Gear oil question

So I read the awesome sticky about the diffs. And manual trans.

My question is...my Tacoma has 150k miles on it and is a 2006 model.....original oils in the diffs and transmission and transfer case.

Do you think switching to mobil1 synthetic will be ok or do you think it will cause leaks?

 

You'll be fine..

The worry about switching from reg to syn comes from older cars with older seal designs like rope and stuff.

 

The information about synthetic oils causing leaking is incorrect. This does not occur on modern vehicles.

Switch to synthetic, especially if you aren't going to be changing the oils but every 150K miles. Diff oil should be changed every 30K. Your dino oil in there is way past it's life.

Amsoil makes a severe gear with 100K miles of protection.

 

Change those oils soon! That's a long time to go without a change ... should smell wonderful when you open them up.

 

150,000K? Good luck getting the plugs out. Open the fill plugs first.

 

Appreciate it....ill just spray them with on blaster tonight, than touch them with a little propane torch if need be.

 

Yeah, synthetic is still oil, it's just got more uniform molecules. Honestly, for gear boxes the dino stuff is just fine as long as you change it according to schedule. Spend some time cleaning up the front diff plug so you don't strip it out.

 

I would suggest just having a new front diff drain plug on hand, when replacing the gear oil. It's unlikely that you'll get the old one out without at least doing some damage to the hex, and then you're definitely in for it the next time.

They're cheap, and they're flimsy. And it sucks to have to wait for a $15 part while your truck sits in the garage for a week.

 

My experience is more with engines than gear trains, but I bet the principles still apply.
Way back in '79, I started using synthetic oil and the only times I've seen a leak show up after changing from petroleum to synthetic was when the seal had a previous flaw - and the sludge (a result of using petro oil) actually "plugged" that flaw. The synthetic would clean the "plug" away, the flaw then was revealed, and it leaked.
In fact, back in the day... before good oil... it was specifically recommended to use an Engine Flush when changing from petro to syn for the first time - in an engine with more than 40k miles. Because of this cleaning property of syn oil, if you didn't flush it first, the syn would promptly clean all of the built-up sludge & varnish in the recesses of the engine and take it to the filter, which quickly clogged! You can guess the result of that.
The flush procedure was: warm engine; drain about a quart of old oil & replace the drain plug; replace the filter with a cheap one (less than a dollar then). Pour in the quart of flush; run the engine for 15 minutes; and then drain it & remove the junky oil filter. The nasty goop that was shit out during the oil drain was shocking!
Afterwards, when the syn oil was installed, with a quality filter, it could be allowed to perform it's miracles without contamination from the petro oil garbage.

My point to all of this is: that "garbage" is what sometimes hides the seal flaws and the cleaning action of the syn oil makes it look like it caused the leak. It doesn't. Synthetic oil (specifically Amsoil) is formulated with a seal sweller to enhance sealing properties.
(Know that aircraft jet engine synthetic oil is not automobile compatible. It will cause seal deterioration and multiple leaks!)

 

I've swapped all my vehicles over to synthetic engine oil on the first oil change since the mid-2000's. It gives me peace of mind but probably doesn't make much of a difference since I change the oil every 5K miles. My old '92 pickup had dino changes with Castrol GTX every 3K, and when I sold it at 130K miles the buyer was convinced I had replaced the motor. I had just cleaned things up when I did the timing chain and replaced the valve cover gaskets, what engine internals were exposed looked pristine.

I just use dino oil in the gearboxes since I change it on the 30k heavy-use schedule anyway. But I wouldn't be worried about switching to synthetic at any time.

That said, if your truck were mine, I would do an initial change with dino oil, run it for 5K miles or so, then change it again to whatever you want to use long-term.

 

...here's something I did.On my 135K 2010 MT I had a-very mild-synchro chirp once in a while when going first to second.Bought it used so I had no history on its gearbox lubes.Drained what smelled like dino...filled it with Mobil 1 looking for maybe just a little help...
The chirp was immediately worse.I've read where synthetics can be 'too slippery' but didn't really believe it.Now I'm thinking differently.I plan to try Redline MT conventional (dino again) to see if it helps but a weak/worn synchro/second gear is just that I guess...my .02

 

The transmission fluid needs to be gl4. Try redline mt90 synthetic.

 

GDT,
Thanks for that,I will,and say what the result is...

 

Sure thing. You can search on here for a lot of info on it- it's very popular for this transmission. I used it in my transmission when I changed the oil at 40,000 and 75,000 miles, and I've been very happy with it. I've never had any noise, but I do find that the shift from 1st to 2nd can be rough/notchy, when it is very cold outside and it hasn't had a chance to warm up yet. Goes away after a few miles when it warm up. It seems to just be a characteristic of this transmission that that synchro is a little weak.

 

So....i replaced all the diffs, transfer case, and transmission with mobil1

$28 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 gl5. My owners manual states that is fine for all for drive train components.

I sprayed all the plugs with PB blaster and let them sit for 15 minutes... then each time I removed a plug I used a propane torch on it for about3 minutes. Every plug came out fine with no issues. Truck is running great....seems to shift smoother and roll farther.

 

Your owners manual is WRONG. The diffs should get GL5. Any good GL5 will do, but Amsoil and Redline are the best. The transmission and transfer case need GL4, and Redline MT-90 is by far the best for those boxes. You will ruin you synchros using Mobile 1, and your shifting will deteriorate.

My suggestions:
For the diffs if you tow, haul, or wheel use Redline 75W110 or 75W140 in the rear, 75W90 or 75W110 front (or equivalent Amsoil products)
For the diffs if you lightly use the truck: Redline 75W90, Equivalent Amsoil, or any good GL5 synthetic
For the Transmission: Redline MT-90 only
For the Transfer case: Redline MT-90 only

 

Agreed, only gl4 for the transmission, but I don't think the transfer case has any synchros, and gl5 is fine for it. Last time I changed mine, I used mt90 in the tranny, amsoil 75w90 in front diff and transfer case, and amsoil 75w110 for the rear diff.

 

Sooooo....not to sound rude, because I am genuinely not trying to be rude. But why do you say this? Why would I believe someone who I know nothing about over the manual that came with my truck that was written by the people that designed and built it? I'm not saying you don't know more about this than I do, I have only worked on a couple transmissions. But what is the evidence to substantiate your claim. Telling someone to disregard the vehicle owners manual is a pretty bold move right?

Please, if you have more information I am genuinely interested in seeing it, as I don't want to damage my truck anymore than the next person.

 

Its religious. Do you have an iPhone or Android?