Ultralite Driveline

[m wirth]

Several weeks ago at an HPDE event at Oregon Raceway Park I had the front cv mounting bolts fail, 4 had backed out and the last 2 sheared allowing the driveline to drop in the front and be cradled by the fore aft center frame. Nothing really happened at that time as I just ceased forward motion, from 85 mph, to parking on the side of the track and waited to be flat towed to the pits. Looked up from the rear of the car and yup driveline down. So get home and the next day pull it apart and find the aforementioned bolt situation and then I looked where the cv joint had been rubbing, first when it had come off and then the tow to the pits, right on top of the fuel lines and electrical cord. It had worn through the casing on the cord exposing a white wire and wore a shiny spot on the fuel line probably .005, which at this point I considered my self very lucky.

When I purchased the car, 5 years and 8,000 miles(1600 track)ago, the builder said he had not put in the driveline loop yet, so I took it apart installed the loop and checked all the bolts, which were witness marked and tight to torque. Well obviously this needs to be done more often, but until the next inspection I have installed new bolts, Loctite and have safety wired all six forward driveline bolts, made a nifty jig, rear flange has grd 8 bolts with nylok nuts, also I installed a cross bolt on the loop to prevent the driveline from dropping and if it does I made guards for the front and rear, next time I have the diff out I will make a single piece guard. From pics I have seen of other Ultralite drive shaft areas none have protection of the lines, I hope this helps our small community.

[WestTexasS2K]

I like to put loctite on those bolt saftey wire is a good idea. Thanks for sharing.

[jlumba81]

Stage 8 might have some hardware that will work for that application Edited June 7, 2015 by jlumba81
added link

[powderbrake]

Thanks for sharing, good ideas.

[JohnK]

Protecting the bits that are within the reach of a flailing driveshaft can't be anything other than a good idea. Safety wire is substantial insurance, at the cost of figuring out how to drill G8 bolts for safety wire.

How much to tighten is always a hassle. If everything is installed according to the Helm's book for the S2000 and it fails, I tend to look for something else causing a failure. I notice there are no plates underneath the heads of the allen screws and the allen screw sizes here went from 6 to 8 mm in 2004. Torquing these was a bear in my car and when I removed them to change diffs, they were all absolutely tight. The single-bolt front mount at the diff shell is known to rock and I decided to re-design this, and have done a page on it. I'm currently pulling all the stuff I've done to my car into an easier to follow form and it includes this page on the diff treatment, so stay tuned.

 

Clearly your car dodged a bullet here. That CV joint isn't a light piece of equipment to be banging about in its tunnel.

Edited June 12, 2015 by JohnK

[jimrankin]

I found that the original loop was too large and would allow the shaft to inpact the tunnel walls and floor, including the fuel and electrical lines. I made a stouter and much less roomie one that I think will keep a failure at either end from doing too much damage.

[JohnK]

Jim,

Looks good and stout, and certainly does a good job of keeping the driveshaft from hitting anything other than the loop. But isn't the problem the fact that the driveshaft is being allowed to move around too much because something that's supposed to keep things in place is failing?

[jimrankin]

Hi John K. The driveshaft isn't moving in any direction other than rotation if everything is working correctly. The minor movement of the motor and the differential in their mounts are easily corrected by the sliding spicer shaft and universals. The problem is that the torque of both acceleration and downshifting are carried through the shaft and after a while these forces can create problems like fatigue and the backing off of fasteners, especially if the original cut and weld was a tiny bit off or out of balance. In an Ultralight it's a pain to remove the seats and console cover to get at the driveline for maintenance so I make sure that whenever I have the area open I check the fasteners and pump new grease through the joints. Other than the horsepower crazed Storker drivers on this forum most of us have fairly low torque motors so things like clutch and differential scatter covers aren't really too important. The driveshaft however can become a very efficient war hammer in a hurry if either end lets go so the slight extra weight of an HD shaft loop is well worth it. Things getting "loose" you can hear and feel but sudden shear of a part is all about the "here and now" with no chance to lift or pull over. That's when a really stout and well proportioned loop will save you and hopefully most of the car from serious damage.