Wet torque vs dry torque?

[Yota94]

I was changing the differential fluid in my 2022 4Runner and it got me thinking about wet vs dry torque. The torque spec for the drain bolt is 36 ft-lb and I imagine they install the drain bolt on a new axle assembly dry. When service by the differential, the fluid coats the threads as it drains so I’m actually using a wet torque application when I go to torque the drain bolt down using the same 36 ft-lb spec. Is there a way to convert dry torque to wet torque?

The reason I’m asking is that when I went to remove the drain bolt I accidentally tightened rather than cracking it loose (was using a breaker bar for leverage) and I was concerned that I may have deformed the threads. The drain bolt tightened by maybe 1/16th of a turn, no more than an 1/8th. I felt pretty stupid for doing that on my brand new vehicle so I was trying to rationalize it in my mind when I realized the factory installment of that drain bolt is probably using a dry torque application and when you torque it down after servicing the differential fluid by following Toyotas procedure, you’re using a wet torque application. I was hoping I could rationalize it in my mind as no harm done by concluding that the extra 1/16th to an 1/8th of a turn I accidentally tightened the drain bolt would have applied a less than or equivalent clamping force compared to the clamping force applied when using the same factory torque spec but with a wet torque application.

I know this is silly but these are the things I enjoy thinking about when I’m bored.

 

[MasterSolenoid]

Right or wrong, I always put a small amount of grease on the lug nut (threads) and reduce torque by 10%.

 

[dnewton3]

In high-torque applications that have significant bolt-stretch goals and over-stretch concerns, the topic of wet vs dry is germain to success.

In your application, the drain plug is only holding back gravity acting upon the fluid. The torque value is there just to protect the threads from deformation. While your fears are valid, they are also over-blown in reality. This application is a steel bolt into a steel housing; not a mixed metallurgical application. Fortunately, the margin for error is larger in this type of scenario. Bolt stretch isn't in play here; that's why they use either a crush washer or a washer with a rubber envelope; this takes the place of bolt stretch. What you likely did, if any "damage" occurred at all, is deform that washer past a design intent. Check for leaks. If it's leaking, first replace the washer. Then make another assessment.

 

[MSCH]

Yota94​

on the job you are performing, it isn't going to make a difference.. honestly, you are overthinking it.. you can almost bet anybody in the for hire mechanical world doing the same job doesn't use a torque wrench... not on that sort of thing.

 

[atikovi]

Why are you changing the differential fluid on a 2022?

 

[zfasts03]

What fluid it you run in your 4Runner. I have a `18 4Runner and am thinking about changing mine also.

 

[tnt_motorsports]

I was changing the differential fluid in my 2022 4Runner and it got me thinking about wet vs dry torque. The torque spec for the drain bolt is 36 ft-lb and I imagine they install the drain bolt on a new axle assembly dry. When service by the differential, the fluid coats the threads as it drains so I’m actually using a wet torque application when I go to torque the drain bolt down using the same 36 ft-lb spec. Is there a way to convert dry torque to wet torque?

The reason I’m asking is that when I went to remove the drain bolt I accidentally tightened rather than cracking it loose (was using a breaker bar for leverage) and I was concerned that I may have deformed the threads. The drain bolt tightened by maybe 1/16th of a turn, no more than an 1/8th. I felt pretty stupid for doing that on my brand new vehicle so I was trying to rationalize it in my mind when I realized the factory installment of that drain bolt is probably using a dry torque application and when you torque it down after servicing the differential fluid by following Toyotas procedure, you’re using a wet torque application. I was hoping I could rationalize it in my mind as no harm done by concluding that the extra 1/16th to an 1/8th of a turn I accidentally tightened the drain bolt would have applied a less than or equivalent clamping force compared to the clamping force applied when using the same factory torque spec but with a wet torque application.

I know this is silly but these are the things I enjoy thinking about when I’m bored.

This is a little more complicated than you think. Coefficient of friction plays the biggest part. Each fluid has a different CoF. A rule of thumb would be 30% less torque on a lubricated torque but again that’s not guaranteed

Just my $0.02

 

[dfarr67]

I don't know who was into my 4runner last but I need a bar to get the buggers off- no need for that kind of torque. I do mine a little more than snug if you have the right washers. A little loose a drip of oil- too tight and I don't want to think of the damaged threads.