We Did It Again - Z-car 1/4 Mile Drag Time

[jnjdragracing]

Hello ED,

 

I think the big secret is the pitch / angle of the half shaft u-joint angle under a full load.We installed some rubber spacers on top of the rear sruts. We racheted down the rear to duplicate the car under a load to see what angle / pitch the u-joint was in. Under a load you want the u-joint to be straight as possible with no angle. Please email my brother jerry@jnjdragracing.com for more details he is the one responisble for the rear suspension.

 

John.....

 

I myself am having problems with halfshafts on my L6 with tripple webers' date=' any "secrets" you might care you share would be greatly appreciated, I'm a broke college student, but i'd be willing to throw some cash your way for the helpful info. It's got to be cheaper than replacing halfshafts all the time.

-Ed[/quote']

[BRAAP]

First off, congrats on that wickedly fast Z. Your numbers speak of your abilities to get loads of power to the ground and move the vehicle down the strip… What is truly amazing is you are getting the OE rear end and half shafts to handle that much energy! Awesome!!!

I also subscribe to the theory of reducing the U-joint angles in the half shafts to nil for long life U-joints and it has served my V-8 in keeping the U-joints alive and well under some abusive situations. My V-8 car wasn’t able to produce nowhere near as much as energy through the drivetrain as JNJ is getting, but I did abuse the bejeezers out mine. My ¼ mile times were a mere 12.3 @ 113 MPH, 60 foot times were only 2.0 seconds and I did my share of 1st, 2nd, 3rd and 4th gear burn outs for those that didn’t believe the car would do it. 4th gear would leave well over 200 yards of rubber on the ground with the welded R-200 diff and the OE 1978 half shafts.

Any how, my car was set up with auto crossing and street driving in mind, so the car was lowered with the chassis set up a little tighter than your garden variety street car chassis. Then to get my half shafts level, I raised the diff almost 2” in the car. I had to notch the upper body frame rail to clear the top of the dif as it was close the floor in the hatch area. I manufactured an adaptor that bolted to the OE mustache bar and had new holes in this adaptor for the back of the diff to mount to. I also removed the bushings on the top of the mustache bar and placed them on the bottom. This also helped raise the diff. For the front of the diff, I eliminated the cross member that nose of the diff mounts to and attached a piece of channel in the original holes that retained the “over the nose strap” for the diff. I did cut off the ends that retain the front of the control arm pick ups, had to be able to retain the front of the suspension some how right? I then solid mounted the nose of the diff to this channel using aircraft engine case through studs. In removing the OE cross member that mounts the nose of the diff, this also allowed for LOTS more room for the dual exhaust to run so it wouldn’t drag the ground over bumps. Care was taken to keep the diff input flange parallel to the tranny output shaft as well as eliminating as much angularity as possible in the half shaft U-joints. This also helped to reduce, but didn’t eliminate, the common V-8Z driveline vibe issues. My half shaft were original 1978 OE shafts with the original U-joints form 1978 with over 150,000 miles on them BEFORE in installed in my V-87 Z, I then abused them for another 15,000 BRUTAL miles, they were still good as new. No slop, no binding.

 

That is my $.02 on long life half shafts.