Rear Diff Swap

[Delancy]

Hahaha.

You know what? We may have inadvertently locked it sliding it in, unknowingly, which is why it was locked once reassembled.

Easy fix and learning lesson. Not the hardest I've ever had.

Personally, I'm going to casual hunt front and rear housings for the 80, have them set up 5.29, and start carrying them with me on excursions.

 

[BMThiker]

Now that you mention it, I seem to remember having to lock mine too, before it would go back into the housing. I think I wound up plugging the harness back into the elocker motor so that the switch would match the locker position. Then I slid the third back into the housing.

 

[Delancy]

I should've done the same way as 80, which would've been to lock.

Hated doing it without swapping wheel bearings and seals. Just didn't seem right, but kid's got limited funds.

Haven't heard from him, so assuming all's well. Explained the break in procedure, even though, on good authority, I've been told that after the first two heat cycles you can drive it like normal.

 

[1911]

Mine have always gone out and in unlocked just fine.

I'm pretty anal about breaking in gears.

 

[Delancy]

Mine have always gone out and in unlocked just fine.

I'm pretty anal about breaking in gears.

To be honest, I still broke mine in as called for, even though it was stated they were "good to go".

One thing we didn't have time for was FIPG instead of paper.

What's y'alls thoughts on FIPG for this application?

What's on the 80 and wanted to do on this, but no time to let it sit.

 

[1911]

One thing we didn't have time for was FIPG instead of paper.

What's y'alls thoughts on FIPG for this application?

I use both; paper gasket with about as thin of a coating of Toyota FIPG as I can get on both sides. I do almost everything this way, and non of my engines/drive trains leak a single drop. IH8 oil leaks.

 

[Gwagg]

After I blew my rear I went with 4.56. Mine also got locked going in and we used a screwdriver to slide it back. I also worried about the bearings and not renewing the seals but no one thought it was worth the expense so I skipped them. It has been a year an all is well. Looking back I should have sold my soul and put an air locker in the front while I had it out....

 

[BMThiker]

I usually do FIPG, skip the paper. Just make sure the surfaces are smooth and clean before applying the goo. I let it set-up a few minutes before bolting it on.

 

[Delancy]

Based on a mental note during a discussion with powderpig, I thought FIPG on a diff had a 12 hour cure, before being exposed to gear oil or heat cycle.

What's y'alls take/experience?

The time has never been an issue, but wouldn't want someone else FJC, or my wife wouldn't, taking a spot in the already overrun garage and driveway, for that length of time.

Also, asked a buddy about a shop rate, and he said it's listed (not at Toyota) as a 9 hour job, putting it in the $900 range.

Anyone ever paid to have done? (I know a dumb question here)

 

[Delancy]

Side note:

Swapped all the poly's on my Total Chaos links and front CAs, and a nightmare job.

"While I was in there" did some other minor stuff and swapped diff fluids.

Stopped the front Marlin hex head drain on the way in, not badly, but enough that I wanted to replace, and couldn't find one anywhere in town (OE) so oversized and torqued on, cussing myself (because I know it'll big me an be a waste of $$ synthetic when I fix, right.....in a few days).

Was digging around looking for a new OE lower link nut (swapped all bolts on suspension. I had them, so why not?) and lo and behold found the extra drain and fill plugs I'd forgotten I'd ordered.

The heat here has fried my brain....

 

[1911]

Based on a mental note during a discussion with powderpig, I thought FIPG on a diff had a 12 hour cure, before being exposed to gear oil or heat cycle.

What's y'alls take/experience?

Yeah, I always wait 12-24 hours before filling or starting/driving, maybe overboard but my s*** doesn't leak.

 

[1911]

Was digging around looking for a new OE lower link nut (swapped all bolts on suspension. I had them, so why not?) and lo and behold found the extra drain and fill plugs I'd forgotten I'd ordered.

I find myself doing that more and more often, the older I get!

 

[Delancy]

I find myself doing that more and more often, the older I get!

Me, too.

I stripped the plug double checking to make sure I'd filled the diff.

In defense, for the most part, income is derived from talking on the phone and no task goes uninterrupted.

 

[BMThiker]

Hope this isn't too bad of a hi-jack...

Blew out my rear diff a week ago just daily driving it. Haven't wheeled it since March (Round-Up). Just got around to tearing it down this past weekend. My Nitro 4.56 gears lost about 5-6 teeth. The pinion didn't lose any teeth, but it looks like hell from meshing with jaggedness.

Posted on FB and learned a bit more from an old friend from the Trail Teams. Turns out these 8" diffs experience flex within the carrier. The ring gear deflects enough to bind up the gear pattern. Same issue Ford 9" diffs have. The Ford fix is to install a "load bolt" into the housing which is positioned a gnat's hair away from the back of the ring gear just to keep it from flexing too much out from true center. Yukon even makes a 9" carrier with the load bolt already there. Doesn't look like I can do that with the TEQ 8" third housing though. Just not enough smooth surface area behind our ring gears.

The TEQ 8.4" thirds used in older Tundras, Tacos and T100's had trusses across the carrier reinforcing the side bearings. I'm wondering if I can fabricate something similar. Like this one:

Probably means making more space within the housing...like blowing out the backside of the axle housing and fabricating a diff cover. Or adding more structural support from the outside of the axle housing that penetrates the housing and reinforces the side bearing caps inside the diff.

 

[Delancy]

To me, seems less daunting and feasible to support from outside the housing.

Could it be as easy as plating, tapping, and running a bolt through?

 

[BMThiker]

I'm going to see if I can find a junkyard 8.4" diff and scavenge the trusses out of it. Would be peachy if they bolted right up.

Wished I hadn't scrapped that bent axle housing just a couple weeks ago. Could have provided some good prototyping exercise.

 

[Delancy]

Have you seen the 8.2s on the +'10s?

Are they similar in design?

Wonder if enough meat on the 8" housing to run studs in, then a cover like the older LCs?

 

[BMThiker]

ECGS shows this picture. Also notes that the housing studs are bigger on this axle (14mm vs 12mm)

 

[BMThiker]

would like to avoid this option...especially at +$4k
https://www.allprooffroad.com/fjcdrivetrain/330

 

[Delancy]

Still think there's better options.

Think I'd opt for a Tru-Hi 9 over a 60, but they're even more money.

The 8.2s haven't had the same issues and there's bound to be a few housings that've hit salvage by now, or running the 8.2-8.4" in a custom housing.

When I was researching and planning the FJC front and rear swap, always came back to keeping it Toyota, as far as thirds and axle ends were concerned.

Built housing with 8" HP front, 9.5" rear.

Custom axle shafts for FJC WMS-WMS
80 axle ends/full float
Adapted harness to maintain e locker
Adapted WSS to keep the ABS/VSS happy

One benefit of this plan was the ability to regain a little clearance by running 37s, but honestly, I've drug the rear diff on the FJC over everything and the Budbuilt barely shows signs of.

Haven't had any instances where I've hit the pinion or driveshaft in the FJC, but have beat the crap out of both on the 80, so don't know if the 1.5" difference really matters, not the HP on the Dana.