Front Diff (3rd member) question
 

I have a 1st gen '89 SR5 V6 5spd 4Runner.
I need to swap out the 4:10 front diff with a used one. I have found conflicting info regarding if it matters if it came with auto hubs or not. One fitment guide I found showed that it matters on 4runners 1990 and after and Pickups 1989 and after, but on the years before that it doesn't matter. But i had also read that if I use a front diff from one without ADD and install it in one that came with ADD, then it requires modification. I need to nail this down so I can order the correct one... BTW, the used one I am looking at is out of a later year, but are supposed to be the same for 86-95. There is only one option, if came came with ADD or not.
FYI, my Runner came with auto hubs, but I swapped them out for manual hubs a while back and have no plans on ever reversing that.
Thank you for any info you can offer.

If you find another diff you can convert the long side axle either direction with what you have. If your diff is hashed but the outer axle is fine you can take a ADD front diff and swap your axle on to it. Really straight forward. Just converted another 2nd gen 4runner to non ADD style by swapping long side axle the other day.

Thank you.
Which gaskets did you need to replace when you did that?

I helped my uncle do a swap on his. He has a 86 pickup and we got a 94 4Runner ADD front diff. Swapped his old long side and installed a new seal for that side and it’s been fine ever since.

So you’ll need the seal that goes to the long side shaft housing. All mounting on our project was exact same.

I have a follow up question.

The front diff I ordered from a shop off ebay arrived. I opened the top to double check it and replace the gasket. Well, it is not a 4:10 like they said it was. It is a 3:90. I triple checked, it has 39 teeth, not 41.

Am I correct in assuming that I can't use this and need to get another 4:10?

Also, they said the one that was sent to me came off a '95 4runner V6 4wd. Did they even come with 3:90 gearing?

Yes, depending on stock tire and/or transmission, some had a 3.90 ratio.
No, you can't run a 3.90 front with a 4.10 rear. You need to get a proper 4.10 front diff.

As upset as you may be now it would have been worse if you completed the swap and found out on the first test drive.

I know I have good R
& P if you want to put a set of used 4.10 gears in.

Well, I got the replacement 3rd and it's a 4.10 this time thankfully. But I have another problem. The legs are not interchangeable as I was told they would be. You can see in the pics that both the input shaft on the diff and the legs are very different.
So, my question is this. Can I just pull off the vacuum unit and bolt on a cover and use that leg instead? Or would it not engage the 4wd not having the vacuum or cause some other problem? I would very much like to find a way to get this done and use what I have if possible.
I know I could take my original 3rd with some broken teeth on the ring gear and have them use the good ring gear from the used one I just bought... But that would totally defeat the purpose of buying a used one. I don't want to pay an arm and a leg to have it rebuilt.
As a reminder, I have a 1st gen '89 that came with crappy auto hubs (that don't use vacuum) that I swapped out for Warn manual hubs.
Thank you