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Pulling the differential or working on it in place?


Idaho Jim
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Someone apparently reversed the differential so it would go backwards. Some people's kids....... I need to flip the ring gear back to the original configuration. I can't figure out how to get to all the bolts that hold the differential in. 4 are virtually impossible to get to. Can the diff be opened up in place? I know I'll have to pull the axle halves out to remove the ring gear if I work on it in place. That may be easier than wrestling it out and back in. I suspect the previous owner split the diff in place, as only the input side is painted blue. (Blue??)

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Oh the fun of the rear drive!

I have had three out over the last 6 months. 

First, if you want to remove the whole unit, you need to take a 3/4 inch box/combination wrench and bend it like a banana.  Test and adjust until you can access the rear lower bolt from the top rear down and the one under the rear drive from the front.  Generally, the closed side of the wrench will stay on once you start unscrewing...so you can use an impact/socket on the outside and get it right out by yourself.

Now, you can absolutely just pull the front half and leave the rear case mounted to the hull.  It is an even messier way if that is possible, because you will get 1 gallon or so of oil all over the place, as opposed to pouring some amount out of the sides when you lift it up. 

Please take pictures....I guess you could just flip the guts and have the pinion gear line up?  Very interested to see what they did here.

Good luck!

 

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Hi Patrick,

I was hoping there was some magical access port to get a wrench in there, but I see my hopes have been dashed.  😞  I just finished yarding the starter out of the engine, without removing or even tilting the engine up. I did a similar thing with a wrench. I made a college educated weld (i.e., really poor weld) of a half broken 9/16 wrench and a handy piece of steel to secure the nut on the starter flange. Why nobody designed threads in that hole, I will never know. It would have sure cleaned up some of the language needed to get the starter out....  It acted like it was shorted out. Turns out; it was. Generally fine, but 75 year old friction tape failed to insulate the brush wires and it was shorting to the frame. Should be an easy fix.

Turns out my transmission is not the right one and will have to be replaced with the correct one. It's a truck transmission and has a pto port on the side.

I also noticed that there is no bracing rod between the axle carriers and the body. Is there supposed to be one there? It shows it in the manual. I don't even see a place for it to hook on. I think my body number is around 6189. Maybe it's not supposed to have one.  ??

On the differential, I'm tempted to feed a tiny plastic tube down into the diff and slurp the oil out before I open it up. There is a 1/8 NPT gadget on top. Don't know what it is, but it unscrews. Vent, maybe?

Can you tell me for certain which way the engine cooling fan rotates, as viewed from out in front of the Weasel? MOST fans rotate clockwise, but a very few don't. I need to know so I can commit to or ignore flipping the ring gear. Does the fan pull air through the radiator and then over the engine, or is it the other way around? Dozers push it away from the engine, as does the DUKW and XM501 Hawk missile transporter. The fan blades are backwards on those. Rare as hen's teeth.

Thanks mucho for all your help! I'll try to get some pix and videos, along the way. I may edit out some of the audio...  😮

 

Jim

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Hi Jim,

    I removed the center section the way you propose. To remove the oil I did use a hand vacuum pump from my hydraulic brake bleed kit. I removed what I could from the fill port in the side of the pumpkin. A 1/4” copper tube will fit in the top tapping you mentioned. It will take a little maneuvering to pass the ring gear and carrier. With plenty of patience slowly the oil can be evaluated. I filled 1 gallon milk containers to determine how much was removed. In the end less than a quart will spill. Block the drain holes inside the hull to keep the oil from migrating to the drain on the bottom side of the outer hull. 
    Before removing lay some rags or oil absorbing mats on the tunnel floor. Create a dam with anything you can. When the piece separates it will lay down. I laid it on cardboard. You may want to rig this to lift it out of the hull. It is heavy and not well balanced. 
    This will work but still a small mess. In Idaho you must have low temperatures by now. I used my heater to blow hot air under the hull to warm the oil, seeing at it is supposed to be 30 weight and may be thick. A light bulb next to the housing for a few hours might warm the oil to. 
    Good luck!

