Breaking in new LOW gears

[Hedgehog]

In the Trail report forum one of the drivers installed a new set of low gears in his Transmission . I suggested a break n period and Mr. Bass came back with his break in experience with heat. Since I have a Transmission /Transfer Case ready to install my curiosity created this new thread.

If you have a set of low gears in your Transmission how did you do a proper break in of those gears. I understand running for 15-20 minutes and letting things cool. How many times did you do this? Did you run for a while in 4wd high, then drop it into 4wd low for 15 minutes each? How did you do the break in?

I suppose this would do for my Transmission as well, it had some rusty gears that were swapped out for good used gears.

I imagine this would be true for all gear driven parts like the differentials.

 

[Torxhead]

That's interesting Hedge, but I have never considered it actually. I was able to get a brand new T-18 for my CJ7 and just started driving it. Although an oil change after a short while would be a good idea. When I installed the Transfer Case with the 4 to 1 gears, it was pretty much the same procedure. Everything does seem to work well, so I am o.k. with the way it all works.

 

[mriplaybass]

Hedge, my mistake in the Trail Report section. I was thinking differentials. Like Torx said, transmissions and transfer cases are pretty much build and run, though I always change the oil after a few hundred miles.
Differentials are built tight, as in pinion pre-load, carrier pre-load, and R&P back lash. All these things have to be broken in until they settle where they are happy, (assuming correct assembly ). Once there, things run considerable cooler.
Transmissions and transfer cases, though there are shims in various places, are not subject to pre-load. Instead, the shaft or gears in question are set up with clearances, and shaft end play. My understanding of this is that once set, things pretty much stay the same inside, unlike differentials which once broken in, the pre-loads will be looser, the back lash will increase, etc. So, you would not have the kind of heat in a Transmission or Transfer Case as you would in a differential.
Make sense? This is just how I see things working.

 

[Hedgehog]

One thing I never understood is that there is no drain in our differentials. So draining or changing fluids require a replacement gasket along with all the scraping and cleaning and hope the new gasket seals properly. I almost drilled and tapped for a plug he last time I had my axle out.

Mr. Bass - Not entirely true. The T-18 didn't have much in the way of preload, that is true. Although not as tight or nearly as critical the Dana 20 Transfer Case does have some preload shimming in both out put shafts. But you are right they are both built to run right out of the box. I wasn't so very sure about after market gears. The over all quality seems good, but what do I really know about gear quality.

 

[gert]

This is something I havent ever given thought to

 

[JR74CJ5]

when I swapped in my New SM420 and newly rebuilt Dana 20 , I just drove it - never thought of breaking them in at all either...

Everything also seems to be running good.

I should probably change the fluids by now though (couple rubicon trips later... )

 

[Lumpy Grits]

Put a couple thousand on the gears and then do a drain. Don't be surprised with this first drain at the metalic content as they are new syncros and such.
LG

 

[Hedgehog]

But But I already put a thousand on it ..... Ohhh you are talking about miles not dollars. The thing is still sitting in the garage lookin' pretty.

 

[Lumpy Grits]

But But I already put a thousand on it ..... Ohhh you are talking about miles not dollars. The thing is still sitting in the garage lookin' pretty.

So...Doez that mean you won't need to change the oil then?
LG

 

[Hedgehog]

Not yet anyways. .... so many projects, such little energy....

 

[Lumpy Grits]

Not yet anyways. .... so many projects, such little energy....

Know that, oh-so well.
LG

 

[Hedgehog]

Lets see, my guitar project is darned near finished. The x-wife is in her new house so my project list for her is close to being done and the weather is far better. This weekend WILL see some movement on jeep projects.