Driveshaft bolts.

[Guest Anonymous]

What type of bolts are everyone running to attach the driveshafts to the differential. Mine came loose yesterday . I am going to lock-tight them, but there must be a better bolt/nut combo. Are grade 8 bolts stronger or weaker then the stock bolts.

[johnc]

Use the stock Nissan nuts and bolts, something from ARP, or go with AN/MS. Its almost impossible to find good Grade 8 nuts and bolts anymore.

[Dan Juday]

The driveline guy I used made the drive shafts for the original Scarabs. He was very adamant about using the right bolts. The bolts should have an unthreaded shank where the part faces mate. He said that most failures happen when the parts slip under heavy torque and shear the bolts. If the bolt is threaded at the mating surfaces the cut thread acts like a score and aids in shearing.

 

I felt this was so important that I made a note in my JTR book: " 5/16x24x1 5/8 cut down to 1 1/8 grade 8. Grade 8 split lock washer and nut. Locktite."

 

Considering that it is impossible to get a torque wrench on these bolts, and very difficult to even get them very tight because of the limited access, I followed his instructions. I can't imagine anyone with more experience with V8Z drive shafts.

[260DET]

If you use Loctite or similar, the stock bolts with stock flanged nuts should be OK without washers. But if you want to go aftermarket, make sure that the plain shank of the bolt is the same diameter as stock and not less.

 

And as DJ said, the plain (unthreaded) shank of the bolt should be long enough so that it goes through both mating holes.

[pparaska]

I had a buddy have a buddy make a driveshaft adapter since I couldn't find a 2.25" pilot flange for the diff. He used a powerglide slip yoke, and a ~0.4" thick steel plate welded to the yoke next to the u-joint. The distance from the flange surface to the u-joint centerline is less that 1.5".

 

What I like about the 2.00" (actually 1.969") pilot R200 flange is that the bolt circle is larger and the bolts are larger than the 2.25" pilot flange. The 2.00" flange has 10mm bolt holes and the 2.25" flange has 8mm bolts.

 

The problem with the yoke that I had made was the guy did it so that the bolts threaded into the driveshaft adapter- not a good thing since bolts in shear should not have the loads transmitted through the threaded portion! I'm currently going to drill out the threads so that the holes are 3/8".

 

I spent $3.80 a piece for NAS1106-13 high strength aircraft shear bolts. These bolts have a 13/16" unthreaded shank and just enough threads for an AN nut and an AN washer when the R200 flange and my adapter are assembled. NAS bolts have a 160000 psi tensile strength and a 95000 psi shear strength - better than Grade 8. They are also less brittle than grade 8 bolts. It seems I remember Carroll Smith saying to NOT use grade 8 bolts in shear, but I'm fuzzy on that - I need to read up on that. The NAS bols are very high quality and close tolerance bolts. They come drilled or undrilled in the shank for a cotter pin when used with a castle nut.

 

I made up some shims to make up the difference between the 10mm hole in the differential pinion flange and the 3/8" bolt shank. (just a strip of shim stock curled around in the hole - works well)

 

It's important to not have slop in these bolted connections. The OE bolts are very good for this reason.

 

Also, when putting the parts together, take up any slop in the bolt holes/bolts by rotating the driveshaft in the direction it sees when accelerating the car forward while holding the diff from turning. While holding the driveshaft against the bolt shank in this fashion with the bolts barely finger tight you take up that slack in the important rotation direction. Now tighten the bolts. If you're not using cotter pins to keep the nuts from backing out, use lock tite.

This same procedure should be followed for the halfshaft bolts.

 

I'm open for other ideas.