Need to find out rear diff ratio....help please?
 

My rear diff is making a horrible roaring sound when I let off of the accelerator. This has been a problem ever since I bought it. I had a rear diff seal replaced to stop a bad leak several months back. The mechanic that did it works on my step-dad's service trucks, but I'm having a hard time getting a hold of the mechanic. The mechanic said, when he put my seal in, that my rear diff is about to fail any day. He said he guessed I had 4-5 months left and that was 3 months ago. The roaring is getting louder and worse, so I have to get me a used diff or have it rebuilt. Not having much cash to spend on this kinda bulls**t, I think finding a used one from a reputable salvage yard is the ticket.

I called the salvage yard today and the guy said he needed to have the ratio in order to locate me a rear diff and I have no clue where to find it. He told me, but he was talking a million miles a minute and sounded like he had all his front teeth missing. So, that said, can anyone show me, with pics, or tell me how to find out the rear diff ratio. I do recall him saying it was on a bolt or something on the rear diff.

Never heard of the diff ratio stamped onto the housing itself, could be though I suppose. I can give you a few ways to find it. Easiest, but slowest, would be to go to Toyota's website, go to the owners section and there is a way to send them an email. If you include your vin and ask your gear ratio they should send back an email with that info, I did this with my 00 just to see if they would respond.
Second, in the door jam there is an axle code, for 4Runners it starts with an A, something like A03A, this designates the ring size, number of pinion, 4 vs 2, and the gear ratio. There are conversion charts on the web, so just google toyota axle conversion charts and use the info from your truck. Some of the charts seem to be correct for Tacomas but not for 4Runners, so I don't recomend this method.
Lastly, and best, is the jack up and spin tire method. Jack up the rear and mark both the driveshaft and rear tire with chalk or tape. Then rotate the tire one complete turn counting how many revolutions the drive shaft makes. If it makes just over 4 turns you have 4.10, just under 3.90 and so on. Chances are if you have a 4wd auto you have either 3.90 or 4.10, it is also possible but rare to have 4.30 and if a 2.7 you may have 4.56.

Just saw its a 97 Limited, if you have the locker you probably have the 4.30, but make sure you get the right diff, the locker version used the older 8" diff, while the non locked had the 8.4, both are really an 8" but they are slightly different.

Thanks for the information. I would just do the "jack up" method, but I don't have a good jack and don't feel like using the crappy one for tire changing. I think I'll just try emailing toyota, or it would probably be quicker to just drive by a dealership. There's a Toyota dealership near my house.

I would not recommend the jack up and spin method. I had to replace my entire rear and tried that method with no luck. The codes on the door jamb are worthless and the dealerships were lost in the sauce on it as well as the salvage yards. The best is absolutely to take apart diff and count teeth. Terrible I know. I finally found some random sight highlighting the 4:30 rear on the '00 limited with rear diff lock and shift on the fly 4x. I went with it and it was right.

Hmmm, well, this really is isn't feasible for me. I don't have the tools, the time, nor the "know how" to attempt what you recommend.

I found a website that is pretty informative and even he recommends to "spin n count" method. Why wouldn't it work?

Here is the website I found: http://home.4x4wire.com/erik/diffs/

If done right, the jack 'n' spin method works just fine. Never failed once in my lifetime! (I've done this prolly over 100 times).
Just be very accurate on the reading.