Swapping the rear diff center... how hard is it?

[thedapperbenz]

I’ve been searching for a rear auto locker after posting my previous thread (re auto lockers).

As luck would have it, there’s someone local that is looking to swap their full center with an Eaton auto locker installed, for a standard LSD center, as they’re putting in e-lockers soon.

How hard is it to pull the rear diff center out? Can I pull it out and put the new one back in the same day? (It’s my daily)

Are there any steps where people tend to get stuck, or anything to look out for?

In terms of parts to pre-order I’m thinking
- gasket for the pumpkin
- outer axle hub gaskets
- diff oil
- bearing grease

 

[baldilocks]

It’s a Saturday morning affair. As always, it will help to have a copy of the FSM instructions.

Your list of supplies looks pretty much complete. You can skip the paper gasket and seal the third member with grey permatex or Toyota fipg instead. You don’t need too much. Assmebling with a torque wrench is advisable.

 

[super40]

im not a mechanic and i swapped my rear pumpkin in about 2 hours. i took my time cleaning all the surfaces. i did not use a rear gasket. just used that black silicone stuff they sell at the auto parts. 1yr later and all is well. if your rear axel has never been rebuilt id do it too while your in there.

 

[super40]

one more thing... do 50 push-ups each day for about a month before you do this. that thing is heavy.

 

[thedapperbenz]

It’s a Saturday morning affair. As always, it will help to have a copy of the FSM instructions.

Your list of supplies looks pretty much complete. You can skip the paper gasket and seal the third member with grey permatex or Toyota fipg instead. You don’t need too much. Assmebling with a torque wrench is advisable.

Good point, I’ll try and find a service manual to give me the torque specs too..

Is it less likely to leak with the proper gasket? How about on the outer hub gaskets?

im not a mechanic and i swapped my rear pumpkin in about 2 hours. i took my time cleaning all the surfaces. i did not use a rear gasket. just used that black silicone stuff they sell at the auto parts. 1yr later and all is well. if your rear axel has never been rebuilt id do it too while your in there.

That sounds promising. No mechanic here either but reasonably handy with the tools (just finished a 2y resto on a 68 benz, and will be air-bagging a 67 beetle this weekend)... just never pulled an axle or diff before!

I’m assuming I need to put some sort of jack up under the center before I pull it, as the weight of it would likely push my nose into my face.

I’m not sure if the rear axle had ever been done.. just picked the 80 up a few weeks ago and haven’t touched it. It’s got 200k km on it, so I could give them a going over whilst in there. Are there any additional parts I’d need for that?

 

[shocktower]

Ok here ya go 1 drop rear drive line 2. Take all of the nuts and cone washers out of the rear hubs pull the axles out about 6" 3. Remove all of the fasteners holding third remember in place hit with dead blow lightly pull out third

 

[bwakeling]

It is a simple job. I used RTV after reading that there are a lot of leaks with the paper gasket. I second doing 50 pushups a day prior to pulling the diff to work up some stamina. It is a heavy bit$h and a jack isnt going to help much.

 

[YMT]

one more thing... do 50 push-ups each day for about a month before you do this. that thing is heavy.

I second this. I stripped an old non-locked axle and it was around 80 lbs for the rear diff assembly, including cover; it fits well into a 5 gallon bucket, which I would also suggest you add to your list.

 

[-Spike-]

The paper gaskets often leak on trucks that are wheeled hard, the theory is that the gasket allows some movement of the third member. I had a gasket piece get spit out on my front diff, and leaking ensued. I have been using RTV since then. I don't think anyone has experienced a leak when RTV is used in lieu of a paper gasket. The joint is then metal on metal and glued together, which eliminates any risk of unwanted compression and reduces the chances of anything moving around.

 

[Dave 2000]

As above and an easy job. While the shafts are out look for oil contamination of the wheel bearings. No big deal but if contaminated you could put a couple of seals on your future PM list?

I recently found my first customer with the seal so bad the grease seal failed and oil managed to find it's way to a brake disc, never seen this before on an 80, in fact my own car had a leaky seal, I left it about six months before getting around to it, it never got bad enough to leak out from the bearing housing.

Regards

Dave

 

[thedapperbenz]

Damn this forum is good.

Probably the best car/truck/tech related forum I’ve been on (and that’s going back 20 years!)

Thanks for all the help fellas.

 

[mudgudgeon]

A bottle jack placed under the pinion to jack it up is a useful way to crack the seal in a controlled manner if the current gasket won't let go.
If you're laying under that thing, you don't want it to let go in a hurry.

Agreed is a couple of hours job, add an hour and a half if your going to change wheel bearings while you've got it opened up

 

[super40]

Don't use a hammer!! use the bottle jack for breaking the gasket seal as described above way safer and easer

 

[mmajsw]

Here are the steps I used when I changed my rear diff last week. It sums up all the info above which was good advice.

1. Drain the diff oil. A 24mm socket and oil pan was all that was needed.
2. Remove the driveshaft. Two 14mm box end wrenches quickly removed the 4 bolts and nuts. My driveshaft nuts had definitely never been removed in the 20 year life of the truck. U joints were good as I keep greasing them when I change the oil so no need to worry about them. But I checked anyways.
3. Remove the axle shafts. A 12mm socket took care of the bolts. A sacrificial 8mm nut on the stud along with a brass drift and a hammer removed the cone washers. I chased the two threaded holes in the shafts with a 8mm tap and inserted the bolts to press the axle shaft out. Pull the shafts out about 6- 9" to clear the diff.
4. Crawl back under the truck and remove the 10 housing nuts with a 14mm socket. I had to use a deep socket as well as a 6" extension so that the impact could clear the diff housing.
5. Using a jack, I put a little pressure on the front of the housing and broke the seals. I then pried the assembly loose. An oil catch can was placed below the axle to catch the inevitable oil that would not drain out of the drain plug.

Enter assistance.

6. Together, we removed old housing and got it out from under the truck. It weights about 80 - 90lbs and unless you have a car lift, it is in an awkward place.

While the assistant scraped the paper gasket off the axle housing, I went and cleaned Ken's diff with some brake cleaner. I got rid of the lead paste used to check the gear tooth mesh patterns as well as most of the dust that accumulated on it. Once completed, I used some black silicone gasket maker to lightly coat the sealing surface of both the diff surface and the axle surface.

Next, with the help of the assistant, we lifted the new locked diff assembly onto the axle studs. The diff was pushed back to mate against the axle and the nuts and washers were installed. Everything was assembled finger tight and left to dry overnight.

The next morning, the nuts were torqued to 54 ft. lbs. on both the housing and the driveshaft and the rear hubs were serviced.

I also replaced the oil seals on the axle shaft as it is a 30 second job.

 

[thedapperbenz]

Massive thanks @mmajsw
That’ll help me heaps. I should have everything I need in hand, just need to finish the other car so I can get some garage space!

 

[bigredmachine]

if you decide to go with the Toyota fipg go with the red fipg, its designed to be used with gear oil. make sure that you scrape off all of the old paper gasket, if you have access to a wire wheel thatll help a lot