Rear diff fluid? 99 3.4l 4x4 automatic.

Hey guys,

At least one, but probably both of my rear axle seals are leaking gear oil into my drums. I know that there is plenty of information on how to do that job, but that is not my question.

I am wondering if I drain and fill my rear diff as a temporary solution, would that cause the leaks to get worse?

I topped off with some non-synthetic (I guess you would call that "dino" oil?) "limited slip" 75-90 weight gear oil. I only put in a half a quart as my intention was just to make sure my rear diff didn't run dry before a short trip. I have no idea what type of gear oil was used previously, as I just bought the truck a couple months ago.

I want to do the seal job myself, I just don't have the money/time at the moment. What would you guys recommend that I do?

I read that "dino" oil is recommended over synthetic. Is this true? If so, why? What specific brand and type do you use?

Also, whenever I decide to do the drain and fill, is it recommended to replace the gasket for the diff cover or anything like that? Ill obviously replace the crush washers.


Thanks again

Zayne

 

You do realize that the leaks are ruining your brake shoes right? Also, the leak is washing the grease out the axle bearings. But if its been leaking for a while both of those things are beyond saving at this point. Hopefully, the axle bearing(s) wont fail totally on you on your 'short trip' because they could potentially take out the axle too.

Oh, and no diff covers on our diffs.

 

Yes. I fully planned on replacing the bearings and shoes and whatever parts aren't salvageable. I'm hoping the bearings won't fail, but I haven't removed the drum covers to see how bad the leak is.

I guess I should get on doing the job sooner rather than later.

I've also got a steering rack to replace :/

Thanks for the input

 

I do almost everything myself, but I let the local show swap my rear axle bearings when the seals started leaking, and I'm glad I did. A special tool is required to do it correctly. The seals are most likely leaking BECAUSE the bearings are shot, allowing too much shaft movement. I got my old bearings back from the shop and they had all sorts of looseness. Anyway, if you replace only the seals then I doubt the leak will be fixed. Replace everything back there and you'll be set for a long time.

As for your question; I believe the manual states 80-90 or 75-90 (depending on which rear end you have) GL4/5 oil. I've been using Valvoline GL5 for years and it has been fine. The oil you put in is probably fine, especially for the short term.

 

When you say "depending on which rear end" what do you mean?

I have an automatic 1999 3.4l v6 4x4 sr5.

Do you mean 4x4 vs rwd?

I was definitely planning on having a shop take the old bearings out and press the new ones in. I don't have enough confidence to make sure the new ones are seated properly.

 

I mean depending on if you have the electric locking rear diff or not. Or maybe it's the same for all rear diffs but only different for front diffs based on the front diff option.. I don't remember, but the manual says for sure. And the difference is only whether to use 75-90 or 80-90 so it's not a major difference.

 

I know these are stupid questions that I should already know, but how do I know if I have e locking diffs? I havent even used my 4wd yet so I have no idea. Is this something available only on the TRD models?

 

Yes.

Trucks with the elocker will have a switch on the dash (to the left of the steering wheel) marked RR Diff. Also, your rear diff will have a visible motor sitting on it, that manages the locker engagement.

 

Here you go, from the 1999 Tacoma manual (attached pdf).