Time Frame for Switching to Synthetic in Diffs and Xfer Case?

[dsfra]

I know that the whole subject of diff / xfer case gear oil is a recurring theme around here, and having pretty much decided to switch to synthetic I'm now wondering if anyone has any concrete personal experience regarding the point (mileage and/or time) at which it becomes unwise to make the switch. I vaguely recall seeing a posting or two on Bobistheoilguy about how if you wait "too long" to make the switch, then the diffs / xfer case have somehow become used to the molecular structure of the factory non-synthetic oil and all sorts of dire ugliness can / will happen after switching - leaking seals, unhappy bearings, etc. It's not so much that I'm looking for reports from people that switched x miles ago and everything is still "just fine", but rather if the consensus is that "I made the switch and shortly thereafter had problems", then that would be useful information to have. I have 15,000 miles on my TE that was built ~ 2.5 years ago. Yes, I searched and didn't find any recent postings pertaining to switching diff / xfer case gear oil. Most of the discussions regarded switching engine oil - not gear oil - from non-synthetic to synthetic.

The question is in part the result of screwing around with the local Toyota dealer regarding the official Toyota-branded diff and xfer case oil. The dealer first said that it was not available to customers through Toyota dealer parts departments, then said I could order 55 gallons of the stuff, then said I could order it but no one could me tell whether I was ordering liters or quarts or gallons. Turns out that it would be quarts, but I'll be damned if I'm going to spend $75 (they gotta be kidding) for a quart of xfer case oil unless there are compelling reasons to do so.

 

[BlackWorksInc]

This is the first I have ever heard of the bearings and seals going bad in modern vehicles because of switching to synthetic differential fluid. Any chance you can link a thread or two from BITOG for us to read?

 

[KidVermicious]

HowStuffWorks "5 Engine Oil Myths"

HowStuffWorks "Myths about Synthetic Oils"

Early synthetics were made of esters, which were harder on seals, especially those made of neoprene. However, synthetic oils have come a long way since the early 1970s, and they're much nicer to delicate seals. But while synthetic oil won't create a leak, it will find one. Its streamlined molecular structure has no mercy for cracked or otherwise marginal seals. The oil and its additives may even clean deposits from the engine, which is good -- unless those deposits are acting like spackle on questionable seals.

You're fine to switch to synthetic any time you want.

 

[1engineer]

I know that the whole subject of diff / xfer case gear oil is a recurring theme around here, and having pretty much decided to switch to synthetic I'm now wondering if anyone has any concrete personal experience regarding the point (mileage and/or time) at which it becomes unwise to make the switch. I vaguely recall seeing a posting or two on Bobistheoilguy about how if you wait "too long" to make the switch, then the diffs / xfer case have somehow become used to the molecular structure of the factory non-synthetic oil and all sorts of dire ugliness can / will happen after switching - leaking seals, unhappy bearings, etc. It's not so much that I'm looking for reports from people that switched x miles ago and everything is still "just fine", but rather if the consensus is that "I made the switch and shortly thereafter had problems", then that would be useful information to have. I have 15,000 miles on my TE that was built ~ 2.5 years ago. Yes, I searched and didn't find any recent postings pertaining to switching diff / xfer case gear oil. Most of the discussions regarded switching engine oil - not gear oil - from non-synthetic to synthetic.

The question is in part the result of screwing around with the local Toyota dealer regarding the official Toyota-branded diff and xfer case oil. The dealer first said that it was not available to customers through Toyota dealer parts departments, then said I could order 55 gallons of the stuff, then said I could order it but no one could me tell whether I was ordering liters or quarts or gallons. Turns out that it would be quarts, but I'll be damned if I'm going to spend $75 (they gotta be kidding) for a quart of xfer case oil unless there are compelling reasons to do so.

If a case seal starts to leak, it was going to leak anyway regardless of which type of fluid is in it. You'll be fine.

 

[STX4Runner]

I just put Redline 75w85 synthetic in the rear dif at 45,000 miles. No problems so far and its been at least 6 weeks since I did that. I guess I was mistaken, but I thought the difs had synthetic already in them. Either way, Redline was the only supplier of the exact weird factory weight that I could find.

 

[cbreze]

Thought it was all synthetic oils/fluids throughout. I was wrong once before. Good to know.

 

[T4RT]

I just put Redline 75w85 synthetic in the rear dif at 45,000 miles. No problems so far and its been at least 6 weeks since I did that. I guess I was mistaken, but I thought the difs had synthetic already in them. Either way, Redline was the only supplier of the exact weird factory weight that I could find.

A guy in my office was telling me I needed to switch my entire 4Runner over to Redline Synthetic products since they are polyester based and not polyolefin based. When I did the research I saw what you found [MENTION=80024]STX4Runner[/MENTION]. Redline was the only vendor to have the 75W85 Synthetic dif oil.

I know that Polyester based synthetics are used in jet engines because of heat requirements but is there really a need/benefit for running polyolefin vs polyester based synthetics in our 4Runners? I like the idea of extra projection but is there any substantial evidence that it is worth it long term?

 

[dsfra]

Hey Guys - thanks for the feedback.

On a related topic, is there a consensus regarding the viscosity? I'm thinking of going with Mobil 1 largely due to it's wide availability, but it would be 75w-90, not the 75w-85 that Toyota specifies. Surely a slight increase in viscosity wouldn't hurt when things get toasty hot?

BlackWorks - Sorry, but I can't find the thread(s) I was thinking of on Bobistheoilguy. It was a couple of years ago, and now I'm thinking that maybe it was in some other forum.