Another rear diff gear oil question

[Canatct]

I have a '05 Tundra DC 4x4 with the limited slip diff. It has 120,000 miles and has never had the rear gear oil changed (which I plan to do tomorrow). I know Toyota recommends the 80w90 conventional but I can buy Amsoil 75w90 severe gear for about $11/qt here locally. I am apprehensive because of what I have read about inner axles seals leaking when switching over. The price I'm getting is a good deal but is it worth the risk, or should I just get the 80w90 conv and add 4 oz of additive and be done with it? Any suggestions are welcome.

[cpearson817]

I have a '05 Tundra DC 4x4 with the limited slip diff. It has 120,000 miles and has never had the rear gear oil changed (which I plan to do tomorrow). I know Toyota recommends the 80w90 conventional but I can buy Amsoil 75w90 severe gear for about $11/qt here locally. I am apprehensive because of what I have read about inner axles seals leaking when switching over. The price I'm getting is a good deal but is it worth the risk, or should I just get the 80w90 conv and add 4 oz of additive and be done with it? Any suggestions are welcome.

You will be fine with the 75w90, the 5w will not make enough difference.

A lot of people have used the 75w90 amsoil gear oil on here

[Highwaylizard]

I have a '05 Tundra DC 4x4 with the limited slip diff. It has 120,000 miles and has never had the rear gear oil changed (which I plan to do tomorrow). I know Toyota recommends the 80w90 conventional but I can buy Amsoil 75w90 severe gear for about $11/qt here locally. I am apprehensive because of what I have read about inner axles seals leaking when switching over. The price I'm getting is a good deal but is it worth the risk, or should I just get the 80w90 conv and add 4 oz of additive and be done with it? Any suggestions are welcome.

If your fluid has not been changed in 120,000 miles I would not waste Amsoil on it for the first change. Run regular Valvoline in it first and then do another change 3-5,000 miles later with Amsoil.

Switching from dino oil to synthetic oil per say does not cause seals to leak. What causes the seals to leak is if the breather is clogged. The other cause is if the seals have shrunk due to being coated with sludge or gunk inside the differential and thereby not being exposed to the lubricating or "hydrating" properties of the oil. The new oil (synthetic or otherwise) tends to clean this junk out and expose the shrunken seals which allows oil to leak. It may be possible to pre-treat the seals by running some AutoRx but you should consult with Remmy700 first as he knows more about this than I do.

[Remmy700P]

The issue with axle seals leaking after switching to synthetic gear oils was a function of the design of the early model's seals. That has been corrected, so you will be fine switching to a full synthetic.

The 75W-90 Mobil 1 is an excellent gear oil. Some have been lucky and not required any LSD friction modifiers, others have needed to add a couple ounces to quiet it down. I'd suggest having a tube on hand just in case.

I would also suggest a 500-1000 mile "flush run" with a less expensive gear oil like Highwaylizard recommended before refilling with the (expensive) Amsoil.

I don't see any benefit to treating it with ARX unless there are symptoms of heavy contamination.

[Canatct]

Thanks for the replies guys. I actually have a degree in auto technology and used to work on bowties (reason I drive a Toyota) but it has been many years ago and when I did diff fluid changes on the chevy trucks it was always conventional back then. I will use a cheaper dino for a 1,000 miles or so and then run the Amsoil. Thanks again!

[Raider Man]

I have been using Valvoline 80-90 with 4 oz. GE additive for 90000 miles with no problems. Changed every other year for me about 28000 miles total with no problems.

[Invid]

I ran AMSOIL 75w90 for the past 80K miles without issue and just replaced it all last month. It came out looking like NewCastle Brown Ale and went in looking like Corona Light.

[2003bajatundra4x4ac]

corona light is what i produce after drinking a pitcher of "yellowtail pale ale...."

just sayin.

[INDYMAC]

I'm afraid what you see when you pull the drain plug will look frightful (remember to always remove the fill plug before the drain plug). Here is what I would recommend how you procede after so many miles of neglect:

Mag-Hytec

Next I would fill with any conventional GL5 gear oil (Valvoline, Castrol, etc.) with LS additive and then add 2 ozs of Auto-Rx for every quart you put into the diff to fill to the fill hole. Drive for 1000 miles and then drain. Then fill with whatever gear oil that you want to start using for 30K mile OCI's.

Fortunately, the Tundra has a fill and drain plug instead of a bolted faceplate, so it's an easy procedure to do yourself.

Good luck!

[Highwaylizard]

My rear differential fluid at first change right after I bought the truck used at 103,000 miles

Tundra Fuel Economy: Changing the Rear Differential Fluid

After changing I blew three rear axle seals until I did the breather modification (mine was missing) and have had absolutely no problems since. I think the rear axle seals would have blown regardless of changing the fluids as the hole that the stock breather cap was supposed to be in was completely clogged.