Mud Taco

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 (or vice versa), 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 these 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.

millball

Any '86 to '95 IFS 3rd will work. If you were able to get a cheap ADD version, you could easily switch the straight leg from your old unit over to it.

In that case, It is also necessary to install an inner seal in the punkin on the long side.

Mud Taco

Would opposite work as well? Meaning, that I get a non-ADD 3rd member and use the leg from the one currently on the runner (ADD version)?
The vehicle came with auto hubs, but I switched them to Warn manual hubs. I did not change anything else at the time. So, all else (including the front diff) are still stock.

millball

Yes, you can switch that leg both ways. I wasn't aware that ADD came on '89' 4Runners

Can you post an image of your current front diff???

If you go from straight leg to ADD, that inner seal must be removed so that the ADD mechanism might be lubricated.

Mud Taco

Sorry, I don't have any pics of it, as I haven't pulled it off yet. I was going to have to drop it out of the way to do the dreaded oil pan gasket. When I drained the front diff fluid in preparation, a chunk of one of the gear teeth came out. Which probably explains the loud sound (like I was hit with a golf ball rather hard) that I heard while just driving down the road about 1k miles previously. Not wanting to pay somebody to rebuild it, I'm planning to just swap it out with a used one. Anyway, since my garage is rather small, I'm not pulling it off till I get the replacement.
Thanks for the tip. It is very helpful. All Toyota could tell me was confirming that it's a 4:10 after looking up my VIN#.

millball

I am interested in seeing the ADD front end in your '89 4Runner, as all info I can find says none were built that way.

A pic from the front with it still installed would do.

wallytoo

iTrader: (1)

as far as i know, no US-destination '89 4runners were factory-equipped with the ADD version. auto hubs are not the ADD system (i know millball knows that).

millball

Yes, auto hubs are Not ADD

No machine built with ADD would have automatic hubs, only solid steel drive flanges.

I think the OP is misinformed about the operation of his '89 4Runner. and that he does not, in fact, have an ADD equipped truck.

A picture of it would tell the tale.

Mud Taco

I got under it and checked it out. Yall are correct. I was going by some misinformation I found while searching this out. It's amazing how much false and contradictory info gets posted, and only by random posters, but sometimes by reputable sites and supposed authorities. Anyway, I'm rather happy I don't need to worry about that and can get any 87-95 3rd member and use the leg I currently have.

I do have a follow up question though. Since I switched to manual hubs, should I remove or cap off any of the vacuum associated with it?

I will attach the pics I took while under there today.

millball

There should be no vacuum lines associated with the operation of your front drive. . None.

So, therefore; no lines to remove.

coopster

Totally unrelated, but do you have the V6? I would have missed the question on Jeopardy that you had 4.10. I thought the manuals (almost) had 4.56's.

And I'd remind you that (I believe it was) Abe Lincoln once said "Don't trust everything you read on the internet."

millball

I can see from the images he posted that the oil pan is 3vz

As to whether or not it's 4.10 Who knows?? The ID plate would at least tell how it came from the factory.

Mud Taco

Yes. It is the 3.slow.
I did call Toyota, gave them my VIN# and the guy said it was 4:10. In fact it was the only thing he could say for sure.
The info could always be wrong, but I'll assume it is correct and get a replacement 4:10. After it arrives, I pull off the old one and double check it by opening it and counting the teeth.
Thanks for the info and help fellas.

Mud Taco

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?

Thanks in advance

Mud Taco

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?

Thanks in advance

millball

The gear ratio in the front absolutely, positively, has to match the ratio that is in the rear.

Mud Taco

That's what I assumed. Thank you for confirming good sir. I will contact the seller asap about a replacement.

wallytoo

iTrader: (1)

39 teeth doesn't mean it has a 3.90:1 ratio. the ratio is determined by the number of teeth on the ring gear (39 in your case) and the number of teeth on the pinion. count the teeth on the pinion before assuming your ratio isn't 4.10:1.

Mud Taco

it's 10 teeth on the pinion

Mud Taco

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