Front Axle Service and Diff Swap

[stringtwelve]

I'm in the process of getting my ducks in a row for my first axle service. I've been hitting up the threads, youtube, and have some service manuals on order.
I'm doing my best to make sure everything is ordered correctly to minimize my downtime. The one variation to this process is the fact that I'm doing a diff swap at the same time as my axle service.
The PO (2manycruisers) swapped the rear from a 4.11 to a 3.73 diff for highway cruising but didn't get around to swapping the front so it's first on my to-do list.

My questions are:

1) Where in the sequence should the diff swap take place? Before or after axle removal?

2) What other items should I consider servicing or upgrading during this process?

3) Should I be aware of any surprises with this being an Aussie HJ45 with disc brakes of unknown origin?

Here are some pics I took last night for reference.

Also, here is an email from 2manycruisers with his input:

Hi Kevin, The axle itself is definitely 40 series. The brakes could be 45/47 or 60 series. Apparently both had the air vents in the Aussie market. All the knuckle parts would be the same, either way. Things that vary: bolt pattern of the trunion bearing caps/steering arms changed in '79 to a larger pattern. I think all the Aussie ones would have the larger pattern because they didn't have disk brakes before '79 like we did. Similarly, the Birfield grew in '79, so these should be the larger ones too. The length of the birfield (the outer axle and CV joint) changed, also I think in '79. If there is a snapring or retaining bolt in the end of the axle when you pull the lockout hub flange off, you have whichever length is correct for the Aisin hubs. That probably is not an issue on the Aussie ones, as here many came with drive flanges on the front axle and were changed to Warn hubs. Those have a different length Birfield. If the disk brakes were swapped from another axle from the knuckles out, rather than the entire axle, you may have some combination of the different years of parts, but I don't know how it was done.

What I would do: I would confirm you have the larger knuckle pattern, probably by searching on Mud. I think they have larger studs and 19mm nuts, which would also confirm. Order a knuckle rebuild kit for '79-up if you have the larger pattern--the only difference in the kits is the proper shims for the steering arm bolt pattern. I have ordered from Marlin Crawler in the past. He uses good parts and I like him. They also make a heavy duty inner axle seal that I would order with the kit (1 seal per side). Up to you whether to buy new wheel bearings at the same time or just repack yours. I didn't hear or feel anything up there, but might think about replacing them just so you know what's in there. Same with the brakes--I don't know if the rotors have enough to be turned or not. If you can check that before you order, you could make the decision. I would also consider rebuilding or replacing the calipers. I haven't priced them, but if they are reasonable from Autozone or someplace like that, I'd order some for a V6 truck to get the bigger pistons (a little research here, as I haven't actually done it before). And since the rotors are heavy, if you can get them from a local autoparts store for a decent price, it might be better than shipping. Front axle service is a chore of a job and you don't want to have to tear into it again any sooner than you have to, so I would encourage you to replace anything you have any question or concern about to save doing it again later.

Also, when you rebuild, there are shims under both the trunion bearing cap on the bottom of the knuckle and the steering arm on top. There is a fancy tool for determining the exact center of the knuckle for birfield alignment. I don't think it requires that much precision. I would use the same shims on the bottom trunion bearing as what you find when you remove it then shim the steering arm to get proper preload on the bearings (you can use a fish scale for this, Marlin sells one I think). Also, the Marlin Crawler inner axle seal is designed to maintain a good seal with a higher level of deflection, giving a little more room for error on centering the knuckle.

I appreciate any input you might have to add to my research

-Kevin

 

[pb4ugo]

Are you repalcing the whole axle or just the 3rds?

 

[Fast Eddy]

The diff won't come out with the axles in place, so that one's easy to answer. Use a nice Toyota cork diff gasket and get yourself some Marlin axle seals.

When you pull the knuckles, keep track of where the shims come out and put them back the same.

Get some nitrile gloves, an extra trash can and a stack of newspaper, and a gallon refill-size of orange degreaser from the dollar store. It is the messiest job there is.