Fred

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The original transmission as you know is a T84J....they are a little hard to find, but you will.  The Army replaced the T84 with a side shift T90 and there is an MWO so you might find a T90 too...depending on how original you want the Weasel to be.

The bracing rod is a very late modification - your Weasel is a '44 if my memory is correct so no bracing.

It is a great idea to slurp up that oil if you have a vacuum pump etc...on my list of tools to acquire.

The fan definitely pulls air into the engine and sends it out the back duct by the muffler.  The engine is turning counter clockwise.  The personnel "heating" system for the Weasel is that air flow...across the engine...through the ducting/small holes behind the driver seat in the bulkhead and under the rear floor. 

I understand the need to edit audio😅

Good luck!

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Hi guys,

That sounds like good advice from those who've been there and got the shirts. My Weasel data plate says Feb 1945. I have my Weasel in a heated shop, fortunately. When we moved here, I figured we needed it during the winter. Forget doing anything outside. Looks like 21F outside, and snowing. Hence; the Weasel need.

I would be happy with either transmission. I will probably adhere to the 20' rule in this restoration. Fred's advice to block the hull drain holes sounds good, but has already been tended to by old man rust. I will approach the issue with puppy pads and Dollar Store aluminum turkey pans underneath the Weasel.

Heating the oil sounds like a very good idea before draining it. I'll try putting a little 1500 watt heater in front of the punkin' for a while before tying to drain it.

 

Thanks, guys!

Jim

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I took the opportunity to fit an access plate to make life easy when draining the final drive. Might be worth considering for the future. Gary Szecy's excellent article on how to remove the final drive is worth a read as well. Be very particular on what grade of SAE 30 oil you use when refilling the final drive. Using the correct grade of SAE 30 makes a big difference on your steering response. I have attached the spec sheet for the oil I used. Take note of the API rating. IMG_3336.thumb.JPG.0cb7388e96cd40ed547caccd1740b417.JPGIMG_3338.thumb.JPG.4031d04b0e763f690037fa5e9b06a6ba.JPG

CAstrol Classic XL30.pdf

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Very clever! I like the access port. I have to undo some changes someone before me made. They opened up the differential and flipped the ring gear to the other side, so the vehicle would go backwards instead of forward. They tore up the whole crew cabin and made a new driver position. I am bringing it back to normal. Being lazy, I chose a different approach. I wanted to avoid pulling the differential, but also wanted to avoid the oil spill. I used a 1.5mm welding rod and dipped it in the vent hole at the top of the diff. There was about 50mm of oil in there. Then I scrounged up a 6.35mm copper fuel line and stuck it down in the hole. It goes to the bottom of the diff easily. Then I grabbed a cheap Harbor Freight liquid transfer pump and a 6.35mm clear hose, jut to get the pump tubing to match the copper fuel line. Add an old milk jug and start pumping. It took, maybe 5 minutes and the diff was empty. I will use a load balancer for pulling car engines to straddle the front half of the diff and lift it out. I will get pictures at that time.

Jim

.1842814982_Differentialoildrainsetup.thumb.jpg.a7ffa1a0ab8ccbbb10b04119613804ff.jpg

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How odd. Nicely done, though. All I can figure is that they wanted a 2 seater, side by side and didn't care or consider the fact that the weight distribution is now weighted heavily in the rear. That might affect the flotation (not sure) but according to the guy I got mine from, it's vulnerable to wheelying over backwards if you jump on the gas, especially going up a hill.

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Here's what the diff looks like. Planning on laying it nose down between the forklift forks, and swapping the diff guts around, after removing the brake bands, of course. When all is said and done, the Weasel will have been returned to the proper direction of travel.

 

20211207_213127.jpg

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Yes, I agree on the TM9-1772B, which I did procure. Very helpful. Since I will be flipping the carrier assembly around, the shims as they were probably don't apply. I will do my best to get the gear engagement as slick and smooth as I can.

I did get the carrier out and will post a picture. It goes back in shortly.

Jim

20211208_160425.jpg

20211208_160444.jpg

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