Diff and t-case fluid change question

[RikRunr]

I have a 97 SR5 with 245K miles. I'm planning to change the fluids in both diffs and the t-case (no maintenance history). I anticipate this hasn't been done (at least in the last 7 years and 120k miles from PO). I was wondering if anyone among you have run new fluids through the diffs/t-case to "clean" them up a little then swap out the fluids again after a couple weeks or a couple hundred miles. My theory is that the new fluid will dilute what's left of the old stuff and help knock off any sludge that may be present. Ultimately, I'd like to go with synthetic fluids. Your thoughts?

 

[fourwd1]

That's a common way of changing fluid on an auto trans, because you can't completely drain it. Or an engine to clean the sludge like you said.
I don't think it would be worth it on a t-case or diff, they can be drained completely and don't build up sludge the way an engine does, but it wouldn't hurt to do it.

 

[Gerdo]

A word of advise. Open the fill holes first. Sometimes the plugs (fill and drains will seize and are very difficult to open, opening the fill first assures that you can refill)(put some anti-seize on the plugs before reinstalling)

I would drive the vehicle and heat up the oils, maybe a half hour drive.

Then drain them and see what they look like. If dark, I might consider running a cheap oil for a few hundred miles.

How about your transmission? Is it an auto or a manual?
If a manual... http://www.toyota-4runner.org/maintenance/76100-manual-trans-gear-oil.html

 

[RikRunr]

It's an automatic transmission. I've already had it (and the coolant system) flushed. Good advice on the fill holes. I've read that in several other threads on this forum. Can't imagine how much it would suck to drain and then realize the fill hole plug is stripped.

 

[RikRunr]

That's a common way of changing fluid on an auto trans, because you can't completely drain it. Or an engine to clean the sludge like you said.
I don't think it would be worth it on a t-case or diff, they can be drained completely and don't build up sludge the way an engine does, but it wouldn't hurt to do it.

It's good to know you can completely drain them. I might be prepared to go straight to synthetic, depending on how the fluids look when I drain them. Thanks.

 

[fourwd1]

... Can't imagine how much it would suck to drain and then realize the fill hole plug is stripped.

On a manual trans, and t-case, you can always remove the shifters and fill thru there. That's how I do it normally.

 

[RikRunr]

Rear diff and t-case fluids changed. I'm going to wait until I can get to a lift to do the front diff since I need to pull the skid plates. I had a couple skid plate bolts broken off. Managed to get the broken pieces out and replaced all of them with new bolts. Didn't have the new gear lube on hand when I did this, or I would've done the front diff.