rubbinisracing

I need some advice from the experts.....I'm installing the half shafts to the rear diff. and trailing arms. There are 2 frenck locks on each half shaft flange with a pair of bolts running thru each to attach the flange to the trailing arm. According to the shop manual the bolts are to be torqued to 70-90 ftlbs, when I torgue them in this range it just rips the frenck lock apart. There are no washers underneath the bolts to provide a slip/bearing surface and there is not enough clearance for an SAE flat washer. I think I can keep the lock from tearing apart by lubing the side of the lock where the bolt head bears against it and using less torque on the bolt but I'm not sure this is advisable. The car is a 63 and uses the locks pictured below.



Any suggestions would be appreciated!

Hitch

I've done just as you are planning to, put a little bit of antiseize on the bolt head and it should help. I say help because it will still want to rotate the french lock and destroy it. Dave

67vetteal

Any bolt that requires a Torque to Specification should have the Threads cleaned by Wire Brush or Wheel and then be well Lubricated with an appropriate material. By this I mean sometimes an light Oil, other times a Lubricant Sealer such as Teflon. Other times a grease is a better choice. As to your French Locks, try a drop or two of engine assembly Lubricant. And remember, only one Tab needs to be engaged completely. Al W.

rubbinisracing

Thanks for thr reply Al W. But lubricating the threads before assembly is not proper. Most torque specs are given for "dry" installation, the only time it's acceptable is when the torque spec specifically mentions a specific lubricant and the corresponding torque. Each lubricant reduces friction differently and would change the corresponding spec. For a simple test you can tighten a new nut on a new bolt till failure and record the torque required and then lube another new bolt and nut and try the same. Big difference, as 95% of the torque is used to overcome friction and the remaining 5% is used to preload the fastener.

66since71

If the photo is of the actual locks you are using, the problem may be the locks.

They should be relatively flat to start with, with only a raised boss on the section that spans the two holes. The one in your photo has that section (the one that spans the two holes) turned 90* to the mounting surface, and would account for the tendency to turn as you turn the bolts.

Adding a flat washer, by the way, may limit thread engagement. A risky modification...

Last year I bought some correct locks from Paragon. Try their web site for a photo.

http://www.corvette-paragon.com/cata...4-A77725953DBA

I understand 63-64 was different, but these should work in any case as the GM parts book lists them as fitting 63 to 67.

Scott Marzahl

I suggest only using the Stainless version of these locks or they will definately tear apart at around 60 pounds. I've found that anti sieze does help, but there is a night and day difference when you use the stainless ones from Paragon.

Chuck Gongloff

That's the "correct" lock for mid to late 63's and 64's.

The style you describe is later.....65 and up.

Chuck

66since71

Thanks, that's what I suspected, Chuck. It is interesting though that GM serviced 63's and 64's with the later lock (P&A 30B). Either just out of convenience, or the newer lock actually fixed a problem (like this one?).

Chuck Gongloff

Dunno for sure.

The "late" style was sold as a service replacement for 63 and 64.

BTW, EARLY 63's didn't use the locks at all.

I suppose the change was to prevent "twisting", although I've crunched and twised a few of the later style too.

Chuck

67vetteal

Not to chase our Tails on this but, light oil is most times better than no oil. My reasoning is that Threads do Gaul and this will cause an incorrect Torque result. In this day of "Calibrated" wrenches I'd like to here more on our thoughts. JMHO Al W.

67-427ci

Check out this Bolt Torque Calculator. Select your bolt grade & size, coarse, fine or extra fine thread, click on "calculate" and it gives you the correct torque for dry, plated and lubricated threads. There is quite a difference between dry/clean threads & lubricated threads.
Roy

67vetteal

Interesting Thread! So, I stand corrected as to Dry VS Lubricated. But for all my assemblies I will continue to practice Due Diligence. I still feel more confident in a good tightening with a lubricated thread VS a dry one. Just me. Al W.

geo65

sure wish i would have read this two nights ago..I used the Stainless and they twisted up at the torque limit. Some lubricant under the head may have saved them I believe...

ghostrider20

I agree. Unless the bolts and the holes are new, or in new condition, there is contamination from rust or corrosion. I try and chase all the threads and or use my round wire brush on the drill to clean threads. But they are still not new. I spray WD-40 on the threads or use the silver anti seize. The anti seize is used sparingly, as it seems to stain everything it touches, almost like paint.

Mark

rubbinisracing

Thanks for the advice.....I'm going to lube the washer face of the cap screw with "Tri-flow", in my past experiences with torque/tension relationships this lubricant is the slickest and should ease the friction significantly. I'll then torque the cap screw till the lock starts to twist and quit.

I'll report back in a week with results as I'm waiting on new locks from Paragon as I have already destroyed 2 I previously got from them.