Detailing a ZF and have a few technical questions:
1- Did the factory use any thread locking agent on either the in board or out board portions of the 10mm and 8mm studs for the axle carriers and rear cover respectively?
2- II in the case the factory didn't use a thread locking agent, would it be prudent to do so in reassembly?
3- Is thoroughly cleaning and spraying these threaded studs with a self etching primer not recommended for any reason
4-What are the torque specs. for these fasteners?
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I can't answer whether the factory put thread locker on the studs. However in my experience, there isn't any and gear oil tends to weep thru the studs. Last year I re-sealed (for the second time) my ZF to reduce weeping and leaks. It worked great and now I don't have an actively leaking ZF. I used high-temp thread sealant instead of PTFE paste or tape on the side cover studs. It seems to be working great.
I'm not sure on the self-etching primer.
Torque specs vary with the part. I will look but the manual is available to download if you're a POCA member.
A very knowledgeable transmission technician recommended the use of Loctite 518. What was it that you used?
I used a high temp thread sealant. You can get it at an auto parts store. I haven't ever used Loctite 518 for this application.
Regardless of the Lock-Tite part number, their reps say that Red Lock-tites will need heat (typically, a few seconds from a torch) to loosen. Blue Lock-tites can be disassembled with a good wrench and no heat. And Green Lock-tite (used to fill larger gaps) unfastens even easier than the blue stuff. So if you don't plan on removing something, use Red. If the thing will need to come off now 'n then, use the Blue.
@bosswrench posted:Regardless of the Lock-Tite part number, their reps say that Red Lock-tites will need heat (typically, a few seconds from a torch) to loosen. Blue Lock-tites can be disassembled with a good wrench and no heat. And Green Lock-tite (used to fill larger gaps) unfastens even easier than the blue stuff. So if you don't plan on removing something, use Red. If the thing will need to come off now 'n then, use the Blue.
I'm sure in an aerospace (or racing) application we might consider something like Loctite blue or red. However on a street car that isn't going to be subject to extreme vibration, I'd rather have the threads sealed and rely on the torque setting of the nut/stud assembly.
Hmmm I use blue quite a bit… red only for “killer”-Applications…. In Aviation I never used that stuff..
The studs that go through the ZF rear cover often seem to weep past the gasket face and along the threads and then past the nut . The open nut cannot fully seal it . As long your exposed thread length is compatible, you can cap the stud off with an Chromed acrorn nut and seal the base of the acorn nut with a copper crush washer or aviation gasket . Then the main leak path along the threads is fully encapsulated and sealed .
No more leaks. And the back of the ZF looks really nice !
I have used the acorn nut thing as well as copper washers, and it works fine. I have to admit; I prefer addressing the stud issue at the source with thread sealant.
Wilkinson explained to me that the rear cover on the ZF leaks from about half of the 16 studs. The reason is that half of the studs are very long and extend all the way through to the main case. The spring washer and 8mm nut do not provide a correct seal. He suggested to take the nuts off one at a time (you can actually do several), clean the stud and surrounding area with acetone or brake cleaner, apply a small amount of black silicon, and reassemble and wipe off excess silicone. I have done on three ZF's and the rear cover does not leak. This fix costs nothing if you already have a tube of black silicone.
I have done the same with the rear cover, where the studs aren't removable without separating the transaxle front and rear cases. Many do the acorn nut thing there too. I used a gear lube specific sealant. I think it's the green Permatex stuff that has a funny smell to it, not the regular RTV sealant smell.
