Engine/Transmission (1998.5 - 2002) Don't reuse bolts???

[EdK]

Anyone know why Mother MoPar says in the factory manual, "Do not reuse fasteners. " when referring to the bolts attaching the front bearing retainer to the NV4500 transmission? There is a torque value listed, so I doubt they are torque-to-yield fasteners. Maybe sealant in the threads (patch?).



I was going to recoat with Loctite Blue and reuse unless someone knows why I shouldn't.



Ed

 

[Grizzly]

If you inspect them and they look okay, I'd reuse them. What I don't reuse are lock washers.

 

[DCreed]

Heed the warnings, bolts are cheap!

 

[WestTN]

They provided a torque spec' because you will need to install the new bolts.

 

[ToolManTimTaylor]

Because bolts stretch when torqued to a certain spec. Depending on the bolt's composition there can be a level of fatigue when backed out and re applied. Bolts of a certain size have specific specs to maximize their clamping effectivity.

 

[EdK]

In other words...

What I meant by referring to a torque spec is, some bolts are given a torque spec then "give a quarter turn. " These "torque-to-yield" bolts or studs cannot be reused.



The front bearing retainer bolts are not "torque-to-yield. "



Ed

 

[ToolManTimTaylor]

Mother MoPar says "Do not reuse fasteners. " when referring to the bolts attaching the front bearing retainer to the NV4500 transmission? There is a torque value listed, so I doubt they are torque-to-yield fasteners.

Bolts are elastic. When you tighten a bolt to specs, you’re actually stretching the bolt. As you stretch the bolt, it wants to return to its original length. Based on the quality of steel used in the fastener, the diameter of the fastener and how far you stretch it, the load or force applied to whatever it is that you are bolting together, the holding power of that bolt changes.



Every fastener has an elastic limit, commonly referred to as its yield point. Up to this point, if the load on a fastener is released, the fastener will spring back to its original length. When a fastener is stretched into the yield zone, (i. e 50 FtlBs + 1/4 turn) the elasticity is permanently lost, and the fastener will remain elongated and thus weakened when the load is removed.

 

[DCreed]

There is also heat/vibration/centrifugal force/ect. that affect the re-useability of fasteners.

 

[EdK]

Final answer

I had the front seal on order at the dealer and went to pick it up today. I was going to have him get me the bolts, but there were none within 350 miles! The parts guy asked his transmission tech about the bolts and he said they recommend replacing them because the bolts are coated with a sealant, aka "patch. " He suggested to recoat with Loctite "Blue" and don't worry about it! Oo.



Thanks to all who replied.



Ed