Axel tramp

[Layne3]

Hi there. Having some issues with axel tramp in my a31 cefiro (Same as r32)

Only occurs when I first drop the clutch in first for about half a second then it will light up normally

Also happens if I change gears hard during loss of traction. Ie 1st to second and dump the clutch

Have bc gold suspension and have fitted locking collars (pineapples) however they were no help.

Any ideas what's up?

[GTSBoy]

Poor rear anti-squat geometry.  It's really hard to beat on that era of Nissan IRS.  The next gen cars (R33/S14) were much better.

[Layne3]

My mates with similar setups dont seem to have this problem

[Dose Pipe Sutututu]

change your subframe bushes to solid items, change your diff bushing, get better shocks/springs

[GTSBoy]

Well, after my previous suggestion, the list of things that can cause axle tramp includes,

• Tyre compound,
• Tyre pressure,
• Control arm bush compliance, (specifically worn, damaged, or simply mismatched between upper and lower arms, etc),
• Driveshaft twist,
• Hub spline wear,
• CV joint wear,
• Diff bushes,
• Subframe bushes,
• Damper settings (should have put this one closer to the top, but I don't believe that adjusting dampers to fix axle tramp as the first priority is the way to set a car up - you should set the dampers to control the springs in normal usage, which is cornering),
• And, probably, even anti-roll bar stiffness and/or the bushes in the links on the ARB.

Does that help?

[mr_rbman]

Tyre pressures were my biggest issues (S15)

[Layne3]

Thanks gts boy. Being older the diff is solid mounted to the subframe. I'll check all the other bushes for the suspension.

How do I check for driveshaft twist?

[GTSBoy]

You can't check for twist.  All such shafts twist when loaded.  An example, the tailshaft in a 928 racecar I knew of (actually, it's a torquetube, but that's not a problem) twisted up to 8 full turns on launch!  Short axles like on your car won't twist that much, but they still twist.  The problem with that twist with regard to axle tramp is simply harmonic motion.  You load it up, it twists until it is transmitting the torque to the tyre, then the tyre breaks traction and the shaft rapidly unloads and untwists the shaft which will "untwist" past the neutral point and recoil, oscillating around the neutral point.  This happens in all such shafts, but sometimes it just reaches a condition where it drives the oscillations instead of allowing them to dampen out.  The same is true for all the other causes of axle tramp.  It's something that's moving or soaking up the torque, then releasing it and allowing it to swing back and forth without damping away.

[Layne3]

I took my mechanic for a drive today just to show him whats up. He got out and I dumped it and he said the wheels werent hopping at all. We put it in the air and he wasnt black and white sure but he things it might be my hanger bearing. I'm hoping this is the case. However I've recently installed an rb25 big box and hence had a custom driveshaft made up..