yes, I did a search but the are tons on driveshafts. the last thread I saw evrryone said you should replace the nuts with new one, anyone know the size off hand?
Do the have to be nylocks or can I just use washers and locktite?

 

I believe they are 3/8-24, (3/8 fine thread). Take a bolt with you to the hardware store. If you are going to buy new nuts you may as well replace with the same that came from the factory - Nylock. If you are stuck in the middle of the desert you can make-do with what-ever-works.

 

thanks

 

As stated, nylock 3/8 fine thread. The original nuts+bolts are grade 5, replace with the same. Someone is going to chirp in and say get grade 8. If you use the original grade 5 bolts then put grade 5 nuts on them, simple as that. Something else in the drive line will break before those grade 5 bolts shear.

 

Here are the ones I bought. Found them at Lowes. People in here told me to get Grade 8 so that is what I got and put on. I'm sure they have the same in Grade 5. Honestly though like Bundu said it doesn't matter, and something else will break long before you have a Grade 5/8 issue. And no, don't get the bolts if the old ones are OK.

 

no, he said something else will break before the grade 5 bolts shear. That's a big difference between mixing grade 5 and grade 8 fasteners.

 

I agree...but same goes for a 5/8 combo. If I had 500+ HP I might be concerned. The fact is for slightly stronger nuts to strip out slightly weaker bolts (not just one, but all which would be required) would take forces way beyond what will ever happen.
I would have put the Grade 5 on if that is what people said. I checked around afterward though to make sure it would not be an issue, and confirmed it with a couple experts on the topics. Especially on that part, the force is a rotational and not the bolt being pulled away from the nut. I just think replacing them now would be worthless. I promise you that when my new drive shaft blows to pieces because of grade 5 vs 8 I will publicly say you were correct. I just don't see it happening in this rig. And one again, I'm not disagreeing I'm just saying "no biggie" on this one.

 

It's not stripping in service that is the issue. Nuts are designed to fracture before the threads strip, when used with matching grade bolts.

When using mismatched bolts and nuts the threads can strip on torquing before the nut fractures. They can strip a lot, in which case you notice it and fit a new one (requiring removing the flange and replacing the bolt in the case of grade 8 nuts on output flange bolts). Or they can strip only slightly in which case they enter service in a defective condition and fail somewhere down the road.

 

grade 5 nuts it is then

 

Yup...should be able to get the same ones I got but in 5. Go nuts