T-case leaking

[Carl McFly]

HUGE thanks to John and Kurt for all the time and help yesterday with my slip-yoke-ectomy (planned work) and fabrication-and-welding of sections of my frame (NOT planned!)

Have a minor problem today, t-case is spewing tranny fluid. Seems to be coming from the top part of the t-case, I didn't have a flashlight when I was under there but that's what it looked like. A quick Google search and I found this excerpt from Tom Woods SYE instructions.... "Next you will remove the speedometer housing. First, mark the orientation, then remove the speedometer drive gear."..... "Reinstall the speedometer gear assembly. Make sure it is aligned as it came out."

Didn't see that yesterday!

Anyone have any experience with this, and can you tell me why the alignment is crucial? The speedo works so it's not like it's just shoved in there. The service manual doesn't have any warnings or gotcha's when it talks about removal

thanks!

[johnsxj]

Come to think of it, I don't think we finished tightening down the drive gear retainer!!!!!!!!!
I had it tightened enough to hold it in place so we could check that the speedo worked, but never crawled back under there to finish snugging it down

As far as alignment goes.... The hole in the speed sensor that the driven gear goes into is off center to allow for different tooth count drive gears to be installed. It's possible to have the sensor and gear in but not making contact with the output shaft which would cause the sensor not to read anything.

[Kurt]

The way the speedometer sensor is made the shaft the speedometer gear spins on is not in the center of the sensor assembly.
It's actually offset from the center of the unit.
Here's why.... (as best I can explain)
The sensor can accomodate various diameter speedo gears (the plastic gear sticking out of the sensor assembly)
The larger the speedo gear the more teeth is has which alters it's "gear ratio" causing it to spin slower.
One may need to use a larger or smaller speedo gear when the re-gear their axle, change tire diameters, etc.
This is necessary to correct the reading on your speedometer.
For instance if you kept the same diameter tires and went from 3.07 axle ratio to 4.56's your engine (and tcase) rotational speeds would be ~50 higher in order for you to do a given over the ground speed.
Since your engine and tcase are spinning faster your un-corrected speed will read ~50% higher than your actual speed.
Changing the diamter of the gear on the speedo sensor will correct the speedometer reading back to normal.
So... when putting a different diameter speedo gear in requires the sensor to be closer or farther from the tcase shaft in order for the plastic speedo sensor gear to correctly mesh with the rotating tcase shaft.
Here is where the offset speedometer shaft come into play. As you turn the speedo sensor in it's mounting hole in the tcase the plastic gear on the speedo either gets closer or farther from the rotating tcase shaft.
Setting the speedo sensor to the correct rotation allows the speedos plastic gear to correctly mesh with the tcase shaft.

The speedo gear setting would have nothing to do with the minor leak.
The directions on TW's site did warn to not over fill otherwise you may have leaks.
The directions did say to fill it so it's 1/4" below the fill opening, not up to it.
You may want to check your tcase vent hose connection. May have pulled off yesterday.
Also it's possible the vent hole is cracked, pinched, clogged which would cause a leak.

John - I did see the bolt for the retainer tightened, at least mostly

[johnsxj]

Yeah, but I don't think it was all the way snug.

[Carl McFly]

tx guys! And Kurt, that makes sense. Thanks for that explanation

I'll crawl under there with a flashlight and take a better look. And when it came time to add tranny fluid I used the fill-it-til-it-pours-out method

[nostaw]

There is an o-ring on the speed sensor... If the retainer didn't seat it right then you may get leakage, though I don't know how much. It is easy to pull out the sensor to replace the o-ring if it is damaged.

JW

[Carl McFly]

Tx JW