M923A1 Transfer case rear output shaft seal

[Lee L]

My M923 has been sitting unused for a couple of years. I recently moved it 100 feet or so clean it up and do a little work on it, I guess the rear output shaft seal tore and now it is leaking oil quite badly. Is it feasible to change that seal with the T-case in the truck by dropping the rear drive shaft, removing the brake drum and pulling the flange off the T-case - without having to mess with the shim pack and shaft end play?

The only mention I can find, in the TM, on changing that seal is during a complete teardown and rebuild of the T-case. Anyone ever done it "on the truck"?

 

[Valley Rock]

I see no reason whatsoever to remove a million pound T-case just to change an output seal, just pull that rear dl out and get after it, you'll learn first hand that it's not that difficult .

By the time you get done reading someone else's opinion of how to do it, you could almost be done .

 

[simp5782]

My M923 has been sitting unused for a couple of years. I recently moved it 100 feet or so clean it up and do a little work on it, I guess the rear output shaft seal tore and now it is leaking oil quite badly. Is it feasible to change that seal with the T-case in the truck by dropping the rear drive shaft, removing the brake drum and pulling the flange off the T-case - without having to mess with the shim pack and shaft end play?

The only mention I can find, in the TM, on changing that seal is during a complete teardown and rebuild of the T-case. Anyone ever done it "on the truck"?

You can do it in the truck. Remove the shaft. Yoke nut, yoke, drum will come off. You can access the seal with everything brake attached. Drums can be a pita to get off.

 

[Lee L]

Thanks guys ... guess I better get some parts ordered!

 

[Lee L]

@simp5782 Do you or anyone else have any suggestions on what kind of puller will fit the transfer case brake drum on this thing. You are right, it is stuck TIGHT and none of the pullers I have access to will fit it.

Thanks for any suggestions!

 

[simp5782]

@simp5782 Do you or anyone else have any suggestions on what kind of puller will fit the transfer case brake drum on this thing. You are right, it is stuck TIGHT and none of the pullers I have access to will fit it.

Thanks for any suggestions!

I've had better luck putting the truck in gear with the rear driveshaft removed using a torch while the drum is spinning heating it up while someone smacks it with a hammer on the face

 

[Lee L]

Hmmm .... I'll have to see if I can get my son-in-law to come play "soldier B" and hold the torch. Thank you sir!

 

[Lee L]

Posting this in case it might help someone else: Ordered this from Amazon: https://www.amazon.com/dp/B012P0QV5K?psc=1&ref=ppx_yo2ov_dt_b_product_details It bolted right up to the drum and had it off in about 2 minutes.

 

[Defcon-1]

Posting this in case it might help someone else: Ordered this from Amazon: https://www.amazon.com/dp/B012P0QV5K?psc=1&ref=ppx_yo2ov_dt_b_product_details It bolted right up to the drum and had it off in about 2 minutes.

View attachment 908916

When able can you post more pics of the repair? I would love to see more removal/install pics

 

[Lee L]

I will see about getting some more pictures posted when I get home where the truck is. Am at the ranch in Fredericksburg for the next week or so. After getting the brake drum off I now have to figure out how to get the shield/deflector off to even get to the seal to get it out. I did find the deflector for sale on eBay and ordered a couple since it looks like the old one will probably be bent up getting it out.

taking small steps at a time ... I am old, and getting up and down from under the truck ain’t as easy as it used to be! Besides, everything is heavy as hell and I work by myself.

 

[Valor]

taking small steps at a time ... I am old, and getting up and down from under the truck ain’t as easy as it used to be! Besides, everything is heavy as hell and I work by myself.

Same way here!

 

[Defcon-1]

I will see about getting some more pictures posted when I get home where the truck is. Am at the ranch in Fredericksburg for the next week or so. After getting the brake drum off I now have to figure out how to get the shield/deflector off to even get to the seal to get it out. I did find the deflector for sale on eBay and ordered a couple since it looks like the old one will probably be bent up getting it out.

taking small steps at a time ... I am old, and getting up and down from under the truck ain’t as easy as it used to be! Besides, everything is heavy as hell and I work by myself.

Dang I wish I was closer to you I would 100% give you a hand wrenching on it, that's the best way to learn lol. Good luck Sir

 

[Lee L]

Dang I wish I was closer to you I would 100% give you a hand wrenching on it, that's the best way to learn lol. Good luck Sir

That would be great! My main problem is I only have a few days here and there to work on the truck ... running back and forth between three ranches spread across half the state of Texas, fixing things that are broke, leaves little time in any one place. Retirement was supposed to be relaxing! Ha!

 

[Lee L]

Managed to get back to the truck this afternoon, and it all went pretty smoothly! Here are pictures of all the steps ... remember, this is after the parking brake drum is off:

The deflector is the first thing that comes off, came off much easier than I thought it would, bent it up a little so it will be replaced with a NOS part:


Now the seal is reachable and I managed to get the puller on it, had to do a little grinding on the puller arms to get everything in place. Took a LOT of force to get the seal out (you can see it was way past time to change this seal):


Old seal out:


Pre-lubing the new seal and deflector:


New seal in place, again, it took a LOT of force to get it in place:


New deflector in place:


This seal does NOT seal on the shaft, it seals against this boss on the brake drum, it gets pre-lubed too:


The brake drum goes back on and the splines get sealed with high temp RTV under the thick washer and a new locknut:


My biggest torque wrench only goes to 250 ft/lbs, the TM calls for 350-400 ft/lbs for the lock nut. After torqueing it to 250 ft/lbs, I hit it with the Dewalt high torque impact wrench. Hopefully it will be enough:


Will give it overnight for the RTV to cure, refill it with oil tomorrow and run it a bit with the driveshaft off to make sure it actually stopped the leak. Will pick up the driveshaft at the driveshaft shop and get it all back together. More pictures of that evolution to follow.

Hopefully some of this will help someone down the line.

 

[Defcon-1]

Hopefully some of this will help someone down the line.

This is amazing and I'm certain this will bail out someone in the future who is nervous about doing this kind of work, A+ job Sir!

Also to note, Amazon has some good 600 ft/lb torque wrenches for around $120, I picked one up to do the wheel lugs and I'm sure I'll be using it somewhere down the line lol. But the impact gun method you did is good too, *thumbs up*

 

[Lee L]

I could barely get enough leverage on the 250 ft/lb ratchet to get it to click ... No way on anything heavier! Going to be on the road for a week or so, will hopefully get it finished up before Thanksgiving.

 

[Lee L]

Well ... it moves under it's own power again!

Happiness is a rebuilt driveshaft (shop apologized that they didn't paint it OD green) :


I won't bore everyone with the monkey motion required to get that heavy SOB in place, let's just say it involved a LOT of sweating, swearing, chains and ratchet straps. New lock nuts on the front:


New grade 8 bolts and lock nuts on the back:


Torque 'em all to 40 ft/lbs and it works good, hopefully lasts a long time.

Next up, work on the slow to build air pressure that leaks down through the intake stack when shut off, and this nice little leak on the main oil pump line at the front of the engine:


It does build enough air pressure to release the spring brakes and it never drops low enough to turn on the buzzer or low air light. The truck is never driven on the street, it's a "fire truck" for use around the ranch.


Other than needing a few minor repairs, paint and a little body work, it is absolutely reliable. Will start first time every time, even if it sets for months at a time.

thanks for following along!