dizzle Posted April 2, 2012 Share Posted April 2, 2012 Does anyone with know what the stock driveline angles are in the s30? I have been battling a vibration in my rb swapped s30 for over a year now and have had it! I am 1 more try away from just dropping the car off somewhere. So if someone could measure their stock angles (someone with no vibration hopefully), I have the RT diff mount so I have adjustability. I am getting vibration at 60 mph and above that it is just growling from the rear with this high speed vibration. Please help! Quote Link to comment Share on other sites More sharing options...
yellowoctupus Posted April 2, 2012 Share Posted April 2, 2012 (edited) Stock driveline angles (although intersting to find out) shouldn't be necessary to get your driveline vibe free. The biggest thing that gets overlooked by swappers is getting the input and output angles matched. If you have 3° coming out of the tranny and 1° into the differential, that can give you vibrations. One of the side-effects of a universal joint is that they don't have a consistent input/output speed. (it's actually sinusoidal, ie. 8rpm,8.1rpm, 8.2rpm, 8.1rpm, 8rpm, 8.1rpm etc) The way you get around that is having a universal joint on the other side at the same angle, so they will cancel each other out. I think a general rule of thumb is to keep the angles under 3°. Over 3° will give you fast universal joint wear. Should be a non-issue on a Z, but your Jacked UP PICKUP, well, that's another story. Of course all this is assuming the engine is actually in straight (L-->R). Mine was in cockeyed originally, because I offset the engine to the passenger side by about 3/4", and centered the tailshaft in the tunnel. I ended up having to also offset the transmission, so my L-->R offset was about 1° on the input and output of the DS; the up-->down was about 1.5°. This link has some pretty good info on driveshaft angles as a reference: I also saved a PDF of it and attached it to this post incase the Jeep site ever turns to dust. http://jeep.zerok.ru/index.php?page=86 driveshaftalignment.pdf Edited April 2, 2012 by yellowoctupus Quote Link to comment Share on other sites More sharing options...
dizzle Posted April 2, 2012 Author Share Posted April 2, 2012 Is the diff mounted dead on center or is it set off to one side? And I understand the 3 deg but is that the physcial angle of the engine or is it the operating angle of the joint (i.e. the angle between the 2 sides of the u joint which in this case is the output/input flange of diff or tranny in relation to the driveshaft)? right now I am at 2.5 deg down on the trans and 2.3 deg up on the diff. I am running the STI diff with stock mustache bar (w/ stock bushings) and an RT mount diff mount. I am starting to wonder if the engine is set off to one side or something. Is there a good way to measure this side to side placement? It can be kind of hard to get a good frame of reference on a 30+ yr old car. I would still love to know what the stock angles are if anyone has them Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted April 2, 2012 Administrators Share Posted April 2, 2012 1) The diff is offset laterally. 2) The angles that matter are the U-joint angles. They need to be equal to each other, and minimal. 3) Knowing the stock angles is not going to help you. I've fought this very thing with V8 conversions. An aluminum driveshaft can make a tremendous difference. Quote Link to comment Share on other sites More sharing options...
yellowoctupus Posted April 2, 2012 Share Posted April 2, 2012 (edited) Side to side engine placement doesn't matter much, as long as it's straight and parallel with the differential. All of my setup work was done with the driveshaft removed, so you can put a square on the diff input shaft and a square of some sorts on your trans output shaft and compare them. I had a few pictures in doing mine: DS angles Back when I still had the inline 6 in the car I had a bad vibration from 70-90 (yes, it cleared out over 100.... ) It ended up being I was missing two of the bolts that go from the diff to driveshaft, and the other two were loose. Yikes! Did you have any vibrations whatsoever before you did your swap? Edited April 2, 2012 by yellowoctupus Quote Link to comment Share on other sites More sharing options...
logr Posted April 3, 2012 Share Posted April 3, 2012 I had trouble with my swap too, SR. I tried to keep the angles equal and opposite but in the end I shimmed the diff both ways until it went away. All it took was a 1/4 inch up to eliminate the issue. Ron, do you mean an aluminum driveshaft makes it better or worse? A Z driveshaft is so short the weight difference would be minimal, unlike my SX one. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted April 3, 2012 Administrators Share Posted April 3, 2012 Ron, do you mean an aluminum driveshaft makes it better or worse? A Z driveshaft is so short the weight difference would be minimal, unlike my SX one. Better. Much better. It's not about the weight. Quote Link to comment Share on other sites More sharing options...
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