then pull out that diff and replace it with a known good one. Not worth rebuilding IMO, unless its an LSD. Since youre running a rb25, you should really consider putting in an lsd. Since the longnose z31 lsd is impossible to find and very expensive, shortnose is the way to go. I am putting a GTR lsd with 4.11 into mine. Will cost me a few bucks but it is half the car after all. Quote Link to comment Share on other sites More sharing options...
cheftrd Posted September 20, 2009 Share Posted September 20, 2009 I had a Z brought to me for a 26 swap that already had a 200 installed with the AZ billet bar. The pinion angle was about 10 degrees. There are numerous rear covers for the 200 with the studs in different locations. Use the wrong one and you'll get the wrong angle. I use 2-3 degrees for most RB engine swaps. Quote Link to comment Share on other sites More sharing options...
dizzle Posted September 21, 2009 Author Share Posted September 21, 2009 I ground down the mustache bar bushings, to get it to tilt the nose down some more. That helped some, but the vibration is still there. It seems that it am just have a hard time finding a way to meausure the angle accurately. Putting the cr on jack stands is not exactly level:( I will keep trying I guess. If I can't get this thing right soon I may just swap it over to a newer r200 shortnose. The longer driveshaft would be more forgiving right? Ugh...... Quote Link to comment Share on other sites More sharing options...
fast-datsun Posted September 21, 2009 Share Posted September 21, 2009 We offer OEM style rubber if you need. What you have are our STD POLY mounts not the semi solid...Most people love the poly, but we can send you the OEM style if you need... Mack Quote Link to comment Share on other sites More sharing options...
cheftrd Posted September 22, 2009 Share Posted September 22, 2009 The angle the car is sitting at isn't importnat at this point. The angle of the engine needs to be the same as the angle of the differential. Put the angle gauge on the dirve shaft companion flange for the differential Then put it on the front of the crank pulley. These need to be the same or you will always have drivetrain vibration. Quote Link to comment Share on other sites More sharing options...
dizzle Posted September 23, 2009 Author Share Posted September 23, 2009 I will give hell this weekend and let u guys know what happens. Thanks for the help Quote Link to comment Share on other sites More sharing options...
ZT-R Posted March 30, 2011 Share Posted March 30, 2011 dizzle did you get it figured out yet or are you still under the car now? Quote Link to comment Share on other sites More sharing options...
piston Posted April 2, 2011 Share Posted April 2, 2011 I did mine by leveling the chassis as flat as possible to ground. Measure the tail shaft center end from ground to shaft. Then measure the r200 flange the same way from ground to center. Place your magnetic angle finder http://thorvie.com/supplies/Angle_Finder.JPG from auto part store or hardware store on the tail shaft and diff flange and make sure the two have an angle of 90degree...this means they are both parallel to the ground. Example... from ground to center tail shaft I had 12" height.. From ground to diff center flange, I had 9.5" height. with a slight angle going downward from tail shaft to diff center flange because of the height difference(2.5")! I got a cheap 1" pvc pipe from home depot and cut it to drive line length and put it on the ground and raise one end to 2.5" for the height difference of the two measurements. Place the angle finder on center pvc pipe and found my 3 degree. You might wanna go a bit more on your degree since load will change the angle but all my mounts are solid so wasn't an issue for me. Hope this helps out or at least give you an idea. Quote Link to comment Share on other sites More sharing options...
piston Posted April 2, 2011 Share Posted April 2, 2011 By the way, you dont want the tailshaft and diff flange pointing directly at each other as you will have 0 degree and your u-joint wont have the 3degree needed for the ujoint caps to roll around so the needle bearings inside the ujoint can rotate and work properly. Quote Link to comment Share on other sites More sharing options...
ZT-R Posted April 2, 2011 Share Posted April 2, 2011 this is making my head hurt. i am messing with the lasers but thats not working out too well. currently my transmission is sitting at a 86.5 degree and my rear end is sitting at 88.5 but the rear is pointed downward so i need to move them both to 90 i am thinking. Quote Link to comment Share on other sites More sharing options...
dizzle Posted April 4, 2011 Author Share Posted April 4, 2011 here is one of the sites that I used for reference. Right now my car is fairly smooth, I think driving it with the poor drivetrain alignment might have ruined one of u joints. But trust me I feel your pain, I messed with this way too may times... http://www.therangerstation.com/tech_library/pinionangles.htm Quote Link to comment Share on other sites More sharing options...
ZT-R Posted April 5, 2011 Share Posted April 5, 2011 i understand how it works but maybe i will just hit up the gun store and find some gun site lasers. i think they have threads on them i can screw into. really i need to take a break from her.. been working on it everday since nov 19th except for 2 weekends. im just getting to burned out to get anything done, running around in circles... i did order the driveshaft today though. Quote Link to comment Share on other sites More sharing options...
piston Posted April 5, 2011 Share Posted April 5, 2011 Your angles can by as good as it is but if your trans is sitting way up and diff is way low, that will throw the angles off the u-joint. I suck at explaining! Put a pvc pipe(imitating drive line) from tail to diff flange and hold it in place. Put the angle finder on the trans output shaft and measure the angle of the trans, then measure the angle of the pipe. Subtract the two and see what the number you have left over is your degree. Do the same for the diff. 3 degrees is 3 degrees, just make sure when measuring each end and subtract from the drive line angle, you get 3-4 degree left over each end. Hopefully you can raise or lower your diff or trans to correct angle needed. Hope this helps. The laser thing just points at each other and I wouldn't count on it to find correct angles. Quote Link to comment Share on other sites More sharing options...
ZT-R Posted April 5, 2011 Share Posted April 5, 2011 you can also measure the angle of the crankshaft pulley, that should match the diff angle (same tilt, if you measure the trans output its opposite) Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted April 5, 2011 Share Posted April 5, 2011 (edited) By the way, you dont want the tailshaft and diff flange pointing directly at each other as you will have 0 degree and your u-joint wont have the 3degree needed for the ujoint caps to roll around so the needle bearings inside the ujoint can rotate and work properly. When I did mine 2.5 years ago I built the cross member to accept the stock R33 transmission mount as its the same as a lot of other newer Nissan models. My main goal was to get the engine and transmission level with the ground/frame rails and centered in the car for mostly oil reading purposes. I then installed the whole engine/trans into the car with about 2" of height off the center flange of the differential. So its installed so that the output shaft on the trans and the diffy pinion angles are as close to parallel as possible 2" apart. So I ended up with the same u-joint angles on both sides. I knew straight was bad not because of loading but because the U'joint bearings needed to spin to load them evenly without abnormal/excessive wear. So placing the driveshaft at any minor angle would achieve the bearing rotation I needed. I believe and I could be wrong that my 260Z(one that isnt totally dissimilar to a 73 model) stock actually had the stock transmission offset to one side and almost/but not quite level with the pinion angle. Take it for what its worth, but I have no vibration issues at all. Maybe its a case of dumb luck that mine worked out or maybe its because I have a soft transmission mount that doesnt transfer all the vibration into the car IDK? Edited April 5, 2011 by rayaapp2 Quote Link to comment Share on other sites More sharing options...
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