Good Diff Reassy thread?

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Vae Victus

Vae Victus

Posting more than I know
10 Year
Joined
Mar 7, 2013
Threads
88
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3,202
Location
Nashville, TN
I'm putting back together an Fj60 3.70 diff I bought from Roma, disassembled . Problem is, FSM doesn't show exactly how to put the 4 small gears back in. Actually they (I've checked 3 different year FSMs) don't show the shaft or bolt that goes in there at all.

Anyone got a better reference or some photos or just a textual description to help?

Confused....
 
FSM doesn't show these parts. I assume these are part of the diff.

ImageUploadedByIH8MUD Forum1413059420.546786.webp


ImageUploadedByIH8MUD Forum1413059445.769460.webp
 
The parts are the spider gear pinion shaft, the pinion block and the shaft retaining pin for your average rear cruiser differential from 1958 to 1992. The shaft holds the spider gears in place, the pinio block is used in rear C-clip axles to retain the clips and the pin holds the shaft into the carrier. I know the FJ40 FSM shows where these go.
 
Thanks @Pin_Head. So front and rear are different. This is the front that I'm setting up/swapping out. Can I make this work for the front?

And thanks B y r o n. Great reference. Learning a lot with all those pictures of rebuilds.
 
Pin_Head said:
The front and rear diffs are the same, with the exception that the rear needs to have the pinion block installed to retain the C-clips while the front does not need it and may not have it.
Click to expand...

If I have the block I can install it - correct?

Surprised there's not a "how to" on the pinion gear installation. That's tricky.
 
Installed the gears, block, shaft and pin. Inserted axle to rotate the gears and check things.

The block is stopped from rotating by the axle shaft coming into contact with it, correct? Otherwise if the axle is flush with the side gear, the block rotates, which I'm sure isn't good.

Below, Temporarily inserting axle to rotate and check gears.
ImageUploadedByIH8MUD Forum1413142242.926068.webp



Below, Block rotating if axle isn't touching block. Clearly there is a wear pattern on the block from the axle end.
ImageUploadedByIH8MUD Forum1413142261.613369.webp


Below, Block held in place by axle end touching block. I'm assuming that the axles will align precisely and lightly touch the block when it is all assembled.
ImageUploadedByIH8MUD Forum1413142277.440745.webp


Am I good here?
 
I've been messing around in my diffs all summer - I would say if there is any component of these trucks that are seriously lacking a good write-up here on MUD, it's the differentials. Sounds like it's time to make another @Vae Victus level step-by-step rebuild thread!

As Pinhead already pointed out - you're going to want to install that block and the cross-pin last. First push the axles into the space in the center, then install the C-clips. Pull the axles back out so the C-clips "lock" against the side gears, then install the block, push the cross pin through it, and button it up with that bolt/pin and lock washer at the bottom of the carrier.

Don't forget the domed washers that go outside the spider gears, between the back of the gear and the carrier - they like to slide out (or at least mine did). It was tough to keep them in place, and run the cross-pin through the washers, gears, and block at the same time. They will all be held in place by the cross pin once everything is in place.
 
RWBeringer4x4 said:
I've been messing around in my diffs all summer - I would say if there is any component of these trucks that are seriously lacking a good write-up here on MUD, it's the differentials. Sounds like it's time to make another @Vae Victus level step-by-step rebuild thread!

As Pinhead already pointed out - you're going to want to install that block and the cross-pin last. First push the axles into the space in the center, then install the C-clips. Pull the axles back out so the C-clips "lock" against the side gears, then install the block, push the cross pin through it, and button it up with that bolt/pin and lock washer at the bottom of the carrier.

Don't forget the domed washers that go outside the spider gears, between the back of the gear and the carrier - they like to slide out (or at least mine did). It was tough to keep them in place, and run the cross-pin through the washers, gears, and block at the same time. They will all be held in place by the cross pin once everything is in place.
Click to expand...


Dude, where were you a few hours ago? I had to figure this put all by myself! (Poor me). Saw your update on the Aussie Lockers just before looking here. I just did the front, so no block, no c-clips.
 
Well, I only spend about 1/2 the day on Mud... :D You have my number, feel free to use it.

Although today I would have been a little slow to respond, engagement photo shoot with:princess:

Glad you got it figured out!
 
If those gears are as sharp as mine were, and you were dumb like me and didn't wear gloves, then you know the joy of 1000 tiny paper cuts all over your hands now too! I totally love this...
 
FJsnoozer said:
Is the rear assembly R and R in the FSM or should I use the hanes?

I am merely swapping 3.70 chunks for my stock 4.11s
Click to expand...

Let's put it this way, I own a paper copy of the Haynes, and I don't know where it is. I downloaded 3 different year engine and chassis FSMs from TrollHoles thread where he put them.

Between FSM and Mud, I get it done.

I'm doing the same. It is plug and play except for the flange that attaches to the drive shaft. You need a universal one of those for each diff since the splines are different sizes between the 40 and 60 diffs.

See photo of the 40 flange,

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And the Universal (why can't I add photos from the IPad app when I'm editing a post? Frustrating)

image.webp
image.webp
 
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