 

[inkpot]

I would swap the front 3rd member while you have the both ends of the axle torn down for service. The Birfs have to come out a bit to change out the diff, so do it all at once. The little air scoops on the disc brakes is very similar to what was on the 89-90 FJ 62 series here in the states. I would guess that just the outer ends of the axle were swapped out from one of these, as the housing is about 3" wider than an FJ 40 series. John

 

[tucker74]

Too bad your not closer, I'm doing the same swap the other way (3:73->4:11). Like they've said, you have to disassemble the birfs and pull the axles before you can remove the third member. Your knuckles look pretty clean, you can probably get away with just removing to the spindle instead of all of it. You'll still need most of a birf rebuild kit and a thin rubber 3rd gasket (*not cork like suggested above*). Once you get the axles pulled and all the nuts off the 3rd, put a floor jack right behind the pinion and it will pop right off Those backing plates are from a FJ62, they have better ventilation.





Good luck! It's really just taking stuff apart and cleaning it up, make sure you get the correct torque specs and set the preloads (won't have to mess with the trunion pre-load if you don't pull the knuckles, just the wheel bearings).

Tucker

 

[Vossie]

hi. unfortunately nothing to contribute here, but i would love to know ho you get on with this as I am also going to have to do the same thing shortly in my 40. hope it goes well.

 

[stringtwelve]

Thanks to everyone for all the input. I've been swamped with work this week so it looks like next weekend before I can get greasy. I'll keep you updated on the progress.

 

[stringtwelve]

Rebuild kit from Marlin Crawler is now on order.

Grease and Diff Oil along with misc tools (54mm socket, seal puller, etc.) on their way as well. Ended up going with Redline lubes.

Looks like I'll be gettin' greasy this weekend!

 

[stringtwelve]

Well she's up on stands and ready for some lovin'.

Got a couple more questions regarding the diff:

The PO provided a 4.11 diff from the rear and a 3.73 each in a garbage bag painted with what ratio each one is.... So, is there a way to tell a 3.73 from a 4.11? I trust David but I should also do my due diligence to make sure I'm putting the right one in before I get a lot of time invested. (Trust, but verify.)

Are there any things I should check to ensure the health of this diff before I install it?

What serviceable parts (if any) should I address on the diff while it's on the shop floor?

As always, thanks for the input!

This is how frame off restorations start... better not let it sit too long.

Late model discs.

 

[cruiserjunkie]

You can count the teeth on gear and divide them by the teeth on pinion for the ratio

 

[cruiserjunkie]

I see i didnt read cafefully enough as you have 3rd memebers not gear sets

 

[stringtwelve]

Ok so I answered my first question after some more research...

Putting this here for future newbies like me to reference:

Count the teeth on the pinion gear and ring gear. Then divide the ring gear teeth by the pinion teeth.

Mine was 37 ring gear teeth and 10 pinion teeth so 37÷10 = 3.7

Still interested to know what I should service on my diff before installation if anyone has any input.

Thanks,
Kevin

 

[stringtwelve]

Got her front end dismantled this weekend. Now just waiting on the Redline grease to arrive for reassembly. Going to give all the components a good cleaning and paint job before reassembly.

Evidence of some moisture.

Marlin Kit Ready to Go

 

[stringtwelve]

Two very helpful videos for reference:

http://www.youtube.com/watch?v=_3CI4mmEv6A&list=PL2300F541CBC79BA5
Dis-assembly

http://www.youtube.com/watch?v=VFWWEmLHBN0
Reassembly

Should I keep my vented backing plates or ditch them? There seems to be two very different schools of thought on this. (I'll be running 17x8 Mojaves with 1/4" spacers very soon.)

 

[stringtwelve]

Just a quick update for those interested...

That kit up in the previous post IS NOT a Toyota axle rebuild kit. It's for a Suzuki Samurai! I didn't realize this until I started trying to use it...

I double checked my invoice, which was correct, and then called Marlin Crawler. They got right on it and sent me the right kit... (What's really funny is that they don't even sell Suzuki axle kits!)

Should be all back together this weekend. Trying to locally source some V6 calipers and longer flex hoses for the backing plate delete now.