Looking for a bit of advice, rear diff gear oil mistake

Hello Friends,
I frequent the forums and own a 99 with 215k miles and an 06 with 105k miles. The 06 needed a rear diff oil change along with a few other things, so i took it to a shop and had it done. 9 months later, there is a roaring vibration from the rear of the 06 truck. I had 2 evaluations done, one at a toyota dealer and one at a different shop i trust.

Both came to the conclusion that the rear differential needed to be replaced to fix the vibration/noise from the rear. This is not cheap at all.

Here's where it gets interesting. I researched exactly what the first shop did to the rear diff 9 months ago. They used 75/140 weight with an LSD additive after a flush. All my research says its supposed to be 75/90 with an LSD additive. Could this have destroyed the rear diff? My 99 still runs like a top and I was absolutely shocked when they came to me with that repair bill for the 06. I have had nothing like that happen at all with the 99 in 17 years of ownership. I put 10k miles roughly on the truck with the higher weight gear oil.

Furthermore, could they be legally liable for the damage that was caused to the truck based on the wrong gear oil being used? A bill for a 2500$ rear end rebuild is a shocker at 105k miles imo.

Thank you for your time guys, and make sure to get your leaf springs checked by a dealer! just got a recall on mine.

 

I could be wrong, but I doubt running 75w140 would hurt it. I used to own a Jeep Cherokee that called for 80w90 in the rear diff unless you did a lot of towing, then it was supposed to use 75w140.

 

I would be more wary of the LSD additive (both amount and type) that they used than the oil.

 

I am inexperienced with the gear oil weights/ratings. I was told its an "In-House" oil used and that's all the information i got on it after speaking with the first shop.

 

This^
Maybe, GL4 instead of GL5?

 

I wouldn't suspect it being the VG of the oil unless you live in a very cold climate. Both oils start out at the lower number but as the get hotter the viscosity improvers actually make the oil thicker. I would be more suspect of under or over filling. Over filling can cause foam and bad things happen in oil when air bubbles are compressed and explode. If you are thinking about litigation then have an analysis do on the oil that's currently in there. They can tell you what the viscosity is, different wear and additive metals and particulate contamination. It's not cheap but without this info you have no chance in court. My .02$ is bite the bullet and have it fixed. Try to identify what failed and why this will help from the same mistake happening again. Sometime things just wear out and fail but with proper quality lubrication and not operating outside the design it should last the life of the vehicle. Sorry this got so long winded.

 

Is it possible to overfill a diff? Under filled could be a problem but you would have to really not be paying attention to do that.

 

Thank you for all of your insight everyone. I think I am just going to have to do as maxtherat said and bite the bullet. The first shop wants me to bring it to them but they aren't touching my truck again. I asked the dealer to save the oil from the old rear diff for testing and the rear end itself for inspection. The new rear end will be put on tomorrow. I do not have my truck at the moment, and cant verify anything without it, or check the oil that has been removed.

 

Yes it is possible. A lot of people think more is better. Since gear oil is somewhat like honey it thickness one can pump a bunch of oil into the diff and quickly put the plug back in before much of the excess drains back out of the fill hole. Likely no... Possible yes. Are you having your diff replaced or repaired/ overhauled? Id be curious as to what's found. I had something similar happen years back to my wife's Jeep Grand Cherokee and it was the driver side axle bearing.

 

Brand new assembly completely replaced. 2400$ from toyota dealership :/ I asked the service tech whats going to happen if he makes this change and the sound persists. He says it wont. Im hoping this kills it.

 

don't waste your time with trying to pin blame, to many variables and likely will cost more than the gain.
That being said. $2500 is plain ridiculous !

the diff assembly already built can be had for $700 with a 5 year warranty ( on the gear/diff parts and assembly ) you and a knowledgable friend can swap the third member out in an afternoon, it is NOT hard, just need to pay attention to details.

www.eastcoastgearsupply.com I have no affixation other than I know a few of the guys that work there (and the owner) NOW would also be the perfect time to upgrade to something better ( Tru Trac over the stock LSD, no need for friction modifier and works better )

YES, you can probably have your existing one rebuilt, but by who and what warranty is there ?

whatever you decide, DO spring for a solid spacer replacement in place of crush sleeve, requires a bit of knowledge to install, but far superior so the crush sleeve ( which is possibly the cause for your problems anyway, it is a known weak point of Toyota diffs )

good luck !

 

Whaaaaat? Sometimes this place just amazes me.

 

be sure it is the diff

my 99 4runner roared like a bastard and everyone said it's the diff

it was axle bearings on both sides...dead from muddin....diff was 100% fine

so, theres a lot that could be roar. pop that diff cover and have a peek

 

Dallas Tx - hot

My area is just as hot. I've run x/140 gear oil in a number of vehicles...cars/SUVs. No problem

As 127.0.0.1 said - look around for things in that area that are not necessarily DIFF related.

 

Just curious what you mean by that? Just didn't know or you think I'm full of shit? If it's the latter id be happy to explain it to you. By no means am I on here to have conflicts so please don't take it that way. Just want to share my opinion with those who ask.

 

Please do - as a degreed engineer I am interested in your technical explanation of this phenomenon. Specifically, how are the "air bubbles compressed" and the "exploding" effect. Also, how is the lubricity of the lubricant compromised by the "compression - explosion" effect. Thanks

 

I think he may mean gear oil cavitation, which can cause damage. it will cavitate if overfilled almost to the top and run hard, like 100mph hard, and for weeks...eventually a tooth may bust

but won't cavitate if filled halfway like it should be, it'll just splash around

 

Perhaps he did, but by definition, his explanation was WRONG if he was describing cavitation. So he must be describing some other phenomena. Let's wait and see.

 

I thought gear oil is more resistant to cavitations than say motor oil or the like.

I remember seeing the cleargearz differential covers years back and those would cavitate and nearly immediately settle down when stopped.

Diff oil is thick but still you would nearly have to try and purposely overfill one

 

I don't think you will be able to lay blame on the shop it is also doubtful that they had any thing to do with your issue with 200K any thing goes. It would not matter what oil they put in there as long as it was gear oil to cause an issue in such short time. My guess would be a pinion bearing failure.